ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
What does your work place look like?
by HotLine1 - 11/23/20 03:35 PM
Where is Everyone?
by Lostazhell - 11/21/20 04:17 AM
Ground fault remover :-)
by dsk - 11/21/20 02:47 AM
Work Gloves?
by gfretwell - 11/20/20 10:17 PM
Reverse-feeding transformer in PV system?
by winnie - 11/19/20 06:49 AM
New in the Gallery:
Facebook follies, bad wiring
FPE in Germany pt.2
Who's Online Now
0 registered members (), 35 guests, and 14 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
phase failure protection #180730 09/07/08 08:04 PM
Joined: Feb 2008
Posts: 9
T
tradesmen Offline OP
Member
I have been called to a church that is having a problem with losing the "b" phase of a 120/208 volt system.This problem has happened 3 times in 2 weeks. Power company had a problem somewhere along the line which was causing the problem,but not at the church though.The church has 3 phase air conditioning equipment and are concerned about damage to the equipment do to low voltage.The service is 3 seperate 400amp fused disconnects,which are located in different parts of the facility.My question is,is there some type equipment that would shut down the power total if a phase is lost.better to have no a/c than run it on partial power
thank you for your in put

Work Gear for Electricians and the Trades
Re: phase failure protection [Re: tradesmen] #180731 09/07/08 08:32 PM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
Member
Yes, there is. And installing it might be easier than you think.

The newer starters have electronic 'overloads.' Apart from doing what the 'heaters' used to do, they also kick out for low voltage, or a phase imbalance. Motor is thus protected.

The best part? If you can stay with the same make, the new guts will fit in the old enclosures.

Re: phase failure protection [Re: renosteinke] #180733 09/07/08 08:39 PM
Joined: Sep 2002
Posts: 892
N
NORCAL Offline
Member
What about a phase failure relay and tie it in to disable the A/C's?

Re: phase failure protection [Re: NORCAL] #180734 09/07/08 10:40 PM
Joined: Jul 2007
Posts: 1,335
S
sparkyinak Offline
Member
Yep. A phase failure relay has a dry contact on it so it will open the contact. All you need to do is run the control circuit though the contact.


"Live Awesome!" - Kevin Carosa
Re: phase failure protection [Re: NORCAL] #180735 09/07/08 11:02 PM
Joined: Nov 2005
Posts: 820
J
JoeTestingEngr Offline
Member
I would go with the phase loss monitor (lotsa names for the same thing) as NORCAL suggested. I would also add a Time Delay Operate relay set to at least 5 minutes to prevent short cycling. The PLM looks for phase loss, imbalance, or reversal. A set of contacts from the PLM feed the timer at the HVAC control voltage. This wouldn't be necessary if the controls are already of a smart type that protect compressors. You could drive an indicator from the timer's NC contacts so that building maintenance staff can see that you are waiting for the power to be on long enough before turning on the AC.
Joe

Re: phase failure protection [Re: JoeTestingEngr] #180746 09/08/08 11:11 AM
Joined: Jun 2007
Posts: 301
J
JValdes Offline
Member
A phase monitor is the way to go. But do not try to open the service, only the critical equipment like the air.
Use one set of contacts for the alarm.


Featured:

2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

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

 

Member Spotlight
BEAMEUP
BEAMEUP
WA
Posts: 27
Joined: December 2004
Show All Member Profiles 
Top Posters(30 Days)
Trumpy 9
Popular Topics(Views)
271,897 Are you busy
205,757 Re: Forum
193,867 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3