Adding cooling to a service with electric heat question

[olc]

Adding air conditioning to a building that has a service sized for electric heat but no spare.

Noncoincident:
1. Cooling and heating noncoincident enough and no further action (control) required?
2. The electric heat serves a different area for than the cooling. If the cooling is heat pumps which could be coincident, can we add control so one is disabled if the other is in use?

In this case it could be done in the control circuit of the heating – or – could be done but disabling the power to the heating (shunt trip breaker or something).


Bonus question:
Does not apply in this case but – 220.51 - Does a 2 stage electric heat coil in an air handling unit count as “fixed electric space heating”?

 

[Eddie702]

Just my opinion your AHJ may have other ideas:

If the heating and cooling serve the same space and cannot be run at the same time (a rooftop unit with heating and cooling) then it would be noncoincidental

If they can run at the same time (like an hvac unit for a computer room or lab

where they run the cooling and the electric reheat for humidity control then you have to have enough power for both.

Having cooling in one area of a building and heating in another area they could run at the same time you would have to power both


To me to be nocoincidential that have to heat/cool the same area and /or be part of the same equipment.

I would call an AHU with electric heat "fixed electric" space heating

 

[LarryFine]

Adding air conditioning to a building that has a service sized for electric heat but no spare.

As long as A/C isn't a greater load, you're okay ampacity-wise.

1. Cooling and heating noncoincident enough and no further action (control) required?

If you're talking about a single T-stat, okay, but heat must exclude heat pump if equipped.

2. The electric heat serves a different area for than the cooling. If the cooling is heat pumps which could be coincident, can we add control so one is disabled if the other is in use?

As long as you can prevent the simultaneous operation that would cause overloading.

In this case it could be done in the control circuit of the heating – or – could be done but disabling the power to the heating (shunt trip breaker or something).

I would definitely do everything in the low-voltage wiring. You might need to add a relay or two.

Bonus question:
Does not apply in this case but – 220.51 - Does a 2 stage electric heat coil in an air handling unit count as “fixed electric space heating”?

Absolutely, yes. There is no better definition.

 

[ptonsparky]

Non coincident, unless you office help doesn’t think ahead far enough to to turn one or the other off. grumble…mumble..