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#60285 - 12/27/05 05:02 PM Finding the correct breakers for Delta service
renosteinke Offline
Cat Servant

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
I have encountered the (rare here) 240/120 Delta 3-phase service. I need to install a panel, and clean up the existing circuits.

As I read the UL "White book," breakers marked "120/240" are limited to use where the line to ground voltage does not exceed 120 volts. This presents a problem for me, as one of my service legs measures 208 volts.

I seem to recall seeing breakers that were simply marked "240." My visits to the supply house, however, were met with confusion.
A call to one company's service line resulted in the person there giving information contrary to what is in the UL white book.

Has anyone out there seen "240 volt" breakers in Square D, Siemans, or GE? Part numbers are appreciated- especially for any single pole breakers!
(I happen to be serving 208 volt rated equipment, so the ability to use a single pole breaker would be nice! As you might guess, I do n ot wish to spend the $$$$, and use the larger breakers, designed for 480 volt service).

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#60286 - 12/27/05 05:47 PM Re: Finding the correct breakers for Delta service
codewarrior Offline

Registered: 12/26/05
Posts: 17
Loc: Camden,New Jersey
Hi there are a number of online breaker distributors that deal with old breakers of that sort ,there is one in South Jersey in Camden, called All Current Electric,they deal with all kinds of odd breakers, I think there sales department might be able to help You.

#60287 - 12/27/05 06:00 PM Re: Finding the correct breakers for Delta service
Redsy Offline

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA

I just went through this bout 2 months ago.

Be careful, a push-in, 2-pole, 30-amp Seimens is about $45.00, versus $7-8.00.
They are listed in the Siemens catalog and are available from most supply houses.
I think the model number for the "straight rated" CB is the same as "slash rated" CB , with an additional letter on the end (R?)

[This message has been edited by Redsy (edited 12-27-2005).]

#60288 - 12/27/05 07:47 PM Re: Finding the correct breakers for Delta service
frenchelectrican Offline


Registered: 02/06/03
Posts: 938
Loc: Wi/ Paris France { France for ...
just be carefull they dont have straight 240v single pole breaker at all useally in double pole format. as for 3 phase breaker useally not the curpit but 2 pole breaker you have to double check the label it will say 240 volt only not 120/240 volt label due the wild leg unless you get it on phase A & C you are ok but not on A & B or B & C phase [ in case you have 120 volt load there ] keep in your mind here the " B " phase is wild leg

most breaker manufacter do have " delta " breaker but cost is pretty steep compared to convental breakers.. I know i did spend over 45 for one with delta verison it was more like specal order item so check it ahead of the time

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

#60289 - 12/27/05 08:24 PM Re: Finding the correct breakers for Delta service
caselec Offline

Registered: 04/14/02
Posts: 557
Loc: San Jose, CA
Standard 3-pole breakers are rated for 240 volts. 1-pole and 2-pole are rated 120/240 volts. Only the breakers connected to the high leg need to be rated for 240 volts. As other have said 240 volt 2-pole are available but not often stocked by supply houses. You could use a 3-pole breaker instead of ordering a 2-pole if you have space in the panel.

Curt Swartz

#60290 - 12/27/05 08:33 PM Re: Finding the correct breakers for Delta service
caselec Offline

Registered: 04/14/02
Posts: 557
Loc: San Jose, CA
I didn’t catch the single pole to supply 208 volt loads part of you post. You should really install a buck/boot transformer to supply 208 volt loads. Delta transformers are not designed to supply loads connected to the high leg and ground.

Curt Swartz

#60291 - 12/27/05 11:42 PM Re: Finding the correct breakers for Delta service
SolarPowered Offline

Registered: 07/05/04
Posts: 615
Loc: Palo Alto, CA, USA
The 2-pole Sq D QOH breakers, and the 3-pole QO breakers, are rated for 240V. I don't see any single-pole breakers rated at 240V--they're all 120/240. But then, I don't expect that you'd be connecting any single-pole loads to the wild leg.

Edited to add: Oops, I also did't catch on to the part where you want to power 208 loads from the wild leg to neutral. They actually have loads there that want single-phase 208V, that aren't dual-rated for 240V?

[This message has been edited by SolarPowered (edited 12-28-2005).]

#60292 - 12/28/05 06:02 AM Re: Finding the correct breakers for Delta service
togol Offline

Registered: 09/15/05
Posts: 426
Loc: NW In. USA
I would forget about using the high leg for single pole lighting ! or anything else except 3 phase loads...! if you are cleaning things up, add a 3 / w panel...

how are you going to prevent someone from seeing what is on B phase and trying the same thing for their new computer ?


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