Iso trafo at sub panel garage studio

[BobbyButterfield]

Howdy!

I live in a rural setting with sketchy power and am constantly looking for a way to improve my little recording studio in my garage. At the moment I get noise and interference from the house (something to do with a water pressure tank system) and would I’d like to isolate the studio from the house. I have a Tripp Lite medical grade 1800w box that I use to protect my console from power brown outs etc (roasted two power supplies in the past… argh). The Tripp Lite works well but I was hoping to have a similar concept wall mounted (inside or outside) that would isolate the the power pre-sub panel. I’ve yet to add up my kVa’s yet but prob something around a 5kva I’d guess.

Also if I go this route can I add an isolated ground post iso transformer?

Any tips?

Thanks,

Rob

 

[ccaudle]

Any tips?

First and most important tip: Never rely entirely on something some random person tells you over the Internet. Always check with a licensed electrician, and make sure the electrician remembers and understands the code sections dealing with separately derived system power. Separate transformers to derive an isolated power feed would be unusual in a residential setting.

At the moment I get noise and interference from the house (something to do with a water pressure tank system) and would I’d like to isolate the studio from the house.

Isolation transformers are good for removing common mode noise (i.e. changes in the same direction in both line and neutral simultaneously with respect to earth), less good at removing differential mode noise, i.e. the hot line voltage dips when a heavy load turns on, or more likely the hot line voltage dips and the neutral voltage rises when both are measured against earth or the power entrance.
Especially if the pole to house feed doesn't have a lot of excess capacity and the feed for the entire house dips when the water pump turns on, that dip in the feed to your property is going to show up at the primary to your garage transformer, and unless it is super short in duration, might not be filtered out by the separate transformer. So keep in mind you might spend a lot of money putting in a separate transformer for the garage studio, but not end up with the result you want because you were addressing the wrong problem.

I have a Tripp Lite medical grade 1800w box that I use to protect my console from power brown outs etc (roasted two power supplies in the past… argh). The Tripp Lite works well but I was hoping to have a similar concept wall mounted (inside or outside) that would isolate the the power pre-sub panel. I’ve yet to add up my kVa’s yet but prob something around a 5kva I’d guess.

Is the Tripp Lite an isolation transformer, or a UPS, or just a power strip with surge protectors?
Are you talking about this?
TrippLite isolation transformer

There are surge protectors you can get for an entire building, they would mount in the power feed between the main panel and your sub-panel (and/or could also mount on the main house panel). I don't have personal experience with those, I just know they exist.
Presumably those could be used in conjunction with an isolation transformer.

Also if I go this route can I add an isolated ground post iso transformer?

Only if you have a permanently mounted isolation transformer. Not if you just have surge protection, and not if you have any kind of portable isolation transformer.

One thing to double check on your current wiring is make sure that if the garage sub-panel has a separate ground rod (probably does if it is a separate building, probably does not if it is attached to the house), the ground at the sub-panel must NOT be connected to neutral at the sub-panel. The ground to neutral connection must only be at the main panel power entrance, unless you have a permanently mounted isolation transformer, in which case the sub-panel after the isolation transformer becomes a new separately derived system and the ground and neutral should connect there.

 

[shabtek]

if you have low voltage an isolation transformer won't help unless it has multiple taps ie +/- 5%
if low volts condition is intermittent than you create opposite problem when its not low.

whats range does mains measure rms?

equitek balanced mains trafos does provide some regulation idk if that applies to source (upstream) fluctuations, and they give you an isolated ground system. but do you have the supply headroom?


is water pressure system 240? if thats the source of noise than maybe stop it there.

 

[NOON]

Are grid connected batteries a thing where you are? Still fairly pricey here in Aus but coming down and if it's the mains drooping under load because you're near the end of a line a battery can act like a filter cap in a power supply to help stabilise the voltage. (it's not quite that simple and how much if helps depends on a few factors)

 

[Bo Deadly]

Sounds complicated. I would study the problem before deciding how to fix it. If the only source of noise is really the "water pressure tank system", then maybe it's faulty or you can hack it. If it uses an AC motor maybe it needs new motor run caps. Maybe you can add something to limit inrush currents.

