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#168225 - 08/29/07 04:48 PM 3 Phase Power (490 volts on a 480 volt system)  
acetoday  Offline
Member
Joined: Sep 2003
Posts: 35
Manassas, Va
Help,

I'm a residential electrician and don't work much with 3 phase power. My question is on a 3 phase 480 volt system is it abnormal to read 490 volts? I have a ac unit rated for 460 volts (nominal voltage) however as stated we are reading 490 volts at the unit. Is this a reason to be concerned? I should mention there are 3 other units on the roof also rated 460 volts and are operating normal.

Any feedback would be greatly appreciated.....


Work Gear for Electricians and the Trades

#168226 - 08/29/07 05:05 PM Re: 3 Phase Power (490 volts on a 480 volt system) [Re: acetoday]  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
It's very likely a 480 volt supply system and 490 volts is not that bad.

The AC unit is labeled 460 but is designed to work on 480 volt supply system.

They do not make Motors actually labeled 480 volts.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#168228 - 08/29/07 05:09 PM Re: 3 Phase Power (490 volts on a 480 volt system) [Re: iwire]  
frenchelectrican  Offline
Member
Joined: Feb 2003
Posts: 939
Wi/ Paris France { France for ...
Also most power supply system are useally ± 10% range so with the 480 system you got a bit leeway with it so few voltage over the system is not bad at all

Merci , Marc


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)


#168229 - 08/29/07 05:57 PM Re: 3 Phase Power (490 volts on a 480 volt system) [Re: frenchelectrican]  
leland  Offline
Member
Joined: Aug 2007
Posts: 853
Lowell area, Ma. USA
"leeway" thats a good thing.
N-Star here, has been running "questionably" low lately.

That makes you worry.

You have a fine stable voltage, no worries.


#168230 - 08/29/07 06:15 PM Re: 3 Phase Power (490 volts on a 480 volt system) [Re: leland]  
acetoday  Offline
Member
Joined: Sep 2003
Posts: 35
Manassas, Va
Leland, frenchele,and iwire,

Thank you for all your responses. It's greatly appreciated. I didn't think it was a problem, but I have a customer and his A/C mechanic is advising him not to run his unit. I feel bad for the customer because he's at a loss for what to to do.

Thanks again!!!!


#168232 - 08/29/07 06:39 PM Re: 3 Phase Power (490 volts on a 480 volt system) [Re: acetoday]  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Originally Posted by acetoday
I have a customer and his A/C mechanic is advising him not to run his unit.


Click on the link for a pdf you can print out with a lot of official information to teach the A/C mechanic, maybe you will print out two and give him one.

Air Conditioning Equipment Voltage Ranges

Basically a 460 tagged unit is designed to run from 432 to 508 volts.

Last edited by iwire; 08/29/07 06:45 PM.

Bob Badger
Construction & Maintenance Electrician
Massachusetts

#168234 - 08/29/07 06:42 PM Re: 3 Phase Power (490 volts on a 480 volt system) [Re: iwire]  
leland  Offline
Member
Joined: Aug 2007
Posts: 853
Lowell area, Ma. USA
3- one for the customer to rest their worried mind.


#168241 - 08/29/07 09:50 PM Re: 3 Phase Power (490 volts on a 480 volt system) [Re: leland]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,135
Estero,Fl,usa
Bob said

"Basically a 460 tagged unit is designed to run from 432 to 508 volts."

That is news you can use. I was trying to do the math in my head from the earlier 10% post and I got "brain feeeze" like when you eat ice cream on a hot day.


Greg Fretwell

#168242 - 08/29/07 09:52 PM Re: 3 Phase Power (490 volts on a 480 volt system) [Re: iwire]  
acetoday  Offline
Member
Joined: Sep 2003
Posts: 35
Manassas, Va
Bob,

Thanks again for being so helpful. I printed out the document and filed it away. It was of great use to me as well as the ac mechanic. Thank you again for reaching out.

Respectfully,
Bob Hanifin
Owner, ACE Electric


#168255 - 08/30/07 04:25 AM Re: 3 Phase Power (490 volts on a 480 volt system) [Re: acetoday]  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Originally Posted by acetoday
Bob,

Thanks again for being so helpful.


Glad I could help, I would like to say I have all this knowledge in my head......but really I am just a good 'Googler'. wink


Bob Badger
Construction & Maintenance Electrician
Massachusetts

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