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Replacing a panel rated for 150 amps with 200 amp panel and adding 4 circuits. I counted Amps of existing panel and things don't seem right, it looks loaded incorrectly, for 150 amps. So basically I want to break out the quad duplex on the right, into separate duplexes, and add 4 new 20 amp breakers. 1 is basically putting refrigerator on its own circuit. 1 is a sprinkler system, GFCI in garage, which was on an extension cord. The other 2 are kitchen outlets.

What I want is this.

Left side Right side
60-60 AC Surge-Surge
30-30 Furn 40-40 Range
(20,20) Tandem 30-30 Dryer
(20,20) Tandem 30-30 WH
15 20
15 (20,20) Tandem
15 15
15 20
20 15
20 20
20
(15,15) Tandem

Can someone tell me what the issues with this are and suggest improvement?

New panel enter image description here

The Original panel. original panel

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  • I edited your post to ensure both images showed up. Please make sure I have the Old/New labels on there correctly.
    – FreeMan
    Commented Jul 12, 2021 at 16:19
  • @FreeMan The mobile functionality is a bit more difficult, thanks for fixing the issue.
    – Ken
    Commented Jul 13, 2021 at 0:43
  • Can you provide us with the model number for the new panel? Commented Jul 14, 2021 at 19:19
  • @ThreePhaseEel It is one of these two - HOM4080M200PQCVP, HOM4080M200PCVP . With Plug On Neutral (both of these should be - but if one is not - the panel is Plug On Neutral.
    – Ken
    Commented Jul 19, 2021 at 2:46

3 Answers 3

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Whether breakers are on the left and right is (mostly) irrelevant.

Leg A and Leg B alternate 1" spaces down the panel. Using the most common numbering format, breakers are numbered top to bottom, alternating left to right, odd on left, even on right, spaces 1,2 are opposite each other but both on leg A.

Spaces 3,4 are the second one inch space, they are on leg B. Spaces 5 &6 on A. Spaces 7,8 on leg B. This pattern alternates down the panel.

To balance loads you have to compare all the loads on A (1,2,5,6,9,10...) and all the loads on B (3,4,7,8,11,12...).

Two-pole breakers that supply opposing 120v legs to get 240v like the Two-Pole 60A in spaces 1 & 3 are self balancing. (So you really don't even need to add those types.)

The quad in space 2,4 is a little tricky to describe. The top 40 and top 30 occupy the same 1" space, they both are fed by leg A. The 30/40 in space 4 both are fed by leg B. This configuration feeds one 240v circuit from the outside pair and another 240v circuit from the inside pair. Like the 60A on the left each 240v circuit balances itself.

Continuing down the left side, the 2P30 in spaces 5,7 is self balancing.

So far everything was a 240v circuit, so always balanced.

Space 9 has a split 20/20 breaker both those are on leg A. Space 11 also has a split 20/20 breaker, both on leg B. If the actual total loads on both halves of breaker 9 and total actual loads on 11 are equal they potentially could be balanced. I say potentially because really you can try identify circuits with similar simultaneous loads, but that's really mostly guesswork.

Bumping over to the top right side, spaces 6 & 8 are a two pole breaker, self balancing.

Spaces 10 & 12 are your most obvious cause of potential imbalance. Space 10 has a split 20/20, both on leg A. 12 has a standard full size breaker. If all three of these breakers are loaded 50% then space 10 would be loading leg A at 20A, and space 12 loaded at 50% would only put 10A on leg B.

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  • I posted a picture of new panel layout. Other pic was the original panel.
    – Ken
    Commented Jul 11, 2021 at 22:43
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The tandems can only go where they're allowed

I note your panel has more than 20 actual spaces. That means most likely, the manufacturer restricts tandems to only certain spaces (CTL). They will be shown in the panel labeling, or sometimes, the labeling says to look at the bus stabs (tandem-allowed spots have forked tongues).

DO NOT use alien breakers (other manufacturers) or non-CTL breakers (made for panels before the CTL rules came into effect) to circumvent CTL limits. Your plan to scatter tandems all over the panel is probably a no-go.

The surge doesn't need a dedicated breaker.

