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Favor --- looking for electrical engineer/contractor who knows about transformers

Old 09-29-15, 02:41 PM
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Favor --- looking for electrical engineer/contractor who knows about transformers

Hi-

Mods, please accommodate me on this off subject post and don't delete for a few days.

I'm consulting on the construction of a small hospital, and am being asked power plant questions beyond my expertise. The current one relates to the substation and the transformers needed, wet vs. dry.

If anyone has expertise in the field and wants to help me, please PM or email me through the forum.

Thanks
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Old 09-29-15, 03:02 PM
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Can you hire a consultant and bill it back? If so I could recommend some people. On these kinds of things people don't like to stick their necks out too much.
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Old 09-29-15, 03:12 PM
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Originally Posted by FBinNY
Hi-

Mods, please accommodate me on this off subject post and don't delete for a few days.
s
Reported ........................... kidding

You could also post in Foo ... a broad range of people hang out there.
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Old 09-29-15, 03:14 PM
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Try the IBEW > Home
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Old 09-29-15, 05:08 PM
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Transformers - More than meets the eye.

Hope that helps...
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Old 09-29-15, 05:15 PM
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Originally Posted by rmfnla
Transformers - More than meets the eye.

Hope that helps...
Not really, but I'll have a coupla of beers and see if that helps.
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Old 09-29-15, 05:22 PM
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Originally Posted by FBinNY
Not really, but I'll have a coupla of beers and see if that helps.
Couldn't hurt...
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Old 09-29-15, 06:44 PM
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I thought they were all oil filled past a certain size. The tranformers we have in the lab get hot, I can't see air removing the heat properly
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Old 09-29-15, 07:19 PM
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Originally Posted by FBinNY
Hi-

Mods, please accommodate me on this off subject post and don't delete for a few days.

I'm consulting on the construction of a small hospital, and am being asked power plant questions beyond my expertise. The current one relates to the substation and the transformers needed, wet vs. dry.

If anyone has expertise in the field and wants to help me, please PM or email me through the forum.

Thanks
The utility specifies the size of the transformer based on the requirements of the site. Have you been in touch with the electric provider's design department?
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Old 09-29-15, 07:37 PM
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Your issue goes beyond your transformer question.

the NEC (national electric code) has a whole section on hospital requirements and there's a whole set of state regulations on top of that.

in California it's OSHPD. but every state will have it's own regulatory body.

Uou don't need the IBEW, you need a registered electrical engineer in your state with verifiable hospital regulation experience Just having a PE stamp isn't enough.

CA C-10 for 30+ years.

Last edited by TGT1; 09-29-15 at 07:48 PM.
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Old 09-29-15, 07:53 PM
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Guys, this is in Mexico where things are a bit different. Yes, there are regulations, which are similar to those in the USA though not identical. I'm not doing the basic engineering, that's the job of a local EE/contractor. But there is some room for discretion, and conforming transformers in the range we need come in both dry and wet versions. So it's a question of a choice, and which would be best and why.

I'm not directly involved with that phase of the project, but there's a certain level of distrust between the owners and the engineer who is also the contractor. I was asked to help the owner weigh the advice and better understand the why's and wherefores.

I already know that larger transformers bias toward wet, and smaller to dry, but we're mid-spectrum and can go either way. It's a cost/benefit issue, along with one of trust.

In a way it's like the bike issue where someone is buying a new bike and the dealer is pushing Campy, and he wants to know if a less costly Ultegra group would do the job.
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Last edited by FBinNY; 09-29-15 at 08:12 PM.
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Old 09-29-15, 08:22 PM
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so how much does it save to go dry? I live on a street where the transformers go bang every once in a while, and I'm pretty sure the transformers in a hospital are bigger than that. You want to avoid explosions if possible.
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Old 09-29-15, 08:27 PM
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under 600V, it's a no brainer, Dry

Over 4160V no brainer for oil filled

Oil filled pad mount outside the building, no brainer.

An oil filled transformer is basically a fire bomb waiting to go off so if it is inside the building it must be in a specially constructed fire proof room.

