Air handler unit

jaggedben said:
No, not necessarily. One compressor can have multiple AHUs in some systems.
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I did a VRF system one time in a school building. Three compressors in a single outdoor unit with pretty big three phase circuit supplying that unit (had three sets of these for the whole facility, some as little as 60 amp circuit and others maybe up to an 80 amp circuit IIRC) but all the inside air handling units were all on the same 15 amp 208 volt single phase circuit and the "mode change boxes" were also on the same 15 amp 208 volt circuit as the air handling units they were associated with. System was intended to have all these on the same circuit as well. I don't think any individual unit on that 15 amp circuit had a rating over one amp. Likely none were even over .6 amps.
 
jaggedben said:
No, not necessarily. One compressor can have multiple AHUs in some systems.
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I made an earlier comment saying the same thing. Just wired a Samsung ducted split system with one outdoor heat pump unit and two indoor units no heat kits on indoor units . The total load of both indoor units wasn’t even 8 amps and the manufacturer allows multiple AHU’s on a single circuit but not to exceed 10 amps. I just ran separate circuits and as it was a residence and my panels were within 20’ of each ahu , but I’ve done it before
 
kwired said:
I did a VRF system one time in a school building. Three compressors in a single outdoor unit with pretty big three phase circuit supplying that unit (had three sets of these for the whole facility, some as little as 60 amp circuit and others maybe up to an 80 amp circuit IIRC) but all the inside air handling units were all on the same 15 amp 208 volt single phase circuit and the "mode change boxes" were also on the same 15 amp 208 volt circuit as the air handling units they were associated with. System was intended to have all these on the same circuit as well. I don't think any individual unit on that 15 amp circuit had a rating over one amp. Likely none were even over .6 amps.
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I’ve installed that type of system in a school as well ducted split systems with inverter type outdoor units
 
I would use a disconnect on each air handler to isolate the circuit and provide a lockout provision for each one individually, even though they share a circuit for the feeder.

An auxiliary contact can be added to most disconnects to interlock the associated A/C controls to prevent them from running without the air handler motor running.
 
infinity said:
422.12 would require an individual branch circuit if these were heating units but does that apply to two less than 5 amp air handlers?
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That’s why I asked your opinion lol I assume the outdoor units are heat pump/ac because if he has gas furnaces why have ahu right and the way I read 422.12 is the ahu would considered part of the central heat this is a pic of the enhanced content from link 422.12
 

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infinity said:
I try not to assume anything. He said AC and blowers nothing about heat.
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Your correct, and I’m familiar with the saying of what happens we we assume so for the purpose of the post your definitely correct . But my assumption was based on practicality because if there was existing furnaces for heat why install two seperate ahu for ac only , and most new outdoor units don’t need backup heat kits because the outdoor units can operate at much lower temps then they will ever see nowadays but their could be hydronic heat which would require the jnstall of ahu’s anyways so you are correct
 
Stubby said:
I have two air handler units that have no heat strips just a blower motor only. The inspector said I had to separate both air handlers I could not put them on one circuit breaker max amps are 5 amps per ahu. I do have a disconnect at the air handler for both of them
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Are your outdoor units heat pump units or ac only ??
 
hbiss said:
I'm thinking that they mean the air handler and outdoor compressor as "permanently connected air conditioning equipment". Not two separate systems.

Like I said above, is there a label that shows the electrical requirements and would prohibit a shared circuit? I'm trying to relate these to unit heaters which can share a circuit.

-Hal
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I think exception 1 would apply to additional air handling units it may not be in the language but I would think the intent is to keep the circuit dedicated to the system in an earlier comment I may have mispoke saying exception 2 but now we know it’s seperate systems it wouldn’t apply here, but I agree with your interpretation of exception 2
 
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