Tandem Breaker - Box incompatible?

hyunelan2 · 08-01-2012, 10:08 AM

Hello all. I installed 2 new outlets in garage, each on their own circuit (GFCI protected outlets, 12g THHN in conduit). I wanted to use a tandem breaker so that these two outlets were easy to identify in the box. Upon trying to install the breaker, I think that perhaps my box is not compatible with tandem breakers - or I got the wrong breaker. From what I've read, the bus stabs are not notched, so they are not compatible/allowed to be used with tandems.

Just double checking here. I can get the breaker in, but it doesn't seat all the way, so that's wrong. I've got room to put 2 single pole 20a breakers, so it's not the end of the world, just not what I wanted.

(click image for larger picture - tandem and single pole 15a side-by-side)

**oh'mike** · 08-01-2012, 10:23 AM

What brand box---what do the existing breaker have printed on them---

hyunelan2 · 08-01-2012, 10:26 AM

Square D box, don't know the model (installed in 2002).

Existing breaker is pictured (15a):
Type HOM
DP-4075

Tandem is:
Type HOMT
DP-4075
CTL

Upon further reading, I need to look at the diagram in my box. It is possible that there are slots that allow tandems, they are just all in use by standard breakers.

Oso954 · 08-01-2012, 02:07 PM

The box model number should be on the inside of the door.
It will be something similar to
HOM12M100C or
HOM1224M100TC, etc.

hyunelan2 · 08-01-2012, 02:13 PM

HOMC40UC
Series 501
Type 1 Enclosure

The HOMC40UC is no tandems allowed. This should be a lesson in do your homework before buying supplies. Looks like I'll need to go pickup 2 standard 20a breakers.