They are called "transformer vaults" for a reason.

If your engineer/contractor is pushing for oil filled in a one to one replacement for dry in a hospital without the required fireproof enclosures (concrete and rebar with fire doors and drains etc) that's approaching criminal behavior.

Last edited by TGT1; 09-29-15 at 08:36 PM.
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Old 09-29-15, 09:05 PM
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Originally Posted by TGT1
under 600V, it's a no brainer, Dry

Over 4160V no brainer for oil filled

Oil filled pad mount outside the building, no brainer.

An oil filled transformer is basically a fire bomb waiting to go off so if it is inside the building it must be in a specially constructed fire proof room.

They are called "transformer vaults" for a reason.

If your engineer/contractor is pushing for oil filled in a one to one replacement for dry in a hospital without the required fireproof enclosures (concrete and rebar with fire doors and drains etc) that's approaching criminal behavior.
Actually it's the opposite. All the transformers are outside away from the building, (except for one small one) but the engineer is pushing for all dry transformers, which is what's causing confusion. If he had proposed a mix or larger oil filled ones, then a shift to dry on the smaller ones it would have made more sense.

In any case, I think I have enough info to give the owners, who can now ask more pointed questions and get the answers that will (hopefully) make them more comfortable with the proposal.
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Old 09-30-15, 01:38 AM
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Really isn't much to add here.

Oil-filled units - with their better cooling - can be made smaller, which is "good". But might not be important for your particular application.

But since they need to be kept filled, more engineering has to go into their casings - which is "bad".

The oil in itself can be quite nasty to deal with - which is bad.
Although the oldest guys at my first job always kept some that they used as hand lotion...

And they need to be checked, topped up, have desiccants refreshed etc. etc. which is "bad".

And - depending on local laws - might need their foundations doubling as catch basins in case of an oil leak.
Looking at installation cost, definitely a "bad".

Dry gives you bigger units, less maintenance, no special foundation requirements.

For an equal level of engineering (margins), both should work fine.

Best as I recall, wet units CAN be rated for "indefinite" life.
Meaning there's no functionally important ageing going on as long as they are properly maintained and left within their stated operating range. Dry units MAY have a defined life due to degradation of the insulation. Meaning eventual replacement is unavoidable regardless what.
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Old 09-30-15, 09:16 AM
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Originally Posted by dabac
Really isn't much to add here.










Dry gives you bigger units, less maintenance, no special foundation requirements.



Best as I recall, wet units CAN be rated for "indefinite" life.
Meaning there's no functionally important ageing going on as long as they are properly maintained and left within their stated operating range. Dry units MAY have a defined life due to degradation of the insulation. Meaning eventual replacement is unavoidable regardless what.

Oil has a longer lifespan but will need to be replaced eventually. Do you have to deal with accreditation inspections or approvals like we do here?
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Old 09-30-15, 10:26 AM
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B
Originally Posted by Rubato
Oil has a longer lifespan but will need to be replaced eventually. Do you have to deal with accreditation inspections or approvals like we do here?
We Megged them and drew oil samples yearly. As long as that was OK compared to the manufacturer's plate, they were considered OK for another year. 40+ years and counting. Probably they'd end up replaced eventually out of sheer embarrassent, even if the engineering still held up.
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Old 09-30-15, 12:31 PM
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Does that mean Chain-L filled? (sorry could not resist)
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Old 09-30-15, 12:35 PM
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Originally Posted by squirtdad
Does that mean Chain-L filled? (sorry could not resist)
Dammit, now the whole world knows what's in Chain-L.
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Old 09-30-15, 04:16 PM
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I've purchased both wet and dry transformers installed in Mexico. Do yourself a favor: hire a proven specialist to provide answers you can sleep on. If you don't like them, hire a different one. You can't get what you don't pay for.
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Old 10-03-15, 06:16 PM
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HI -Do you still need help with this? I know someone who spent his life in this industry.
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Old 10-03-15, 06:52 PM
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Chain-L is "transforming" the world of chain lube.....
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