Load Center at heat pumps

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k0y0te

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I've got a project under construction with a few water source heat pumps that where spec'd with integral backup heat strips. The designer on the project picked up the full load (heat pump + heat strip), but didn't catch that the heat strips are only for backup and that the manufacturer requires a separate circuit for them (one circuit for the heat pump & one for the heat strip) at each unit.

Now we have 110A circuits installed to each of the units that actually require two 50A circuits to each. To complicate things a little more, each of these units are mounted up high (not accessible).

I'm about to recommend that the contractor install a small load center at each unit with two breakers in each to feed the unit and the heat strips separately. According to 240.24(A)(4) this would simply be overcurrent devices adjacent to utilization equipment, so the load center would not be required to be accessible. Am I missing anything?
 
That's is what I would do. Seems to me you need a disconnect anyway so a 125amp load center with two breakers should do the trick.
 
How about just using a 125a disconnect with double lugs or insulated connectors by polaris and forget about the load center. I am sure there is a breaker for each load on the unit.
 
Ensure that those heat strips will not run with the heat pump. They most often do in this area. Someone suddenly turning up the thermostat or a sudden change in room temp will bring them on at the same time as the heat pump. I believe they are also used when the outside unit goes into defrost. Air to Air units.
 
Sparky, you are correct. The heat strips are not supplementary heat, they are intended as backup only if there is a problem with the unit such as hot water failure. My understanding is that the controls activate the heat strips and the heat pump at the same time. But they are not really intended to work together. The manufacturer recommends leaving the heat strip breaker turned off unless it is required.

Seems like an odd design to me, but it is what it is.
 
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