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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
jea48
4,451 posts
 
BTW I'm still curious how it is less isolated wired as 120-120.
Did you take the time and read the Bryston link I provided?
They recommend running the primary in balanced mode, 120/240V (120V 0 120V), instead of single ended 120V in.

As for recommending the OP try it first.... As a rule I try to stay within the boundaries of NEC code as well as UL safety guide lines.

NEC Article 647
Equitech
.

Curious, what are your thoughts on running the xfmr on 1/2 its designed rated voltage? (Series primary windings connected to 120V instead of 240V). What does it do to its efficiency?
herman
2,259 posts
 
Yes, I did read it.

It doesn't say anything that I can find about 120-120 having less isolation, in fact it says "The advantage of operating a Balanced Input or a Balanced Output is noise reduction as a result of the balanced line common mode noise rejection."

As far as I can tell their argument against going balanced has to do with safety and adhering to code, which are both valid concerns, but your point about "less isolation" isn't discussed as far as I can tell. I would be interested to hear the explanation if you would be so kind to provide it..

,
dmatt200
13 posts
 
Herman,

I think Jea48 is talking about these sentences from the Bryston link:

"If the 240 Volt version is used then the Torus Powerline
Conditioners are BALANCED at the INPUT."

then ...

"The advantage of operating a Balanced Input or a Balanced Output is noise reduction as a result of the balanced line common mode noise rejection."

finally ...

"On some larger models Torus uses a 240 Volt Balanced Input because of the noise reduction advantages
in the typically long wire runs from the hydro panel to the Torus unit."

So I guess they are saying if running the dual primaries in series (0-240V) can be considered "balanced" at the input, and balanced can reduce noise through common mode rejection, then a 240V primary should reject more noise than a 120V primary.

But I am not an EE, so I am just making educated guesses.

Cheers.

David
cpalcott OP
14 posts
 
I have a friend who is an electrician coming over tomorrow. He has some experience with wiring isolation transformers. But I need to be able to tell what I want. So, if I am understanding this correctly, some are suggesting wiring this as 240v in 240v out even though it will be on a 120v circuit to help keep it cool. Is this correct? Will this work? It seems consenus that if I have it wired balanced, it will half the kva rating. If I do that, will .9 kva be enough to run the digital part of my system (Apple TV, Monarchy DIP, Tube Audio Designs TADAC Tube Pre/DAC, AV Switcher, and perhaps a Tivo)?
ngjockey
1,042 posts
 
Check the print on the back of the units or the manuals for the equipment's maximum amp draw.

V (voltage) times A (amps) = VA = watts

Rule of thumb for audio is that xformer should be at least double the combined draw. 80% is the "industrial" rule.

As far as the rest, wow, leave it to the electrician. You started off good.
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