Discussion:
Water Cooled Power Resistor Gets Rusty
(too old to reply)
D from BC
2007-09-19 07:38:21 UTC
Permalink
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.

The terminals and tap are rusting. :(

Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...

Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..

Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...

Did some reading on:
http://en.wikipedia.org/wiki/Corrosion_inhibitor

Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P

I dunno...maybe these ions might do some funky electrolysis.

Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil

Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?

Canola oil?
Brake fluid?


What to choose?


D from BC
Phil Allison
2007-09-19 07:54:26 UTC
Permalink
"D from BC"
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
** All you need do is coat the terminals and any exposed metal that is
submerged with something waterproof.

Use shrink on tubing, silicone adhesive and/or spray on lacquer to seal it
up.

I had much the same problem with tubular WW dummy load resistors used to
test power amplifiers but have managed to make them last many years.

Forget using oil - far too damn dangerous.

If it don't smoke and catch fire, it will spill sometime and burn YOU like
hell.




....... Phil
ChairmanOfTheBored
2007-09-19 08:06:35 UTC
Permalink
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
Use 3M's "Fluorinert" dielectric fluid.

FC-40 first one on the list.

http://products3.3m.com/catalog/us/en001/oil_gas/specialty_materials/node_HX0DNRHXKWge/root_GST1T4S9TCgv/vroot_G1F6DNZDBVge/theme_us_oilgas_3_0/command_AbcPageHandler/output_html

1500V per mil breakdown strength.

As soon as your water gets into contact with those metals, it becomes
ionized water.
D from BC
2007-09-20 04:16:35 UTC
Permalink
On Wed, 19 Sep 2007 01:06:35 -0700, ChairmanOfTheBored
Post by ChairmanOfTheBored
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
Use 3M's "Fluorinert" dielectric fluid.
FC-40 first one on the list.
http://products3.3m.com/catalog/us/en001/oil_gas/specialty_materials/node_HX0DNRHXKWge/root_GST1T4S9TCgv/vroot_G1F6DNZDBVge/theme_us_oilgas_3_0/command_AbcPageHandler/output_html
1500V per mil breakdown strength.
As soon as your water gets into contact with those metals, it becomes
ionized water.
It's the liquid breathing rats stuff!
http://en.wikipedia.org/wiki/Fluorinert

It's going to be exxxxpennnsive....
D from BC
Rich Grise
2007-09-20 17:23:29 UTC
Permalink
Post by D from BC
It's the liquid breathing rats stuff!
http://en.wikipedia.org/wiki/Fluorinert
It's going to be exxxxpennnsive....
Did you read the part where all of the test rats died? It's probably
excellent for heat transfer, but I wouldn't recommend using it for
deep-diving until they solve that pesky "died of lung trauma" problem. ;-)

And, well, "The Abyss" was pretty stupid overall anyway.

Cheers!
Rich
Tim Williams
2007-09-20 23:35:37 UTC
Permalink
Ah, but they're refining it more now. In fact, it's used standard these
days for some cases, drowning for instance. Displaces the water while
carrying O2.

Tim

--
Deep Fryer: A very philosophical monk.
Post by Rich Grise
Post by D from BC
It's the liquid breathing rats stuff!
http://en.wikipedia.org/wiki/Fluorinert
It's going to be exxxxpennnsive....
Did you read the part where all of the test rats died? It's probably
excellent for heat transfer, but I wouldn't recommend using it for
deep-diving until they solve that pesky "died of lung trauma" problem. ;-)
And, well, "The Abyss" was pretty stupid overall anyway.
Cheers!
Rich
D from BC
2007-09-21 01:12:58 UTC
Permalink
Post by Rich Grise
Post by D from BC
It's the liquid breathing rats stuff!
http://en.wikipedia.org/wiki/Fluorinert
It's going to be exxxxpennnsive....
Did you read the part where all of the test rats died? It's probably
excellent for heat transfer, but I wouldn't recommend using it for
deep-diving until they solve that pesky "died of lung trauma" problem. ;-)
And, well, "The Abyss" was pretty stupid overall anyway.
Cheers!
Rich
I liked The Abyss..
I think my favorite scene was when some guy uses his wedding band to
hold open a pressure door.
http://en.wikipedia.org/wiki/Wedding_ring
(Damn..wiki is useful..)
Wedding bands come in titanium, tungsten carbide and stainless steel.

