In floor heat

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nizak

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I was called to a residence where the in floor electric heat will not exceed 70 degrees. I checked the amp draw and it corresponds with the listing on the cable sets. I checked resistance on the floor probe and it's within parameters.

The GFCI function on the wall stat works properly and all programming functions work.

Owner tells me that it worked fine for several years after install in 2006.

The system has not been used in a couple of years and they just tried using it a few days ago.

Any ideas on where to look next?

I don't want to spend $140 on a new stat until I can verify that'd the problem.

Incoming voltage was also verified at 122V
 
Is the floor on slab, above a crawlspace, or on second floor?
If the stat stays on constantly and the amp draw is nominal, then the only explanation would be greatly increased heat loss underneath the floor.
Checking the stat by bypassing it seems like the first test to make though.
Might there be a thermal safety switch in the circuit that has changed its set temperature for some reason?
 
Like gold digger said, what type of substrate is the heating on top of, if slab and cold it could take days or weeks or never to bring up to temp. Cement is a large mass. Id bypass the thermostat and see how hot you can get it.
 
Sierrasparky said:
Like gold digger said, what type of substrate is the heating on top of, if slab and cold it could take days or weeks or never to bring up to temp. Cement is a large mass. Id bypass the thermostat and see how hot you can get it.
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In addition to the long time constant to heat the (hypothetical) slab, it is possible, for example, that the contractor used open cell rather than closed cell insulation underneath the floor and it has since become saturated with water.
Another good question to investigate is how low the floor temp goes when the heat is left off for a couple of days.
 
Could even be something as weird as an intermittent break in the floor that opens with heat.
 
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