Mini Split over Current Protection

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atbear

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Tri-Cities WA
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inspector
What is the max over current protection allowed for a Mini Split system? Power head label shows max 15amp and the condenser outside shows a max 20amp breaker. The panel has a 40amp dbl pole breaker. The electrician is saying the NEC prevents him having to separate breakers for the system.
 
atbear said:
Power head label shows max 15amp and the condenser outside shows a max 20amp breaker. The panel has a 40amp dbl pole breaker. The electrician is saying the NEC prevents him having to separate breakers for the system.
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I see two circuits, 14/2 and a 15A breaker for the indoor unit and a 12/2 with a 20A breaker for the outdoor unit. He could have installed a sub panel maybe next to the outdoor unit fed by that 40A circuit which would double as the disconnect.

I assume that both are either 208 or 240V hence the two pole 40 and he is supplying both units from the same circuit? That's no good. Or is everything 120V and he is doing a MWBC and supplying each unit from each side? That's no good either with the 40A breaker.

-Hal
 
hbiss said:
I see two circuits, 14/2 and a 15A breaker for the indoor unit and a 12/2 with a 20A breaker for the outdoor unit. He could have installed a sub panel maybe next to the outdoor unit fed by that 40A circuit which would double as the disconnect.

I assume that both are either 208 or 240V hence the two pole 40 and he is supplying both units from the same circuit? That's no good. Or is everything 120V and he is doing a MWBC and supplying each unit from each side? That's no good either with the 40A breaker.

-Hal
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MWBC and supplying each unit from each side. 120V
 
Years ago those units were common with power inside and a different circuit outside. The low voltage between the units control the start and stop. I had one 240 v unit inside and a 120V outside. We never looked at it because we had never seen a 120V unit. It was amazing we didn't blow the unit up. It would act right so they had the tech look at it and say oops- we screwed up badly on that fortunately it ended up okay.
 
Used to be multi-head units would have building power run to each head, and single head units were the only ones to be fed from the outdoor unit.

As @Dennis Alwon mentioned, the outdoor unit would be 240v with 120v heads.
 
James L said:
Used to be multi-head units would have building power run to each head, and single head units were the only ones to be fed from the outdoor unit.

As @Dennis Alwon mentioned, the outdoor unit would be 240v with 120v heads.
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I was just going to post to find out about feeding a mini split. I was going to ask if the mini split electric requirements on the label includes the blower indoor section. Are you saying some indoor sections need separate power with one zone and require 2 circuits one for each blower if two zone? I wired four or five single zone units years ago and I recall feeding the outdoor compressor with the circuit and feeding the air handler indoor from the out door compressor. Thank you.
 
ritelec said:
I was just going to post to find out about feeding a mini split. I was going to ask if the mini split electric requirements on the label includes the blower indoor section. Are you saying some indoor sections need separate power with one zone and require 2 circuits one for each blower if two zone? I wired four or five single zone units years ago and I recall feeding the outdoor compressor with the circuit and feeding the air handler indoor from the out door compressor. Thank you.
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About 8-10 years ago each head needed separate building power. I would install a handy box with single pole switch for disconnect right next to it.

But the last several I've done, even multiple heads were powered from outdoor unit.

I ask for specs
 
ok thank you. one more quick question please, the owner mentioned the ac guy quoted the unit is 208-230 volt.
I'm thinking it's a 3 phase unit but the building power is 120-240 single phase. If the ac quote is for a single phase unit 208-230 volt will 240v be ok ? Or he should it be rated for 240v ? Thanks
 
ritelec said:
I would expect it to be rated at 250.
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Don't mix nominal supply voltages with maximum voltage ratings.

230v is about in the middle of typical voltage range at the load terminals.

Look at the acceptable voltage limits on the AC nameplate.
 
This is becoming a common question ... I only install Daikin ductless systems which are low voltage DC units (Mini Split). I found out recently that another manufacturer produces line voltage units.
 
I have powered a few units made by Samsung that both the indoor unit and outdoor unit required separate 240 volt circuits. The indoor units typically had low amp usage than the outdoor units. If memory serves me right, I had a 50 amp outdoor condenser and multiple indoor heads which shared the same 15 amp circuit as spec’d by Samsung. Each indoor head is fused separately off the 15 amp circuit at about 3 amps each. Not sure about other makes though.
 
mtnelect said:
This is becoming a common question ... I only install Daikin ductless systems which are low voltage DC units (Mini Split). I found out recently that another manufacturer produces line voltage units.
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Are you sure about that?
I just looked at at spec. sheet for a random Daikin mini split unit and it shows the indoor unit to operate at line voltage. I have never seen a Daikin unit in person but all the Mitsubishi and Fujitsu units I have seen are line voltage between the outdoor unit and indoor unit.
 
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