Outdoor 2000KVA dry-type transformer install 7

[hugo.c]

Hoping someone can help point me to a standard that I can reference regarding the installation of an outdoor MV transformer that has its underside open to the elements. I have a gut feeling that these transformers should not be energized as installed.

I have looked up the manual for this Federal Pacific 2000kVA transformer (IN7750) and NFPA-70E paragraph 450 but does not explicitly state not to install the transformer with the transformer core exposed from underneath. NETA-ATS also does not provide any insight.

I do not have access to IEEE C57.93-2019 for additional reference.

The best reference I have found thus far that validates my concerns is the following: "The transformer enclosure is designed to prevent the entrance of most small animals and foreign objects. In some locations, however, you may have to consider additional protection. Transformers installed in public areas must be constructed to be impenetrable to foreign objects or the units must be protected by a fence in a manner that would prevent accessibility by the public and animals." source:

https://www.ecmweb.com/content/article/20890017/gu...

I don't want to simply "recommend" to the customer that transformer's base needs to be redone and/or filled-in. I want to be able to present something in black-and-white to ensure they will do the right thing and fill in under the transformer.

 

[cranky108]

I was asked to write a spec for a dry type outdoor transformer years ago, and they do exist. The issue was for a specific customer that did not want oil transformer (local government).
I don't remember the brand we went with. I recall looking at ABB, and several others.
I do remember also purchasing an Acme transformer as a backup (much cheaper, and did not completely meet the spec.).

 

[dpc]

This is an outdoor enclosure, so that's not a code issue, but I've never seen one that wasn't sitting on a concrete slab. I'd be mostly concerned about vegetation growing up into the windings. I'd consult with the manufacturer and review their installation requirements. It seems like a bad idea.

I'm not a fan of conventional dry-type transformers located outdoors.

 

[waross]

If the plans for those bases are stamped, the engineer may be subject to sanction for stamping an installation outside of his area of expertise.
I would not suggest but rather I would demand that a proper base be installed.
I would refuse to accept responsibility for a transformer designed to be mounted on a floor that was instead mounted with the underside exposed.

The transformer enclosure is designed to prevent the entrance of most small animals and foreign objects. In some locations, however, you may have to consider additional protection.

It is obvious by this statement that the transformer must be mounted on a flat floor.

Or suggest a warning sign:
Warning Access by Insects, Rodents or Other Creatures is Strictly Prohibited.
Intrusion by Vegetation is Prohibited.
In the Event That This Transformer is damaged by Insects, Rodents, Other Creatures or Vegetation,
Such Insects, Rodents, Other Creatures or Vegetation Will be Held Legally Accountable and Will be Subject to a Lawsuit to Recover the Cost of Repairs and Lost Revenue.

Is the sign ridiculous?
No more so than that installation.

It's sometimes hard to legislate common sense.
ps: You have my permission to share this post with the owner.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Heaviside1925]

OP,
From Federal Pacific:

Category C enclosures are intended to provide a degree of protection against contact with enclosed equipment in secured installations intended to be accessible only to authorized persons.
(Category C will only be constructed after factory consultation
and required signed waviers)

It appears from the pictures, this is not a secured area. I would feel the customer would need to be made aware of what they purchased, and the implications of the waivers signed. In the end, I would recommend you have Federal Pacific tell your customer what level of protection they need to supply to ensure against crispy critters.

 

[hugo.c]

cranky108/dpc/waross/Heaviside1925,

Huge hanks for your input. I'm thinking we're all in agreement.

I have actually tried to call Federal Pacific several times with the phone number provided on their website to no avail. I have reached out via their website as well. Hopefully they come back with something more concrete.

@waross, regarding drawings, it does show a "structural slab" under the transformer. We will see. They have city electrical inspection this week. Hopefully that inspector says something.

 

[jghrist]

I have seen several oil-dilled power transformers installed in substations on railroad ties. I don't think that this is common anymore. The OP referenced "with the transformer core exposed from underneath". Is there no bottom? As long as the transformer has steel beams underneath for adequate support and a bottom, I don't see a major problem.

 

[Compositepro]

The transformer requires good airflow through the casing for cooling, so the bottom cannot be entirely closed.

 

[hugo.c]

jghrist, there is no bottom. You can see up towards the transformer core from underneath. Plenty of room for rodents even children to climb up into.

Compositepro, I would think the airflow would be plentiful with the NEMA 3R enclosure alone.

 

[waross]

I have seen several oil-dilled power transformers installed in substations on railroad ties.

In support of this statement and in explanation:
Oil filled transformers must have an enclosed bottom.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Heaviside1925]

OP,
Just a note on getting ahold of the correct person at Federal Pacific. The "1-800" numbers are notorious for getting to the wrong people provided you can even get out of the automated loop. A method I have has success with is looking up employees on LinkedIn. Normally you can review peoples title and basic work background as well as what division / department. Many times, the profile will have a direct email and sometimes an extension or phone number and if not, google helps too. Another method, if you can't find the person specific to your issue just blanket email some sales managers, they seem to jump on issues very quickly.

 

[edison123]

Fix a SS mesh under the opening to keep away the critters.

Muthu

http://www.edison.co.in

 

[cranky108]

Many electrical inspectors may not be up to date on special items like transformers, as these would typically be in the area of utilities. That said, utilities are typically outside of the requirements of most electrical standards which might follow the NEC. Utilities are under a different set of standards called the NESC.

 

[stevenal]

C57.93 is for oil-filled, you want C57.94. The standard speaks of weather resistant enclosures, protection from traffic, and drainage. If accessible to the public, the NESC is referenced. Prevention of rain, sleet, and snow entry are addressed, but no there are no references to weeds, animals, or insects.

But why dry when there are liquids available that are biodegradable and not very flammable?

 

[waross]

Many electrical inspectors may not be up to date on special items like transformers,

I have to throw the flag at this one.
I have installed and worked on hundreds of dry type transformers over the years that were user owned and subject to inspection by the AHJ.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[waross]

I did the planning and estimate for a sawmill. (Unfortunately the economy crashed and the mill was never built).
Primary metering, the mill would own the main transformer.
Secondary metering the utility would own the transformer.
The electrical code demand sizing worked out to 1 KVA per HP installed.
The utility sizing was 0.5 KVA per installed HP.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!