One just for Charley

and NO i didn’t check the coils. I only had 84 deg coming out of the vents so I figured no need.

This was a condo with electric only heat. The hvac unit was over 20 years old.

I suspected the left leg must have been the burnt out coil due to the fact the other side was the only one working. ( and the fact the left side was a crispy critter)
I shut it down at 107 deg, the other breaker was only 83 deg.


Sean can you clean the thermal picture it is a little blurry . LOL just kidding

That appears to be a 240 volt circuit/contactor one side burnt out what was the other side feeding should have been no load???

I need to get your terms straight you say electric heat only and then you say HVAC is twenty years of age do you have central heat and A/C or just central heat

air and electric heat only. no heat pump and gas
There was a 30 amp below it feeding the air. The 50 amp was feeding the heat strips

Electric heat requires “two to tango”!

Equal load on both legs.
You need to amp out both legs. If you have excessive load on one leg then the coil is broken and one side of the element is touching the cabinet operating at 120 V, at up to twice the amperage draw of the 240 V circuit. Thus overheating!

What would have cause the left side to burn up? Also why would I stillbe getting some heat, unless half the strip is working due to it touching the cabinet…

You can easily get 84 degree air output for awhile with no heat operating if the ducts are up in a hot attic and the system fan has been off for awhile.

Ah I think we are on the same page how many strips in the furnace usually each strip will be fed individually from one breaker you need to amp out each strip individually to tell which one is working

It was a stacked condo with no attic space and 70 deg a/c running until the end when I tested the heat.
Try again…:cool:

Me thinks you have more than one element and at least one was still operating need that amp meter;-):wink:

That was my general thought to begin with. Still curious why the burnt side was a no load situation, but I guess that’s for the others to deal with. :smiley:

I have never been good at trouble shooting over the phone or the internet need to see the big picture.
Very possible to have the load/heat on the one leg in your pic as a result of the fan motor being in the circuit assuming the blower was 110 and not 240

Ok here is a electric furnace I doctored up just for you it has four elements as indicated by the arrows and numbers they are on one side of the element. The other side of the element is indicated by the round yellow thermal overload one can place his amp meter on either side of the element to get a reading. These elements are staged on by a sequencer controlled by the thermostat so make sure your stat is turned up sufficiently to ensure that both first and second stages of the stat is calling for heat. Generally speaking each element will draw roughly 20 amps per element

7076 Regatta Acres PC 7-7-11 062.jpg

This is what a heater element looks like.
Two things can basically go wrong (electric heaters are extremely simple).

The overload can be damaged and incompletes the circuit.

Second and most commonly, the heater coil burns out (like a lightbulb). Sometimes these wires will come in contact with other parts of the equipment frame. This produces a direct short to ground (as the equipment is a grounded appliance).

The heater that is designed to use two legs of electricity to produce heat now operates on one half voltage capacity.

The heater element is still capable of drawing a specified amount of amperage.

Ohm’s law says if you reduce voltage you end up increasing amperage.
So if you have a 20 amp electric heater that operates under 240 VAC and you eliminate one leg of power, the element can draw 40 A at 120 VAC. (This depends how long the element is after it breaks/burns out).

I tried to find the most simplistic electrical schematic for an electric heater… This one has two heating elements.

Note #1: different equipment is designed differently.

You indicated that there are two circuit breakers in the subpanel.

I will assume (at 99.99% accuracy) that one circuit breaker controls the air-conditioning system and the low-voltage controls. The Second Circuit is dedicated to the electric heaters entirely. Designs may vary.

You will note in this schematic that electrical power comes in on L1 from the circuit breaker, passes through an overload device, passes through the heating element, then passes through a sequencer (that is controlled by the thermostat as Charly pointed out) that completes the circuit back to L2.

If you break the heating element (indicated in blue) and a section of this heating element touches the chassis ground, your heater becomes a 120 V heater.:
It will continue to operate at twice the amperage draw (or less, depending on its length ).