4 Pole transfer switch feeding 3 Pole switch -4w+g 1

[Live2learn]

I have a system where the generators are a seperatly derived system and the utilty feeds the normal and generator the emergency.

From the xfmr switch for a number of reasons it feeds another transfer switch. (all loads are have are 4w+g)

So the long and short in a 4W+G system can a four pole seperatly derived system feed 3P switches?

 

[davidbeach]

By xfmr switch (which as close I can make out would be a transformer switch) do you mean transfer switch? What are the two sources into the 3 pole switch?

 

[Live2learn]

xfmr switch should have read transfer switch.

the two sources for the three pole downstream switch are a portable 4 pole generator transfer switch and a normal source

the normal source which is upstream has the 4 pole transfer switch with the utility and permenant generators.

so a 4 pole with permenant gens and utility feeds a 3 pole switch which is fed from portable 4 pole generator transfer switch and the normal source.

 

[Live2learn]

yes xfmr was meant to be transfer - sorry

1. but the service entrance transfer switch is 4 pole with permenant generators and utility

2. the downstream switch has two connections from different swbds within the facility. the 4 pole switch feeds a 3 pole switches with L-N loads.

so I have 4 pole systems permenant and utility. downstream of those I have a 3 pole switch.

I don't see anything wrong with this because all sources are seperatly derived. I have ground fault protection on both sides of all transfer switches.

 

[davidbeach]

You can't connect separately derived systems with 3-pole transfer switches, they have to be switched using 4-pole switches.

If I understand correctly you have
[tt]
_ _
| | | |
|U|--N |G|--N
|_| | |_| |
| | | |
| G | G
| |
| _____ |
|____| |____|
| 4-P |
| ATS |
|_____|
| _
| | |
| |G|--N
| |_| |
| | |
| | G
| |
| _____ |
|____| |____|
| 3-P |
| ATS |
|_____|
|
|
\|/
Loads

[/tt]
Where there is a utility connection with its own neutral-ground bond, a permanent generator with its own neutral-ground bond, and a connection point for portable generators also with a neutral-ground bond.

If that is correct then either the neutral-ground bond at the portable generators has to go or the 3-pole ATS has to become 4-pole. You can not switch between separately derived systems without switching the neutral.

 

[thisisnotatest]

Honestly - That is amazing that you can draw like that with characters.

But on the topic at hand - I do apologize for this confusion. So if the portable was a 4 pole then life would be good?

I have attached a picture - which should have been step 1.

 

[waross]

This depends on several factors such as ground fault detection schemes and excess distances, but:
The simplest and most foolproof installation uses the system ground and runs a solid neutral and a solid equipment grounding conductor from the system ground point to the standby generator. Then three pole transfer switches may be safely used.
This scheme is most applicable to smaller standby installations. The largest set that I remember installing with this scheme was a 500KW/KVA set.
There are installations where this scheme is not applicable but it is my first choice.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[thisisnotatest]

thanks for your valuable input!