Supplemental strip heat

[nizak]

I have a 20KW heat strip that’s been installed in an air handler for a Geo thermal system.

Nameplate on strip is 111.4 A MCA and 125A MOCP.

I planned on using a 125A circuit breaker in a 2 space main lug load center as the disconnect means.

Do I still need to add the 25% factor or is the MOCP if 125A all the larger it has to be?

My wire size is #2THHN

Thank you.

 

[ptonsparky]

You need to meet the MCA of 111.4 for the conductors. That is equal to the 89 amp load of your heat strips. (Rounded) *1.25
MOCP is the maximum over current protection. 125 is the max allowed.

 

[LarryFine]

MCA and MOC numbers are all you need to use, without adding fudge factors.

Is the blower fan included in those numbers?

If the heat strips are separated, I would use a larger panel with multiple breakers.

 

[Dennis Alwon]

I have never seen a 20kw unit that had 20kw of heat strips. Usually there are 2 smaller strips of 9.6kw or so. My guess is the fan is included in the mca.

 

[nizak]

Yes blower is included.

Heat strip kit is designed for single circuit feed.
I asked the HVAC contractor to get the kit that subdivided the load , this is what they installed.

MCA and MOC numbers are all you need to use, without adding fudge factors.

Is the blower fan included in those numbers?

If the heat strips are separated, I would use a larger panel with multiple breakers.

 

[kwired]

I have never seen a 20kw unit that had 20kw of heat strips. Usually there are 2 smaller strips of 9.6kw or so. My guess is the fan is included in the mca.

With geothermal units often the heat strip is a completely separate circuit(s). The compressor and blower are on the same circuit and possibly so is a circulating pump for the heat transfer loop, but those are usually similar pumps to what you see in hydronic heating systems and are tenth or less HP.

I see I for some reason did not hit the post reply button or it did not post for some reason. Since I initially wrote it OP did say blower is included. Though that is not typical of what I have seen on geothermal units. Usually blower and compressor are all wired into same control board. heat strips are add on equipment with their own power supply and a control wiring harness that plugs on to the control board or into an existing wiring harness from the board.