D from BC
ChairmanOfTheBored
2007-09-23 07:07:03 UTC
Permalink
Post by Rich Grise
Post by D from BC
It's the liquid breathing rats stuff!
http://en.wikipedia.org/wiki/Fluorinert
It's going to be exxxxpennnsive....
Did you read the part where all of the test rats died?
You're a goddamned idiot.
Post by Rich Grise
It's probably
excellent for heat transfer, but I wouldn't recommend using it for
deep-diving until they solve that pesky "died of lung trauma" problem. ;-)
As usual, you don't know what the fuck you are jacking off at the mouth
about... again.
Post by Rich Grise
And, well, "The Abyss" was pretty stupid overall anyway.
No, actually, YOU are pretty fucking stupid anyway... any way one
looks at it, you are a fucking uninformed, over-aged dweeb.
Post by Rich Grise
Cheers!
Rich
Yes, YOU!
ChairmanOfTheBored
2007-09-23 07:05:22 UTC
Permalink
Post by D from BC
On Wed, 19 Sep 2007 01:06:35 -0700, ChairmanOfTheBored
Post by ChairmanOfTheBored
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
Use 3M's "Fluorinert" dielectric fluid.
FC-40 first one on the list.
http://products3.3m.com/catalog/us/en001/oil_gas/specialty_materials/node_HX0DNRHXKWge/root_GST1T4S9TCgv/vroot_G1F6DNZDBVge/theme_us_oilgas_3_0/command_AbcPageHandler/output_html
1500V per mil breakdown strength.
As soon as your water gets into contact with those metals, it becomes
ionized water.
It's the liquid breathing rats stuff!
http://en.wikipedia.org/wiki/Fluorinert
It's going to be exxxxpennnsive....
D from BC
Wrong.

That media was, and is a PERFLUOROCARBON fluid. Highly oxygenated, it
can and IS used in human medical procedures.

The stuff I pointed out is specifically made for electronic industry
use.

Both for infants born without fully developed lungs, and for elderly
folk that have damaged their lungs to an extreme point.

The stuff is real.

http://www.google.com/search?hl=en&q=liquivent&btnG=Google+Search

So is fake blood, made by the same pharma co.

http://www.allp.com/

They took a dump though.
D from BC
2007-09-23 07:17:02 UTC
Permalink
On Sun, 23 Sep 2007 00:05:22 -0700, ChairmanOfTheBored
Post by ChairmanOfTheBored
Post by D from BC
On Wed, 19 Sep 2007 01:06:35 -0700, ChairmanOfTheBored
Post by ChairmanOfTheBored
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
Use 3M's "Fluorinert" dielectric fluid.
FC-40 first one on the list.
http://products3.3m.com/catalog/us/en001/oil_gas/specialty_materials/node_HX0DNRHXKWge/root_GST1T4S9TCgv/vroot_G1F6DNZDBVge/theme_us_oilgas_3_0/command_AbcPageHandler/output_html
1500V per mil breakdown strength.
As soon as your water gets into contact with those metals, it becomes
ionized water.
It's the liquid breathing rats stuff!
http://en.wikipedia.org/wiki/Fluorinert
It's going to be exxxxpennnsive....
D from BC
Wrong.
That media was, and is a PERFLUOROCARBON fluid. Highly oxygenated, it
can and IS used in human medical procedures.
The stuff I pointed out is specifically made for electronic industry
use.
Both for infants born without fully developed lungs, and for elderly
folk that have damaged their lungs to an extreme point.
The stuff is real.
http://www.google.com/search?hl=en&q=liquivent&btnG=Google+Search
So is fake blood, made by the same pharma co.
http://www.allp.com/
They took a dump though.
Well..It's probably cheaper than inkjet ink. :P
$8000.00/gallon
http://www.ebusinessforum.com/index.asp?doc_id=7159&layout=rich_story

D from BC
Stanislaw Flatto
2007-09-19 10:04:10 UTC
Permalink
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
Should post to plumbing.sci.
We don't repair umbrellas.

Stanislaw.
Ecnerwal
2007-09-19 13:10:00 UTC
Permalink
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Surprise, surprise...not.
Post by D from BC
I dunno...maybe these ions might do some funky electrolysis.
Not to mention messing with the resistance. When you want a serious (but
not altogether stable itself) resistive test load, just stick a couple
of copper electrodes in a copper sulfate solution - it's what we used to
do at the lab for making BIG power resistors.
Post by D from BC
Or just give up on water and go to icky oil
One of my least favorite memories of lab work would be working in marx
generator tanks dripping with oil.
Post by D from BC
Pharmacy mineral oil?
Should be fairly benign.

Nichrome from an old toaster or heater in a box (to keep you from
touching the live wires) with alligator clips is a nice adjustable test
load that works fine when air-cooled, so it's nice and clean and
non-icky.

