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Joined: Jun 2004
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Harold,
The EE can't state that the buss can handle more than 800amps. They must follow whats prescribed in 705.12(D)(2)
705.12(D)(2) says the added value of the breakers feeding a buss can't exceed 120% of its rated value.
This is probally why it was drawn on the original plan as a line side connection. But a line side connection would be in front of the CT cabinet for metering which is cold sequence connected with the 800amp main.
They can't connect before the cash register.
This happened in our area and the MDP was upgraded to an MDP with 1200amp bussing.
Anyway...keep us informed on how this works out.
Telsa, my last post was for you?
shortcircuit
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Joined: Apr 2002
Posts: 7,382 Likes: 7
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Harold:
A 'line side tap' cannot be before the CTs. Line side taps are installed after the meter.
The first thing to be determined is the rating of the buss.
If the job was not installed to the submitted & approved plans, you definetly need 'as-builts' which require review and approval. (The review may be a "fee" depending on your Twp fee schedules & ordinances)
The EC should have been at the site for the inspection!
I understand what Tesla is saying, and agree with him.
John
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Joined: Jun 2004
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Hotline...
A "line side tap" or "supply side connection" which is the description used by the NEC, is allowed by 230.82(6) for a PV system
This is allowed to be before the meter, but if done like this it would need to be set up as a seperate service, which is allowed under 230.2(A)(5) requiring the configuration to have its own metering and service disconnecting means, etc.
In my area, with a similar installation as Harolds (400amps of backfed solar load side connected to an 800amp MDP with cold sequence metering), an 800amp MDP was replaced with 1200amp equipment to comply with 705.12(D)(2)(known as the 120% rule) because they didn't want seperate metering for the PV.
shortcircuit
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Joined: Apr 2002
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Shortcircuit:
Yes, an additional meter can be installed for a PV, as you described, and will be compliant.
Usually, the intent of the proposed installation as Harold explained is addressed in Plan review. Sometimes, as we are all human, it may get missed, but caught at field inspection.
The solution you stated above, is a usual remedy.
Harold has to get the actual rating of the buss from the existing MDP for starters.
John
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Joined: Feb 2002
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John,
Called up the PV company and told him that his plans showed a line side tap, but they were claiming a load side tap. I told him that either way, he has to re-draw the plans to show what is really there. I will also go back out to make sure that the plan matches the work done there.
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Joined: Apr 2002
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Harold:
Did you check the mfg nameplate data on the piece of gear? It may have a higher buss rating then the main CB.
John
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Joined: Feb 2002
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John,
When I go back, I will check that out. I also have the EE drawing up new set of plans to show what has really been done. I also want a letter stating that the bus can handle the extra load.
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Joined: Jun 2004
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The Jan/Feb edition of the IEIA has a good article on the 120% rule by John Wiles on page 52
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Joined: Feb 2002
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Short circuit,
I don't remember if I read that article or not, but I do have the magazine and I will check it out.
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Joined: Jun 2004
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I would also question tapping the buss in the MDP. Does the manufacturer allow tapping the buss? If not, it may void the listing on the equipment.
A FE by UL may be in order if the equipment was modified.
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