[NoneRequired]

Looking for tips to add a subpanel to a full 125A Pushmatic split buss box.

My plan is to add a subpanel in a newer style (probably Square D) box. Since the Pushmatic branch circuit buss is already full, I'm thinking on getting a new 60A breaker (double pole) for the Main Disconnect side of the panel since that side only has the one 60A breaker feeding the branch circuit side of the box and 3 open slots.

It seems pretty clear this was the original design intent of the box, or feeding 240V circuits from those "main disconnects". Since my house has no 240V equipment other than the A/C which runs off it's own meter and disconnect, I'm not seeing much downside to feeding a subpanel for my basement shop from one of them.

I realize it would be a better plan to just rip out the Pushmatic box and replace with something more modern, but that's not happening yet.

Am I missing something?

Thanks...
Jon

 

[IslandGuy]

Looking for tips to add a subpanel to a full 125A Pushmatic split buss box.

My plan is to add a subpanel in a newer style (probably Square D) box. Since the Pushmatic branch circuit buss is already full, I'm thinking on getting a new 60A breaker (double pole) for the Main Disconnect side of the panel since that side only has the one 60A breaker feeding the branch circuit side of the box and 3 open slots.

It seems pretty clear this was the original design intent of the box, or feeding 240V circuits from those "main disconnects". Since my house has no 240V equipment other than the A/C which runs off it's own meter and disconnect, I'm not seeing much downside to feeding a subpanel for my basement shop from one of them.

I realize it would be a better plan to just rip out the Pushmatic box and replace with something more modern, but that's not happening yet.

Am I missing something?

Thanks...
Jon

The design of the split buss panel was intended for squeezing an extra 25a out of what would otherwise be a 100a service. This was permitted for a time for what was then newer "all electric" houses where for short, limted amounts of time a consumer really needed a hair more than 100a when say, cooking dinner. The typical install would have 3 or 4 240v branches that constitute the "mains" - a stove, a water heater, a clothes dryer and the 60a "lighting main" for all the other individual remaining circuits. Since the panel although possibly labeled 125a is most likely fed with 100a, the combined 60a lighting main plus what you add shouldn't really exceed 100, so you're limited to a 40a circuit breaker to protect your sub. Would it kill someone if you went to 60? Probably not.

 

[rjniles]

For the $48 that 60 amp breaker cost you can almost buy a 100 amp 20 slot main breaker panel.
http://www.homedepot.com/p/Square-D...Center-with-Cover-Value-Pack-HOMVP5/100197589

 

[Oso954]

The idea of a Homeowner installing a breaker on a live bus w/o protective gear and the knowledge of how to use it, gives me the shivers.

Hire an electrician to install the breaker or call the POCO to pull the meter.