A few ordinary 25-50W air-cooled power resistors and some switches to
configure the bank could also work, though the resistors are rather
expensive if not found surplus.
--
Cats, coffee, chocolate...vices to live by
Jim Yanik
2007-09-19 13:48:59 UTC
Permalink
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
most people cool their power resistors in mineral oil.
That is also what my USAF cal lab(PMEL) kept their standard resistors in.
It can get a bit messy,though.
--
Jim Yanik
jyanik
at
kua.net
G
2007-09-19 13:55:05 UTC
Permalink
Post by Jim Yanik
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
most people cool their power resistors in mineral oil.
That is also what my USAF cal lab(PMEL) kept their standard resistors in.
It can get a bit messy,though.
The old Heath Cantenna, used mineral oil.

I made up some fixtures with screw on resistors and heat sinks, with the
capability to use a fan.


greg
Phil Allison
2007-09-19 14:44:13 UTC
Permalink
"G"
Post by G
The old Heath Cantenna, used mineral oil.
** A dummy 'antenna ' by name and use.
Post by G
I made up some fixtures with screw on resistors and heat sinks, with the
capability to use a fan.
** Very expensive and tends to stink the room out when it gets hot & there
is any dust on the parts.

A water submerged, tubular WW resistor never smells or catches fire,
dissipates huge amounts of power & self temp limits to just over 100C -
keeping the resistor value accurate.




...... Phil
Phil Allison
2007-09-19 14:39:10 UTC
Permalink
"Jim Yanik"
Post by Jim Yanik
most people cool their power resistors in mineral oil.
** Only if the load is for RF use and there is a safety temp cut out.




..... Phil
Tam/WB2TT
2007-09-19 19:57:09 UTC
Permalink
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
Commercial liquid cooled loads, like Heathkit and MFJ, use oil. Supposedly
transformer oil is best, followed by mineral oil. I knew of one person who
used automatic transmission fluid. Antifreeze may or may not work. The ones
I mentioned are built into unused gallon size metal paint cans. You should
be able to find a lot of info if you do a search on Cantenna.

Tam/WB2TT
Phil Allison
2007-09-20 00:53:53 UTC
Permalink
"Tam/WB2TT"
Post by Tam/WB2TT
Commercial liquid cooled loads, like Heathkit and MFJ, use oil.
** Realise that is because you CANNOT use water for a radio frequency dummy
load.

The OP is not restricted to using a bad and highly DANGEROUS heat
absorber like oil.




........ Phil
Tam/WB2TT
2007-09-20 18:59:29 UTC
Permalink
Post by Phil Allison
"Tam/WB2TT"
Post by Tam/WB2TT
Commercial liquid cooled loads, like Heathkit and MFJ, use oil.
** Realise that is because you CANNOT use water for a radio frequency
dummy load.
The OP is not restricted to using a bad and highly DANGEROUS heat
absorber like oil.
........ Phil
The commercial units I referred to are all used at RF. The one I have will
take a KW for short periods at 50 MHz. Like you say, probably overkill for
DC or power line frequency. For those, I would use a bank of resistors with
a fan blowing air across them, or just bigger resistors. I think the OP said
100W, which doesn't seem like a big deal at low frequencies.

Tam
Michael A. Terrell
2007-09-22 18:49:21 UTC
Permalink
Post by Phil Allison
"Tam/WB2TT"
Post by Tam/WB2TT
Commercial liquid cooled loads, like Heathkit and MFJ, use oil.
** Realise that is because you CANNOT use water for a radio frequency dummy
load.
The OP is not restricted to using a bad and highly DANGEROUS heat
absorber like oil.
........ Phil
Your ignorance and ego know now bounds. There is nothing dangerous
in using the right oil to cool electronics. Pole pigs are full of it,
and I have NEVER hear of anyone overheating a properly filled cantenna.
They have been around for at least 40 years. If they were dangerous,
they would have been pulled from the market.
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Jamie
2007-09-20 00:05:24 UTC
Permalink
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
how about using mineral or transformer oil instead?
--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
Spehro Pefhany
2007-09-20 01:49:27 UTC
Permalink
On Wed, 19 Sep 2007 20:05:24 -0400, the renowned Jamie
Post by Jamie
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
how about using mineral or transformer oil instead?
How about peanut oil? About 50% higher dielectric constant than
mineral oil, better temperature characteristics, IIRC, and available
at any grocery store. But any oil is going to be vasty inferior to
water in heat capacity (like 1/2 or 1/3 as good). Maybe just add a bit
of radiator antifreeze to the water (it contains corrosion
inhibitors).


