Will underfloor heating work without a floor sensor?
Yes, but between electrical code compliance and achieving a more efficient system, you’ll want to use one. Sometimes even the most organized installer forgets an important detail. If you forgot to install the sensor (typically placed between runs of heating wire and encased in thinset to control your floor temperature) and already finished the flooring, don’t panic! Try these tricks to control your floor temperature.
Option 1: Set the thermostat to use ambient air mode.
Set the thermostat to ambient air mode, if it is available on your thermostat model. This will sense the temperature around the thermostat and adjust the floor heat accordingly. Please note that this may cause some issues in reaching your desired temperature. If the area is warmer or gets direct sunlight, it may not kick on the floor heat. Also, if there is an air conditioner blowing cold air directly into that room, the floor heating system will continue to heat.
Option 2: Chisel out some of the grout between the tiles.
- If your drywall is already in and your grout lines are at least 1/4” wide, you may run your sensor wire from the control location behind the wall and fish it out through a hole near the floor by using a fish tape or a nail on a string.
- Use a cutting tool and gently remove the grout from between the tiles for a distance of 6–9 inches into the heated floor. Be careful not to cut too deep and damage a heating wire. Locate the sensor between the tiles, but make sure not to put it directly on top of a heating wire.
- Re-apply grout and then cover the sensor hole in the wall with trim.
Option 3: Install the sensor under the subfloor by accessing the joist bay.
If your grout lines are not wide enough, or if you are uncomfortable with cutting the grout AND you have a raised foundation (not concrete), you may be able to fish the sensor wire below the subfloor.
- Use a 1/4” drill bit to carefully drill a pocket under the heated floor in the subfloor up to the underlayment. (Stop before you get to the mat!)
- Secure the sensor in the pocket with adhesive and then insulate.
Jeremy says:
Can a temperature sensor wire be cut and spliced back together and still work?
Floor Heat Expert says:
Hi Jeremy, Yes, a temperature sensor wire can be cut and spliced back together, using solder and heat shrink tubing is ideal if the cut is within the floor. Verify the resistance is in the correct range (which varies somewhat by manufacturer)
For SunTouch…
10,000 ohms @ 75 F
Brian Mann says:
Hi Mathhew & Scott,
I’m installing an underfloor system in my bathroom. I want the underfloor thermostat to be maintainable, I don’t want to be lifting tiles every time the thermostat reaches the end of it’s life. I’m thinking maybe I install the thermostat in an exposed position just behind the bath panel with a plastic conduit to the accessory box where the controller will be mounted. What do the professional do? and what do you think I should do.
Brian
Floor Heat Expert says:
Hi Brian, Under Floor Heating is a terrific solution to cold floors!
If the thermostat fails, you do not have to remove any flooring – you would simply replace the thermostat which is mounted on the wall in the heated room.
Take a look at p.21 for a cut-away view…
SunTouch Install Manual
Gabriel says:
Hi I forgot to put sensor down underneath tile and now has done . Honestly don’t know what to do with sensor. I’m not sure if is work to put between tiles. How hard is it getting a tile up after stuck to adhesive or,
The bathroom floor is wood floor and I have access by under bathroom floor by kitchen area and, I am not sure if it will be ok to bring over the the thermostat sensor and place under the bathroom floor .
Thanks Gabriel
matthew@warmyourfloor.com says:
Hi Gabriel,
You have a few options here.
You can try to pull up a tile and get the sensor in the floor.
You could also try drilling a hole from underneath and putting the sensor in that way.
The easiest method would be to just turn the thermostat to “Room mode” and it will operate based on the air temperature.
Let us know if you have any other questions.
Thank you, Gabriel.
Brent Brotine says:
Hi, Matthew and Scott. Our 12-years-old NuHeat Harmony thermostat-controlled bathroom floor heater has stopped heating; display shows the temperature and heating power indicators but the GFCI test and reset buttons no longer light up or do anything. Called NuHeat and they feel thermostat needs to be replaced with the Home AC0056 as it lasted beyond its expected life. Before I order, is there a test procedure I can do myself with a multimeter to make sure it is the thermostat and not the floor mat itself? You’ve alluded to that in some of your past comments but I have no idea how to do it Thanks!
Austin DeSico says:
Had my heated floor in for 5 years. Never had an issue. Noticed floors weren’t heating. No errors on thermostat. Power is fine. Decided to replace thermostat with a new one. Still won’t heat. Should I run a new heat sensor? I can’t imagine the heating line went bad. ***I used the heating cord, not the mat***
Marci says:
Hi..my electrician just replaced my Flextherm thermostat with a a brand new Sunstat command..after install the thermostat turns on but the floor is not getting hot. He said it might be the sensor, but I figure even if the sensor is no good the floor should still heat. Any ideas as what might be going on?
Len Elias says:
What is “Error 3”? I can’t seem to find that error code definition anywhere.
