Help with Manual Transfer Switch

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mxstar211

mxstar211

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I ran into this situation in Iraq on a site we are inspecting. A 3-pole MTS was fed from the utility transformer and by a back up generator. There is a 4wire cable coming from the transformer, and a 4 wire cable coming from the generator, and the generator is bonded. The transformer has its own ground rod.

Inside the MTS, the neutral bus is isolated, and the neutrals land on it, as well as the connection to the ground rod. There is another wire connecting the case to the same ground rod. This wire is attached to the bolt that holds the hinge on the door. There are no wires landed on the grounding bus.

I think this is in violation of 250.6(A), Arrangement to prevent objectioanble current. I feel a 4-pole MTS is needed, and the neutals should be switched.

I would greatly appreciate any input anyone has, I am not very familiar with transfer switches. Thanks a lot!
 
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Sorry the pictures are so big. I wanted to go back and delete or edit them, but I could not find where to click so I can edit my post.
 
mxstar211 said:
Sorry the pictures are so big. I wanted to go back and delete or edit them, but I could not find where to click so I can edit my post.
Click to expand...

You have about 10 minutes. The edit button should be in the right hand corner next to the quote button.
 
Dennis Alwon said:
You have about 10 minutes. The edit button should be in the right hand corner next to the quote button.
Click to expand...

Thank you, it was due to a combination of lack of sleep and lack of computer skills.
 
mxstar211 said:
I ran into this situation in Iraq on a site we are inspecting. A 3-pole MTS was fed from the utility transformer and by a back up generator. There is a 4wire cable coming from the transformer, and a 4 wire cable coming from the generator, and the generator is bonded. The transformer has its own ground rod.
Click to expand...

Where is the OCPD for the transformer and the generator set?

mxstar211 said:
Inside the MTS, the neutral bus is isolated, and the neutrals land on it, as well as the connection to the ground rod. There is another wire connecting the case to the same ground rod. This wire is attached to the bolt that holds the hinge on the door. There are no wires landed on the grounding bus.
Click to expand...

Providing the OCPD is not in the transfer switch, the grounds and neutrals should be isolated. the ground rod connection should be to the case with the ground wires from the transformer and the gen set.

mxstar211 said:
I think this is in violation of 250.6(A), Arrangement to prevent objectioanble current. I feel a 4-pole MTS is needed, and the neutals should be switched.

I would greatly appreciate any input anyone has, I am not very familiar with transfer switches. Thanks a lot!
Click to expand...

The transformer and gen set grounding and grounded conductors will be parallel with each other. The commom point between the two SDS is the bonding jumper.

Rick
 
The generator has a 630A breaker inside its frame, its a 440 KW gen. The OCPD's for the transformer are dropout fuses on the high side.

There is no OCPD in the MTS. Its just a 3-pole switch.

I drew up a diagram, but the file was a little too big too open. It would have shown the sitiuation a little more clearly.

Thanks!
 
RUWired said:
After rereading your post, is there a grounding conductor installed between any of the equipment?
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Everything except the transformer is ran to one ground rod. The generator, MTS, and 2 MDP's.

If anyone can tell me to reduce the size of a word document, or a paint document, I could post the diagram. Its 150 mb, but can only be 146.5. I could e-mail if you would like.
 
mxstar211 said:
Everything except the transformer is ran to one ground rod. The generator, MTS, and 2 MDP's.

If anyone can tell me to reduce the size of a word document, or a paint document, I could post the diagram. Its 150 mb, but can only be 146.5. I could e-mail if you would like.
Click to expand...
If you have a paint document you can resize the drawing this will change the size of the file.

edit: Sorry in paint go to view and then stretch and skew or ctrl W
 
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mxstar211 said:
If anyone can tell me to reduce the size of a word document, or a paint document, I could post the diagram. Its 150 mb, but can only be 146.5. I could e-mail if you would like.
Click to expand...

Are you talking about the photos?

If so post them as before and I will make them links, I actually did that before but you deleted them.:D
 
mxstar211 said:
Everything except the transformer is ran to one ground rod. The generator, MTS, and 2 MDP's.

.
Click to expand...

It sounds like there using the MTS as the service disconnect for the utility transformer and the MDP's for the OCPD. That is why everything is bonded along the way. I still gather that a seperate grounding conductor was not ran?
 
I'd welcome a criticism of this, but I think that this arrangement is "ok".

I think this tranfer switch is before what would be thought of the service entrance so effectively it is in PoCo-ville, where three wire switching is the norm. My supporting evidence for this is that the output of the MTS is four wire no ground, and thus I suspect the neutral-ground service entrance bond is downstream of this MTS.

As I said this is just a suspicion, and thus please do chime in if you think I'm up the wrong tree.
 
Does this help at all???

1113854482_6.jpg
 
dbuckley said:
I'd welcome a criticism of this, but I think that this arrangement is "ok".

I think this tranfer switch is before what would be thought of the service entrance so effectively it is in PoCo-ville, where three wire switching is the norm. My supporting evidence for this is that the output of the MTS is four wire no ground, and thus I suspect the neutral-ground service entrance bond is downstream of this MTS.

As I said this is just a suspicion, and thus please do chime in if you think I'm up the wrong tree.
Click to expand...

Over here, they run 4-wire to everything. Recently they did bond at the MDP. In the past over here, they would never bond the neutral and ground bus. Only a few of the "electricians" here understand bonding.
 
iwire said:
Are you talking about the photos?

If so post them as before and I will make them links, I actually did that before but you deleted them.:D
Click to expand...

Sorry, I thought you meant I had 10 minutes to delete the pictures, or the thread would be deleted.
 
I will try to add pictures and diagram later today, time permitting. We recieved guidance from our master electrician at a different location, and he says that the bond at the generator needs to be removed.
 
I don't know if this will help at all, but the xfrmr is in the upper left corner, generator upper middle, MDP bottom right, and MTS bottom middle. I only drew in grounding conductors and neutral conductors. The cables that were run are 4 wire.

I know its small, but it should help explain the system. Thanks.
 
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Here are a few pictures, not sure if they will help much. The MDP on the right, I didn't mention in the description of the situation, but it is wired the same as the other MDP on the left. It has a ground wire running to the common ground rod. The transformer is not shown in the pictures, but it is located behind and a little to the right of the MDP on the right.
 
mxstar211 said:
I don't know if this will help at all, but the xfrmr is in the upper left corner, generator upper middle, MDP bottom right, and MTS bottom middle. I only drew in grounding conductors and neutral conductors. The cables that were run are 4 wire.

I know its small, but it should help explain the system. Thanks.
Click to expand...


xfrmr is in the upper right
 
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