And it sounds like you would benefit a lot from switching the PS to SMPS. SMPS are actually current regulators and so they will very effectively filter out noise from mains. And they're way better than linear supplies in just about every way regardless.

 

[BobbyButterfield]

Hey thanks for the replies!

The garage is tied to the house panel. Only one ground rod at the moment attached to the main panel. My original plan was to lift the ground at my garage sun panel and create a dedicated ground plate system just for the studio. I’ve done a bunch of reading up on this and it tends to go against code all over North America! I’m on a small island off the coast of Vancouver, Canada.

Water pressure tank system creates a hiss thru any speaker (hifi or gtr amp) and also along any mic lines. I don’t want to mess with the noisy water pressure system because I think we will need to update it soon plus we are about to adapt the house to rain water collection and we I’ll need to build a filter system etc… not ready to mess with pre existing one yet. Also don’t want to bore you with my broken house issues. I figured this new idea I am exploring is going the extra mile to create clean power. Not something in would’ve cared about in my younger years but am sure fussing over now!

My Tripp Lite will make the noise disappear if I run a gtr amp thru it in the garage studio and at the same time run the house water system. That leads me to believe that a beefed up transformer system would also be successful. my Tripp lite is prob a bit small to run my console, rack gear, computers, power amps, multiple tube amps etc. I plan to add all this up soon. Curios I that size transformer is need. Something like this but bigger I’d guess https://www.larsonelectronics.com/p...fbb0X04v1gjAqO9-kzHkFu3PqSaG4JwxoCfr0QAvD_BwE

My Tripp Lite is:

https://www.tripplite.com/1800w-120...tion-avr-ac-surge-protection-6-outlets~lc1800

 

[ccaudle]

The garage is tied to the house panel. Only one ground rod at the moment attached to the main panel. My original plan was to lift the ground at my garage sun panel and create a dedicated ground plate system just for the studio. I’ve done a bunch of reading up on this and it tends to go against code all over North America! I’m on a small island off the coast of Vancouver, Canada.

That is against code for good reason. Think about the current paths: say you have a fault which allows mains voltage to contact the chassis. That is the primary purpose of the safety ground, giving a low impedance current path back to the voltage source so that the breaker will trip, hopefully before you touch the chassis which is sitting at 120V.

If you have a separate ground rod, which is not tied to the main building grounding system, that path from chassis back to source is going through many tens of ohms of dirt, at the minimum, possibly much more in an area with dry or rocky soil, rather than a couple of ohms of wiring.
With a proper chassis safety earth connection and e.g. a 1 ohm path resistance (to make the math easy), you will get 120A flowing through the safety ground connection, which is about 7x the rated current of a 15A breaker, which according to the trip current vs. time tables from Schneider should trip the breaker within 2 seconds.

If instead you have a separate ground rod, and the resistance between the second ground rod, through the ground, through the primary ground rod, and back to neutral is e.g. 10 ohms (unrealistically low, but again makes the math easy), then you have 12A flowing, and the breaker will never trip. Your equipment will be sitting with the chassis at 120V forever, and the only thing limiting current flow through your heart when you touch it is the insulation of your footwear (including any capacitive reactance between your feet and earth). A current of 0.1A through a person is considered lethal, so I guess make sure you wear good rubber boots with thick soles when working in your studio.

Water pressure tank system creates a hiss thru any speaker (hifi or gtr amp) and also along any mic lines.

Literally a "hiss" noise, not "hum" or "buzz" or clicks or pops, or some other description? Wide band noise like white or pink noise?
That is kind of unusual for motor interference. Is it just a plain AC motor with an on/off relay like a traditional air conditioner or refrigerator? Or is it some kind of more sophisticated speed or power control of the motor?

My Tripp Lite will make the noise disappear if I run a gtr amp thru it in the garage studio and at the same time run the house water system. That leads me to believe that a beefed up transformer system would also be successful.

