Smelled a burning smell coming from 1 of my Honeywell T4700B 4 wire line voltage electric heat thermostats(electronic). Pulled it out and found 1 of the neutral wires melted at the wire nut. Installed a spare thermostat and it seems to be ok. Just wondering what would cause this?
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One wire is "IN" the other is "OUT" A Thermostat works by "Breaking" the "Phase" line. It is just that simple. You usually have a pair of wires that connects, on the "Hot" side, to the always power ON line, & neutral. The Circuit, or Load, on the "Cold" side, has a a pair of contacts that open & close depending on Thermostat, in series with that conductor.
Hot Contacts Cold
P In-------------------><-----------------P Out
First of all keep this in mind.
You will need to locate the wires that got hot. If you can't or if your not sure, I suggest that you call a service company. If they ok the unit and it catches on fire after wards, their insurances will cover you unit and or home if god forbid it burns. This is to be on the safe side.
Now, this is where I would look. Your element should be on it's on circuit. There should be a disconnect within reach of the air handler. Some are fused and some are not. The wires that got hot enough for you to smell them should show signs of being hot like the plastic will be melted around the wire. You said that the heater was running. Was this the first time you have used it this year? If so, are you sure it was not the dust burning off the elements? They will smell like something burning when you first turn them on each year. Although if your sure you smelled wires getting hot, please continue looking for just that. Keep in mind that the elements have 220 volts coming to them. It comes into the unit and go to a switch or relay. From there the power goes to the elements and then to a neutral. These are the wires you will need to pay the most attention to. Good luck.
Mhenn, It is my guess that the 'electrical burning' smell is from your heating system. Since there is no smoke and the walls are not warm.... then there is no real problem. The smell maybe just dust has collected in the duct work that is burning off the central heating systems electrical heat strips. If you have electrical heat strips then that may be the problem. If you have a central gas heat system, it may be the same type problem. Hope this helps you. Henry
IF IT SMELLED HOT, I WOULD LOOK A THE ELECTRICAL WIRING FROM YOUR OUTLET, THROUGH THE ENTIRE DRYER. START WITH PLACES OF EASY ACCESS AND WORK YOUR WAY INWARD. LOOK FOR MELTED OR BARE WIRES THAT MAY HAVE COME INTO CONTACT WITH THE METAL FRAME OF THE DRYER.
TRY SELECTING FLUFF AIR (NO HEAT) AND SEE IF IT WILL RUN O.K. IF IT DOES, I WOULD SUSPECT THE HEAT CIRCUIT. TAKE THE BACK PANEL OFF AND INSPECT THE WIRES AROUND THE HEATER ASSEMBLY.
On paul 306, I don't have any info on you're system, but the old thermostat that has the smaller wires with the colors you described is a low voltage (24volt) controls. The new one you purchased sounds like it is for a system that is made for line voltage (120 volts or more) connecting this to the unit may have bad results. This also may apply to GUEST. COACOOCHEE, the white and black coming into the box is the line, even though white should not be used for line, the connections for the other side of the thermostat is the load. The new thermostat you have be a single pole break as opposed to the old one may be a double pole. You should have a meter to check the voltage coming into the box, it may be 120 or 220 depending on what you have. Without any more info I cant be sure, but you may be able to connect the black wires to the switch and the white together. But it would be wise to test with a meter to be sure before doing this.