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
***@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Straw Man
2007-09-20 02:11:20 UTC
Permalink
Post by Spehro Pefhany
On Wed, 19 Sep 2007 20:05:24 -0400, the renowned Jamie
Post by Jamie
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
how about using mineral or transformer oil instead?
How about peanut oil? About 50% higher dielectric constant than
mineral oil, better temperature characteristics, IIRC, and available
at any grocery store. But any oil is going to be vasty inferior to
water in heat capacity (like 1/2 or 1/3 as good). Maybe just add a bit
of radiator antifreeze to the water (it contains corrosion
inhibitors).
I use Olive oil and Balsamic vinegar.
Spehro Pefhany
2007-09-20 03:37:30 UTC
Permalink
On Wed, 19 Sep 2007 22:11:20 -0400, the renowned Straw Man
Post by Straw Man
Post by Spehro Pefhany
On Wed, 19 Sep 2007 20:05:24 -0400, the renowned Jamie
Post by Jamie
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
how about using mineral or transformer oil instead?
How about peanut oil? About 50% higher dielectric constant than
mineral oil, better temperature characteristics, IIRC, and available
at any grocery store. But any oil is going to be vasty inferior to
water in heat capacity (like 1/2 or 1/3 as good). Maybe just add a bit
of radiator antifreeze to the water (it contains corrosion
inhibitors).
I use Olive oil and Balsamic vinegar.
It's a heat transfer medium *and* a salad topping.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
***@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Michael A. Terrell
2007-09-22 18:51:34 UTC
Permalink
Post by Spehro Pefhany
On Wed, 19 Sep 2007 22:11:20 -0400, the renowned Straw Man
Post by Straw Man
I use Olive oil and Balsamic vinegar.
It's a heat transfer medium *and* a salad topping.
Just not at the same time! ;-)
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Michael A. Terrell
2007-09-22 18:50:31 UTC
Permalink
Post by Spehro Pefhany
On Wed, 19 Sep 2007 20:05:24 -0400, the renowned Jamie
Post by Jamie
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
how about using mineral or transformer oil instead?
How about peanut oil? About 50% higher dielectric constant than
mineral oil, better temperature characteristics, IIRC, and available
at any grocery store. But any oil is going to be vasty inferior to
water in heat capacity (like 1/2 or 1/3 as good). Maybe just add a bit
of radiator antifreeze to the water (it contains corrosion
inhibitors).
A can of water pump lubricant has more inhibitors, and costs less.
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
D from BC
2007-09-23 03:23:43 UTC
Permalink
On Sat, 22 Sep 2007 14:50:31 -0400, "Michael A. Terrell"
<***@earthlink.net> wrote:

[snip]
Post by Michael A. Terrell
A can of water pump lubricant has more inhibitors, and costs less.
"Zerex Water Pump Lubricant and Protector The Zerex Water Pump
Lubricant and Protector is a patented 5,702,631 cooling system
additive formulation designed to protect all cooling system metals
from corrosion. It also helps protect nonmetallic parts in the cooling
system, like gaskets, hoses and seals. The Zerex Protector prevents
the accumulation of cooling system deposits and helps lubricate the
water pump. The Zerex Protector is recommended to boost any engine
coolants protection and for those who want to recharge the coolant
corrosion protection but do not want to change the fluid. It can be
used in stored vehicles like collector cars, classics, hot rods and
specialty vehicles, for applications where enhanced corrosion
protection is a concern."

"Gunk
Anti Rust With Water Pump Lube
- Mixes with all ethylene glycol based anti-freeze/coolants.
- Prevents evaporation, formation of rust and corrosion.
- Keeps entire cooling system clean and running efficiently.
- Lubricates and protects all aluminum and/or metal parts, hoses and
seals"

This is a proposed solution if I don't want to coat the metals that
are rusting on the power resistor in the bucket of water.
After reading (the above), I think there's a chance that electrolysis
erosion at 100VDC may happen on the resistor terminals.
Funky trade secret stuff is in those lubricants.
Free ions or not, I dunno....

Gunk Msds is:
Naphthenic petroleum distillate
Triethanolamine
Zerex MSDS is: Unavailable!
Ah...so what.. I'm not a chemist.

10 hours of research or just buy it and try it in an hour.
Risky..Nah..

I still like the ideas of coating the terminals and greasing the tap
for 'in the bucket' tap water cooling.

D from BC
G
2007-09-24 12:47:30 UTC
Permalink
Post by Michael A. Terrell
Post by Spehro Pefhany
On Wed, 19 Sep 2007 20:05:24 -0400, the renowned Jamie
Post by Jamie
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
how about using mineral or transformer oil instead?
How about peanut oil? About 50% higher dielectric constant than
mineral oil, better temperature characteristics, IIRC, and available
at any grocery store. But any oil is going to be vasty inferior to
water in heat capacity (like 1/2 or 1/3 as good). Maybe just add a bit
of radiator antifreeze to the water (it contains corrosion
inhibitors).
A can of water pump lubricant has more inhibitors, and costs less.
It gets moldy.