Scott Cook says:
Hello Len
If its a 500775 Pro II
here’s the manual : https://www.warmyourfloor.com/pub/media/pdf/SunTouch-SunStat-Pro2-owners-installation-manual-English-current.pdf
and here’s an excerpt below
this is the direct replacement thermostat if you need/want a new one
https://www.warmyourfloor.com/suntouch-sunstat-command-programmable-thermostat.html
No heat Err1
Floor Sensor may be wrong type.
Electrician: Check floor sensor resistance. See Table 1 in the
Installation section above.
No heat Err2
Floor Sensor wires may be crossed.
Electrician: Check if the Floor Sensor wires crossed and
short-circuited. Check Floor Sensor resistance (see Table
1 in the Installation section above).
No heat Err3
Floor Sensor wires may not be connected.
Check Floor Sensor connections and mounting screws as
stated above.
Electrician: Check if Floor Sensor is attached. If not, attach
and reset the circuit breaker.
No heat Err4 or Err5
and Air
Internal air sensor may be faulty.
Change setting to Floor Sensing mode (see Table 3 above).
No heat Err6
Internal temperature limit may be exceeded.
Check if sunlight or other heat source is causing added heat
to thermostat.
Electrician: Check if load exceeds 15 amps.
No heat Err7
Contacts or internal connections may be faulty.
Check connections and mounting screws as stated above.
Reset circuit breaker.
No heat Err8 Internal device error.
Jimi says:
My Heatweave thermostat is 12 years old. It has always worked perfectly. This fall when the thermostat is set a warmer temperature floor either does not heat up or if I turn the thermostat off and then back on the temperature may go up for a short time, but then goes back down. All the icons and settings are visible on the thermostat screen. Is it my thermostat or could it be something else?
Scott Cook says:
Hello Jimi – Your thermostat has likely reached the end of its life. One last thing to try: Turn off the T-stat, then the breaker, leave off for 5 min, and then power all back up.
If you do need a new Thermostat, the Command is our top-selling replacement and we can ship it today for arrival in 2-3 days. HeatWeave was an old brand of SunTouch, now discontinued, but the stats are the same.
See all SunTouch Thermostats here
James says:
Can I use one heat probe for 2mats
matthew@warmyourfloor.com says:
Hi James,
You need a floor sensor for each thermostat you have.
If the two mats are controlled by the same thermostat, you can use the sensor for both mats.
Jason McQuade says:
Hi please can you help our tiler has forgot to put sensor down underneath tile and now has done a disappearing act. Honestly don’t know what to do with sensor. Won’t be able to put between tiles. How hard is it getting a tile up after stuck to adhesive. Thanks for any reply
matthew@warmyourfloor.com says:
Jason,
If you’re going to try to remove the tile we’d recommend having a tile setter do that if you haven’t before.
Depending on the thermostat you have, it may have a mode to operate on the air temperature in the room.
Give us a call at 866-558-3369 and we’ll be happy to help.
David Inzerillo says:
hi
my radiant heat worked fine for a few months then stopped because of E2 ground fault external sensor fail errors. electrician replaced the thermostat but same issue and he disappeared. when set to room it clicks on but the floor does not heat. not sure what to do next.
thank you
matthew@warmyourfloor.com says:
Hi David,
If you are getting an “ER 2” code, the sensor wires may have too much exposed copper wire at the terminal connections to the control. This can allow bare sensor wires to touch.
Turn off the power to the control at the breaker panel. Remove the sensor wires from terminals 1 and 2 and test the resistance with a digital ohmmeter set on the 20k Ω scale (20,000 ohms) as described in the installation manual.
If the sensor test shows it in range for the present floor temperature, trim the stripped ends to no more than 3/16″ long and reinstall. Turn the breaker back on.
Tom Jervis says:
Just installed the tapemat & thermostat with 2 T sensors. With 2 T sensors wired in parallel, temp reads 99 degrees. If I disconnect one of the sensors, it seems to be happy.
Why did you sell me 2 sensors if I could only use one with this system? I feel like I was mislead when ordering.
matthew@warmyourfloor.com says:
Hi Tom,
The idea behind having two sensor in the floor is that you have a backup already down there in case the first one fails.
But you can only use one sensor at a time and that’s all you need for the floor to work.
Apologies if this was not clarified, we just recommend doing this so you don’t have to rip up any part of the floor if the first sensor does fail.
Matt says:
Can I run the sensor wire along a wall, down in the heat matrix, for about a foot before going out into the center of the room. There isn’t a lot of room to come straight out from the wall as the heating wire is coming out near a toilet and I’m keeping it 2″ from the edge of the toilet and the 6″ from the flange.
If I have to I can cut out more drywall. Thanks.
matthew@warmyourfloor.com says:
Hi Matt,
Thank you for contacting us!
Try to get the sensor toward the center of the room as best you can without crossing any heating wires.
And just make sure the sensor probe sits in the middle of two heating wires, and is away from any other heat source(sunny spots, air vent, baseboard, etc)
Do that and the sensor should be in ideal conditions to read the floor temperature.
Thank you, Matt!
