The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!


2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Parking lot pole light swap....
by gfretwell
Yesterday at 08:46 PM
International Wire Colour Codes
by Tjia1981
10/23/16 12:08 PM
Son of Sparky
by HotLine1
10/20/16 07:43 PM
Speaking of Plugmold ...
by gfretwell
10/17/16 02:37 PM
Broken battery charger? Check for cobwebs!
by gfretwell
10/17/16 02:30 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 14
HotLine1 7
ghost307 7
renosteinke 6
Potseal 4
Who's Online
1 registered (Tjia1981), 297 Guests and 5 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#72374 - 11/27/06 05:59 PM 277 V Unit Heater
highground Offline

Registered: 11/14/04
Posts: 50
Loc: Chama, NM
I recently went on a service call for some high bays. While up in the lift I noticed the electric unit heaters had 277V nameplates but were installed in a building with 240V. No 277V is available.

(The motors are 277V rated as well)

The customer says they are about two years old?

Any thoughts as to potential problems?


Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#72375 - 11/27/06 06:11 PM Re: 277 V Unit Heater
Roger Offline

Registered: 05/18/02
Posts: 1779
Loc: N.C.
Is there a chance that there are some Buck/Boost transformers somewhere?

We have done this before for this very situation.


#72376 - 11/27/06 06:19 PM Re: 277 V Unit Heater
highground Offline

Registered: 11/14/04
Posts: 50
Loc: Chama, NM
No Transformer Roger,

Small building, panel in sight of heaters.
I checked to see if there was one hiding.


#72377 - 11/27/06 07:02 PM Re: 277 V Unit Heater

Registered: 12/08/05
Posts: 862
Loc: Titirangi, Akld, New Zealand
You won't get you maximum power output for heating.
240 volts is 86 % of 277 volts.
By V²/R you only get 75% of your heating capacity.

For the motors it depends if they have to start a heavy load or not.
If it is only to drive a fan i can't see any problems with it.
The product of rotation, excitation and flux produces electricty.

#72378 - 11/27/06 07:31 PM Re: 277 V Unit Heater
JoeTestingEngr Offline

Registered: 11/04/05
Posts: 786
Loc: Chicago, Il.
I doubt that you will have any problems but it wouldn't hurt to contact the mfg. to put your mind at ease.

#72379 - 11/27/06 09:42 PM Re: 277 V Unit Heater
Lostazhell Offline

Registered: 02/21/04
Posts: 1248
Loc: Bakersfield, CA (Originally Or...
Only thing I can think of would be a conflict of something meant to run with a grounded phase vs. phase to phase... I'm not sure if this would be an issue in your case though...


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals