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Discussion Starter #1
I have not done one of these in quite a few years, want to make sure I am not missing anything; appreciate a second set of eyes…

Building has an existing 400 amp, 3 phase 120/208 volt service at the other end of the building (say 200 feet away, that is subdivided into four 200 amp services). New 600 volt, 200 amp service at the other end of the building.

600 volt, 200 amp service, 3 phase, four wire (thinking I might only need 3-wire)
200 amp fusible disco (3R) on the outside of building
200 amp 7-jaw meter socket (most likely) (speced by local utility) on the outside of the building
#6 bond from exterior disco to existing ground system on 120/208 volt system
Interior disco? I don’t think so… Exterior disco acts as service disconnect.
200 amp splitter (may not be needed, but if there was future 600 volt loads...)
200 amp disco for 225 KVA transformer (thinking I need this for isolation / maintenance)
225 KVA transformer (either wye to wire or delta to wye), bond XO to #6 system ground
600 amp 120/208 fused disco? Would have to determine the load, but I don’t know what it is so I think I will need the disco
600 / 800 amp 120 / 208 splitter

Building is block with an open steel web joist, about 10,000 square feet that is sub divided into five 2000 square foot units. Like I said, I don’t know what the final demand will be, I am assuming it is bitcoin mining as I don know what else would take so much power for such a small space. Both the building and location is not suitable for growing. There are no 600 volt loads so I am told; they need 600 amps at 208 volts.

Cheers
John
 

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Professional Electrical Engineer, construction industry.
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I think I understand the configuration. A few informal comments:

  • Transformer should be delta-wye.
  • 4W on the 600V side is definitely preferred in case they ever want to run some 347V lighting.
  • The transformer XO bond needs to be sized for the secondary 600A rating (same rules as your neutral system bond). Min. #1 copper.
  • The 600A fused disconnect on the 208V side is not required. It is sufficiently protected by the 200A fused disco on the 600V side.
  • Like you said, you may want a maintenance disconnect on the secondary side of the transformer.
  • 600A 120/208V splitter is minimum required based on the primary fuse size. 225kVA transformer is a little oversized for the 200A incoming but next size down (150kVA) is too small. If it were me, I would probably go with 800A splitter to eventually utilize the full capacity of the 225kVA transformer.
  • Out here, the primary transformer conductors would need to be sized for 125% of the transformer capacity regardless of primary fuse size. Your primary conductors would need to be sized for 270A instead of 200A. Inspectors in your area may let you install 200A conductors but you may want to open a dialog.
On a side note, a lot of mining farms are switching to 240/415V (euro voltage) configurations. It is a weird transformer and you need to install 480V rated panels but it cuts your panel and breaker quantity in half.
 
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Discussion Starter #3
Thanks for taking the time to look at it...

  • The transformer XO bond needs to be sized for the secondary 600A rating (same rules as your neutral system bond). Min. #1 copper.
Just to clarify your comment, I am running a #6 from the 200 amp 600 volt service to the existing 400 amp 208 service grounding conductor (some 200 feet away) and then running a #1 from the XO to some point on that #6 or are you saying that I need to run the #1 (Table 16) all the way back to the grounding conductor on the 400 amp 208 service?


  • Like you said, you may want a maintenance disconnect on the secondary side of the transformer.
I think I need to have something, while I agree that the 200 amp disco outside protects the XMfr, I think I need something inside to isolate for maintenance… the question is it fusible or non-fusible and on the primary or secondary? I think non-fusible is fine on either side, but a 200 amp disco I think would be less expensive then a 600 amp one…

  • Out here, the primary transformer conductors would need to be sized for 125% of the transformer capacity regardless of primary fuse size. Your primary conductors would need to be sized for 270A instead of 200A. Inspectors in your area may let you install 200A conductors but you may want to open a dialog.
Do you have a rule number for that? Are you saying that all my service conductors would all have to be 250MCM CU? I would have to check the lug size in a 200 amp switch and meter socket.

