ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
1897 paper on 110-220 incandescent lamps
by dsk - 08/25/19 01:02 PM
Southwire Recalls Electrical Outlet Boxes
by Admin - 08/21/19 06:39 PM
Fuse blower plug?
by HotLine1 - 08/20/19 01:50 PM
100 year old Light Bulb
by HotLine1 - 08/20/19 01:26 PM
Forum Updates Coming Soon.
by Admin - 08/18/19 01:55 PM
New in the Gallery:
What is this for?
Plug terminals
Who's Online Now
0 registered members (), 2 guests, and 9 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Wire size #220057 05/02/19 06:29 PM
Joined: Mar 2005
Posts: 233
watersparkfalls Offline OP
Member
If you have a hydronic heat pump with a minimum ampacity of 23 amps and max of 35 amps wired with mc...wouldn’t sizing the wire to max current make the most sense? Has anyone ever had a problem with sizing motor to minimum ampacity before? Probably should have worded as a code question.

Thanks,
H20

2017 / 2014 NEC & Related Books and Study Guides
Re: Wire size [Re: watersparkfalls] #220060 05/02/19 10:34 PM
Joined: Jul 2004
Posts: 9,383
G
gfretwell Offline
Member
The bottom line is, "what does the label say" . You don't need to wire any motor load for the locked rotor current because it is only there for a second or less. We wire for 125% of the full load amps. In a complex box like an HVAC system the industry engineers evaluate that box and give you a label for guidance. As an electrician or inspector we should just believe. You can use a #12 for that if everything is rated 75c (breaker, conductors and HVAC lug)


Greg Fretwell
Re: Wire size [Re: gfretwell] #220094 05/27/19 10:35 PM
Joined: May 2005
Posts: 984
G
ghost307 Offline
Member
I agree with Greg with one exception.
Fire pumps are wired differently because they are expected to run to destruction rather than trip on normal overloads like a regular motor.
The wire sizing is capable of carrying LRA for 20 seconds or more since the motor may have issues getting up to speed.
Nobody wants to console the owner of a burning building by telling them "hey...at least the fire pump motor got tripped offline and is still okay".


Ghost307

Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
Grover
Grover
Sebago, ME, USA
Posts: 109
Joined: January 2005
Show All Member Profiles 
Top Posters(30 Days)
Admin 21
GeneSF 6
Popular Topics(Views)
257,981 Are you busy
193,706 Re: Forum
183,313 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3