jneilson
Good afternoon!
I have a model 07174 13kw set with a 16-circuit limited transfer switch, and I'm trying to figure out a smooth process for moving circuits without taking the whole house down at one time.  My first order of business is to add a 100A breaker in the main panel and feed the transfer switch and then over a period days move circuits.  Is this how it's normally done?
One issue that I have is that my 1980 Murray Panel has 1 bus which all neutrals and grounds share.  It's loaded to capacity and there's no room for a #3 neutral and #6 ground associated with the 100A breaker.   Any suggestions?
I will appreciate very much any help.
Thanks,
John Neilson
Quote
Cobranut
Not sure, but don't all the neutrals and grounds need to be separate in the Xfer switch, which is now a sub-panel?
Quote
grsthegreat
You are supposed to move the neutral associated with the circuit to the new transfer switch. This will free up some neutral bus locations. The neutral HAS to be located within same panel as the breaker. The transfer switch will be a subpanel so grounds and neutrals must be separate. No inspector has ever made me move the grounds to the new panel though.
Quote
Brian Baughman
The neutral conductor for every circuit or multiwire branch circuit has to be moved to ATS subpanel.  The NEC also requires all circuit conductors from a multiwire branch to originate from the same panelboard.
Quote
Geoff Z
All good advice. We have never been made to move the grounds either.
Quote
DanS26
I know this is a month old thread but I'd like to suggest a method that I believe is required code in Canada but not in US.

I installed a junction box on the load side of the critical loads panel (ie ATS).  In the JB I installed a pass through block mounted on a DIN rail.  I then moved  the protected circuits completely out of the main panel and routed them to the JB and through the pass through block to the ATS both the hot and neutral for each circuit.  I also install a ground bar and ran a single #6 from the bar to the ground in the ATS.

This method avoided all the wire nuts in the main panel and freed up a lot of space in the main panel which made for a clean and tidy installation. The pass through block made the connections simple and very secure but it is very important to follow the box fill and conduit fill guidelines.
Quote
Geoff Z
Regardless if you are routing the branch circuits from the main panel to a JB or transfer switch. If the branch circuit wiring is not long enough you can’t avoid wire nuts in the main panel to extend wiring. 
Quote
DanS26
In my case I was fortunate enough to be able to place the JB in a position so that each circuit removed from the main panel was long enough to make the transition without need for an extension.  In other words I removed everything related to the 11 branch circuits from the main panel and routed to the JB.

I agree with you that if the branch circuit is not long enough then in most cases you have to make the transition with wire nuts (or WAGOs) in the main panel and thus the advantage of this method is lost.
Quote
Geoff Z
I’ll bet that made a nice looking installation. 
Quote
Brian Baughman
The installation manuals have specific sections for Canadian installation requirements.
Quote
jneilson
I appreciate all the advice; it's very helpful.  I'm in the process of adding an 8X8X4 junction box beneath where circuits feed into the main panel where I can easily drop grounds and neutrals down where they can be made up with grounds and neutrals from the TS sub-panel.  That will eliminate all the clutter in my 1980 model Murray split bus panel.  The hots will be made up in the main panel.
Thanks You!
John
Quote
DanS26
John,

You should not separate hot and neutral in any circuit, they must remain together.  
Quote