# Suspended transformers



## madtrapper21 (Nov 14, 2014)

My question is regarding hanging transformers. I understand that many transformers come with brackets for mounting on the block walls. If the transformer is being suspended from an I beam, who should be responsible for designing the supports. I believe it should be a structural engineer especially if it is significant weight. What are your thoughts? I think electrical inspectors would deal with this situation often and I'm curious if they have some guidelines they go by? 

Thanks for your time.


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## ponyboy (Nov 18, 2012)

If it's an engineered job I'd let the engineers determine how to support it. It makes them feel warm and fuzzy. If it's a design build job the EC can handle it. I've hung 500 kva transformers with 5/8 rod and angle iron plenty of times.


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## Big John (May 23, 2010)

If you're unsure, look up the load limits for the supporting hardware in the manufacturer's specifications. B-Line has a whole book on what stresses equipment can be put under in specific configurations, but if you're simply hanging straight down from a ceiling that's a dead simple design. Give yourself a 4X safety factor and go for it.

The only information you might need for really heavy transformers is how the roof will tolerate the point-loading, especially if these are trusses, and you might involve an engineer for that.


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## wcord (Jan 23, 2011)

If they are wood trusses, I will go up to 30 kva.
Steel trusses, max 45 kva (600 lbs)
Over those weights, an engineer has to give us a design.
As for supporting on a block wall, I won't go over 300 lbs, without support to the trusses or floor above.


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## ponyboy (Nov 18, 2012)

wcord said:


> If they are wood trusses, I will go up to 30 kva.
> Steel trusses, max 45 kva (600 lbs)
> Over those weights, an engineer has to give us a design.
> As for supporting on a block wall, I won't go over 300 lbs, without support to the trusses or floor above.



600 pounds?!? Cut that in half maybe


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## jza (Oct 31, 2009)

I've hung plenty, 75kVA and below. Not a big deal.


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## wcord (Jan 23, 2011)

ponyboy said:


> 600 pounds?!? Cut that in half maybe


There was an earlier post on the placement of loads on joists.
http://www.electriciantalk.com/f2/suspending-transformer-72655/?highlight=joists
We've hung 45kva many times, and haven't had any concerns from the inspectors.
That being said, the inspectors are all over the plumbers when it comes to hanging hot water tanks


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## rookie sparky (Nov 6, 2014)

ponyboy said:


> If it's an engineered job I'd let the engineers determine how to support it. It makes them feel warm and fuzzy. If it's a design build job the EC can handle it. I've hung 500 kva transformers with 5/8 rod and angle iron plenty of times.


Never in my life have i seen a suspended 500. We changed a750 padmount last year that had a crane teeter tottering. You're not hanging that from a 5\8 rod.... no, no, no


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## adamv7010 (Mar 21, 2011)

rookie sparky said:


> Never in my life have i seen a suspended 500. We changed a750 padmount last year that had a crane teeter tottering. You're not hanging that from a 5\8 rod.... no, no, no


My thoughts as well...a 500 should be somewhere in the neighborhood of 7500 lbs.


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## ponyboy (Nov 18, 2012)

adamv7010 said:


> My thoughts as well...a 500 should be somewhere in the neighborhood of 7500 lbs.



Dude where are you guys getting your info. A general purpose 500 kva dry type transformer weighs no more than 2500 pounds. Not nearly the static load you are imagining.


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## Big John (May 23, 2010)

Sounds like the difference between dry and oil filled. The same size oil transformer can run definitely run well into 3-4 tons. But nobody hangs an oil filled 750kVA, either.


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## adamv7010 (Mar 21, 2011)

ponyboy said:


> Dude where are you guys getting your info. A general purpose 500 kva dry type transformer weighs no more than 2500 pounds. Not nearly the static load you are imagining.


Yep. You're right. I was thinking oil filled for whatever reason.


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## McClary’s Electrical (Feb 21, 2009)

I actually was thinking oilfiled, however, I've still never seen a500 suspended. Entire Walmart distributing centers run of of (2) suspended 75 kva . Why would you ever need to suspend such a beast? If it's industrial, I'm sure there's a place to set it on the floor?


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## McClary’s Electrical (Feb 21, 2009)

ponyboy said:


> Dude where are you guys getting your info. A general purpose 500 kva dry type transformer weighs no more than 2500 pounds. Not nearly the static load you are imagining.


5/8 threaded rod tensile strength is only around 1250 lbs. Why would you need to suspend such a transformer?


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## ponyboy (Nov 18, 2012)

mcclary's electrical said:


> 5/8 threaded rod tensile strength is only around 1250 lbs. Why would you need to suspend such a transformer?



