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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8298
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I recently installed a brand new wall heater.

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I recently installed a brand new wall heater. All the wiring was already there, the old one was bad. Every time I turn it on, regardless of the heat setting, it runs for only 30 seconds, then quits. I have to turn the thermostat all the way off, wait for awhile (not sure how long....never timed it), then I can turn it on again with the same results. There are two controls. One on the wall above the heater, and one on the heater itself. I have tried adjusting both to lower settings, but no matter....still times out after 30 seconds. This is actually the second heater I have tried. The first one did the same thing and I returned it because I thought it was the problem. I will attach a couple of pictures with my next response. Any suggestions for troubleshooting this? Thanks in advance, Kolin

Welcome to Just Answer!

Do you have the model number of the heater? Does it have a fan in it?
Is it gas or electric?

Let me know, we can go from there.

Customer: replied 3 years ago.

Phil, It is a Cadet, Model CS101. Electric, 120V, with fan.

Hello again, thanks for the data.

If the fan is running then there is either a restricted air flow, or the wall thermostat is bad...or... the high temperature safety limit switch inside the heater is bad.

We can check it out this way.:

First turn off the power and twist the two wires that attach to the thermostat together and tell me if heater will run longer than 10 minutes or not....

If it keeps running, then the thermostat is bad.

If the heater still goes off after a few seconds and fan is blowing plenty of air, then the high temperature over load switch inside the unit is bad.

An experienced technician might try connecting the two wires attached to the High temperature safety together.... then running the unit FOR NO MORE THAN 1 MINUTE... if it runs that long, when it had not before... then the high limit is most likely bad or has a loose and burnt wire connection.




Tell me what size wire you ran to the unit please.

We can go from there as long is takes to get this issue resolved and as long as you continue to rate my work *positively... there is no time limit. I hold the question open for you in that case.


Customer: replied 3 years ago.

Phil, When you say the wall thermostat, do you mean the one that is mounted on the wall above the wall heater, or the control on the heater itself. The heater control looks very simple with just a piece of metal (probably dissimilar) that makes or breaks a contact. Are these two wires the ones I need to connect? And where is the high temp sensor?

Hello again, that switch in the last picture you posted is there to kill power to the heaters and fan when the cover is removed.

I could not find a wiring diagram for the unit....

You mentioned the temperature adjustment at the *top of the unit... if you installed it so that the thermostat is at the top and the black label behind the louvers reads upside down.

Then the heat from the heating elements would shut the heater off way too soon.

Tell me if the knob you set the temperature with is on the bottom left as you look at the unit, or at the top. Make sure you have it wired for 110v to 120v , not 220 volts

see picture, click here

We can go from there until we get this resolved as long as you choose to rate my assistance positively.

Phil and other HVAC Specialists are ready to help you
Customer: replied 3 years ago.

Phil, the control knob on the heater is at the bottom left. The reference to the control above the heater is the separate control on the wall (see pictures I sent with original question). It is wired 110.

Hello again, you have the heater installed correctly from what I can tell.

However if the wall thermostat is placed above the heater, it will tend to get warmer than if it is placed further from the heater, ideally below it where it will sense the room air returning to the heater. That is a *possible problem. It could be getting hot and shutting off the heater.

Test that as mentioned in my first response, twist the two wires that go to it together, if the solves the problem then we know it was getting hot and shutting off the heater.


This raises a second issue. Why have you installed a thermostat above the heater when it has its own built in thermostat with the control knob on the lower left? It should work that way though. I am just wondering why.


Is that thermostat above the heater rated for 110 volts? are the wires attached to it at least size 14 AWG?



This heater should not be going off after 30 seconds of course, The check out procedure is to simply bypass each of the control components as mentioned earlier, briefly, as tests only.

The high limit safety t hemostat is a small round device mounted close to the electric heating coils near the hot air outlet inside the factory built unit.


I could not find a diagram for that unit on line. An appliance man would have no trouble finding it by just following the wires... that however is not something you should have to do with a brand new unit, especially if you don't have the necessary skill set.



this is a typical high limit safety thermostat.

The thermostat that controls the temperature in the room is located directly behind the knob on the lower left of the unit, with two wires attached. to check that one you can remove both wires and tie them together, if the unit keeps running after that, then you know the thermostat is bad.