What leads you to believe a transformer would help? An isolation transformer is completely different than the Tripp Lite model you referenced. That is why I specifically asked if your TrippLite was "an isolation transformer, or a UPS, or just a power strip with surge protectors."
The model you have is a "power conditioner" which probably has a transformer, but also has some type of tap switching to increase or decrease the voltage when the incoming power is out of spec. It does not seem to be a UPS, so I don't think it is regenerating the power, but hard to compare to just a plain transformer without a lot more detail than the TrippLite brochure has.

Unfortunately the situation at the moment is that you know you have a problem, but you don't know exactly what the problem is. Without knowing the details of the problem you are likely to throw a lot of money at a solution which may or may not actually solve your problem.

If the TrippLite power conditioner solves the problem for you, why not get another one of those? The model you have seems to work, and is a couple of hundred dollars. That wouldn't even cover labor for an electrician to wire in a new transformer for you, not to mention that an isolation transformer in a case for mounting on the garage wall is probably going to be several hundred dollars.
From that same company you referenced earlier, a 3kVA transformer is almost $650:
Larson 3kVA isolation xformer

With parts and labor I don't see how you are going to get out for less than $1000, and it might not even solve your problem.

 

[abbey road d enfer]

Also if I go this route can I add an isolated ground post iso transformer?

The idea of a clean earth being the ultimate in noise-killing is most of the times a wild goose chase.
Most of the clicks and noises are due to heavy transients that exceed the rejection capability of power supplies.
A surge protector is often useless because it doesn't filter the surge, it just clamps it, often making things worse by creating current spikes in the system's circulation.
An isolation xfmr does not filter diff-mode noise. It does filter extremely well common-mode noise, but it's overkill compare to a good common-mode choke.
As pointed by Bo, said CM choke would need to be a rather large value, but is really CM noise the issue? I don't tthink so.
Unless you find a fault in your pump ( induction motors have very intense starting surges), I'm afraid the only solution is the use of an on-line UPS of adequate power. You don't need to feed everything from it, for example the monitors/amps can still be powered directly, because noises don't go to "tape".

 

[Bo Deadly]

My Tripp Lite will make the noise disappear if I run a gtr amp thru it in the garage studio and at the same time run the house water system.

That's interesting.

That leads me to believe that a beefed up transformer system would also be successful.

Those UPS systems do not necessarily run the AC through a transformer. But they all almost certainly have a number of chokes and caps. A transformer large enough to handle everything in the studio would be very large and probably quite expensive. However, you might find a suitable common mode choke and suitable XY capacitors. The common mode choke in series and caps to neutral / ground would reduce the common mode noise. Meaning you could make, or maybe just buy, an exceptionally large "line filter". That would be a much more practical project. In the simplest case you could just get a large ferrite torroid, remove the jacket from some mains cable and wrap the load and neutral wires around the torroid like in this graphic:

But this would not yield an inductance high enough to get down to where you are seeing noise. You would need to buy one in the mH range.

You might also want to take the time to verify that your neutral and ground lines are not mixed up at the sockets. Not sure if that could be a problem but it's something you would definitely want to fix if you're trying to make a studio in and old house.

UPDATE:

Something like Schaffner FN2090-16 is 16A and according to the datasheet inductance is 4mH which is pretty high. That might reach down to 10kHz. Put one of these in an electrical box with a mains plug on it and a short / fat extension to plug into the wall. See if inserting that helps. Does the console take more than 10A or so?

 

[MisterCMRR]

if you have low voltage an isolation transformer won't help unless it has multiple taps ie +/- 5%
if low volts condition is intermittent than you create opposite problem when its not low.

whats range does mains measure rms?

equitek balanced mains trafos does provide some regulation idk if that applies to source (upstream) fluctuations, and they give you an isolated ground system. but do you have the supply headroom?


is water pressure system 240? if thats the source of noise than maybe stop it there.

A transformer, in spite of marketing BS claims, cannot improve line voltage regulation. The wire in a transformer unavoidably adds resistance to the circuit. And a series resistance always makes voltage regulation worse (more current = more voltage drop). The only ways to improve regulation are 1) heavier gauge wiring (less resistance) along the current path up to the utility company's "pole transformer" and 2) an active electronic device that responds to drops in voltage by changing taps on a step-up transformer (typically in 5 V steps) or by a "regenerator" or full-time UPS.

