I have a 50 year old Murray box that will not take the current circuit breakers. I need to find out how to order or find the number for a 4 pole 20/30/30/20 breaker that will fit the old style box or universal version with the deeper cutout on the plugin back?
The 20/30/30/20 (called a "quad" breaker) is created by coupling two tandem or "twin" breakers; a 20/30 and a 30/20. In older panels twins will only fit in certain slots, because there were limits to the total number of circuits you could have in those panels. So only a few of the slots allowed the use of twins. On the directory sheet, usually glued to the inside of the door of the panel, there will be a difference in the way the breaker slots are shown, indicating which ones will accept twins.
The slots that will accept twins will also accept full space breakers, but not the other way around. So one thing you can do is to check your directory to see which slots you can use and if they have full size breakers in them, move those to other slots and open up the slots that will accept the twins/quad.
If there are no slots left in your panel that allow twins, then you have to either replace the panel, or add a "sub panel".
There's no such thing as a universal breaker
Several of the 1" breaker lines will seem to interchange. But they don't. The critical point, where they clip onto the bus stab, is different. That means instead of a curved surface contact, they are making a point contact, with all the current going through a tiny spot of metal. This causes overheating, arcing, and fire. At the least, it damages the bus stab, so that breaker space is no longer usable.
You must use breakers listed for your panel; which will generally come from your panel's manufacturer or its successor. There's good money in supporting panels, so the vast majority of panels have current maker support. Murray is at the top of that list!
"Double-stuff" breakers are even more sensitive to this, because they put 2 circuits on 1 bus stab. For instance yours will pull 50A on each stab. Mind you: a bus stab, which supports that breaker and the one across from it, are only rated 125A for both. So fooling around with random breaker makes is madness. They snap in, but they don't snap in right.
If a store sold you the wrong brand of breaker, they should take it back. Shame on them!
Siemens still markets that line as Murray. Yes, I know you got a Siemens breaker and it didn't fit. That's because you got the wrong Siemens breaker; we'll come around to that.
In certain rare cases, one manufacturer makes a breaker specifically for competitor and obsolete panels, and goes through the UL-Listing product testing process to get the breaker UL-Classified for that competitor panel. Siemens QD breakers are specifically made for Square D QO boards (and won't fit anything else). Eaton CL is UL-classified for Murray boards (but they don't make double-stuffs in CL).
Your trouble probably relates to CTL
You're using a type of breaker we call a "double-stuff", which puts 2 breakers in the space normally used by one (or in your case, 4 for 2).
Obviously, double-stuff breakers would let you put 84 circuits in a panel with 42 spaces. That worried some, so in 1965 they made a change to NEC called Circuit Total Limitation, or CTL, which requires panels only support double-stuffs in a limited number of spaces, and required special gating/keying to prevent abuse. This change took effect around 1966-67, right near your "50 year" claim.
However, there were plenty of legacy panels that still needed support. So double-stuff breakers continue to be made in "Non-CTL" versions, which do not have the necessary keying. These are often called "cheater" breakers, since they can often be put in illegal positions in CTL panels.
In 2008, CTL was repealed from NEC. So manufacturers no longer are obliged to put CTL keying in new panels. (However, changing a panel requires going back to UL and getting the panel re-listed, so naturally manufacturers are slow to it; so CTL limited panels are still sold today.)
So now that CTL is repealed, is cheating legal? No. In 2008, this language was added:
408.54 Maximum Number of Overcurrent Devices. A panelboard shall be provided with physical means to prevent the installation of more overcurrent devices than that number for which the panelboard was designed, rated, and listed.
For the purposes of this section, a 2-pole circuit breaker or fusible switch shall be considered two overcurrent devices; a 3-pole circuit breaker or fusible switch shall be considered three overcurrent devices.
That means CTL restrictions still apply to CTL panels (since UL has not tested the panels in "cheat mode", and cannot vouch for their safety).
Had you said "51 years" I would have taken it to be a 1969 panel. But a super-round number like "50 years" is usually a rough number, so I cannot tell if your panel is old enough to pre-date CTL. If you look at JRaef's answer, that has an example of what CTL labeling looks like on a CTL panel.
Since your breaker does not fit, you are trying to use a CTL breaker in a non-CTL panel or vice versa; ... or you are trying to fit a CTL breaker in a CTL panel in a space where that is not allowed. You will need to look at your panel's labeling and determine whether you have a CTL or non-CTL panel. If a non-CTL panel, get a non-CTL breaker. If a CTL panel, get a CTL breaker and only put it in approved spaces.
I cannot possibly tell you to put a non-CTL breaker in a CTL panel.
If your panel is over-stuffed and you want to put more circuits in it than the panel allows, then it's time for a subpanel. A subpanel is within the reach of a careful and diligent DIYer. Since you are resorting to double-stuff breakers, your panel is already past full - get a BIG subpanel, like a 30-space or more. I would get one large enough so you can de-double-stuff your panel entirely and still have at least a dozen spare spaces. You can stay with Siemens/Murray if you like it.
We bang the "get a BIG panel" drum really hard around here, because spaces are cheap at purchase time, and we see so, so many questions about difficult, complex, or expensive problems that arise from running out of panel spaces. Just like yours!
You may still get the "Murray" made by Siemens breaker you need, but I was unable to get the downloadable tool from the website below to work. If you have a non-CTL panel it looks like Q23020CT2NC could possibly what you're looking for, the NC in the model number is non-ctl.
From the Siemens website:
Murray Phase-Out in 2020 The Murray brand will be phased out and replaced by equal Siemens products. This adjustment will better align with changing markets, help simplify offerings, improve supply chain stability and enhance inventory positions. The Murray phase-out will be accomplished in three phases: 1). Murray Circuit Breakers and small circuit load centers will be discontinued in December 2019 2). Murray Rock Solid Load Centers will be discontinued in Summer 2020 3). Murray Meter Sockets will be discontinued in Fall 2020
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