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#220048 04/25/19 05:27 PM
Joined: Mar 2005
Posts: 236
Member
I seem to have stuck in my head that the National Electrical Code requires all commercial buildings to have a minimum of 20 amp breakers...BACK STORY: the job I am on (15 story BLDG in Seattle) has heat pumps (hydronic type) with a MAX over current protection of 15 amps of course they wired them with the cheapest disco possible being a snap switch, hence the 15 amp breaker question, and the simplest fix they want to do.

2017 / 2014 NEC & Related Books and Study Guides
Joined: Jul 2004
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G
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I am unfamiliar with that rule. If the label on the HVAC unit says max breaker is 15 I think you are done. Install a 15 and it is Miller time.


Greg Fretwell
Joined: Mar 2005
Posts: 236
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Thanks...What about inrush current on the breaker? Do you think not having time delay fuses will cause nuisance tripping?
Thanks,
h2o

Joined: Apr 2002
Posts: 7,274
Likes: 2
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H2O

The factory MOCP has inrush calculated within. You have to comply with the nameplate data.

Does it say MOCP....15 amp 'FUSE' or 'HACR-CB' or Fuse/CB.



John
Joined: Mar 2005
Posts: 236
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The nameplate says fuse or HACR breaker...
Thanks again,
H20

Joined: Jul 2004
Posts: 9,644
G
Member
That is pretty much a slam dunk at that point, no matter if there is some local rule or not. You are required to use the manufacturer's installation instructions and on things like MOCD, it could easily be a safety issue. You could make the manufacturer happy if you just used a breaker or a fused disconnect as the local disconnecting device and still have a 20a circuit tho. We see that a lot on AC replacement units when they specify a lower MOCD than the original unit so they just change the breaker in the disconnect. Since you say they are using a snap switch there it would have to be the branch device in the panel.

Last edited by gfretwell; 04/26/19 07:18 PM.

Greg Fretwell
Joined: Mar 2005
Posts: 236
Member
Thanks...
H20


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