Whats the matter with silicon oil.

Westleys used to sell pint bottles. I like that for different uses. After
my plastic bottle developed a whole in it. I lost all the stuff, and
I never saw it being sold after that.

greg
D from BC
2007-09-24 15:58:43 UTC
Permalink
Post by G
Post by Michael A. Terrell
Post by Spehro Pefhany
On Wed, 19 Sep 2007 20:05:24 -0400, the renowned Jamie
Post by Jamie
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
It's my ~100W test load. I move a tap to create different
resistance's.
Terminal voltages can get around 100VDC.
The terminals and tap are rusting. :(
Is there something safe I can add to the water to reduce or eliminate
the rust.
With 100VDC in the water I'm concerned about electrolysis erosion...
Perhaps add..
Automotive coolant?
(Propylene glycol, the nontoxic one.)
Or use it pure..
Or maybe use methyl alcohol?
(+ some water to reduce fire hazard. )
I dunno...steaming methyl fumes :P
Vodka might be better...
http://en.wikipedia.org/wiki/Corrosion_inhibitor
Vitamin C + water ??
Get calamine at the pharmacy. Add to water.?
Zinc oxide sun block + water?
Go nuts and toss in a hot dog (Sodium nitrite) :P
I dunno...maybe these ions might do some funky electrolysis.
Or just give up on water and go to icky oil
Like on
http://en.wikipedia.org/wiki/Transformer_oil
Pharmacy mineral oil?
Baby oil will smell nice.. :P
Hydraulic oil ?
Canola oil?
Brake fluid?
What to choose?
D from BC
how about using mineral or transformer oil instead?
How about peanut oil? About 50% higher dielectric constant than
mineral oil, better temperature characteristics, IIRC, and available
at any grocery store. But any oil is going to be vasty inferior to
water in heat capacity (like 1/2 or 1/3 as good). Maybe just add a bit
of radiator antifreeze to the water (it contains corrosion
inhibitors).
A can of water pump lubricant has more inhibitors, and costs less.
It gets moldy.
Whats the matter with silicon oil.
Westleys used to sell pint bottles. I like that for different uses. After
my plastic bottle developed a whole in it. I lost all the stuff, and
I never saw it being sold after that.
greg
I'd check the msds on that...I suspect it's carcinogenic.


D from BC
Phil Allison
2007-09-25 01:26:55 UTC
Permalink
"D from BC"


** Ever heard of trimming ???

Wanker !



....... Phil
D from BC
2007-09-25 03:09:51 UTC
Permalink
On Tue, 25 Sep 2007 11:26:55 +1000, "Phil Allison"
Post by Phil Allison
"D from BC"
** Ever heard of trimming ???
Wanker !
....... Phil
As in grass and hedge trimming? :P
Sure...
Like this?
Loading Image...


D from BC
Phil Allison
2007-09-25 03:14:17 UTC
Permalink
"D from BC"
"Phil Allison"
Post by D from BC
Post by Phil Allison
** Ever heard of trimming ???
Wanker !
....... Phil
As in grass and hedge trimming? :P
Sure...
Like this?
** Last help or advice you will ever get from me.

You pathetic FUCKWIT !




....... Phil
John Tserkezis
2007-09-25 03:32:07 UTC
Permalink
Post by Phil Allison
** Last help or advice you will ever get from me.
Can I get that assurance too, Phil? Pretty please!
--
Linux Registered User # 302622
<http://counter.li.org>
Phil Allison
2007-09-25 03:47:25 UTC
Permalink
"John Tserkezis Fuckwit Jerkoff "
Post by John Tserkezis
Post by Phil Allison
** Last help or advice you will ever get from me.
Can I get that assurance too, Phil? Pretty please!
** Go find the Harbour Bridge.

Jump off.




...... Phil
John Tserkezis
2007-09-25 05:42:11 UTC
Permalink
Post by Phil Allison
** Go find the Harbour Bridge.
Jump off.
They won't let you. I've already asked.
--
Linux Registered User # 302622
<http://counter.li.org>
D from BC
2007-09-25 04:18:16 UTC
Permalink
On Tue, 25 Sep 2007 13:14:17 +1000, "Phil Allison"
Post by Phil Allison
"D from BC"
"Phil Allison"
Post by D from BC
Post by Phil Allison
** Ever heard of trimming ???
Wanker !
....... Phil
As in grass and hedge trimming? :P
Sure...
Like this?
** Last help or advice you will ever get from me.
You pathetic FUCKWIT !
....... Phil
Is it about decorating Christmas trees?

