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Wiring an Isolation Transformer

I found a pristine, never been used, Topaz (Square D Company) 91018-31 1.8 KVA Ultra Isolator Line Noise Suppressor for $40. Other markings include .0005pF, 50/60 Hz, 120/240, Indoor Type 1, Enclosure Class 1-80 Insulation. However, it has no receptacle or chord.

My first question to the forum, is how to wire it? Could I just take a short extension cord, cut in half, wire the male end to the output side and the female end to the input side? Should I use bare wire under the screw terminals, or should I crimp/solder on spades? What wires go on what screw terminals? Some suggest balanced is the way to go. But some suggest this cuts the power in half, some suggest it doesn’t. Here is an example I found of balanced wiring:

Input:
Neutral (white) to H1
Hot (black) to H4
Ground to chassis

Output:
Hot 1 (white) to X1
Hot 2 (black) to X4
X2/X3 center tap connected to chassis ground and outlet ground.

Is this all there is to it? I am a complete newb when it comes to electrical work. Is this something I can do myself, or should I hire an electrician? Any assistance would be greatly appreciated.
cpalcott
xti16
1,525 posts
 
Wired balanced will cut the VA rating in half.....
NO IT WILL NOT. What you will see is 60V between ground and neutral and 60V between ground and hot. You will have 120v between neutral and hot. I have the 2.4KVA version
jea48
4,425 posts
 
NO IT WILL NOT.
Yes it will!

You must treat the output rating the same as if it was configured with the two windings in series.
herman
2,253 posts
 
First of all, if you are not sure how to do this I seriously suggest you enlist the help of someone locally who can help. It is possible to kill yourself or burn your house down if you screw up with electrical work.

To run it balanced you'll need to connect it as you stated but also jumper H2-H3 on the primary otherwise no current can flow. That puts the 2 primary windings in series and also the 2 secondaries so it is a 1:1 transformer.

The full VA rating at 120VAC assumes you are running the 2 primaries as well as the 2 secondaries in parallel so each winding carries half of the current.. Running balanced you will have them in series so VA rating is half since full current runs through each winding, not half of it.

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jea48
4,425 posts
 
120V in 120V out will not yield all that much isolation. Better to wire the xfrm 240V in, single ended 120V out.

Series the primary windings, parallel the secondary windings.
One paralleled leg of the secondary must be connected to earth ground making the new derived ac power system a grounded ac power system.... it's a safety thing. The earth ground used must connect to the main grounding system of the main electrical service.

For this you would need to hire an electrician.....
herman
2,253 posts
 
Please explain
120V in 120V out will not yield all that much isolation. Better to wire the xfrm 240V in, single ended 120V out.

If the purpose of the exercise is to have a balanced secondary then he has no choice but to wire it as stated above. You can't have a 240 primary and balanced 120 secondary. Granted, you can argue that balanced might provide no benefit, but he won't know until he tries it.

Wiring it 240-120 means he will need to run a 240 line to it. I didn't gather from his initial post he was wanting to hire an electrician to run new lines.

And why does 120-120 not "yield all that much isolation"?

I didn't know there were varying degrees. I thought it was either isolated or it was not. How can it be less isolated as 120-120?

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