If you followed the wiring diagram that came with the unit however, the thing to do is to return the heater and get one that works properly...working the unit will void its warranty along with wasting your time.

Let me know why you put an additional thermostat above the heater... and what size wires are attached. (I want to make sure it is not a millivolt rated thermostat, which would be dangerous in this application.)


Customer: replied 3 years ago.

Phil, the additional thermostat was installed when we bought the house. Both bathrooms have the same setup, so I just left it the way it was. However, you last response got me thinking. It occurred to me that both bathroom heaters haven't worked right since we bought the place, but I was only concentrating on the one in the master bath since we never use the other. So, I figured this might be something common between both. Then, I realized the circuit breaker was ganged....


It is wired for 220! When we bought the place, the original heater did not work at all. When I removed it, I saw it was a 120V heater, so I replaced it with the same, and then replaced it again when the replacement wasn't working right (doing the same thing this one is). The original heater probably was not working at all because it had been finally burned up by the previous owner.


It was really stupid of me to never make the connection in my mind between the ganged breaker and the supply voltage....and to not check the voltage prior to installing a new heater. I just made an assumption.


At any rate, the question now is: What is my best bet going forward? Rewire for 120 and use the heater I have (assuming I haven't ruined it), or get a 220 heater? What would you do?



.Hello again,

First we need to determine with wire size, it is stamped every 8 inches or so on the wire insulation.... unless it is the old rubber and cloth covered wire.

If it is size 12 awg wire you can most likely reuse the existing 110v heater you just installed... it is probably not damaged by running on 220v for the short time you have been testing it. You can always replace it later if necessary. That breaker size should be no larger than 20 amps (stamped into the breaker switch)

If the wire is size 14 awg wire then buy a new heater rated for 208-240 volts and wire it as the old one was to the two pole 230v breaker.. that breaker should be no larger then 10 amps. (that is stamped on the breaker switch end)... the breaker size is important.


***The breaker in the panel needs to be a GFCI type breaker, to meet the new safety codes...if the panel is old enough it will not accept a GCFI that case a small sub panel will have to be installed and that panel fit for GFCI breakers


GFCI = Ground-Fault Circuit Interrupter.


There MUST be a bare copper ground wire attached to the metal cabinet of the new heater and that must run to the ground bar in the main breaker panel.

The new heaters all come with a built in thermostat. Remove the old one on the wall.


Electrical work in bathrooms can easily be done incorrectly. It will be a good idea to call an electrician in to do this work, especially since you will very likely need a sub panel to accommodate the the GFCI breakers..and to insure you have a good electrical ground at the heater.

Let me know, we can go from there.


Customer: replied 3 years ago.

The breaker is 30A (ganged 15s). I can't see the wire gage stamped on the insulation, but I have attached a picture so maybe you can tell. The house was built in 1988. The wiring is all encased in the white insulation with the paper wrapping (nomex?) with the two wires you see and one bare copper wire. I will have to remove the metal heater box (still installed in the wall) to see the markings on the wire insulation.


Also, the current breaker is not GFCI. Since I will be removing the existing thermostat from the wall above the heater, can I use that spot to install a GFCI breaker inside the bathroom? And If I do that, do I leave the existing 30A breaker installed? This would give me two breakers inline....

Hello again,

If each ganged switch has 15 stamped on in it.. it is a 15 amp breaker (they don't add)

The wire in the photo is most likely 12 or 14 awg.. 95% chance of that.. you can snip off half an inch and take it to a hardware store to compare with known sizes.

You can most likely put a GFCI where the old thermostat was... that gets complex in this case.... it will take a good electrician to do that correctly.

You can also remove one of the breakers and take it an electrical supply store or Home Depot or Lowes, and ask the electrician there if he has a GFCI breaker, 15 amp rated that will replace the sample. Give him the brand name of the panel as well.

We can go from there.


Customer: replied 3 years ago.

Thanks Phil. I will go ahead and rate now and I will get back with you after I get the GFCI and check the wiring gage. Learned a lot on this one....

Hello again, thanks I will put up the ratings box, and hold the question open for you further coaching if need it.

Do have an electrician check your work... it is possible to make life threatening mistakes wiring this sort of thing in bathroom, recent codes require the heater to be out of reach of any sink, shower or tub as well.

Phil and other HVAC Specialists are ready to help you

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