Relplacing Flextherm Controller for in- floor comfort electric floor heat system

Joined
Dec 31, 2017
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15,069
Location
SE British Columbia, Canada
I had to replace my Flextherm controllers for my in-floor electric heat system under the tiles in a main bathroom and kitchen area. The controllers were 10 years old and all had failed at between 3 and 5 years. A quick call to suppler revealed that yes they tended to fail but had a new improved version, the FLP 35. I didn’t want to change brands ( but I should have just to spite the supplier.) The original heating wires and sensors were still OK. The controllers were available on Amazon.ca for about $80 US each.

Here is what I found: All the wiring terminals were clearly marked on both the old module and new module. There are two supply line wires labeled L1 and L2. It was important to keep these properly in their proper terminals. The two load wires can be mounted in the two load terminals, and polarity does not matter. The two sensor wires are mounted to the sensor wires and polarity does not matter.

For those uncomfortable with wiring please use an electrician. The job went well and works great. Programing is pretty easy. I set my temp readout to degrees C..

Here are some shots with the new unit to the right. A third photo shows the “ out of the house mode” and the floor is cooling from the previous “morning setting” of 25C back to the “ out of house mode” of 22 C.

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120 or 240v?

240v L1 & L2 are both hot makes no difference single phase. 120v L1 hot and L2 neutral.. then the load wires would matter do to you want to switch the hot leg.
 
120 or 240v?

240v L1 & L2 are both hot makes no difference single phase. 120v L1 hot and L2 neutral.. then the load wires would matter do to you want to switch the hot leg.
Thanks for mentioning. It’s dual purpose. The small bathroom is wired on a 110 breaker. The larger kitchen area is wired to a 240 breaker. The electrician did the original wiring 10 years ago and I just transferred the wires over. The module does have a “L2 neutral” marked on one terminal.

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Yes I did a little research on this to educate myself not all that familiar with radiant floor heating but am familiar with line voltage heat and thermostats. I had 240v baseboards as a secondary heat source in my old home. Based on a video I watched made my flextherm it’s a double pole switch within the thermostat therefore switching both hot legs on 240v and both the hot and neutral on 120v installations.
 
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