What differentiates a Siemens 30/30 panel from a 30/40 exactly?

[NoahsArc]

Same amperage, same number of breaker slots, one just happens to be able to take 10 tandem breakers, what exactly distinguishes these two panels other than larger neutral/ground bars? What's the risk in using a 3030 for 40 circuits in the real world?

 

[hbiss]

I really don't know why they even make the 30/30. AFAIC just sell the 30/40 and if someone wants to use tandems use them, if not, don't.

-Hal

 

[Jraef]

The difference is that the spaces for tandems have a slight difference in the bus tangs that the breakers stab onto. I think with Siemens there is a notch in them and a part of the tandem breaker stab assembly has to fit in that notch. That component in the tandem stab then prevents you from stabbing a tandem breaker into any other stab. I'm not sure this image is Siemens, but the idea is the same;

The concept goes back to old rules on circuit limitations that are no longer in place, but the designs remain.

 

[Dennis Alwon]

There are straight 20, 30 40 circuits or you can get 20 spaces with all of them accepting tandems or twin breakers. You also can get 30/40 which means there are 30 space and 10 of the spaces will accept twins.

Personally, I always got the straight 40 circuits and occasionally the 30 circuit panels because I like the space that the panels afford you. It makes it easy to have a good looking panel.

 

[electrofelon]

The concept goes back to old rules on circuit limitations that are no longer in place, but the designs remain.

Ok but why isn't every load center just a X/2X? There must still be something that allows or disallows for the number or where tandema can go. Is it neutral bar space? Does the product standard still have some minimum dimensions or something that would perhaps provide incentive to not allow tandems in all spaces?

 

[Jraef]

Cubic inches / fill space, temperature rise, neutral connections, wire bending space, and the fact there used to be a limit of 42 circuits in a panel which, if you have a 2 pole main, resulted in 40 circuits in the feeder space (no longer the case).

 

[letgomywago]

My favorite Siemens panel right now is their 3048. The issue with the tandem slots is there's less contact area so that portion of the buss is lower contact area. Big loads can go on the full stabs with that panel and small ones in the tandems if for some reason they have a need other than afci and gfci. I haven't seen a new 3040 since 2020. Always gotten a 3048 since then. Also I might be wrong but the tandem slots I think are only rated 110a instead of 125 but I haven't looked at that sticker in a while

 

[ramsy]

Also I might be wrong but the tandem slots I think are only rated 110a instead of 125 but I haven't looked at that sticker in a while

that would explain why 50/50 quads are available, but 60/60 quads don't exist.

 

[ramsy]

Cubic inches / fill space, temperature rise, neutral connections, wire bending space, and the fact there used to be a limit of 42 circuits in a panel which, if you have a 2 pole main, resulted in 40 circuits in the feeder space (no longer the case).

Sounds like Non-CTL tandems are violating equipment listings, especially if all tandem bus stabs are full?

 

[kwired]

My favorite Siemens panel right now is their 3048. The issue with the tandem slots is there's less contact area so that portion of the buss is lower contact area. Big loads can go on the full stabs with that panel and small ones in the tandems if for some reason they have a need other than afci and gfci. I haven't seen a new 3040 since 2020. Always gotten a 3048 since then. Also I might be wrong but the tandem slots I think are only rated 110a instead of 125 but I haven't looked at that sticker in a while

If you plugged a 125 amp breaker onto a notched bus space I pretty certain you still get full contact with the breaker. So I don't think you lose any contact area. If anything you lose a little heat sink area on the bus.

 

[NoahsArc]

My favorite Siemens panel right now is their 3048. The issue with the tandem slots is there's less contact area so that portion of the buss is lower contact area. Big loads can go on the full stabs with that panel and small ones in the tandems if for some reason they have a need other than afci and gfci. I haven't seen a new 3040 since 2020. Always gotten a 3048 since then. Also I might be wrong but the tandem slots I think are only rated 110a instead of 125 but I haven't looked at that sticker in a while

I priced out the replacement, and a 3048 with 6 tandems was about the same cost as a 4060 without tandems, and my main supplier doesn't have any Siemens tandems in stock anyway. I don't see the value in going from a 3030 to a 3048 when tandems are 5x the cost of a single cct breaker.

The difference is that the spaces for tandems have a slight difference in the bus tangs that the breakers stab onto. I think with Siemens there is a notch in them and a part of the tandem breaker stab assembly has to fit in that notch. That component in the tandem stab then prevents you from stabbing a tandem breaker into any other stab. I'm not sure this image is Siemens, but the idea is the same;

The panel I'm looking at is a 3030 with 6 tandems already installed, so unless they notched the bus...

 

[James L]

I don't see the value in going from a 3030 to a 3048 when tandems are 5x the cost of a single cct breaker.

The price difference isn't that much.

I just left the blue big box store.
A single 15a breaker was $7.00
A 15a twin was $17.00

The price per breaker on the tandem would be $8.50 ($1.50 higher for each handle)

For me, a 40 space panel is egregiously tall. A 30 space panel just looks a little nicer in my opinion

 

[electrofelon]

My favorite Siemens panel right now is their 3048.

For what type of work? For residential now not much opportunity to use tandems/quads. For most houses now I don't think I would want anything less than 40 full spaces , and even that is often not enough. Of course 30's should be fine for a double panel service or with a sub somewhere. My "new" thing is to almost always install a sub in a house.

 

[James L]

My "new" thing is to almost always install a sub in a house.

My "new" thing is to set every panel up to become a subpanel later.... Add a ground bar on each side, and land only the neutrals in the neutral bar.

 

[LarryFine]

My "new" thing is to set every panel up to become a subpanel later.... Add a ground bar on each side, and land only the neutrals in the neutral bar.

Absolutely! I have been doing that for over 50 years (unless impossible).

I did a service upgrade for an uncle when I was 15 (I remember because I didn't have a driver's license yet and had to be driven), and years later, I went back to add a generator. I replaced the SE with SER, but I had already separately landed the whites and bares.

 

[James L]

Absolutely! I have been doing that for over 50 years (unless impossible).

I did a service upgrade for an uncle when I was 15 (I remember because I didn't have a driver's license yet and had to be driven), and years later, I went back to add a generator. I replaced the SE with SER, but I had already separately landed the whites and bares.

It seems to me like it's actually faster to do that.

No more counting holes in the neutral bar to see if I need to double or triple my grounds to make sure there's room.

$15 on ground bars. Can save a whole hour making up that panel

 

[LarryFine]

$15 on ground bars. Can save a whole hour making up that panel

Or a lot more time having to re-make up a panel.

 

[electrofelon]

My "new" thing is to set every panel up to become a subpanel later.... Add a ground bar on each side, and land only the neutrals in the neutral bar.

I do to, but with a twist! I install the ground bar horizontally up top (or sometimes both top and bottom depending on where cables come in) and that keeps my egcs neatly at top so they don't clutter up the gutter.

 

[electrofelon]

$15 on ground bars. Can save a whole hour making up that panel

I usually Siemens and it's nice they come with two ground bars. SQ D drives me crazy , have to buy them separately

 

[electrofelon]

Absolutely! I have been doing that for over 50 years.

Oh look at you mister way ahead of the times. I suppose you've had a "Mr Fusion" personal fusion generator for a few years now too?