 

[abbey road d enfer]

A transformer, in spite of marketing BS claims, cannot improve line voltage regulation.

Ferroresonant regulators are actually transformers that provide significant line regulation.
https://ustpower.com/comparing-auto...guide-constant-voltage-transformer-operation/May not be ideal because of poor efficiency (<80% typ) when online UPS typically run at 92-95%.
OTOH they are cheaper and extremely reliable.

 

[Brian Roth]

Ferroresonant transformers (commonly called Sola xfmrs, named after the inventor) are amazing devices. Downside, they tend to be mechanically noisy. And they throw off some heat into the room.

Bri

 

[abbey road d enfer]

Ferroresonant transformers (commonly called Sola xfmrs, named after the inventor) are amazing devices. Downside, they tend to be mechanically noisy. And they throw off some heat into the room.

Bri

Yes. The 20+% that are not passed to the secondary have to be dissipated in a way or another.

 

[abbey road d enfer]

My Tripp Lite is:

https://www.tripplite.com/1800w-120...tion-avr-ac-surge-protection-6-outlets~lc1800

Well, reading the owner's manual, I had to google POAG. It corresponds to a german term "Potentialausgleich" (equipotential bonding), a fancy word for what turns out to be a secondary grounding point.
Safety ground 101 for doctors.

 

[Brian Roth]

Brian Roth said:
Ferroresonant transformers (commonly called Sola xfmrs, named after the inventor) are amazing devices. Downside, they tend to be mechanically noisy. And they throw off some heat into the room.

Bri

Yes. The 20+% that are not passed to the secondary have to be dissipated in a way or another.

I've been around a few systems using Ferros. Most recently, I was working on the "final stretch" of a large facility (tracking room with an API Legend, mix room with a cut-down SSL 6K). In the electrical room for the whole complex was a large "iso" xfmr. suspended from the roof of the building; it fed the breaker panel with all the isolated ground "technical" branch circuits.

I noticed an irritating acoustical "brrrrzzzzzz" noise in that room when I first arrived, but had bigger fish to fry. As I was mopping up, the manager was grumbling about the constant noise and was going to call the electrical design engineering firm and the contractor to complain.

Out of curiosity, I set up a ladder to read the spec panel on the xfmr. Somewhere I have make/model written down, but bottom line....it was a ferro, and hence the acoustical noise. You could also feel the warmth around it up there suspended in the air. I forget the KVA rating, but it was sizeable.

I told the manager "well, you have a great regulated voltage to your gear, and the acoustic noise is typical." Fortunately, the electrical room had very good acoustical isolation, so it wasn't a problem once the various doors were (normally) closed.

Bri

 

[FIX]

You can spend as much money as you can on power, but here are some tips that will save you a lot:

1. remember that your panel is (most likely in a house) a 2 phase panel. Coming into the house, it's 220, with a earth ground, but off the pole, so it may be dirty. The US way (back in the day with DC, it was around 100V, DC, but who knows why) creates a phantom center or NEUTRAL, that is supposed to be 110-110 and it is tied to the incoming ground which is "sometimes" tied to a pipe coming in, though many houses use plastic pipe now.

In the panel, going vertically, EVERY OTHER breaker is on the same phase, meaning 1, 3, 5, 7, 9, etc. For an inexpensive way to fix ground loops, hum and noise issues, have an electrician move your breakers around so your control room and studio, plus any other recording space, is on the same phase. This creates a grounding system that is at least in common with the rest and will, in most cases, eliminate any issues.

2. balanced power. This is a very expensive way to do power, and in my humble opinion, is a waste of money. No piece of equipment is designed or really needs to have that kind of power source. Instead (I have done this in several A list studios with 100% success, plus most recording and broadcasting trucks do this exactly) get a 240 to 110 transformer that is about 30% higher rated than your load, (usually in KVA, for a small studio, 1KVA will do, a large one 5KVA, huge facility, 10KVA) (a 5KVA transformer is about $2K). Then wire the breaker panel as shown in the attached pix. This will resolve any grounding issues you have.

