Non fused 400A manual transfer switch

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bristlepad

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Need some help here. I am code savvy and been doing this long enough to know how to properly design a service. With that being said, this particular service (newly installed and passed by inspector) is single phase 400A with just a meter can outside and the 400A OCP in the main panel directly back to back with meter. The main panel feeds through to an additional 400A rated panelboard.

We installed a service entrance rated non fused 3 position manual transfer switch directly after the meter and inspector doesn’t like it citing 230.82. I figured with 230.91 saying either integral or “immediately adjacent” but inspector says that’s a completely different category. Of course I called the inspector and asked him everything except for this before I quoted the job. A fused version of this switch is $7000 but it wasn’t originally about money as this customer has plenty.

Thoughts?


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This has been discussed before, whether back to back but separated by a wall is immediately adjacent there to. Unfortunately it just comes down to interpretation of those words and I can't think of any other way to make your case then arguing the meaning of those words
 
Short answer: I agree with the Inspector.

Longer answer: 230.91 is about the relative locations of the service overcurrent device and the service disconnecting means. Without the MTS, the 400 amp breaker in the main panel serves both purposes. 230.82 says you can have only certain things upstream of the service disconnecting means. An MTS is not on that list. So if you want to put an MTS upstream of the main panel, then the MTS has to become the service disconnecting means. So the MTS must be service entrance rated, the N-G bond must be in the MTS and not in the main panel, and there must be an EGC between the MTS and the main panel.

That said, what remains is the question of whether the MTS (i.e., the service disconnecting means) can be across the wall from the service overcurrent device (i.e., the 400 amp breaker in the main panel). Good news: I believe 230.91 would allow it. Bad news: I think 240.21(C)(4)(2) would not allow it. Unless there is an OCPD at the transformer secondary (not likely), then the secondary conductors must land on an overcurrent device. Putting an unfused MTS between the transformer and the main panel would violate that rule.
 
bristlepad said:
Need some help here. I am code savvy and been doing this long enough to know how to properly design a service. With that being said, this particular service (newly installed and passed by inspector) is single phase 400A with just a meter can outside and the 400A OCP in the main panel directly back to back with meter. The main panel feeds through to an additional 400A rated panelboard.

We installed a service entrance rated non fused 3 position manual transfer switch directly after the meter and inspector doesn’t like it citing 230.82. I figured with 230.91 saying either integral or “immediately adjacent” but inspector says that’s a completely different category. Of course I called the inspector and asked him everything except for this before I quoted the job. A fused version of this switch is $7000 but it wasn’t originally about money as this customer has plenty.

Thoughts?


Sent from my iPhone using Tapatalk
Click to expand...

I assuming your existing 400 amp service disconnect is still in place and you just inserted the non-fusible manual switch between the meter and the existing service disconnect.
If the non fusible manual switch is service rated (some are such as RONK manual switches) it is not the service disconnect-the existing 400 amp breaker is the service disconnect.
This would comply with 230.82(5) in my view. I know is says "tap" but this is the equivalent. I've seen this done a number of times over the years. I would just caution that it needs to be bonded like any other metallic items on the line side of the service disconnect per 250.92.
 
Just got a reply back from the head inspector. Essentially the “immediately adjacent” phrase has been downgraded in my city from 6’ to right next to it and within sight. Also, since the service entrance cable was intercepted the MOCP now needs to be in the MTS.

I guess it’s time to buy a redundant 400A NEMA 3R enclosure and install it ?

Thank you for the replies and the insight all!


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charlie b said:
I think 240.21(C)(4)(2) would not allow it. Unless there is an OCPD at the transformer secondary (not likely), then the secondary conductors must land on an overcurrent device. Putting an unfused MTS between the transformer and the main panel would violate that rule.
Click to expand...

Charlie, That would not apply to utility transformer secondary conductors, AKA service conductors. The overcurrent protection rules for those are in part VII of 230.
 
Put me in the camp that says this is legal as long as you meet 230.91. My folks have an Eaton service rated nonfused 200A MTS in the exact arrangement you're proposing on their farm.

Per that article, this is considered the service disconnecting means, just not the service OCPD, which would be located adjacent to it.

I don't see the issue personally.
 
Cow said:
Put me in the camp that says this is legal as long as you meet 230.91. My folks have an Eaton service rated nonfused 200A MTS in the exact arrangement you're proposing on their farm.

Per that article, this is considered the service disconnecting means, just not the service OCPD, which would be located adjacent to it.

I don't see the issue personally.
Click to expand...

My house is the same way.
 
LarryFine said:
I agree the T/S should be after the main disco, not before it.
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Put me in Larry's camp.

I haven't looked it up, but, for some reason I'm thinking the OCPD must be at the location that the Service Conductors terminate, which was the way it was prior to the MTS being installed.

Now they are not.

I don't feel the termination point of the Service Conductors can be a moving target or in multiple locations prior to landing on some type of OCPD.

Another problem I can fore see is even if the Non-Fused Manual Transfer switch was changed out to a "Fused" style, unless someone did some fancy rerouting of the raceways, I can see another violation of Service and Feeder Conductors sharing a common raceway in the very near future of this installation.

JAP>
 
jap said:
Put me in Larry's camp.

I haven't looked it up, but, for some reason I'm thinking the OCPD must be at the location that the Service Conductors terminate, which was the way it was prior to the MTS being installed.

Now they are not.

I don't feel the termination point of the Service Conductors can be a moving target or in multiple locations prior to landing on some type of OCPD.

Another problem I can fore see is even if the Non-Fused Manual Transfer switch was changed out to a "Fused" style, unless someone did some fancy rerouting of the raceways, I can see another violation of Service and Feeder Conductors sharing a common raceway in the very near future of this installation.

JAP>
Click to expand...

Service conductors are conductors that terminate on the service equipment. the OCPD, even if separate and downstream from the service disconnect, is still service equipment. See definition of service equipment and part VII of 230.

One other potential issue here is one that was mentioned in this thread:

https://forums.mikeholt.com/forum/active-forums/photovoltaic-forum/2539675-pv-utility-non-fuse-disco

Where the manufacturers seem to say you must have an OCPD ahead of a NF switch. As I state in that thread, I find their reasoning very flawed and nonsensical. Also odd there are "Service rated switches" then :dunce:
 
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