ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Flexible Conduit?
by gfretwell - 10/24/21 01:59 AM
May I backfeed 3 phase transformer?
by dsk - 10/22/21 04:37 AM
Wire sizing
by gfretwell - 10/21/21 10:12 PM
GFCI's pops in large numbers
by dsk - 10/21/21 02:03 AM
Need some info on Japanese outlets, 200V 15A
by andey - 10/20/21 08:05 AM
New in the Gallery:
240/208 to a house
240/208 to a house
by wa2ise, October 9
Now you know.
Now you know.
by Tom_Horne, September 7
Who's Online Now
0 members (), 22 guests, and 16 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#195483 08/05/10 05:42 PM
Joined: Mar 2010
Posts: 5
D
Davo Offline OP
New Member
I just got back from a booster pump re-and-re. The new pumps are 3 25 HP 575V pump assembly with control - each pump is labeled with a 22.2A draw. The engineer drawings are specifying that we are to supply 3-#6 to the 3-pump assembly fused with a 80A time delay fuse. Looking immediately at table 13 - an 80A fuse is too large for #6 T90. Yet then there is 28-200(d) in the CEC. Here is my question - given that you can up a fuse size to 225% of the motor FLC if it does not start, does the conductor size have to be increased accordingly? It does not mention this a far as I can see in the CEC.

I realize on the face of it, that it appears the engineer didn't consult the code - I would size the conductor normally (22.2 * 1.25) + 22.2 + 22.2. = cable #4. It appears that one motor is a backup only and may not be used at all unless another is manually disconnected.


Last edited by Davo; 08/05/10 05:49 PM.
Davo #195484 08/05/10 06:03 PM
Joined: Mar 2010
Posts: 5
D
Davo Offline OP
New Member
On a second look at the CEC all appears fine as long as only two motors are connected to operate at once - following 28-204(c) up to 300% of the conductor rating is permitted.

Davo #195516 08/08/10 02:21 AM
Joined: Jul 2002
Posts: 8,407
Likes: 2
Member
Davo,
What sort of system is this if it supplies a 575V motor?
Just inquisitive there mate.

Trumpy #195531 08/09/10 03:04 PM
Joined: Jun 2006
Posts: 613
M
Member
I will reply to Trumpy first. 347/600 is the nominal system voltage. Very common in Canada and usually used where 277/480 is used in the US.
So to Davo 28-204 is the right rule and you are applying the right conditions. 125% if the largest motor with the FLC of each additional motor that must be able to run at the same time = wire size. The overcurrent rules allow a breaker as big as necessary provided it does not exceed %300 of the ampacity of the wire feeding the lot.
So 50 amp wire could have a breaker up to 150 amps. If you use #6 r90 then up to 190 amps, not 200. You probably have to start with a max of 100 amp breaker unless it trips, which lets you go up from there.


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
MarkC10
MarkC10
CA, Inland Empire
Posts: 43
Joined: September 2013
Top Posters(30 Days)
dsk 7
Popular Topics(Views)
284,854 Are you busy
217,421 Re: Forum
203,737 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5