Replies

1. 
   DanH | Dec 25, 2009 09:39pm | #1

   First check to see if your panel will accept "half-size" breakers. These are generally only available for 120V circuits, but using a few could free up slots for some 240V circuits.

   There are several ways you could connect a second panel, either subpanel or "main" panel, depending on the circumstances. The most straightforward is, as you suggest, to install a large 240V breaker in the original panel and power the subpanel off of that. In that case the subpanel generally does not need a separate "main", so long as it's reasonably close to the first panel.

1. 
   zxycho | Dec 25, 2009 09:46pm | #2

   Thanks for your insight. Regarding the half-sized breakers, I've heard that they were somehow inferior to the full slot breakers? If it matters, the service entrance panel is a Square-D.

1. 
   DanH | Dec 25, 2009 10:05pm | #3

   They are not quite as "robust", no doubt, but if they're "listed" for your panel (always double check that your specific panel is listed for them) then they've been through some pretty rigorous testing at UL et al. (Also make sure that the "max circuits" rating for your panel isn't exceeded -- it's usually about 10 more than the number of slots, for panels that accept the half breakers.

   There are (or were, last I looked) half-size breakers for many Square-D panels.

1. 
   zxycho | Dec 26, 2009 07:35am | #4

   Thanks again!

2. 
   JTC1 | Dec 28, 2009 05:42pm | #5

   The answer is "It depends." Nice, huh?

   If you really only need to add 1 additional 240 circuit, I would consider shuffling the existing breakers and buying skinny breakers if your panel will accept them - some Square D's do, others do not. This may free up enough space to add the needed additional circuit.

   The sure thing cure is to remove the existing 240 breaker which feeds your shop and using those 2 poles to power a sub-panel - could be right next to your existing main panel or removed by some distance - whichever is most convenient.

   By adding a sub-panel you will satisfy your immediate need and provide for future needs.

   Bear in mind that skinny and/or piggyback breakers are sold at a premium price because they are "problem solvers". You may incur less cost in the long run by adding a sub-panel.

   If I was adding a sub-panel - I would just nibble the bullet and add a 100A sub-panel with 20 poles and be done for the duration - future needs? no problem.

   Smaller subpanels are also available - or you can use a main breaker panel and use that as a sub-panel, remove neutral bonding and possibly add a ground bar - frequently I can buy a 100A panel equipped with a main breaker (sometimes with a few "free breakers" included) cheaper than a 100A main lug panel. Big box stores do strange things......

   Stick with Square-D QO style breakers - Square-D Homeline style maybe not so great.....

   Jim

2. 
   LIVEONSAWDUST | Dec 28, 2009 06:42pm | #6

   All good advice...

   If it were me,I think I would pull the existing 220 breaker and replace with a 60 amp breaker feeding a new subpanel, sounds like 60 amps might meet your needs and the wire size for that isn't too awfull hard to work with or expensive (#6 or 8 ?? I dont recall).

   Remember that the neutral and the ground wires should NOT be bonded together in the subpanel. You will have to purchase a separate ground bar for your subpanel.