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# Using transformer to convert from 240 to 120 to run 5 outlets

#1
11-04-15, 10:29 AM
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Join Date: Oct 2013
Location: United States
Posts: 5
Using transformer to convert from 240 to 120 to run 5 outlets

So I have an old AC cut off on the side of my house which is still live 240v which is not being used any longer.

it is wired with 3 wire White Black Ground which go back to my breaker panel to 2 50amp breakers.

Can I tap off of this run a line to my shed put in a sub pannel using one for 240 V for my air the use a distribution transformer such as Acme T153006 (0.15 kVA Dry Type Distribution Transformer | Acme Electric) to drop the voltage to 120v and run 2 lights (LED) and maybe 5 outlets if that many?

Or is there a better way?

#2
11-04-15, 11:38 AM
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Join Date: Mar 2006
Location: USA
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Can I tap off of this run a line to my shed put in a sub pannel using one for 240 V for my air the use a distribution transformer
I can't understand that sentence. You can't use it for both a 240 A/C and to supply your shed but you earlier wrote:
So I have an old AC cut off on the side
Which seemed to say the A/C is no longer used. So I don't know what the real situation is.

If it is no longer used for an A/C you could convert it to a 120 volt 20 amp feed to the shed or use it for a 50 amp 120 volt subpanel in the shed.

#3
11-04-15, 01:07 PM
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Join Date: Oct 2013
Location: United States
Posts: 5
the line is no longer used for ac we put in a different system different location so it is just sitting there not being used.

I know I can take it back to 110.

but what I would like to do is to run a 240 line to my shed for my air compressor then step it down to 240 with the use of the transformer if possible.

my circuit looks similar to this diagram except the diagram has an outlet where I have an AC disconnect

[ATTACH=CONFIG]58469[/ATTACH]

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#4
11-04-15, 01:30 PM
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Join Date: Mar 2006
Location: USA
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Yes, you can use a transformer but have you checked the cost compared to other solutions?

Is the compressor motor dual voltage? If so you could rewire it for 120 volts and use a 120 subpanel at the outbuilding.

Tech note: nominal voltage is 120 not 110.

#5
11-04-15, 01:30 PM
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Yes you could use a transformer to derive 120V at the shed, but getting the grounding and overcurrent protection right is a little tricky.

You would need to feed the shed with a 50A 240V-only feeder and subpanel, one of the breakers in that panel would feed the compressor, one would feed the transformer. The transformer would then feed a small 120V-only panel, which then would power your general-purpose light and receptacle circuits. The secondary of the transformer would need to be grounded to the shed's grounding electrode system, which would also ground both panels.

All of the 120V receptacles would need to be GFCI protected.

#6
11-04-15, 02:40 PM
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Join Date: Oct 2013
Location: United States
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Thank you that is what I needed to know.

#7
11-04-15, 03:51 PM
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Location: Wet side of Washington state.
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That transformer you referenced is only 150 volt-amperes or about 150 watts. That is a maximum of 1.25 amperes. Not going to be able to do much with that limited a supply of power.

#8
11-04-15, 10:18 PM
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Join Date: Oct 2015
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Wouldn't it be a lot easier just to make a new run with the correct 3-wire + ground cable all the way from the shed to the breaker box? It would be cheaper than the transformer, and would give you a properly wired subpanel able to supply all of your needs. Be sure to keep the neutral and ground separate except in the main panel, and to add ground rods for the outbuilding.