To flex or not to flex my transformer?

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I have heard transformers that are so quiet, I wondered if they were even enegized, and some so loud I wonder what the cause of the noise is.

In regards to common sense, there is plenty to go around...how one terminates raceways to a transformer has to do with more than just the very minimal vibration most transformers produce.

Some large transformers may be better terminated with a trough making it easier for the installer to enter the conductors into the transformer enclosure. Limited space can also be a factor. Just because one doe not install to the same method that others may be used to does not make it wrong.

It mostly has to do with personal preference, as has been mentioned, it is not a code violation to not use a flexible means to terminate to a transformer.
 
I always try to enter the xformer from the slab underneath if possible it saves lots of time. When I have to come in exposed I always flex to separate mechanical vibration as I was taught . Dont have a code article though. I would check xformer mfgs install instructions at this point.
 
ange said:
There doesn't always need to be a code when common or should I call it rare sense is concerned. I call it rare sense because it's so uncommon to have common sense.There is a code that covers all basic installations.Remember Workman like manner. article 110 ring any bells. Come on, do we all really need a step by step code book for every move we make. Remember electrical is 80% mechanical.
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There is rarely any need for flex, I have wired many with EMT, trough or PVC from below.

All them where neat and workmanlike.:smile:
 
While I would see a simular application with a motor, and the use of flex for vibration - I don't think it is even required there???

That said, I use flex myself on transformers often. But mostly when hung from a cieling on rod to save space. I once had an inspector call for it, as the possibilty of siezmic movement might break or deform conduit. And a few weeks later I had to go repair one that used EMT after a quake, the one I did was still fine, and I have sort of stuck with that since.... Otherwise, I have fed them all kinds of ways if mounted on the floor.
 
e57 said:
While I would see a simular application with a motor, and the use of flex for vibration - I don't think it is even required there???

That said, I use flex myself on transformers often. But mostly when hung from a cieling on rod to save space. I once had an inspector call for it, as the possibilty of siezmic movement might break or deform conduit. And a few weeks later I had to go repair one that used EMT after a quake, the one I did was still fine, and I have sort of stuck with that since.... Otherwise, I have fed them all kinds of ways if mounted on the floor.
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In San Fran are you required to provide a structural calc if the
transformer weights 400lbs or more like we have to in San Diego?
I'm talking about if you mount it on a wall,rod,or piggy back
another transformer using a rack. Not only do I follow
450.13 (B) but we also have to take the weight into account
for siezmic reasons.
 
Karl H said:
In San Fran are you required to provide a structural calc if the
transformer weights 400lbs or more like we have to in San Diego?
I'm talking about if you mount it on a wall,rod,or piggy back
another transformer using a rack. Not only do I follow
450.13 (B) but we also have to take the weight into account
for siezmic reasons.
Click to expand...
Depending on the Inspector they may want to see mounting details - drawn by someone with a stamp for structural if in wood framing or post installed supports in concrete. But if say you precast supports - or if they look at it and it seems good enough to them - i.e. ROBUST they often don't bat an eye. And few will even think of movement, unless it is wholey obvious that it will - say non-supported lateraly. Truthfully the siemic codes have always eluded me - and I have probhably been way over doing it for many years. (locking both sides or ways - taking it to a strut 'ledger' on the wall - and I always over do support values) Larger rod or bolts are cheap IMO - in many cases where even 1/4" rod would due, I'll use 3/8", if not 1/2" - you could park a truck on 4-1/2" rods..... As for venting NMJDI - but have been in some hot rooms. That said - I have only been busted (by an Engineer) for a floor standing UPS unit - that was obviously deflecting the floor.
 
We often use flex as it is easier than running rigid. And I find that flex is misused, and most often not supported per the Code.
But some transformers have rubber isolation mounts for sound, and for that flex should be used.
Small wall hung transformers I will pipe or use flex.
 
When flexing I always try to avoid using 90* connectors as they waste time tremendously. Try to plan ahead and use straight conns as much as possible.
 
On the Issue of VIBRATION and Transformer: Many of today's transformers have Rubber Isolators for Vibration inside thier enclosure. This allows the elmination of the old practice of placing corogated board or rubber underneathe the transfomers feet. Now technically most new transfomers have this Rubber Isolators inside, but I have been on jobs where an inspector comes out and does not care what paper work you show him, they are used to the Rubber Isolators underneath the feet and it will imdedietky send off a red flag and they will ask for it and pick your installation apart.
Also the new transformers usally have a sticker inside or in the paper it will state the the installer after installing the tranfomer should back a quarter turn or more off the bolts going through the rubber isolators . The reason the manufactor ask for this is because when they ship the transformer the tighen the bolts for the rubber isolators all the way down to prevent vibration damage in shippment. BUT ONLY back off the bolts if it is posted. If not install it old-school.

Now after that long explantion about old vs new transformers, I think the above is the reason why people are confused about Flexing into a transformer. On the old ones with the rubber isolators on the bottom you have to flex. On the new ones with the rubber isolators inside, you can hard pipe. But beware many an inspector will look for that Flex and ask for it.

Yesterday I installed a 225 KVA transformer and we hard piped out of the Secondary and primary side . We also did not put rubber isolators underneath. This transformer has the isolators inside. The inspector comes Friday so we will see what happens. Also side note my parallel feeds came out great.
 
I do not know what code requires that . I will note I work in San Franciso and 80% of all transformers I come across have a corgated board with rubber on both sides below the feet of the transformer. ( I do not know the technical name for the coragated board put underneath) Also I would say 95% of these transfomers have flex coming into them.

On the issue of backing of the bolts for the newer transfomer. The last 2 transfomers I have installed it has been on the manufactors directions and thier was a sticker inside to remind you.

I was reading this thread because I know thier is commone practices in the field that, are really just that " practices" . I was just adding what info I have and if someone knows the code then by all means let me know. I mean why build the customer a Cadiallac if they are paying pinto prices.
 
Not big deal, it is just that we are a code forum and we try to dispel code myths.

Now I agree that a transformer with external vibration dampers should be flexed in but I do not know of any requirement to do so. :smile:
 
Pierre C Belarge said:
I am curious...how much vibration are these transformers actually producing?
Over a period of time, stand next to a few of these transformers and place your hand on the enclosure. Feel how much they are actually vibrating.
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Or get yourself on of these handy dandy transformer vibration testers:smile:

I use mine all the time ,.. the last chime transformer I installed was making so much noise,.. I just had to find out how much that baby was shaking:D




TC-55 TRANSFORMER VIBRATION TESTER
tc-55.jpg



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Edit to add you might find this interesting
PPT]
Transformer Vibration Analysis

 
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