does this brilliant idea of mine violate any code sections or UL listing?

[Fulthrotl]

i posted a thread here a few days ago, about a VERY noisy
300 kva xfmr, actually several of them...... nema 1's,
in electrical rooms.

now, this sunday, i'm downing them for PM, megger,
torquing, vibration pad inspection, etc.

assuming there is nothing mechanically or electrically
wrong with these xfmr's, and the noise is just lamination's
fluttering, and that is not something that is solvable without
replacing the xfmr's.... here is my idea....

there is a product called mass loaded vinyl, that is a nonconductive
rubber sheet weighing about 1 lb per sq. ft. it comes with a 1/4"
foam backing, and you attach it to a surface by the foam, so the
vinyl is floating 1/4" above the surface, and not mechanically coupled
to it except by the foam.....

cover the exterior of the transformer case with this, leaving all air
vents, slots, and whatnot uncovered, so that the sheet metal case
and front and back covers are covered with this product, to dampen
sound.....

this stuff has a greater sound isolation than lead sheets of the same
thickness, and is nonconductive, and i'm wondering if, as it is outside
of the enclosure, it would compromise the UL listing of the xfmr?

you still will have airborne sound coming out the vents, but i'm guessing
a huge amount of it would be dampened....

whatchoo guys think?

the stuff is NOT cheap, but it sure does work.... i used it in a sound
studio, and it rocks. nothing much goes thru it.

 

[Cow]

Good question, assuming you leave all the vent holes open and don't cover the data plate, I don't see why not?

I'd wonder how much it'll actually help though, since you're not entirely encapsulating the x-former? If you end up doing it, I'd be curious to hear the results. Technically, not hear, but be told the results.

 

[cowboyjwc]

I've had the same issue with larger transformers, that once you got into the room you could hardly hear, but also the transformer was so hot you couldn't touch it. So I was just wondering if the foam may react to the temperature or if wrapping it like that would cause a temperature rise?

 

[Ponchik]

I guess it goes on the outside and it doesn't interfere with the operation you should be OK. And also what cowboy said about the heat.

what is this stuff anyway?

 

[maghazadeh]

I've had the same issue with larger transformers, that once you got into the room you could hardly hear, but also the transformer was so hot you couldn't touch it. So I was just wondering if the foam may react to the temperature or if wrapping it like that would cause a temperature rise?

I agree with Cowboy, I too will be wondering the effect on the temperature since wrapping it the way you said might not allow enclosure to dissipate heat as is design to do. If this was a good idea, IMO manufacturers would use it.
How about the fire rating of the material mentioned?

 

[ritelec]

there is a product called mass loaded vinyl, that is a nonconductive
rubber sheet weighing about 1 lb per sq. ft. it comes with a 1/4"
foam backing, and you attach it to a surface by the foam, so the
vinyl is floating 1/4" above the surface, and not mechanically coupled
to it except by the foam.....

cover the exterior of the transformer case with this, leaving all air
vents, slots, and whatnot uncovered, so that the sheet metal case
and front and back covers are covered with this product, to dampen
sound.....

this stuff has a greater sound isolation than lead sheets of the same
thickness, and is nonconductive, and i'm wondering if, as it is outside
of the enclosure, it would compromise the UL listing of the xfmr?

you still will have airborne sound coming out the vents, but i'm guessing
a huge amount of it would be dampened....

whatchoo guys think?

the stuff is NOT cheap, but it sure does work.... i used it in a sound
studio, and it rocks. nothing much goes thru it.

I'm not an acoustician.......but I believe that stuff is used together with a combination of other items (types of insulation) which create mass and a air. Double leaf systems.
You can kill certain frequencies ...................the lower the frequency the harder to attach.

As your first thought...........you probably want to stop whats creating it. If you can't, you would address the waves in the room. I doubt rapping it will help as certain frequencies will pass right through. It's some amazing stuff....sound.

Mass and air. A 40 or 50hz sound wave takes about 20' to develop. As mentioned.......if that's what your dealing with, it would go right thru it.

Very interesting stuff.

I might suggest visiting here:
Studio/Building and Acoustics.

Post this topic like you did here,

http://www.gearslutz.com/board/studio-building-acoustics/

There are some guru's there that may be able to help you out..........or at least suggest not to use the mass loaded vinyl as it may not do anything and just be a waste of money.


Some great isolators here too..........but may not help with your problem.

http://www.sorbothane.com/

 

[ritelec]

Just one more thought.

If it is the lamination.......I'm wondering if re-laminating in the field is possible...?

 

[ritelec]

And... I just wanted to post one more time............to answer the Topic Header as probably being a yes.
And to subscribe to this thread via e-mail as I'm very interested and curious to see how it works out.

All the best.

Rich

 

[jim dungar]

Just one more thought.