I dunno..either I've had a rough day or just "trimming" is too vague.

The only thing I think that's most probable is I didn't call it
trimming when I wrote about making a resistance adjustment with a wire
wound power resistor..
Is that it?

D from BC
D from BC
2007-09-20 05:54:27 UTC
Permalink
Reading all replies... (thanks all by the way..)

Water Vs Mineral Oil

Water Pros
Off the tap.
100C bp is commonly known
Non toxic liquid
Non toxic steam
Odorless
Higher specific heat capacity than mineral oil.

Water Cons
Corrosion of ferrous terminals
Ion content increases with rusting and leads to electrolysis erosion
due to exposed terminals at 100VDC.

Mineral Oil Pros
No corrosion.
Obtained at pharmacy.
No electrolysis at 100VDC.

Cons
Possibly more resistance error due to higher boiling point.
bp ~360C??

Vapors can ignite with spark (flash point) around 145C to 193C??.

(See movie of a fire ball from an exploding mineral oil transformer on
http://205.243.100.155/frames/longarc.htm#Blowup )

Lower specific heat capacity than water.

Oil vapor coating everything.. Yuck.

Oil smell.


Soooo..
I'm going to coat the terminals and stick with water.
(as per Phil post).
But.. The tap contact on the tube power resistor is ferrous and I
can't coat that..
It'll rust but not erode due to electrolysis (the other terminals are
coated.)
So if electrolysis can't take place then maybe I can try out Vitamin
C.. :P
I'm no chemist but I'm dying to try Vitamin C as a corrosion
inhibitor. It's got that "fun with chemistry" appeal..
My steaming power resistor may have a nice zippy smell too :)

But ..if the coating fails on the other terminals ...just one
microscopic crack or hole and I think the electrolysis will start
peeling the coating and lead to even more electrolysis.

Seeing Vitamin C getting electrolyzed will be new :P

The device under test is safe to overload..so if I get a liquid short
out..it's ok...


D from BC
Glen Walpert
2007-09-20 13:29:09 UTC
Permalink
On Thu, 20 Sep 2007 05:54:27 GMT, D from BC <***@comic.com>
wrote:

<clip>
Post by D from BC
Soooo..
I'm going to coat the terminals and stick with water.
(as per Phil post).
But.. The tap contact on the tube power resistor is ferrous and I
can't coat that..
You could coat the tap contact and the entire length of the exposed
resistance wire the tap slides on with silicone grease without
increasing contact resistance or losing adjustability. The silicone
grease sold in auto stores as dielectric grease is best as it has no
additives and therefore the lowest water absorption of any silicone
grease, but pretty much any grease should do the job for short term
testing.

At a paltry 100 watts your reason for not using an air cooled load
must be a parts on hand issue. I have used air cooled loads up to
1250 kW, and they make them much bigger than that.
D from BC
2007-09-20 14:31:47 UTC
Permalink
Post by Glen Walpert
<clip>
Post by D from BC
Soooo..
I'm going to coat the terminals and stick with water.
(as per Phil post).
But.. The tap contact on the tube power resistor is ferrous and I
can't coat that..
You could coat the tap contact and the entire length of the exposed
resistance wire the tap slides on with silicone grease without
increasing contact resistance or losing adjustability. The silicone
grease sold in auto stores as dielectric grease is best as it has no
additives and therefore the lowest water absorption of any silicone
grease, but pretty much any grease should do the job for short term
testing.
At a paltry 100 watts your reason for not using an air cooled load
must be a parts on hand issue. I have used air cooled loads up to
1250 kW, and they make them much bigger than that.
Yeah..I've been thinking of grease too. It's a good solution.

Point taken about the Pdisp. qualified for air cooling.
I created a chemistry pita instead of just going back to the surplus
store to dig out a 100W power resistor rated for air.
The one I'm forcing to use with liquid cooling I suspect is an
underrated 50Watts. (No markings.) 0.8"d x 7"L

One the other hand, I find liquid cooling resistors appealing:
* No super hot item on the bench. ( Bad enough I have wires
accidentally land on my soldering pen.)
* A cool down from 100C takes less time to handle the resistor to make
a R adjustment.
* Then there's the camp fire effect.. :) Oooooo Ahhhhh... . Watching
that steaming resistor has an achievement effect.
Ok...that's a bit goofy but it's a "like what you do" thing. :)


