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20amp breakers #220048 04/25/19 04:27 PM
Joined: Mar 2005
Posts: 236
watersparkfalls Offline OP
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
Re: 20amp breakers [Re: watersparkfalls] #220049 04/25/19 09:19 PM
Joined: Jul 2004
Posts: 9,541
G
gfretwell Offline
Member
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
Re: 20amp breakers [Re: gfretwell] #220051 04/26/19 01:41 PM
Joined: Mar 2005
Posts: 236
watersparkfalls Offline OP
Member
Thanks...What about inrush current on the breaker? Do you think not having time delay fuses will cause nuisance tripping?
Thanks,
h2o

Re: 20amp breakers [Re: watersparkfalls] #220052 04/26/19 02:43 PM
Joined: Apr 2002
Posts: 7,216
HotLine1 Offline
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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
Re: 20amp breakers [Re: watersparkfalls] #220053 04/26/19 02:49 PM
Joined: Mar 2005
Posts: 236
watersparkfalls Offline OP
Member
The nameplate says fuse or HACR breaker...
Thanks again,
H20

Re: 20amp breakers [Re: watersparkfalls] #220054 04/26/19 06:16 PM
Joined: Jul 2004
Posts: 9,541
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gfretwell Offline
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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 06:18 PM.

Greg Fretwell
Re: 20amp breakers [Re: gfretwell] #220055 04/29/19 03:11 PM
Joined: Mar 2005
Posts: 236
watersparkfalls Offline OP
Member
Thanks...
H20


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