If it is the lamination.......I'm wondering if re-laminating in the field is possible...?

Transformer laminations are the thin plates of steel used to make up the core of the transformer. If these are rusted, they cannot not normally be fleld repaired, however the bolts clamping them together might be able to be tightened.

 

[Fulthrotl]

Transformer laminations are the thin plates of steel used to make up the core of the transformer. If these are rusted, they cannot not normally be fleld repaired, however the bolts clamping them together might be able to be tightened.

most everything i've seen lately is riveted cores, not field tightenable, and the killer is if they stamp the e's and i's and they aren't flat,
when they reverse them back and forth, building the stack, there are air gaps formed, and the leaves flutter against each other. they
dip the whole thing in electrical varnish or epoxy to insulate and minimize the flutter, and keep moisture out of the stack, cause it's
bare iron, and will rust something terrible if moisture gets into the stack, and the plates will double in thickness, breaking the straps,
rivets, bolts, or anything else.

these things are pretty warm on top, but if they had weatherproof covers for the vents, they could be outside in september in 110 degree direct sun
under full load, without an issue, so i'm thinking it wouldn't be a problem, as the electric room is air conditioned, and not warm, altho the top of the
transformer is toasty.

what seems to be the case is that the tin box is acting like a diaphragm, radiating sound off it's surface..... the core is doing the humming,
just like the core of a subwoofer is doing the pushing, but it's the speaker cone that is making the sound, pushiing air.

that core forms a chimney inside the enclosure, drawing air in the bottom perforations, and flowing out the front and back
vents on the sides... you can feel the heat radiating out and the air movement, and the air changes are what keep the core
from overheating.

i'll know more after sunday... i'll post how it turns out. i'm thinking 3m high tack adhesive sprayed lightly on the foam and then
stuck to the surfaces... i was thinking of an equivalent of dynamat, but the mass loaded vinyl has better acoustic damping.

thanks for your feedback, everyone.

 

[hurk27]

I worked at a 16 plex theater that had many problems via the original installers, I posted about some things a few years ago with the GFP's tripping on the 120/208 system, the 750kva transformer that fed this 2ka MDP also was a problem especially in a theater, it was mounted on the flex core second story floor and sent 60hz sound through half the theater, the engineers came up with a fix of removing the transformer and after some strengthening of the floor from below had a 5' x 5' x 3' thick pad of some kind of acoustic concrete to absorb the low frequency sound from reverberating the floor, they claimed that it was the floor that was acting as a sound board, other methods were discussed but all was rejected after testing showed that the flex core floor was transmitting the 60hz through out the complex.

I also agree with the others and would run this idea by the manufacture before attempting as the engineered rate of removing the heat most likely included the metal cabinet for which the manufacture sized the air openings to, by insulating the cabinet you might cause a higher operating temp for the transformer for the given load which may or may not exceed its rating? other wise you could be buying a transformer in the near future to replace it if is fails.

 

[Joethemechanic]

Transformer laminations are coated with a nonconductive material on the face to reduce eddy currents in the lamination pack. Wouldn't excessive (noise/vibration/relative motion) between each individual lamination plate be an indication of a breakdown of this coating?

If so, how long before the laminations short together causing increased eddy currents and heat?


If you have ever scrapped large amounts of laminations, you will know that they sell as P&G material for bailing and frag.

If they were not coated, I would have been able to sell them as #1 light. And believe me, there is a big price difference (especially when you are dealing in trailer load quantities)

 

[iwire]

If I was an inspector looking at this I would cite a clearance issue with the rubber sheeting but give you the option of providing a letter from the transformer maker that this was ok.

 

[ritelec]

i'll know more after sunday... i'll post how it turns out. i'm thinking 3m high tack adhesive sprayed lightly on the foam and then
stuck to the surfaces... i was thinking of an equivalent of dynamat, but the mass loaded vinyl has better acoustic damping.

That entrapping heat thing and what temperature the vinyl may be rated for (which it probably isn't for this application).............. I would think twice before over extending myself (liability).

You haven't much time since Sundays 2 days away. But if you know a guitar player....... get him to go in there and find the note (and harmonics) that the x-former is creating. Wrap the vinyl
around his amp and see if it does anything.

But again..........even if it did, I would have second thoughts about it.

1) It worked, they love you at the facility, no problems..life moves on.
2) It doesn't work, well you tried, no problems life moves on.
3) It worked or didn't work, there was a problem, they don't love you anymore and want to talk to your lawyer.

Is it worth trying this "experiment"???

 

[ritelec]

Besides absorption you may also consider deflection.... just a thought.

Please realize many people waste alot of money in acoustic treatment if there not doing it right.

There's a gentleman at the forum link who's signature reads,
"Good studio building is 90% design and 10% construction"


Being in construction, I think it may be more than 10% but......it's a great point, and something to consider.

