Two A/C units sharing same circuit breaker

[chuckgassmannm]

I have a existing situation where there are two separate A/C units on one breaker. The one unit has a 40 amp rating the other is a mini- split unit rated at 20 amps. They are spliced together in a j box and are 25 feet apart. I know this is way wrong!!! Is there a code for this? I looked but haven't found it. I wanted to show the customer. Thank you

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[chuckgassmannm]

Also they are being protected by one 2- pole 40 amp breaker.

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[Jraef]

What is the conductor size going to the 20A split unit? It they used #8, are the terminations actually able to accept #8 or did they shave it to fit?

Does the split unit list an MOCP of 40A? I would venture to say that it probably does not, in which case they have violated the installation instructions for the unit.

 

[augie47]

What Jraef says:
440.22
C) Protective Device Rating Not to Exceed the Manufacturer’s
Values. Where maximum protective device ratings shown
on a manufacturer’s overload relay table for use with a motor
controller are less than the rating or setting selected in accordance
with 440.22(A) and (B), the protective device rating shall
not exceed the manufacturer’s values marked on the equipment.

 

[Jraef]

What Jraef says:
440.22
C) Protective Device Rating Not to Exceed the Manufacturer’s
Values. Where maximum protective device ratings shown
on a manufacturer’s overload relay table for use with a motor
controller are less than the rating or setting selected in accordance
with 440.22(A) and (B), the protective device rating shall
not exceed the manufacturer’s values marked on the equipment.

Thanks. Didn't have my NEC handy to give him the reference.

 

[chuckgassmannm]

Thank you. The mini split is rated for 20 amps max. I s it even correct to have Two units on the same over current device? Have never seen that before? Thanks again.

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[LarryFine]

Not really. You could look into replacing the junction box with a small panel as one possibility, but the feeder still has to se sized to suit both units.

 

[Jraef]

If one were a unit heater and the other an A/C, to where they would not be run at the same time, you could get away with that. But for this to be valid, each unit would need to have its own internal branch protective device inside, so the 40A is a feeder. Even then there are limits (tap rules) as to the distances involved and the way it is configured.

https://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/FeederSecondaryTapRules~20020326.htm

Your description sounds more like a DIY / hack job by someone who doesn't know or care about what they were doing.

 

[chuckgassmannm]

I concur. The said part is it was supposed to be a professional a/c contractor. I'm redoing everything up to code. I appreciate your help. Thank you.

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[LarryFine]

Since it's kinda/sorta related, I once had to permit (as if I was the one who did the upgrade) and repair an unpermitted/uninspected service "upgrade" that was done in conjunction with a similarly-illegal central A/C installation.

The load-side-of-the-meter service cable to the panel had been upsized, but the line side was still the 100-amp sized cable. The trouble started when a line-side conductor and lug melted inside the old meter base. Big surprise! :roll:

I also found there was no breaker for the A/C compressor unit. Why not? Because the A/C installer drilled a hole through the back of a nearby baseboard heater (ahead of the T-stat wiring) and the wall to feed the compressor!

It was the hottest day of the year, a young couple with a new baby, their first house, and the service was even glowingly (pun intended) approved by their home inspector. I had to charge as much as an upgrade to fix everything.

 

[chuckgassmannm]

Wow!!! Guess I got off pretty easy. thank you. I'm glad to have people who care and know what's right. Thanks again.

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