ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
nec 110.3 (B)
by gfretwell - 09/22/21 11:11 PM
Grounding electrodes
by gfretwell - 09/07/21 03:41 PM
Looking For Electricians in the Midlands
by Alex247 - 09/06/21 05:26 AM
New in the Gallery:
Now you know.
Now you know.
by Tom_Horne, September 7
February, North East Indiana
February, North East Indiana
by timmp, July 25
Who's Online Now
1 members (Scott35), 40 guests, and 21 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#220057 05/02/19 06:29 PM
Joined: Mar 2005
Posts: 237
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
Joined: Jul 2004
Posts: 9,663
Likes: 4
G
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
gfretwell #220094 05/27/19 10:35 PM
Joined: May 2005
Posts: 984
G
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

Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
mxslick
mxslick
Atomic City, ID USA
Posts: 806
Joined: October 2004
Top Posters(30 Days)
timmp 3
Popular Topics(Views)
283,074 Are you busy
216,807 Re: Forum
203,189 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5