Also, if this interests you................and you've got a pc and a mic..............you can take some measurements to see what your dealing with.

http://www.hometheatershack.com/roomeq/
It's free. It can also be used with a mac for your needs.


on a mac?

http://supermegaultragroovy.com/products/FuzzMeasure/

It's not free, but you get a two free week trial.

 

[Joethemechanic]

What if you spot weld (or bolt) a couple of pieces of small angle across the large flat areas of the enclosure for stiffeners? That's got to shut it up some if it's the tin that's vibrating. It won't hurt the cooling at all. In fact it will slightly increase the surface area so it will cool better.

Lots of times when I have a cover bent up for something that has large flat areas, I get the guy to strike a couple of stiffening ribs in it with a brake. Although, with the cover already bent, it's a little late to have it hit in a brake without warping the hey out of it.

Spot welded angle works just as nice, it just doesn't look as professional.

 

[iwire]

What if you spot weld (or bolt) a couple of pieces of small angle across the large flat areas of the enclosure for stiffeners? That's got to shut it up some if it's the tin that's vibrating. It won't hurt the cooling at all. In fact it will slightly increase the surface area so it will cool better.

Is that in the listing or labeling?

110.3 Examination, Identification, Installation, and Use
of Equipment.

(B) Installation and Use. Listed or labeled equipment
shall be installed and used in accordance with any instructions
included in the listing or labeling.

Now have some fun, call me a code Nazi, but if you are planning on inspections you better know the code sections the inspector could come up with.

 

[renosteinke]

Maybe the problem isn't the 'transformers' at all. Let me use an example ...

Once I installed six "A" rated fluorescent lights in a kitchen, switched in groups of three. Turn either set on, and all was quiet. Turn them all on, and you were suddenly feeling like you were inside a beehive. Digging further into this puzzle, if I disconnected any one of the lights, the sound went away.

Now, you mentioned 'several' transformers. I suspect that the very minor sounds made by each transformer are reinforcing each other, resulting in your noise. In effect, acoustical harmonics are letting the room itself act as an amplifier. So ... what to do? I would start by trying to alter the acoustics of the room itself. You can do this on a 'temporary' or experimental basis by simply hanging a carpet on a wall, and a piece of plywood from the ceiling (in a manner that has it NOT parallel to any one wall). See if that breaks up that harmonic.

Acoustical problems are greatly increased when everything is reflective (hard), uniform in material, and square. The nice rectangular sheetrock 'electrical rooms' we make are acoustical nightmares. You've made a big speaker cabinet. Sound reflecting off one wall reinforces reflections off the neighboring walls. This is the dynamic you need to change.

 

[Fulthrotl]

Maybe the problem isn't the 'transformers' at all. Let me use an example ...

Once I installed six "A" rated fluorescent lights in a kitchen, switched in groups of three. Turn either set on, and all was quiet. Turn them all on, and you were suddenly feeling like you were inside a beehive. Digging further into this puzzle, if I disconnected any one of the lights, the sound went away.

Now, you mentioned 'several' transformers. I suspect that the very minor sounds made by each transformer are reinforcing each other, resulting in your noise. In effect, acoustical harmonics are letting the room itself act as an amplifier. So ... what to do? I would start by trying to alter the acoustics of the room itself. You can do this on a 'temporary' or experimental basis by simply hanging a carpet on a wall, and a piece of plywood from the ceiling (in a manner that has it NOT parallel to any one wall). See if that breaks up that harmonic.

Acoustical problems are greatly increased when everything is reflective (hard), uniform in material, and square. The nice rectangular sheetrock 'electrical rooms' we make are acoustical nightmares. You've made a big speaker cabinet. Sound reflecting off one wall reinforces reflections off the neighboring walls. This is the dynamic you need to change.

i should have clarified this... sorry. i have several transformers, spread across two utility providers, 4 facilities, and three customers.
none of them are in the same room.

i was also thinking.... sometimes this can be a dangerous process for me, but i still persist in it......

to keep the sheet metal from resonating, it's necessary to dampen it, not cover it completely.
dynamat, and a couple other companies make soundproofing that comes in sheets about
1' x 2'. placing a sheet in the center of each panel of the enclosure would dampen the panel
significantly, without wrapping the whole thing in a heat trapping blanket.

downside is, it doesn't come off once applied. anyone who has ever worked with it can vouch for
that. my work van is completely wrapped in it, and it seriously dampens down radiated sound thru
sheet metal.

well, first and foremost is to make sure the things are safe with a meggar, and nothing is loose
mechanically.

i'll post what i find, and toss in some photos.... thanks again for the thoughts.

 

[qcroanoke]

if you are planning on inspections you better know the code sections the inspector could come up with.

So that's why I think that way!
It's Iwire's fault!!! )