ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Recent Posts
Switched Receptacles -Top or Bottom?
by gfretwell - 07/28/21 10:06 PM
Lowes Selling this fan
by timmp - 07/25/21 10:58 PM
How's all our Non-US folks doing?
by djk - 07/23/21 09:13 PM
Do You Travel?
by Bill Addiss - 07/20/21 04:26 PM
Backup Generator Done Right
by timmp - 07/18/21 12:20 PM
New in the Gallery:
February, North East Indiana
February, North East Indiana
by timmp, July 25
Red Green would be proud
Red Green would be proud
by timmp, July 25
Who's Online Now
0 members (), 9 guests, and 20 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#47597 01/19/05 07:01 PM
Joined: May 2001
Posts: 376
frank Offline OP
We have two 600 kw Detroit generators with asco t switches.During our monthly load test on occasion the 800 amp main breaker will trip.This only happens on the transfer back to standard power.It's a known fact that the asco's switch too fast resulting in a short.The generators can be anywhere from 0 to 180 degrees out of phase with the utility.The building motors basically dynamically break and feed back into the busses as they spin down.Other strange things have started to happen as well.For instance in one area of the building up to 50% of the electronic ballasts in the fluorescent lights will fail and have to be replaced.I would think that this is due to either the basic input rating or the K rating the xformer that services that particular area.Has anyone seen this before?It's a new system and the electrical engineers have been out twice in the last year to monitor and solve the problem to no avail.Why not install an in phase monitor to delay the transfer?That breakers going to fail sooner or later at this rate.

#47598 01/19/05 07:34 PM
Joined: May 2002
Posts: 1,716
Why not install an in phase monitor to delay the transfer?That breakers going to fail sooner or later at this rate.
this was my question reading your post until I got to the bottom and saw you are questioning it too.

What is their reluctance to do this?

I have been through the exact same thing (not the electronic ballast part) and it was solved with the In Phase Monitors.


#47599 01/20/05 09:20 AM
Joined: Jul 2004
Posts: 49
Frank, just so I can picture what is happening, are the generators suppose to be in sync with the utility prior to the transfer switch opening. Or do the generators shut down prior to the transfer switch moving back into the utility supply condition. In other words is there suppose to be a blackout prior to the return of utility power? Just trying to learn.

#47600 01/20/05 10:38 AM
Joined: Apr 2002
Posts: 2,527
Foe decades, Asco has offered a synchronized-transfer {pseudo-25 device} option for their UL1008 electrically operated switches, but the feature has to be specified in the original purchase order.

#47601 01/21/05 12:29 AM
Joined: May 2003
Posts: 2,876
e57 Offline
Ok, let me get this straight. Utility, and the gennies are NOT ever linked, but the out of phase load inertia as you go back to the utility trips the breaker? Sounds like some massive motor loads? Darn straight the breaker might not survive the next time you do it. Can't be good for the motors, or anything else either.

Mark Heller
"Well - I oughta....." -Jackie Gleason

Link Copied to Clipboard

Tools for Electricians
Tools for Electricians

* * * * * * *

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


Member Spotlight
Posts: 264
Joined: February 2013
Top Posters(30 Days)
timmp 8
Rachel 4
djk 2
Popular Topics(Views)
281,578 Are you busy
215,216 Re: Forum
202,053 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5