We have a flush mounted 100A. 20 circuit sub panelboard at one of our facilities. It's loaded to less than 50% ampacity. There are no spare spaces remaining. All of the 20 circuit breakers have a wire attached to it. Many of the circuits have a very small load on it. Would it be proper/legal to "double up" on some of the circuit breakers by splicing two circuits together in panelboard with pigtail of one wire to one breaker? We need to free up two spaces for a new 2 pole circuit.
Might I suggest using tandem breakers instead of "doubling up" on the breakers? They are readily available for most panels. I know GE and Square D make them for their panels. They will allow you to keep the circuits seperated like they are now and probably intended to be. Saves a lot of trouble down the road.
Re: Splicing in Panelboard#6967 01/16/0210:44 PM01/16/0210:44 PM
If you're certain that the load on 2 particular branches is that light, there should be no reason you can't combine them with a pigtail. I wouldn't do it as regular practice though. Art 373-8 ('99 code. sorry, I don't feel like going to my truck) allows the splice. Remember some breaker terminals will accomodate 2 terminations. Sq.D QO, for one. And I believe Pushmatics design permits it as well.
Re: Splicing in Panelboard#6969 01/17/0209:35 AM01/17/0209:35 AM
I always use the pigtail method. We use mostly SQ D & our local SQ D rep told me that even though the QO breakers have 2 "tunnels" for wires they are only (UL) approved for one. He had no idea why SQ D puts 2 "tunnels" on the pressure clamp. (And our local inspectors will usually not allow two on the CB.)
Re: Splicing in Panelboard#6970 01/17/0209:56 AM01/17/0209:56 AM
What is the difference between a panelbox that will allow tandem breakers and one that won't? If the panel is old and missing the CTL label is it possible that tandem breakers are still OK? Does the number of neutral wire conncections on the neutral bar mean anything? i.e. there are a lot more holes that spaces for single breakers. Of course some are for different size wires.
The total load on the panel can't increase past the main breaker ampacity of course.
Re: Splicing in Panelboard#6973 01/17/0208:35 PM01/17/0208:35 PM
I am curious as to the difference too? I have never seen a CTL panel that will not accept tandem breakers and I have seen a lot of tandem breakers in use. (Even newly inspected installations that passed.) As you said, you still cannot exceed the amperage rating of the main breaker.
"Go back and talk to your Square D rep again. I have a QO breaker in my hands the wiring diagram shows 2 wires and the UL label gives torque specs for two wires also."
My box of 10 20A QO's don't seem to say anything about being rated for 2 wires under the screw?
"Do not use tandem breakers unless your panel is designed for them (it must have a Class CTL label). Never ever put more circuits into panel than it is listed for."
The last time we checked with our Square D rep, ALL QO panels where listed to accept tandem breakers. Rep: "We wouldn't make the breakers, if the panel wouldn't be able to take them."
Are we talking about the same Square D here? Is there a rep in the group that can shed some light here?
[This message has been edited by bigbluewirenut (edited 01-17-2002).]