Run all lighting copy machines, AC, coffee machines, etc. on the regular AC feeds.

 

[JohnRoberts]

Danger Will Robinson, free internet advice. Caveat lector: I describe rural US mains power.

You can spend as much money as you can on power, but here are some tips that will save you a lot:

1. remember that your panel is (most likely in a house) a 2 phase panel.

When talking about house power from a utility pole (in the US) that is considered single phase (just one leg of the three legs phase spread 120' apart on high power lines).

Coming into the house, it's 220, with a earth ground, but off the pole, so it may be dirty.

Generally a center tapped step down transformer winding with opposite polarity single phase power on the two ends of that winding. The center tap gets bonded to neutral in the panel and earth (cough) ground... The earth ground is probably of more interest to lightning than audio circuits. EGC or "safety ground" has a primary function of blowing fuses or tripping breakers if the hot lead goes rouge and energizes a chassis or whatever.

The US way (back in the day with DC, it was around 100V, DC, but who knows why) creates a phantom center or NEUTRAL, that is supposed to be 110-110 and it is tied to the incoming ground which is "sometimes" tied to a pipe coming in, though many houses use plastic pipe now.

? indeed I replaced my water inlet pipe with PVC after it sprung a leak.

In the panel, going vertically, EVERY OTHER breaker is on the same phase, meaning 1, 3, 5, 7, 9, etc. For an inexpensive way to fix ground loops, hum and noise issues, have an electrician move your breakers around so your control room and studio, plus any other recording space, is on the same phase. This creates a grounding system that is at least in common with the rest and will, in most cases, eliminate any issues.

there is probably more than one kind of panel... my house still has fuses.

Be very careful messing with mains power, people can and do get killed.

JR

2. balanced power. This is a very expensive way to do power, and in my humble opinion, is a waste of money. No piece of equipment is designed or really needs to have that kind of power source. Instead (I have done this in several A list studios with 100% success, plus most recording and broadcasting trucks do this exactly) get a 240 to 110 transformer that is about 30% higher rated than your load, (usually in KVA, for a small studio, 1KVA will do, a large one 5KVA, huge facility, 10KVA) (a 5KVA transformer is about $2K). Then wire the breaker panel as shown in the attached pix. This will resolve any grounding issues you have.

Run all lighting copy machines, AC, coffee machines, etc. on the regular AC feeds.

 

[ccaudle]

It occurs to me that the original description did not describe the current wiring layout. Is the water pump located in the garage by any chance? Or running on a circuit near the garage circuit? Maybe all that is needed is a new separate feed from the main panel to the garage studio. That would be much cheaper than a permanent transformer installation.

I will emphasize this again because it is a general principle that bears keeping in mind: the current situation is that you do not really know what the root cause of the problem is. Various things which have been suggested may avoid the problem, but you really need to get a more detailed understanding of the cause of the problem to fix or avoid the problem in the most cost effective way.

 

[abbey road d enfer]

The US way (back in the day with DC, it was around 100V, DC, but who knows why)

The explanation I was given was that arc lights operated at 50Vdc/55Vac and they were used in series. Maybe a myth, IDK.

balanced power. This is a very expensive way to do power, and in my humble opinion, is a waste of money. No piece of equipment is designed or really needs to have that kind of power source.

Mitigated by the fact that many pieces of gear are either switchble 115/230 or more and more universal 85-265V.
I agree with the fact that there is no real need for balanced (2 equal and opposite phases), since the possible effects (electrostatic field) are very easy to completely annihilate by shielding.

 

[radardoug]

It occurs to me that the original description did not describe the current wiring layout. Is the water pump located in the garage by any chance? Or running on a circuit near the garage circuit? Maybe all that is needed is a new separate feed from the main panel to the garage studio. That would be much cheaper than a permanent transformer installation.

I will emphasize this again because it is a general principle that bears keeping in mind: the current situation is that you do not really know what the root cause of the problem is. Various things which have been suggested may avoid the problem, but you really need to get a more detailed understanding of the cause of the problem to fix or avoid the problem in the most cost effective way.

What he said. Hire a smart electrician, and investigate your feed, and pinpoint the actual problem.