Wiring an Isolation Transformer

Don't see any advantage of the xformer for the video switcher, which is essentially just relays. Wouldn't even try the amp on it, as much for the way it draws (half cycle cap recharging), combined with the capacity. TV is a noise source and one of the things to isolate from. Aside from that, glad it works and happy for you.

Now, you just have to try every brand of power conditioner to it and tell us how they compare.

Would've liked to see the electrician's expression when you mentioned balanced AC.

Thanks for the reply Ngjockey,

TADAC Tube Pre/DAC = 25W According to Paul at TAD)
Apple TV = 20W (according to Apple)
DIP (Original) = 10W (according to back panel)
Tivo HD = 40W (according to tivocommunity)
Video Switcher = (don't know but could it be much?)
TV = 240W (according to manual)
McCormack DNA-1 Deluxe = 400 (according to SmCAudio)
TOTAL = 735W (certainly pushing it depending on the draw of the switcher)

I don't have all this on the xfrmr right now. Just the PRe/DAC, Apple TV, DIP, Video Switcher and Tivo. In your opinion, what would be the most beneficial strategy for using the iso? I guess I just threw everything on there that I thought it could take. Anyway, it is buzzing but I can only hear it when I put my head right up to it. Can'thear it from listening position at all. Just barely warm after running it all night. I have to admit, I was skeptical about how much difference this would make. But it is significant. Not night and day, but very noticeable. The only way I can describe is that everything is just so much more right sounding. Whatever that means.

Math is correct. 80% would be 720W.

Apple TV - reports from 20 to 48W
DIP - negligible 6W

Vide switcher/Tivo ???
My HD tuner/PVR is rated for 4A max (480W) and it can get warm.

Pre/DAC ???
examples: Plinius M8 - 20W, ARC LS17 - 50W, SFL2 -135W

Putting everything on a single isolation xformer defeats some of the purpose, don't you think? Particularly if you're mixing digital with analog or SMPS with linear power supplies.

How is the xformer for noise and heat? Shouldn't be uncomfortable keep your hand on.

Ok, I heard fromn the electrician. I now undertstand the open ground reading was expected behavior. My only remaining question is, how many watts can I safely put on a 1.8 KVA iso transformer? I had it wired for balanced, so I am assuming that knocks the rating down to .9 KVA which would equal 900 va/watts, correct. Cut that in half to allow sufficient headroom would equal 450va/watts to work with. Is my math correct?

Today I had the unit wired as described above. The electrician checked it with a multi-meter and got stable correct voltage. Just for giggles, I decided to hook up one of those cheap Home Depot plug-in testers to the unit, and it is showing an open ground. Is this a misread from the tester or is there something wrong with the wiring? Any help?

LOL

Haven't worked on a Topaz 120/240, but that looks right. Check it with a meter. You can get GFCI cords.

So does the following seem like a practical approach? Will this get me balanced isolation? Are their any safety concerns with this setup? Can I just use a good extension cord, cut in half, and wired in the manner described below?

Input:
Neutral (white) to H1
Hot (black) to H4
Ground to chassis
Jumper H2 to H3
Add appropriate inline Fuse/Holder

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

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.

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)?

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

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..

,

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?

Was it..... Was his mind made up?... Set in concrete?

Having a bad day? No need to be snippy. I said "if." I didn't say set in concrete,, I didn't say his mind was made up.

BTW I'm still curious how it is less isolated wired as 120-120.

.

Ok, maybe GFCI is required. Up here, it's CSA instead of NEC and, technically, there is no CSA provision for balanced AC.

http://minneapolis.craigslist.org/hnp/ele/2144150722.html ??

Yes, balanced output means derating by half. Whether the tranny will be agreeable (relatively cool and quiet) to 120V in/balanced out is always a mystery until it's tried. I've had one where that worked fine in one house but not when I moved. Switched to 240V in and it was happy again. If electricity and "newbies" is dangerous, xformers and "newbies" is a whole new level of fun.

Get a meter (with clamp or fork would be better) and test before hooking anything up. Klein Tools aren't expensive. Balanced is 60V leg to ground on both sides and 120V leg to leg.

I prefer GFCI outlets with balanced AC for added safety ( I like to open covers), but not required. In this situation, install an appropriate inline fuse/holder on the input side.

Wire nuts/"marrettes" are fine.

Also, is there a definitive asnwer out there about balanced halfing the VA rating?

Let me take a stab at it again....
First a power transformer is designed to operate at its rated nominal voltage and frequency. The size of wire used is directly proportional to the power the xfrmr is capable of delivering.

The xfrmr you are looking to buy has dual primary windings and dual secondary windings.

For the rated output voltage/power of the xfmr the primary can be wired for 120V in (paralleled) or 240V in (series)
The FLA (full load amps) rating for the primary would be 15 amps @ 120V (1800Va / 120V = 15 amps) or 7.5 amps @ 240V (1800Va / 240V = 7.5 amps). Output of xfmr fully loaded...

For the rated output FLA of the secondary of the xfmr the xfrm can be wired for 120/240V out (series the two windings, midpoint becomes the neutral) or straight single ended 120V out (parallel the two secondary windings)

The 120/240V configuration is capable of delivering 7.5 amps @ 240V. (1800Va / 240V = 7.5amps)

From each hot lead, leg, to the midpoint neutral of each winding is capable of delivering 7.5 amps @ 120V. (120V x 7.5 amps = 900Va. 900Va x 2 windings = 1800Va)
L1 to neut 7.5 amps @ 120V.... L2 to neut 7.5 amps @ 120V.

For your balanced 60/120V (60V 0 60V) wiring configuration you must use the above 240V calculation.

The most FLA the xfrm will be safely capable of delivering will be 7.5 amps. 7.5amps x 120V = 900Va
>>>>>>>>>>>>>>>

So if each secondary winding is capable of safely delivering 7.5 amps @ 120V (as designed by the manufacture/size of wire used for the winding) then it stands to reason if both windings are connected in parallel (single ended) The xfmr would be capable of delivering 15 amps. 15 amps x 120V = 1800Va.
Jim

I have one dedicated 20A line run to my audio system. My plan was just to run digital components (Apple TV, DIP, Pre/DAC, Video Switcher maybe a Tivo) off it. Run the power amp and tv straight to the wall. 220 is not an option right now. Any ideas about what gauge of wire I should use for the jumper cables and in/out cables. Also, is there a definitive asnwer out there about balanced halfing the VA rating? Also, would I use bare wire, or should I solder/crimp spages on the wires?

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?

.

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.....

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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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.

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

But some suggest this cuts the power in half, some suggest it doesn’t. Here is an example I found of balanced wiring:

Wired balanced will cut the VA rating in half.....

Wire the transformer 120V in 120V out.

Parallel the two secondary windings together.

Warning: Observe the correct polarity. If polarity is not followed the two secondary windings will buck one another possibly burning up the windings.

Is there a data plate on the transformer showing wiring configurations?

Primary? One winding or two? Input voltage/s? Number tags on leads? Polarity marking?

Secondary? One winding or two? Secondary voltage/s? Number tags on leads?
Polarity marking?