Disconnecting means for diesel standby 100kW generator

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mshields

mshields

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Boston, MA
specifying the generator described above for a office building. It's for Optional Standby only.

I'm meeting 445.18 with lockable disconnect within the skin tight enclosure and mechanically held EPO on the exterior.

At the moment I'm showing this feeder coming directly into the ATS in the building without any additional disconnecting means. I think that's koshur but I want to make sure I'm not missing anything. Am I?
 
I believe that 702.12(A) requires a disconnect at the building. The disconnect inside the generator enclosure is not within sight from the building and the EPO is not a disconnect.
 
shortcircuit2 said:
Under 2017 Code if your EPO is lockable in the open position per 110.25 it will satisfy the disconnecting means requirements of 445.18(A)
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An EPO is not a disconnect. It is part of a control system. The disconnect is required to directly and physically open the ungrounded conductors of the circuit.
 
don_resqcapt19 said:
An EPO is not a disconnect. It is part of a control system. The disconnect is required to directly and physically open the ungrounded conductors of the circuit.
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I agree.

So give me your interpretation of what the new 445.18(B) is saying with...

The provisions to shut down the prime mover shall be permitted to satisfy the requirements of 445.18(A) where it is capable of being locked in the open position in accordance with 110.25.

I read it as an EPO switch that is lockable in the open position that shuts-down the prime mover satisfies 445.18(A) for the required disconnecting means...and if it were "In Sight" of the building it would also meet the requirements of 702.12(A)
 
shortcircuit2 said:
I agree.

So give me your interpretation of what the new 445.18(B) is saying with...

The provisions to shut down the prime mover shall be permitted to satisfy the requirements of 445.18(A) where it is capable of being locked in the open position in accordance with 110.25.

I read it as an EPO switch that is lockable in the open position that shuts-down the prime mover satisfies 445.18(A) for the required disconnecting means...and if it were "In Sight" of the building it would also meet the requirements of 702.12(A)
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I would have to know a lot more about the EPO circuit before I could say that it would meet that requirement.
 
don_resqcapt19 said:
I would have to know a lot more about the EPO circuit before I could say that it would meet that requirement.
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The EPO switch would shutdown the prime mover and render it incapable of starting per 445.18(B)(1). To me, "EPO" just means "emergency power off". You can have an EPO without being compliant with that rule.
 
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don_resqcapt19 said:
If it does that fine, but I would not sign off on it doing that without seeing the drawings.
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For example, if the visible EPO switch simply controls power to a contactor, I would not consider locking the visible switch to be sufficient to prevent the contactor from being closed.
That is a pretty well established principle in general control design and LOTO, not just EPO.

If the EPO switch actually physically removes power, then I would probably accept it as a maintenance disconnect too, as long as all the other conditions are met.
 
don_resqcapt19 said:
If it does that fine, but I would not sign off on it doing that without seeing the drawings.
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What drawings? If the EPO (emergency power off) switch shuts down the prime mover and it won't start, won't that satisfy the requirement?

445.18 doesn't provide much guidance on how it should be done except to have provisions to disable the start control circuits.

That provision could be an EPO switch that disables the prime mover from starting.
 
GoldDigger said:
For example, if the visible EPO switch simply controls power to a contactor, I would not consider locking the visible switch to be sufficient to prevent the contactor from being closed.
That is a pretty well established principle in general control design and LOTO, not just EPO.

If the EPO switch actually physically removes power, then I would probably accept it as a maintenance disconnect too, as long as all the other conditions are met.
Click to expand...

Hmmm...it appears this a 2017 Code rule that will be open to different interpretations.
 
shortcircuit2 said:
What drawings? If the EPO (emergency power off) switch shuts down the prime mover and it won't start, won't that satisfy the requirement?

445.18 doesn't provide much guidance on how it should be done except to have provisions to disable the start control circuits.

That provision could be an EPO switch that disables the prime mover from starting.
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The term "EPO" does not tell me anything about the function of the device. It does not tell me that it has anything to do with the prime mover. Without seeing the drawings or the manual from the manufacturer, I have no idea of what the "EPO" actually does.
 
shortcircuit2 said:
...
The provisions to shut down the prime mover shall be permitted to satisfy the requirements of 445.18(A) where it is capable of being locked in the open position in accordance with 110.25.
...
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I like the [highlighted part] first sentence of the following paragraph:
Generators with greater than 15 kW rating shall be provided
with an additional requirement to shut down the prime mover.
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Hmm... provided with an additional requirement... :blink::huh:

The second sentence covers the gist...
This additional shutdown means shall be located outside the
equipment room or generator enclosure and shall also meet the
requirements of 445.18(B)(1) and (B)(2).
Click to expand...
...but the first sentence should stand on its own. :happyyes:
 
don_resqcapt19 said:
The term "EPO" does not tell me anything about the function of the device. It does not tell me that it has anything to do with the prime mover. Without seeing the drawings or the manual from the manufacturer, I have no idea of what the "EPO" actually does.
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I'm not even sure what the OP is using his EPO for. He did not say. I only said if an EPO is connected to a generator and it renders it incapable of starting, it meets the requirement of 445.18(B)...and I further said if the EPO that shuts down the prime mover were lockable per 110.25, it will satisfy the requirement for the disconnecting means in 445.18(A).


I think I understand where your concern is. But the new rule, 445.18(B) as written does not give the detail to support your concern.

The rule does not say the means for the shutdown of the prime mover has to be part of the generator package, or that it has to be listed and labeled as part of the generator, or that it has to be in any drawings or manual from the manufacturer. The rule does not even say where the means for the shutdown of the prime mover needs to be located except that for over 15KW units there has to be an additional means outside the room or enclosure.

This new generator rule reminds me of the new Code rule in 2014 for Rapid Shutdown for Solar PV Systems in 690.12 and 690.12(1) said it had to be within 10 feet of the Array. So installers here in Mass were putting DC disconnects on the roof or high on the wall within 10 feet of the array to comply with the new 690.12. Obviously this is not what was intended.

Well here in Massachusetts when we adopt the new Code on January 1st of the Code cycle (First in the USA) we have to sort out the new rules and do our best to interpret the new Code rules as written. I/we are trying to sort this new rule out here in Massachusetts also. Any input from the members here on the new 445.18(B) will be conducive for a better understanding of the rule for all of us.

So chime in on what you think 445.18(B) of the 2017 Code is saying.
 
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