Cheers
John
 

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Just to clarify your comment, I am running a #6 from the 200 amp 600 volt service to the existing 400 amp 208 service grounding conductor (some 200 feet away) and then running a #1 from the XO to some point on that #6 or are you saying that I need to run the #1 (Table 16) all the way back to the grounding conductor on the 400 amp 208 service?
Your proposal sounds right. The XO neutral bond should be some point near the transformer. No need to run the #1 back to the system ground.

I think I need to have something, while I agree that the 200 amp disco outside protects the XMfr, I think I need something inside to isolate for maintenance… the question is it fusible or non-fusible and on the primary or secondary? I think non-fusible is fine on either side, but a 200 amp disco I think would be less expensive then a 600 amp one…
Choice is yours. The service fused disconnect protects the transformer. No additional fused disconnects required on either side of the transformer. Personally I think it is a little odd not to have a fusable disco off the primary splitter. It gives a bit more versatility in the future.

Do you have a rule number for that? Are you saying that all my service conductors would all have to be 250MCM CU? I would have to check the lug size in a 200 amp switch and meter socket.
26-256 (1) & (2). Annoyingly, the subrule (3) exception uses language like, "required by the demand load" instead of just saying "overcurrent protection". Inspectors around here ignore subrule (3) and only pay attention to (1) and (2). Hence, 125% of the transformer rating regardless of fuse size.

Based on previous threads, it looks like some jurisdictions have clarified and issued their own wire size recommendations:
Previous Thread Link

In either case, this would only apply to the run between your splitter and transformer. Not required on your main service.

On the transformer primary #250MCM copper doesn't quite make it (255A). I usually recommend #400MCM alum. (270A). Not sure about the lugs. Inspectors and the CSA don't care about the capabilities of your equipment :biggrin:
 

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I was reading all the comments saying things to myself then I realized the you are in Canada with different codes than the US. Some jurisdictions here require the second service grouped with the first service unless the building is too big, the required service is too large for one service, Or different voltages or characteristics. Then you have to placard everything. A remote second 480 volt service and then stepping down to 208/120 volts might not fly unless you have 480 volt machinery. Here there are multiple jurisdictions and even the Utility Company has changed several times. What is allowed today might not be tomorrow.
 

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the CEC 6-102 states:

6-102 Number of supply services permitted (see Appendix B)
1) Two or more supply services of the same voltage shall not be run to any building, except that
additional supply services shall be permitted for supplying
a) fire pumps in accordance with Rule 32-304 1);
b) industrial establishments and other complex structures; or
c) completely self-contained occupancies where the occupancies
i) are not located one above the other; and
ii) have a separate entrance with direct access to ground level.
2) When two or more supply services are installed to a building, all service boxes associated with the
various consumer’s services shall be grouped, where practicable.
3) When two or more service boxes installed in accordance with Subrule 2) are not grouped together,
a permanent diagram shall be posted on or near each service box indicating the location of all the
other service boxes supplying power to the building.
Given the separate bays and the different voltages, I think that this install would be permitted. I've seen a few applications where a separate standalone service is installed for a specialty piece of equipment, say a 480V laser cutter in an otherwise 208V building. No big deal.
 

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Your proposal sounds right. The XO neutral bond should be some point near the transformer. No need to run the #1 back to the system ground.
Just trying to clarify this point, i'm not sure if i'm just reading the comments incorrectly.

600V Secondary XO to 600V Bonding Bus = #1 (System Bonding Jumper)
600V Secondary Bonding bus to 208V Bonding bus = #6 (Grounding Conductor)
600V Bonding Bus to 600V Device Enclosure = #1 or others (Bonding Conductor)

It's unclear if what was being discussed matches or if i'm seeing something different.
 

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Discussion Starter #9
It is 600 volt Primary to 208 volt secondary.

200 amps at 600 volts primary and 625 amps at 208 volts secondary... (225 KVA)

Cheers
John
 
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