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#47050 - 01/07/05 03:09 PM 208/120V multifamily services  
GamecockEE  Offline
Member
Joined: Jul 2004
Posts: 49
Georgetown, SC 29440
A question for my electrical brothers & sisters out there. What are the issues that are out there when it comes to using 120/208 services in multifamily dwellings. Any problems as far as voltage on the appliances such as dryers water heaters, heat pumps etc. Thanks


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#47051 - 01/07/05 04:00 PM Re: 208/120V multifamily services  
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
 
240V-rated resistance-heating appliances use/produce ¾ rated kW when operated at 208V.

(208/240)² = 0.75

>HVAC stuff should be labeled 208V or 208/230V. It is a misapplication to connect motorized 230V- or 240V-labeled equipment to a 208V system.

Also, two equal phase-to-neutral loads produce full current in the common {technically not a neutral} conductor of a 3-wire 120/208Y circuit fed from two of three phases — not zero as in 120/240V systems.




[This message has been edited by Bjarney (edited 01-07-2005).]


#47052 - 01/07/05 04:04 PM Re: 208/120V multifamily services  
John Steinke  Offline
Member
Joined: Apr 2001
Posts: 518
Reno,Nv., USA
If this is a single pahse service, no problem (as long as the appliances are rated to handle 208- a 240v rated appliance might have problems)

IF you are talking about a three-phase system, with a 208v "wild" or "stinger" leg, you have a problem.
The three phase panel in this case is not listed for use as a "lighting and appliance' panel, only as a 'power' panel. I just had an experience with someone who didn't appreciate this, and had some receptacles supplying 208v! What you must do is use two of the 120v legs to serve a separate single phase panel, and draw your circuits from there.


#47053 - 01/07/05 05:57 PM Re: 208/120V multifamily services  
Steve Miller  Offline
Member
Joined: Aug 2001
Posts: 325
Loudoun Cty, VA
I serviced a Leisure World community in MD and they had that setup. The only prob we ever had was when people replaced their individual water tanks and dryers without contacting anyone in the maintenance dept. They always complained that the new stuff wasn't as good as the old ... which it wasn't 'cause the old (original) was 208 only and the new was 240. All their HVAC stuff was common to the building so the individuals never got involved.


#47054 - 01/08/05 08:03 AM Re: 208/120V multifamily services  
GamecockEE  Offline
Member
Joined: Jul 2004
Posts: 49
Georgetown, SC 29440
Thanks, for the info. Can you find appliances that are rated for 208 such as Dryers & Stoves? Bjarney, a follow up to your response. Does the NEC 3 phase demand adjustment as applied to washers and dryers that utilize a neutral take care of that issue when sizing the load and then sizing the neutral? If I'm misunderstanding you, give me an example if you will.


#47055 - 01/09/05 12:30 PM Re: 208/120V multifamily services  
Bjarney  Offline
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Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
 
GamecockEE, possibly someone else here can help you with applicable material in Article 220. On appliance-voltage availability, local suppliers can answer that question.



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