45 kva transformer gec

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kjless

Member
Location
plaistow nh
I'm in a parking garage that is all precast no steel in the entire building my transformer is in the main elec em for my gec I was going to bring it in to mdp where my electrode system bonds together from the service. The only thing I saw in the bible was that the only way I could do it is if my xfmr was service rated. It would be the main service is grounded to a 20 foot piece of rebar in slab and the water main witch is next to impossible to get to what would my other options be thanks
 

kwired

Electron manager
Location
NE Nebraska
I'm in a parking garage that is all precast no steel in the entire building my transformer is in the main elec em for my gec I was going to bring it in to mdp where my electrode system bonds together from the service. The only thing I saw in the bible was that the only way I could do it is if my xfmr was service rated. It would be the main service is grounded to a 20 foot piece of rebar in slab and the water main witch is next to impossible to get to what would my other options be thanks
Where did you find this? I don't know that you will find a service rated transformer - wouldn't any transformer need to be fed either from a feeder or a service and not actually be the service?

Shouldn't be anything wrong with bonding it to service in most cases. Could be a problem if size of GEC to water pipe is not large enough for the SDS, CEE doesn't need to be larger than #4.
 
The reference for this transformer is 250.30.
See 250.30(A)(7) to be more precise.
(1) or (2) are the sub/sub sections that are the permitted electrodes for the transformer as you have explained it.
If those are not available, then you reference the exceptions that follow, there are 2 of them. Remember, to be permitted to use Ex #2, the transformer has to be listed as suitable for service equipment.
 

kwired

Electron manager
Location
NE Nebraska
The reference for this transformer is 250.30.
See 250.30(A)(7) to be more precise.
(1) or (2) are the sub/sub sections that are the permitted electrodes for the transformer as you have explained it.
If those are not available, then you reference the exceptions that follow, there are 2 of them. Remember, to be permitted to use Ex #2, the transformer has to be listed as suitable for service equipment.
I don't think there are any transformers that listed as suitable for service equipment.

I think the mentioned exception 2 is for transformers located within gear that also is the service equipment. Chances are all connections will be either factory made or will have instructions of how it is to be connected, if it needs field assembly.
 
Any time one uses the phrase(s), I don't think, or I think is the same as saying "I do not know".

I would love to know if there are any transformers listed as suitable for services, but this industry is in a state of flux, meaning constantly changing. For anyone (myself) to make a claim to know it all is a sure sign to stay away from that individual...;):D
 

dkidd

Senior Member
Location
here
Occupation
e
Also, posts that say "in my opinion" are not worth much. The Code says what it says and is not subject to "opinion", except possibly by members of the Code Making Panel.
 
Changes to the NEC - according to me

Changes to the NEC - according to me

Also, posts that say "in my opinion" are not worth much. The Code says what it says and is not subject to "opinion", except possibly by members of the Code Making Panel.

You may have missed 90.28.
It states that the old venerated members of this forum are permitted to voice their opinion and consider it as code...;)

Article 100
Definition of venerated forum members - any individual who has posted more than 8130 times, but no more than 8140 times on the Holt Forum.

FPN: Posting more than 8140 is usually performed by really old demented members who sit at their keyboards and type due to exercises required by the old age home

I have to say I feel much better now...:D
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
... Remember, to be permitted to use Ex #2, the transformer has to be listed as suitable for service equipment.
That rule does not require that the SDS tranformer be listed as suitable for use as service equipment. It requires that the transformer be installed in equipment that is listed as suitable for use as service equipment.
Based on the NEC definition of service equipment a transformer can never be service equipment.
 
That rule does not require that the SDS tranformer be listed as suitable for use as service equipment. It requires that the transformer be installed in equipment that is listed as suitable for use as service equipment.
Based on the NEC definition of service equipment a transformer can never be service equipment.

I understand what I believe the code section may be saying, but I do not see where it states the transformer is part of a listed assembly. By listed assembly this is how I undertand you to be phrasing this. Meaning a tranformer as part of an assembly for a service lineup, etc...

