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HVAC Guru
HVAC Guru, HVAC TECH
Category: HVAC
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Experience:  15yrs in the HVAC industry with certificates and degrees.
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We have a Honeywell Th115-AF-GA programmable thremostat with

Customer Question

We have a Honeywell Th115-AF-GA programmable thremostat with GFCI installed on a Thremosoft in floor heating system. It is connected to a 110 power supply. This thermostat replaced the one originally installed with the system. Everything appears to be working but the floor does not heat above 65 degrees even thought the thermostat says it is operating at 100%. We changed the thermostat because the floor stopped heating up and we used the back up floor sensor when we installed it. Any idea what why our floor won't heat above 65 degrees?
Submitted: 10 months ago.
Category: HVAC
Expert:  BillyHvac replied 10 months ago.

I am very sorry your question has not been picked up yet.

I just logged on and found you had not been assisted.

Please let me know if you still need help and I will do my best. Please do not "Rate" as we have not worked toward an answer yet.

If you would like to proceed let me know by replying. Once again use reply..not "rate".

Customer: replied 9 months ago.
Hello Billy,Yes I could still use some help.Lezley
Expert:  BillyHvac replied 9 months ago.

thank you,

is the underfloor resistant heating a one continuous series loop or do you have parallel circuits?

Customer: replied 9 months ago.
Continuous loop.
Expert:  BillyHvac replied 9 months ago.

Thank you...now I need the actual voltage coming into the thermostat and then entering the loop.

Customer: replied 9 months ago.
It's 110.It might help for you to know that we got a new electrical panel & rewired the house a couple of years ago. I'm pretty sure that floor was 240 before the rewire but it is now on a 110 circuit. When we got the new Thermostat we made sure it would handle 110 but I'm now wondering if the heating cable specifically requires 240. Is there anyway to test that?
Expert:  BillyHvac replied 9 months ago.

You are correct.

I was questioning the power because the 110v is insufficient for floor heating.

You need a 220v breaker feeding the floor loop.

Expert:  BillyHvac replied 9 months ago.

the wiring there is still ok to use..however at the panel a neutral will need to be moved to a hot on a double breaker with other hot wire. The thermostat should be rated for 220v.

Customer: replied 9 months ago.
Our kitchen floor, which is significantly larger, is also on 110 & works just fine. It is on a dedicated circuit & was ordered as a 110 system. It has the same Thermostat as the bathroom.Could the problem with the bathroom be that the cable in the floor is designed for 240 when we have it wired as 110?
Expert:  BillyHvac replied 9 months ago.

I see these regularly...and 120v is commonly not used for electric resistance heating.

Small units for bathrooms are the exception.

I will opt to the others for ideas but currently I must maintain that it is wired wrong.

Expert:  HVAC Guru replied 9 months ago.

Hello and thanks for using this service, if you have been waiting do not worry or get upset I am just one of the techs on here and I try to get to as many customers as I can and I just picked up your question now.

The heater should be 240 not 120, so you have it wired incorrectly and that is the issue here for sure.

We are on the honor system for our time, all I ask is please rate my service using the STAR RATING SYSTEM on your page before you leave. If you are not happy with the service please let me know before leaving a negative rating. This is the only way I am paid or credited through the site for my time. This will also allow you to get directly back to me for FREE follow up questions and tips are greatly appreciated! Thanks

Expert:  HVAC Guru replied 9 months ago.

If there was nothing more I can do for you all I ask is please rate my service using the STAR RATING SYSTEM on your page before you leave. If you are not happy with the service please let me know before leaving a negative rating. This is the only way I am paid or credited through the site for my time. This will also allow you to get directly back to me for FREE follow up questions and tips are greatly appreciated! Thanks

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