[user_12345a]

I really think you should leave the hvac system alone and run another circuit.

 

[user_12345a]

Normally the larger set of heat strips is the first stage, and 5kw the second stage. Would blow room temp air until the second stage sequences on.

If you have a heatpump and it were to break down, would need more than 5kw likely.

5kw alone is not enough to heat a house normally.

If you have a heatpump and it is larger than 1.5 ton, it will blow cool to cold air during defrost cycles. Defrosts won't show up on ecobee logs.

Not a good idea to rely on "other supplemental heat" unless it's a proper heating system (like hydronic) that's thermostat operated.

If anything, it would make more sense to disable the 5kw if on a separate circuit from the 10kw and use the circuit.

But it's a very poor idea all around.

What are you trying to run anyway?

 

[user_12345a]

Dual head mini-split should need a far smaller circuit than what's used for 10kw of strips.

What's the problem with running a new proper circuit for mini-split system?

Circuits can be run along outside of the house through conduit if running through finished house is not practical/economical.

The aux heat should be sized to handle the entire heating load - may even be required to by code.

I guess I am not following on why it's a very poor idea. I will swap it over to the 10kw though and change the primary breakers to 50.

You can not just up the breaker and put a greater load on the circuit without reducing the wire gauge (going to a thicker wire) unless you want to risk starting a fire!

The second circuit is probably only be sized for 5kw of aux heat.

 

[user_12345a]

In that case you may be able to get away with disabling the last 5kw of heat strip and using the circuit.

But why swap the cables and breakers in that case - don't they use the same chase anyway?)

This is if your heating load is under 34k btu and heatpump is 3 ton or less. (need enough aux heat for properly tempering during defrosts)

Without power to the last 5kw that strip just won't will - but the sequencer/relay will still close.

I strongly recommend leaving it alone and running another circuit, even if it has to be run on the exterior of the house.

 

[user_12345a]

Yes - the 5kw heat strip will just not work.

If desired, you can un-jumper W2 from W1, just have W1 energized and the relay or sequencer for the 5kw strip won't be energized at all.

Right now, the diagram shows the board (transformer and blower motor) being powered from the 5kw heat strip circuit - that will have to be moved to other circuit.

The circuit will have to be able to handle the 10kw plus the blower motor as well. (which is a relatively small load)

All in all I still don't recommend this modification at all and it is at your own risk.

 

[user_12345a]

No harm is done disabling the secondary heating (heat strips) in a heat pump system to cut down on expensive resistance heating utilization.. The easiest way to disable the strips is to flip off their breaker The only problem is the house being cold because the heat pump by itself doesn't deliver enough heat. The latter problem is being combatted with a tertiary system, here, a wood stove although it could alternatively be a stand alone perhaps preexisting gas or oil heating system.

Now that we have established that the strip heating is not necessary (on the OP's project) he is free to commandeer a cable and breaker that feeds only strip heaters and use that for somehing else of his choosing (and also code compliant regarding a white neutral conductor, etc.). It would also be nice to label the protruding orphaned (and unenergized) ends of the wires for the strip heaters so the next owner of the house not wishing to manage a wood stove can reconnect the strips.

I would second running new wiring even if in conduit or Wiremold exposed on the wall as superior to modifying the circuitry within the heat pump unit to free up a cable from the panel for some other purpose. I do not like the idea of being a new homeowner moving in and finding, only after considerable perusing and matching up of actual wiring and the schematic, that an appliance or equipment that looked perfeclly normal on the outside had been bastardized inside.

Did I miss something (by failing to parrot the second sentence of reply 11, by the OP)?

The purpose is to use the wire for something else, not save energy.

A good thermostat will keep aux heat off unless it is needed anyway.

It is not a good idea to disable aux heat anyway - it's needed to temper air during defrost cycles and to carry heating load if hp breaks down completely.

op may not need full 15 kw though and is looking to disable 5kw out of 15kw.

 

[user_12345a]

"6awg to feed a 120v subpanel with a true ground "
Please explain a true ground.

The cable your considering has no neutral and only a ground in the sheath. Not a ground wire.
Sure it may act the same in a 240v circuit but your changing the intent and the purpose of the wire. The cable is not designed for 120v loads.

Thinking like this is why the NEC keeps getting larger and larger.

The neutral is absolutely mandatory when powering 120v appliances - can't have a floating neutral.
Can in theory only run 120v to sub-panel - use one of the line as a neutral and jump the hots so alternating down the panel, they're all on one leg. I doubt that would comply with code though.


@kramttocs - you should really give up on this idea. Run new circuits.