Bill Shedoudy says:
My floor sensor died after 12 years. We have heating mats and currently it is embedded in thinset under the tile, but the easiest way to replace it would be coming up from underneath. Can I just drill a small hole for the sensor tip through the sub-flooring? IOW, is the tip sensitive or is it better to lay it parallel to the floor rather than perpendicular?
Also, there is no way to know if it is next to or between a heating wire, is that a big issue?
matthew@warmyourfloor.com says:
Hi Bill,
It is very rare for the actual in floor sensor to just stop working unless it was damaged.
The thermostat is more likely the issue here and replacing that would likely fix your problem.
If you know it is the floor sensor, you could come from the bottom and drill a whole to put the probe into, the tip is what actual reads the temperature.
You want to get the sensor between two heating wires so you get the most accurate reading.
Deidre says:
I installed 2 mats but didn’t connect them. They are directly wired to the thermostat. Both worked for a few months. Now one has stopped heating. How and what do I check for in the thermostat or cable that runs to the mat.
matthew@warmyourfloor.com says:
Hi Deidre,
What you need to do is get an ohm meter and check the resistance of the mat that is not working.
Make sure the resistance falls within the range listed on the white UL tag attached to the power lead.
If the resistance falls within the range listed then it is functioning.
If the resistance is off then it indicates there is something wrong with the mat.
Also check the connections behind the stat and make sure nothing came loose.
Jhon says:
I forgot to put the probe. The wall concret and the tile done but i have conduit going to floor can i feed the probe in. Its work
matthew@warmyourfloor.com says:
Hi Jhon,
You could route the sensor probe down the conduit but it may not be that effective if the probe is not between two heating wires.
So you can try it and see how well the system functions that way.
Or depending on the thermostat you have, it may have the option to operate on the room temperature.
Consider changing the thermostat setting to Room Mode and see how well that works for you.
Peter says:
My cowboy builder didn’t seal the matting in levelling compound or adhesive and only dabbed the , there is hardly any adhesive on the matting cables, will it overheat?
matthew@warmyourfloor.com says:
Hi Peter,
Can you tell us what product you’re using?
Sounds like you’re using a cable or mat system that must be covered in thin-set or self-leveling mortar.
The cables will not likely overheat but if they are not encased in thin-set then the heat won’t transfer well to your finished floor.
We’d advised you to make sure the cables are covered with thin-set or a self-leveler before installing flooring.
Bruce Townsend says:
I replaced two of 7 heating mats in my enclosed porch. All mats were working properly. Now I have finished installing the click-together vinyl flooring, and I have no heat. I have reset my breaker numerous times, as well as resetting the thermostat from factory setting to increasing the temp, to whatever I could try, but still no heat. There are no error codes that I can see on the thermostat.
What now?
matthew@warmyourfloor.com says:
Hi Bruce,
There are a number of reasons why the system isn’t working now.
I would recommend starting by checking the connections behind the thermostat to make sure everything is secured.
If that looks good, you’ll want to do a resistance test on the heating mats using a multi-meter to verify the mats are not damaged.
If all else fails you want to contact the manufacturer to troubleshoot the system with them.
Steve says:
Our contractor just finished the install, and we are getting a temp showing the floor at 87 degrees. The unit is set at 75, so it’s naturally not heating, but the floor is ice cold. The sensor was installed so what would cause the floor temp to show 87. If I increase the setting to 88, it kicks in and says ‘heating’ but the floor is still ice cold tile.
matthew@warmyourfloor.com says:
Steve,
Check the sensor connection at the back of the thermostat and make sure it is secure.
Also, make sure the sensor wires are in the correct terminals.
If you continue to have trouble, contact the manufacturer to troubleshoot.
Michael Precure says:
I’m less than years post installation. It was installed by a professional… The unit will no longer heat the floor and I’m noticing an error 7 end of life message. Please help.
matthew@warmyourfloor.com says:
Hi Michael,
The error 7 code means that the thermostat has reached the end of its life and needs to be replaced.
The warranty on the thermostat is 3 years though. Since it has been less than 3 years since the date of purchase, contact the distributor you purchased from and they can get you a replacement.
If you bought from us just call us at 866-558-3369 with your original order number and we can get you a replacement.
Thank you, Michael!
Rob C says:
The temperature sensor was installed in a recessed channel approximately 1/4″ below crossing heating cables above it before being covered with leveling compound. Will this cause damage to the system?
Scott Cook says:
Rob,
Having the sensor 1/4″ below the heating cables won’t be a problem.
But you do want to make sure nothing is ever crossing over a heating cable, including the sensor.
David Jueneman says:
The GFI light in the back comes on. (Red) We have had the in floor heat for 10 years. It still appears to be heating. After recycling the circuit breaker, it goes off for awhile but then back on. What should I do?
Scott Cook says:
Hi David,
The thermostats typically last about 5-8 years on average.
So it sounds like your thermostat has reached the end of its life and needs to be replaced.
You can see the current thermostats we carry HERE.
You’re also able to place an order directly from our website.