Air handler with 15 kW of electric heat strip

G

g-and-h_electric

Senior Member
Location
northern illinois
Occupation
supervising electrician
Let me start with, the manufacturers instruction arent clear!

So we have a newly installed air handler with a total of 15kW of electric heat strips in it. They are factory split 2 stages, with stage 1 is 10kW, and stage 2 is 5kW. Onstage 1 is the control transformer, and the blower of about 3 amps.

The unit came with 2 circuit breakers ( yes I checked they truly are breakers not just disconnects. Stage 1 is a 60, and stage 2 is the same. MOCP is 60 for stage 1, and 25 for stage 2. Obviously without swapping the stage 2 breaker I cannot use the "tap rule" to feed both stages from a 125 amp feeder. the main breaker panel is in the same room as the air handler and within sight. Anyone have a problem with removing the existing #1 THW conductors, and replacing them with 2 #6 (on the 60), and 2 #10 (on the 25) with the breakers in the main panel, and the air handler labeled to indicate that there are multiple branch circuits feeding it and which circuits they are?


Howard
 
The unit came with all breakers installed. Correct?
Did it come with one set of lugs for the incoming power? Yes, use the existing feeder.
Two sets? Run circuits to each set, leaving the existing breakers in the unit as disconnects and supplying OCP in your panel. A 25 can supply the larger 60.
 
It's commonplace here to find 60s at the unit despite the MOCP being less. As ptonsparkey notes, they are basically serving as local disconnects.
Commonly here these units are fed by two circuits each meeting the MCA and MOCP requirement.
 
I am not sure but those breakers may be switches and don't have any overcurrent protection in them. If they are regular breakers then you need to either feed it with an 80 amp breaker but the unit may specify. If it is built to handle 2 circuits then one would be a 30 amp and the other a 60 amp
 
Dennis Alwon said:
I am not sure but those breakers may be switches and don't have any overcurrent protection in them. If they are regular breakers then you need to either feed it with an 80 amp breaker but the unit may specify. If it is built to handle 2 circuits then one would be a 30 amp and the other a 60 amp
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OP states MOCP of 60 and 25.
 
dkidd said:
10 KW
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The 5 kw would be connected to the 25 amp breaker in the panel. The panel in the unit can have a 100 amp breaker as it wouldn't matter. That is why I said it may be a switch and not a breaker, per se.

The 10kw with the fan would be on the 60 amp cir.
 
dkidd said:
I don't see anything stating that there is a panel in the unit. I don't see what a 100 amp breaker would be for.
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The unit came with 2 circuit breakers ( yes I checked they truly are breakers not just disconnects. Stage 1 is a 60, and stage 2 is the same. MOCP is 60 for stage 1, and 25 for stage 2.
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My point was there are 2- 60 amp breakers in the unit. If the overcurrent protective device in the house panel is sized correctly, then it doesn't matter what size breakers are at the unit, as long as they are larger than needed.
 
Dennis Alwon said:
My point was there are 2- 60 amp breakers in the unit. If the overcurrent protective device in the house panel is sized correctly, then it doesn't matter what size breakers are at the unit, as long as they are larger than needed.
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They may not be breakers. And you have to install MOCP per the label. Anything inside the unit is not pertinent.
 
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