Looking for a flexible material to transfer heat but not electricity 1

[brentg098]

Hello,

I have a pool system that has a heating pad underneath it. Electricity is traveling though the heating pads and causing a grounding probe which is in the water to shut off the GFCI that the heating pads are going to. The heating pads and the water are separated by 4 layers of flexible vinyl. The water being used is salt water.

We thought that this would be enough electrical insulation, but it is not. I need to add a additional material underneath the pool that will not allow electricity to flow through but will allow the heat to transfer and warm the pool. And, for shipping purposes it should be lightweight.

I am fairly sure that the water is being electrified by a low electrical resistance between the pool and heating pad materials vs a current being induced by the water from electromagnetic energy coming from the pads.

Any answers are welcome,
Thank you.

brentg

 

[GregLocock]

Well, given that we are engineers here we like to know numbers. So what is your desired thermal and electrical conductivity? What are your other requirements?

Al₂O₃ is a material with a high electrical resistivity and reasonable thermal conductivity, but scarcely seems a likely replacement for vinyl.

What do your competitors use?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[GregLocock]

May help

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[EdStainless]

I don't see them on the chart but there at TIM materials, thermal interface, used in electronics. They are electrical insulators and good heat conductors. These are the little pads on top of a CPU or GPU chip before the heatsink is mounted. I presume that you buy this stuff in sheets.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[MintJulep]

Before you invest time in "solving" your problem you really need to understand the problem.

It seems to me that you don't at the moment.

Your construction describes a capacitor.

 

[someguy79]

Does this pool have users with any particular kind of shock hazard? I'll assume you do, and that it's similar to a swimming pool.

You mention that the heaters use GFCI, so I expect that the heaters are well grounded. Have you considered using a grounding system in the pool, or between the pool and heater? I wouldn't want this to be the primary means of making the pool safe, but a good measure to help prevent problems.

I wonder if you're having trouble because the surface area is just so large between the heaters and the pool. Solving that problem by adding the right insulation is probably going to hurt either in cost or performance.

There are some materials sold in sheets that are decent thermal conductors that also insulate, like EdStainless says.

A whole other path would be to have immersion heaters in a fluid chamber beneath the pool. It has advantages for really high heat transfer rates, but probably has drawbacks on cost and complexity.

 

[brentg098]

Thanks for all your responses.

@ someguy 79
Yes there is a ground in the pool and when plugged in it which causes the GFCI to trip. However, when it is not plugged in it does not trip, or rarely.
It does have a nuisance shock hazard if not plugged in.

There is a large surface area between the pads an and when the surface area is reduced as was done in testing then yes the GFCI does not turn off, however performance is lost.

"You mention that the heaters use GFCI, so I expect that the heaters are well grounded. Have you considered using a grounding system in the pool, or between the pool and heater? I wouldn't want this to be the primary means of making the pool safe, but a good measure to help prevent problems."
Not matter how the extra electricity is removed the GFCI senses the difference and shuts off.

@mintjulep:
Perhaps you're right and I do not understand the problem. I have had some limits placed upon me to figure this out and hence not knowing the exact problem.

@edstainless; The Tim Material would have to be contained somehow in way where it could be removed as the pool is meant to be moved from time to time.

@GregLocock; I guess the electrical resistance would need to be enough to keep the GFCI from tripping off. This amount is 0.005 milli-amps. However I believe the electricity spikes when the pads turn on since they are either on or off, depending on thermostat. If I could somehow prove the spiking with the relay causes it to turn off, then perhaps we could leave the pads on and have them just change the amount of electricity going to the pads instead of turning them off and on. This would be an electrical engineering question. Perhaps I need to move this problem to a electrical engineering forum to find out how to measure and see if this is what is happening.

Thank you.

 

[chicopee]

"... This amount is 0.005 milli-amps..." I don't think that is correct as the value should be 5 milliamps.
If the layers of vinyl allows water to leak thru the layers, then there seem to be a problem with bonding the layers.