D from BC
Jim Thompson
2007-09-20 14:47:44 UTC
Permalink
Post by D from BC
Post by Glen Walpert
<clip>
Post by D from BC
Soooo..
I'm going to coat the terminals and stick with water.
(as per Phil post).
But.. The tap contact on the tube power resistor is ferrous and I
can't coat that..
You could coat the tap contact and the entire length of the exposed
resistance wire the tap slides on with silicone grease without
increasing contact resistance or losing adjustability. The silicone
grease sold in auto stores as dielectric grease is best as it has no
additives and therefore the lowest water absorption of any silicone
grease, but pretty much any grease should do the job for short term
testing.
At a paltry 100 watts your reason for not using an air cooled load
must be a parts on hand issue. I have used air cooled loads up to
1250 kW, and they make them much bigger than that.
Yeah..I've been thinking of grease too. It's a good solution.
Point taken about the Pdisp. qualified for air cooling.
I created a chemistry pita instead of just going back to the surplus
store to dig out a 100W power resistor rated for air.
The one I'm forcing to use with liquid cooling I suspect is an
underrated 50Watts. (No markings.) 0.8"d x 7"L
* No super hot item on the bench. ( Bad enough I have wires
accidentally land on my soldering pen.)
* A cool down from 100C takes less time to handle the resistor to make
a R adjustment.
* Then there's the camp fire effect.. :) Oooooo Ahhhhh... . Watching
that steaming resistor has an achievement effect.
Ok...that's a bit goofy but it's a "like what you do" thing. :)
D from BC
I'm surprised that no one has suggested an active load... no sliding
contacts.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

America: Land of the Free, Because of the Brave
D from BC
2007-09-20 15:31:01 UTC
Permalink
On Thu, 20 Sep 2007 07:47:44 -0700, Jim Thompson
Post by Jim Thompson
Post by D from BC
Post by Glen Walpert
<clip>
Post by D from BC
Soooo..
I'm going to coat the terminals and stick with water.
(as per Phil post).
But.. The tap contact on the tube power resistor is ferrous and I
can't coat that..
You could coat the tap contact and the entire length of the exposed
resistance wire the tap slides on with silicone grease without
increasing contact resistance or losing adjustability. The silicone
grease sold in auto stores as dielectric grease is best as it has no
additives and therefore the lowest water absorption of any silicone
grease, but pretty much any grease should do the job for short term
testing.
At a paltry 100 watts your reason for not using an air cooled load
must be a parts on hand issue. I have used air cooled loads up to
1250 kW, and they make them much bigger than that.
Yeah..I've been thinking of grease too. It's a good solution.
Point taken about the Pdisp. qualified for air cooling.
I created a chemistry pita instead of just going back to the surplus
store to dig out a 100W power resistor rated for air.
The one I'm forcing to use with liquid cooling I suspect is an
underrated 50Watts. (No markings.) 0.8"d x 7"L
* No super hot item on the bench. ( Bad enough I have wires
accidentally land on my soldering pen.)
* A cool down from 100C takes less time to handle the resistor to make
a R adjustment.
* Then there's the camp fire effect.. :) Oooooo Ahhhhh... . Watching
that steaming resistor has an achievement effect.
Ok...that's a bit goofy but it's a "like what you do" thing. :)
D from BC
I'm surprised that no one has suggested an active load... no sliding
contacts.
...Jim Thompson
Thinking...
Active load...uhhh.. I can use a power current sink...almost the same
thing I think..
A power fet sprinkled with other components on an aluminum heat.
Perhaps dunk the whole thing in water and use silicone spray to stop
the electrolysis.
...or fan cool.
I'd have to put time into making sure I have a predictable
temperature stability.
The current stability is allowed to be say.. +/- 0.2Amps.
It'll be new for me to design a stable power current sink that can
boil water.
Fun project.. but I think using a power resistor instead has less
implementation time for my app.

D from BC
Rich Grise
2007-09-20 17:31:40 UTC
Permalink
On Thu, 20 Sep 2007 14:31:47 +0000, D from BC wrote:
...
Post by D from BC
Post by Glen Walpert
At a paltry 100 watts your reason for not using an air cooled load
must be a parts on hand issue. I have used air cooled loads up to
1250 kW, and they make them much bigger than that.
Yeah..I've been thinking of grease too. It's a good solution.
Point taken about the Pdisp. qualified for air cooling.
I created a chemistry pita instead of just going back to the surplus
store to dig out a 100W power resistor rated for air.
The one I'm forcing to use with liquid cooling I suspect is an
underrated 50Watts. (No markings.) 0.8"d x 7"L
That's a 100 watt resistor already:
http://www.alliedelec.com/Images/Products/Datasheets/BM/OHMITE/Ohmite_Actives-and-Passives_2960672.pdf

What you need to do is watch your current when you adjust the tap -- the
100W rating is for the whole resistor. (IOW, if you've got it tapped at 50%,
you could only dissipate 50W in air, etc.)

