Electric heat coils don't not hot

I got a new air handler with a new 10kW heat kit. It’s RunTru by Trane, but the heat kit is pretty universal for all Trane/am std. Units.

Earlier I had a tech come by and hook it up. After he left, I noticed the heat was just warm and the coils are not fully red. I checked a few things and I’m getting 245 volts and a little over 5 amps when unit is heating and fan blowing.

Any HVAC or really smart inspectors have any idea what’s going on? I can’t even get decent results on the question from a Google search. Any help is appreciated!


I also had a similar issue with a stove a week ago on an inspection

Sorry Jesse, I’m not in the right mindset to answer you, now.

I’d call the tech back out, myself!

Good luck and heat!


10KW@ 240 volts is 41.66 amps. Either the heat unit is designed for a higher voltage or the configuration of the coils in incorrect.


I was going to recommend @rmeier2 to figure this out. My first, not so smart thought, was there was not enough “juice” flowing to the elements.

Okay, sorry for confusion. My math was horrible. The tech guy does mostly refrigeration and did it as a side job for $40. I had ran the wire from the breaker and he connected the rest. We had problems with the 5 amp fuse popping every time the fan was turned on. So after he “figured” that and I ended up buying a second new thermostat, it looked like it was running. After he left, I realized it wasn’t that hot and I noticed the coils. I hoped I could figure it out without him having to come back.

I got the 5 amp reading at the shut-off/breaker that comes with the heat kit. In other words, at the exposed end of the main power (6 awg) wires, where they go in the breaker.

It must be the configuration of the coils. You think a wire got switched around or something?

When all else fails, read the instructions… :face_with_monocle:


I would love some instructions, where are they? I guess the schematics, but I studied them and wired it perfectly, but the 5 amp fuse would blow. This guy came over, wired it a little different and I got heat. Just not much heat. ;(

There are two strip coils, 5kW each. You’re running them @ 120v instead of 240v.

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There is a small voltage fuse inside the air handlers. Some are 3 amp and this one is a 5 amp fuse. Looks like the one’s in a car.

It sounds like the thermostat isn’t wired correctly.

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I know little about electric heat strips because they aren’t used around here. Is that how they are generally set up (2)-120 volt strips wired in series? He said that he had 245 volts so my assumption is that the strips are 5kw, 240 volts and wired in series instead of parallel.

## Making heat from electricity
There are dozens of interrelated factors to consider in the design of a heating element, particular appliances.
Refer to an appliance repair technician and move along.
Personally, I do not do appliances.

Here’s a video on how to correctly wire a 10kw strip heater in an air handler. You need #6 wire and a 60-amp disconnect. You may need to set the DIP switches on the circuit board. And make sure your strip heater isn’t a 3-phase variety.


It’s quite possible. There is usually 1 or more coils rated at 240v (for 1-phase power). They are never (not supposed to) connected in series (never seen that). It is possible that, somehow, the coils did end up wired in a series (magic of the fridge guy, perhaps :slight_smile: ) But it would take a lot more effort to screw that up (due to contactors/sequencers used) than to wire them at 120v, thus my best guess. As far as measurements (245v), how do you explain 5amp draw from 2x 5kW coils, they are both lit in OP’s pic, should be around 10amp total. At either 120v each or in a series at 240v, they would each use 1/4 of their rated power – the end result would be the same. This can easily be traced visually/checked with a multimeter by a “qualified” person :slight_smile:

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I had a stove like that a year or two ago. Turned out that it only had 110v (one leg) hooked up to the outlet.

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Makes sense to me. Thanks for sharing.

I have no explanation other than some information is missing or incorrect.

I completely agree.