Single phase from existing three phase?

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Old 12-07-18, 07:48 AM
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Single phase from existing three phase?

I'm getting rid of all my three phase machine equipment and changing over to single phase 220 service. Would it be OK to use my existing three phase breaker panel to rewire for single phase. Changing the panel would be a major headache. I'm not concerned with city inspectors or any codes.
 
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Old 12-07-18, 08:21 AM
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Would it be OK to use my existing three phase breaker panel to rewire for single phase.
Unless you give up one of 3 buses on the panel, you won't be able to balance the load because one of the leg will have twice as much loads on it.
It would be best to just replace the panel.
 
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Old 12-07-18, 08:33 AM
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I would give up one of the panel busses and use breakers only in the panel slots powered by the two remaining live phase lines. Balancing the loads will now be no different than working with an original single phase panel and service.

You can install a subpanel if there are not enough live slots remaining. No compelling need to replace the old panel.

Replacing a "main" panel usually requires having the meter pulled while the work is done and usually requires a separate permit. Adding a subpanel can be done as part of the same permit for adding more circuits and power can remain on for the building in turn eliminating the rush to get the work done and power turned back on..

If your old service is 208 volt then any 208 volt or 120/208 volt equipment not rated for 220-240 volts might not necessarily be compatible with the new service.
 

Last edited by AllanJ; 12-07-18 at 08:59 AM.
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Old 12-07-18, 08:48 AM
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Having a 3 phase panel with a single split phase feed means every third row of breakers is dead but otherwise usable.

Option is to add a jumper to the 3rd leg in the panel. Then have to pay attention where you put 2 pole breakers.
 
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Old 12-07-18, 09:51 AM
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If you jump to the third bus in the panel you must remove the dead service conductor from the top lug. This will prevent problems if the power company should accidentally re-energize the other end of that third conductor.

If you jump the third bus, load balancing will be easier if you only hook 240 volt double breakers to those slots. On the 120/240 volt service, 240 volr loads are not part of the balancing formula so no thought (brainstorming) needs to be wasted on them.
 
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Old 12-07-18, 07:14 PM
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A 3 phase panel will work fins as a single phase panel, just one buss will be dead as the others have mentioned. It will be similar to a high leg panel where every 3rd space can't be used (The B phase in a high leg) I would recommend leaving the one bus dead.

On the other hand, a single phase panel is only $75-$100. If you get the same brand panel you can possibly reuse the breakers.
 
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Old 12-07-18, 09:13 PM
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My service is 220V. The main objection to installing a new single phase panel is having to reconnect all the emt conduits. I was planning on deleting the third wild leg in the swap over. Anyways, I have plenty of available slots for existing circuits.
 
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Old 12-07-18, 09:23 PM
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240v service. 220v went out with the button shoes.

So that means you have a red leg service. Are they disconnecting that for you ?
All your 240v breakers will be on the C-A bus. You can't bridge A or C to B.
You'll need some blanks too.

A ...... A
(b) ....(b)
C ..... C
A ..... A
(b) ....(b)
C ...... C
A
...... A
(b) ....(b)
C ...... C
A ...... A
 
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Old 12-08-18, 10:56 AM
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Is there way to keep the panel enclosure and just replace the 3 phase bus and breakers with single phase one???
 
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Old 12-08-18, 11:31 AM
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If you are lucky you may find a new 120/240 volt single phase panel kit whose innards will swap into your existing panel enclosure and all the mounting holes and brackets will match up.

You will still have to call the power company and have your meter pulled while you make this swap.
 
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Old 12-08-18, 04:23 PM
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Is there way to keep the panel enclosure and just replace the 3 phase bus and breakers with single phase one
It is likely not worth the trouble. The existing panel should work fine unless you will have more 2 pole loads then you have spaces for.
 
 

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