Good Luck!
Rich
Gary Tait
2007-09-20 15:19:47 UTC
Permalink
Post by D from BC
But.. The tap contact on the tube power resistor is ferrous and I
can't coat that..
It'll rust but not erode due to electrolysis (the other terminals are
coated.)
Is it a variable tap, or one or more fixed taps? if the latter, bring them
out to external terminals, and seal the contact on the resistor.
Paul Hovnanian P.E.
2007-09-20 17:27:55 UTC
Permalink
D from BC wrote:
[snip]
Post by D from BC
The device under test is safe to overload..so if I get a liquid short
out..it's ok...
If it can tolerate the lower cold filament resistance, use a light bulb
(or several with switches to vary the load).
--
Paul Hovnanian ***@hovnanian.com
-----------------------------------------------------------------------
The blinking cursor writes; and having writ, blinks on.
D from BC
2007-09-21 01:25:03 UTC
Permalink
On Thu, 20 Sep 2007 10:27:55 -0700, "Paul Hovnanian P.E."
Post by Paul Hovnanian P.E.
[snip]
Post by D from BC
The device under test is safe to overload..so if I get a liquid short
out..it's ok...
If it can tolerate the lower cold filament resistance, use a light bulb
(or several with switches to vary the load).
My laziness to get a bunch of sockets.. exceeds my hate of soldering
wires to household light bulbs. :)


D from BC
David DiGiacomo
2007-09-21 19:21:42 UTC
Permalink
I know you like to do things the hard way, but think about buying a
Clarostat 240-C power decade box on eBay. If you are patient, you should
be able to get one for under $50. It saves a huge amount of time.
whit3rd
2007-09-20 06:09:26 UTC
Permalink
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
[100 ohm adjustable, 100W range]
Post by D from BC
The terminals and tap are rusting. :(
You can use several solutions: exchange the water for a nonionizing
fluid
(mineral oil with high flashpoint is cheap, transformer oils and
fluorinert
are also available), or just lower the water's corrosivity (add rust
inhibitor
from the auto parts store to deionized water), or use resistors that
are water-safe.

Every electric water heater, from tea kettles to home hotwater tanks,
has such an immersible resistor. Some have several. One here in my
junkbox
is rated at 4500W at 240VAC - so it's 12.8 ohms. Eight of those,
and you can pick resistances from 1.5 to 100 ohms with no rust.
D from BC
2007-09-20 06:19:03 UTC
Permalink
Post by whit3rd
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
[100 ohm adjustable, 100W range]
Post by D from BC
The terminals and tap are rusting. :(
You can use several solutions: exchange the water for a nonionizing
fluid
(mineral oil with high flashpoint is cheap, transformer oils and
fluorinert
are also available), or just lower the water's corrosivity (add rust
inhibitor
from the auto parts store to deionized water), or use resistors that
are water-safe.
Every electric water heater, from tea kettles to home hotwater tanks,
has such an immersible resistor. Some have several. One here in my
junkbox
is rated at 4500W at 240VAC - so it's 12.8 ohms. Eight of those,
and you can pick resistances from 1.5 to 100 ohms with no rust.
Neat...
I can picture myself filling a shopping cart full of used water
heaters at the local thrift store.. :)

D from BC
ChairmanOfTheBored
2007-09-23 07:16:22 UTC
Permalink
Post by D from BC
Post by whit3rd
Post by D from BC
I have a big O wirewound resistor I keep cool in a container of water.
[100 ohm adjustable, 100W range]
Post by D from BC
The terminals and tap are rusting. :(
You can use several solutions: exchange the water for a nonionizing
fluid
(mineral oil with high flashpoint is cheap, transformer oils and
fluorinert
are also available), or just lower the water's corrosivity (add rust
inhibitor
from the auto parts store to deionized water), or use resistors that
are water-safe.
Every electric water heater, from tea kettles to home hotwater tanks,
has such an immersible resistor. Some have several. One here in my
junkbox
is rated at 4500W at 240VAC - so it's 12.8 ohms. Eight of those,
and you can pick resistances from 1.5 to 100 ohms with no rust.
Neat...
I can picture myself filling a shopping cart full of used water
heaters at the local thrift store.. :)
D from BC
Or buy 8 of those free standing, liquid filled radiant room heaters.
The heat sink (and radiator elements) are built right in!

They're EMI/RFI shielded too! (the element is inside a can).
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