It doesn't actually draw any current (it would get hot if it did). So it can share a breaker with other loads.

You can either pigtail it (though some pooh-pooh this due to some stuff about "surges don't like turning corners" which I don't believe... gee, wouldn't corners protect loads also?) . Or if your breaker is UL-listed for 2 wires under a screw, you can have the surge be the second wire.

Watch your stab limits

The "bus stabs" sticking out of the buses, have "stab limits" - assume 125A if you don't see anything else in the panel label. Tandem and quadplex add up when counting.

Note that your top breakers are a 60A across from a 40/30 quadplex. The 40/30 adds up to 70A. That with a 60A = 130A. Whoops! Gotta watch those quads!

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  • That's the old panel with the 40/30 quad and yes it's odd layout., I intend the new panel to be a home lite, and organized as in the text of question, I have the panel and the surge for the panel mounts in it. I will post a picture of new panel played out like I wrote in text.old panel is obsolete, so no matching breakers- out it goes for that and other reasons.
    – Ken
    Commented Jul 11, 2021 at 22:03
  • @Ken if you stay Siemens you can reuse your breakers. With HOM you must buy all new. HOMeline isn’t unsafe, just poorly supported in general, and breakers are scarce right now. Another Siemens advantage is very good generator interlock support. Commented Jul 11, 2021 at 22:07
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You are (as many people do, don't feel bad) confusing total current rating (i.e., add up all the breakers) with actual usage. The reality is that while your big breakers (60 AC, 30 Furnace) will use close to the full rating (on the order of 60% - 80% of the rating - they actually are not supposed to use (except for startup) more than 80%), most of your other circuits will use a tiny fraction on any kind of regular basis. For example, you might have a 20A kitchen countertop circuit that uses 16A for 10 minutes each day and the rest of the time < 1A. Or a 15A lighting circuit that, even if all the lights are left on, uses only 3A. Etc.

There are formulas and worksheets to figure out what your total utility service needs to be based on electric appliances, size of the house, etc. But in many (probably most) unless you have an electric vehicle charger or on-demand electric hot water heater, 100 - 150 Amps will be plenty.

However, your panel can, and should, be much larger. You can have a 100 Amp service with a "200 Amp" panel - just replace the main breaker with a 100 Amp breaker. The reason to do that is spaces. Each space is an ordinary 120V breaker or 1/2 of an ordinary 240V breaker.

In your case, you probably don't need more power. But you do need more spaces. Not only to add more circuits, but also to have the ability to add GFCI and/or AFCI to existing circuits. Tandem/duplex/double-stuff are not available with GFCI or AFCI. At a minimum, your new circuits will need GFCI, which can be done at the breaker (but not with tandems) or at the receptacle. But they may also need (depends on NEC version in force in your area) AFCI, which, practically speaking, is best done at the breaker.

Ideal would be to have everything on ordinary (not tandem) breakers and room to spare. Counting up the existing breakers + 4 new, that is 29 spaces. A good choice would be a 42 space, 200 Amp or 225 Amp main panel. **GET THE SAME BRAND/TYPE ** as your existing. That way you can reuse the full size breakers and, provided the new panel can handle them (it can get complicated) the tandem breakers. Then after you have all the existing breakers transferred, you can add new breakers as needed. 13 spaces leftover for future expansion.

If you think you really need more than 100 Amp service (and main breaker), you need to do a real load calculation and then discuss with your utility as to how to proceed. It may be "swap the main breaker", it may require a meter swap and new wires from the pole to your meter, all beyond your control.

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  • GFCI outlets are cheaper than GFCI breakers and the added benefit it resets right at the outlet. Also has test button right there. Existing panel is Obsolete Sylvania panel. Nextdoor neighbor has same panel and an insurance company said they will not insure his house unless he changes the panel.
    – Ken
    Commented Jul 12, 2021 at 2:49
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    GFCI outlets can be hidden behind a couch or difficult to access under a dining room hutch. GFCI breakers are always visible and accessible the moment you open the panel door. There are always trade-offs in life, @Ken...
    – FreeMan
    Commented Jul 12, 2021 at 16:23

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