Square D QO Breaker Panel Question

[HandLogger]

Although I've spent over 40 years in the electrical field (as a bench tech and an EE), I'm not familiar enough with the internal design of Square D breaker panels to know whether or not a Square D QO main breaker -- like this one -- is designed to fit into the top of all of the QO-series of breaker panels?

Thank you for your time

 

[Dennis Alwon]

@jim dungar We have a mod who worked for Sq. D for years so I bet he knows the answer. If sq. D is like other manufacturers there are many variation depending on the age of the panel

 

[jim dungar]

I haven't worked with loadcenters for many years.
Square D has had several different main breakers with probably the biggest style change occurring some 30 years ago.

The style in the OP is a QOM1 and goes to roughly 125A. The next size up breaker is a QOM2 style. These two styles are not interchangeable even though they may have the same handle rating.

 

[brantmacga]

For reference, here are the sizes available in each frame …

Sent from my iPhone using Tapatalk

 

[tom baker]

As D has very good tech support. They will need the class, series and date from the panel

 

[kwired]

It only fits QO single phase loadcenters made since they went with that style of main, sometime late 1980's I believe. Definitely was by the 1990's.

Early Homeline panels did not use this but eventually they switched to that style main breaker as well. As mentioned there is the two different physical sizes, the smaller one only goes to 125 amps, but the larger size can include 100 and 125 amp units.

 

[cadpoint]

I'm not familiar enough with the internal design of Square D breaker panels to know whether or not a Square D QO main breaker -- like this one -- is designed to fit into the top of all of the QO-series of breaker panels?

I've never seen a side mounted Sq D breaker either, don't feel bad. FWIW that's why I'm here.

As a para professional, I really do appreciate the Sq D!

 

[Fred B]

Usually the panel enclosure will have a list of approved breakers and part numbers, including the main breaker and or if main lug if a main breaker can be added with it's part number.

Found the hardway (older NEMA 3 panel with all the stickers worn and unreadable or missing) that every panel of a given range by a given mfg of a given age are not the same (purchased a part that ended up didn't fit).

 

[kwired]

Usually the panel enclosure will have a list of approved breakers and part numbers, including the main breaker and or if main lug if a main breaker can be added with it's part number.

Found the hardway (older NEMA 3 panel with all the stickers worn and unreadable or missing) that every panel of a given range by a given mfg of a given age are not the same (purchased a part that ended up didn't fit).

All single phase Square D load centers (other than the small 6-8 space ones with a horizontal bus) made since this style of main came out utilize this style of main breaker. They are all convertible from main lug to main breaker or vice versa as well. Three phase load centers either have a back fed main for 100 amp or less or use a QBL type breaker as the main, which can be turned upside down if you want to bottom feed the panel and still have proper switch orientation of the handle. This been that way for about same amount of time that they been making the QOM style mains for the single phase panels which has been for around 35 years or so. been some minor changes but basic layouts and dimensions have remained the same. I recently had a bus failing in a load center that was around 30 years old. New replacement panel was rather quick and easy as all I had to do was swap guts from new into old cabinet and everything fit just fine.

 

[HandLogger]

Thanks for the information, gents. The panel in question is a Square D Q0B20M100 Series G1. I recall that one can decipher the age range of the panel based on the serial number, but I'm wondering if there's a particular place in the panel that is reserved by Square D for the serial number stamp? I was sent several high-res digital photos of the panel, but I can't find the serial number stamp.

By the way, is there a way to differentiate Square D panel part numbers to verify whether it's a QOM1 size frame or a QOM2 size frame?

 

[HandLogger]

EDIT TO LAST POST:

Although I was looking at the photos of the inside of the panel itself, I eventually discovered a stamp on the inside of the panel cover. Although I had to zoom in quite a bit to make it out, it looks like A02X6491. As I recall, the "A" is for January, the "02" is the day of the month, but I had to look up what the "X" designates...which, as it turns out, is either 1970 or 1991.

Here's a digital photo of a QO120 breaker taken from the panel. Does anything in the photo help nail down the year of the panel?

https://imgur.com/a/Ya5C2EE

 

[jim dungar]

That style main breaker was not used in 1971, so yours is probably from 91.
The part number you gave was for the box, hence the B in the number after the QO. The cover would have a C in that location. Your panel (interior and box) would have been ordered simply using #QO20M100.

 

[kwired]

That style main breaker was not used in 1971, so yours is probably from 91.
The part number you gave was for the box, hence the B in the number after the QO. The cover would have a C in that location. Your panel (interior and box) would have been ordered simply using #QO20M100.

1971ish the 125 amp and less main breakers would been one that took up top two spaces on both sides. Today a replacement for it would simply be a QO2100, possibly with a VH suffix for higher interrupt rating if needed/desired. Today's version only utilizes two spaces on one side should still use the original hold down clamp on the foot of the breaker. Supply conductors possibly will not reach as is because the lugs on the original possibly faced up and now will face to the side. Original would have looked like one in image below. I copied from a place that resells this old stuff and it was like $400. Can get today's QO2100 for about $100 at Home Depot.

 

[jim dungar]

1971ish the 125 amp and less main breakers would been one that took up top two spaces on both sides. Today a replacement for it would simply be a QO2100, possibly with a VH suffix for higher interrupt rating if needed/desired. Today's version only utilizes two spaces on one side should still use the original hold down clamp on the foot of the breaker. Supply conductors possibly will not reach as is because the lugs on the original possibly faced up and now will face to the side. Original would have looked like one in image below. I copied from a place that resells this old stuff and it was like $400. Can get today's QO2100 for about $100 at Home Depot.

View attachment 2561807

The 1971 partnumber would have been QO2100TF. The lugs were on top of the breaker not the sides. These went obsolete in the 80s.

 

[HandLogger]

Thanks again, gents. Back to the main breaker...I was curious if anyone actually chemically treats the exposed end of copper conductors prior to mounting to a main breaker like the one mentioned in the OP (QOM100VH)? The feeders are specified as either 2 AWG or 4 AWG Type THWN-2; hence, the question.

 

[kwired]

Thanks again, gents. Back to the main breaker...I was curious if anyone actually chemically treats the exposed end of copper conductors prior to mounting to a main breaker like the one mentioned in the OP (QOM100VH)? The feeders are specified as either 2 AWG or 4 AWG Type THWN-2; hence, the question.

Anti-oxidation coatings is maybe done by some, though it is more common with aluminum conductors, nothing that is intended to cause chemical reaction is used.