I've actually only done it three. Once was along a wall lined with cnc machines, another was suspended between 2 laser cutting machines and another was in a bay where they service forestry equipment. The places I've worked have always been big on keeping transformers off the floor because śhit spills and people tend to run into stuff


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## adamv7010 (Mar 21, 2011)

ponyboy said:


> I've actually only done it three. Once was along a wall lined with cnc machines, another was suspended between 2 laser cutting machines and another was in a bay where they service forestry equipment. The places I've worked have always been big on keeping transformers off the floor because śhit spills and people tend to run into stuff


Forklifts at 12 mph and transformers don't mix. Most places I've been in prefer them on the wall on brackets.


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## ponyboy (Nov 18, 2012)

adamv7010 said:


> Forklifts at 12 mph and transformers don't mix. Most places I've been in prefer them on the wall on brackets.



Yup. This is a typical transformer setup for me


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## McClary’s Electrical (Feb 21, 2009)

ponyboy said:


> Yup. This is a typical transformer setup for me
> View attachment 39858


Yeah that's a 50 kva. Please show pics of a suspended 500. Please


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## ponyboy (Nov 18, 2012)

mcclary's electrical said:


> Yeah that's a 50 kva. Please show pics of a suspended 500. Please



No that's a 75. And why do you have such a hard on for what I do at work little man?


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## McClary’s Electrical (Feb 21, 2009)

ponyboy said:


> No that's a 75. And why do you have such a hard on for what I do at work little man?


Nothing personal at all. I just wanna see a 500 hung from 5/8 rod. In really curious.


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## madtrapper21 (Nov 14, 2014)

Thanks for the replies guys. Ponyboy, do you have any pictures of suspensed transformers you've done that aren't mounted on walls. Also when you hang transformers that are over 75kva and above, does the inspector asked to see a engineered drawing for the supports?


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## madtrapper21 (Nov 14, 2014)

Thanks for the replies. Ponyboy, do you have any pictures of the bigger transformers you've hung that aren't wall mounted. Do the inspectors asked to see engineered drawings for supporting the 1000 lbs transformers


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## ponyboy (Nov 18, 2012)

mcclary's electrical said:


> Nothing personal at all. I just wanna see a 500 hung from 5/8 rod. In really curious.



It could've been 7/8 but i remember it as 5/8. I can get a picture of one for sure but not the others. Next time I'm in that building I'll get it for you


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## madtrapper21 (Nov 14, 2014)

Thanks man


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## ponyboy (Nov 18, 2012)

madtrapper21 said:


> Thanks for the replies. Ponyboy, do you have any pictures of the bigger transformers you've hung that aren't wall mounted. Do the inspectors asked to see engineered drawings for supporting the 1000 lbs transformers



No pictures on my phone. And as far as inspectors they don't come in our facilities unless it's for a new service. I don't really think it's the electrical inspectors place to judge it unless they have the technical knowledge to determine if it's adequate or not.


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## adamv7010 (Mar 21, 2011)

ponyboy said:


> No pictures on my phone. And as far as inspectors they don't come in our facilities unless it's for a new service. I don't really think it's the electrical inspectors place to judge it unless they have the technical knowledge to determine if it's adequate or not.


Here, they usually don't have the knowledge, but they do have the authority. Lol


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## ponyboy (Nov 18, 2012)

mcclary's electrical said:


> Nothing personal at all. I just wanna see a 500 hung from 5/8 rod. In really curious.



Mcclary I was thinking about and you're right. They were 300 kva that I hung not 500. I remembered the secondary was 800 amps and realized I was wrong. I don't think I've ever even done a 500.


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## McClary’s Electrical (Feb 21, 2009)

ponyboy said:


> Mcclary I was thinking about and you're right. They were 300 kva that I hung not 500. I remembered the secondary was 800 amps and realized I was wrong. I don't think I've ever even done a 500.


Again, nothing personal, I was only curious. Luv ya dude.


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## ponyboy (Nov 18, 2012)

mcclary's electrical said:


> Again, nothing personal, I was only curious. Luv ya dude.



Sorry for yelling. And fwiw I'm pretty sure lowes hangs 300s, or at least they look like it to me


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## KGN742003 (Apr 23, 2012)

ponyboy said:


> Mcclary I was thinking about and you're right. They were 300 kva that I hung not 500. I remembered the secondary was 800 amps and realized I was wrong. I don't think I've ever even done a 500.


Just did a 300 kva and it was close to 2000 lbs, we put it on a mezzanine but I was still a little nervous. Cant imagine hanging it. Biggest one I hung with a contraption I made myself was 75.


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## Bootss (Dec 30, 2011)

In a past life I rewound motors and transformers and they get real heavy real fast.


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