After reading my post, I am not sure if that will be understood by any other than myself.

Maybe I should ask...based on the exception, would transformers potentially not be able to be considered as "listed equipment suitable for use as service equipment,.."?
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
...
Maybe I should ask...based on the exception, would transformers potentially not be able to be considered as "listed equipment suitable for use as service equipment,.."?
I see no way that a transformer could ever be listed a suitable for use as service equipment.

Service Equipment.​
The necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of service conductors to a building or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the supply.


 

augie47

Moderator
Staff member
Location
Tennessee
Square D and some others make a listed assembly that consist of a MDP, a transformer and a LV panel all in one Assembly which is service rated.
In those units the transformer is bonded to a grounding buss that also
serves the MDP & LV section. Somewhat like a multi-section switchboard but with a transformer included. SquareD has trade name for such critters but it escapes me. **

I see no problem with you routing your transformer GEC back to the service GEC and connecting to it (possibly split bolting to the service GEC). You would probably want to route the GEC thru its own PVC conduit to avoid bonding bushings.


**
Integrated Power and Control Solutions
(IPaCS) Equipment
http://static.schneider-electric.us/assets/DIGEST/integrated-power-and-control-solutions-ipacs-equipment.pdf
 
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don_resqcapt19

Moderator
Staff member
Location
Illinois
Which rules out Exception #2 for the OP's installation.
I just don't agree that the transformer itself has to be listed as service equipment. It just has to be installed in the service equipment enclosure. Yes the service equipment has to be designed for the installation of the transformer. One example of of this would be a service rated MCC with a transformer installed in one section.
 

walkerj

Senior Member
Location
Baton Rouge
Square D and some others make a listed assembly that consist of a MDP, a transformer and a LV panel all in one Assembly which is service rated.
In those units the transformer is bonded to a grounding buss that also
serves the MDP & LV section. Somewhat like a multi-section switchboard but with a transformer included. SquareD has trade name for such critters but it escapes me. **

I see no problem with you routing your transformer GEC back to the service GEC and connecting to it (possibly split bolting to the service GEC). You would probably want to route the GEC thru its own PVC conduit to avoid bonding bushings.


**
Integrated Power and Control Solutions

(IPaCS) Equipment
http://static.schneider-electric.us/assets/DIGEST/integrated-power-and-control-solutions-ipacs-equipment.pdf

I see them named MPZ on drawings.
'Mini Power Zone'
I don't know what SqD calls them.

For instance, isolated chiller pads with the main service located on it with a need for a few 120vac circuits.

Or, a mall with limited space for gear in tenant spaces.
 

david luchini

Moderator
Staff member
Location
Connecticut
Occupation
Engineer
If the OP is splicing his SDS GEC onto the service GEC, that makes the service GEC a common grounding electrode conductor, of which 250.30(A)(4)(a) states is required to be 3/0 Copper or 250 kcmil Al.
What you have described does not fall under 250.30(A)(4)(a).

250.30(A)(4) describes the grounding electrode for multiple Separately Derived Systems, not for one SDS and one Service. The common grounding electrode conductor is common to multiple SDS's.
 

kwired

Electron manager
Location
NE Nebraska
Any time one uses the phrase(s), I don't think, or I think is the same as saying "I do not know".

I would love to know if there are any transformers listed as suitable for services, but this industry is in a state of flux, meaning constantly changing. For anyone (myself) to make a claim to know it all is a sure sign to stay away from that individual...;):D

Ok, I do not know if there are any transformers listed for use as service equipment. I also do not see how there could be any. If you know how then correct me on this. I said "I don't think" figuring someone would correct me if they knew I was wrong. Happens all the time here, that is what this forum is about.

How do you install a transformer as service equipment.... without having service equipment ahead of it, which no longer makes it service equipment.

I know that there are transformers within switchgear that also serves as service equipment.

Exception No. 2: Where a separately derived system originates in listed equipment suitable as service equipment...
How do you get out of that statement that the transformer needs listed as service equipment? It says in listed equipment...
 
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