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I want to upgrade my home's service from 100A to 200A. I have a new Siemens 200A meter / disconnect combo panel as well as a new Siemens 200A load center to replace the existing meter socket and 1960s GE TM2010E load center. The exterior meter panel and interior load center are separated only by an exterior wall.

I'd like to have the new meter panel installed before replacing the main load center inside the home. My reason is that I want to hire a professional to upgrade the home's service to 200A, but I would like to replace the main load center myself. The existing meter panel does not have a disconnect, but if I have the professional upgrade the meter panel first, I can then cut off power to the interior load center and have no risk of electrocution from the 200A feeder wires.

Can the new 200A meter panel be connected to the existing 100A load center in a code-compliant way? One issue that I see is that the new 200A meter panel will need to use 2/0 copper or 4/0 aluminum wires to feed the interior load center, but the existing 100A load center may not be able to accept wire that large. The 1960s 100A main breaker does not have a model number that I can see, but what I think is the equivalent modern GE panel (TM2010CCU) lists 1/0 as the max main breaker wire size.

Any help is appreciated.

EDIT: There is no useful labeling on the inside door of the load center (and I don't believe there ever was - the torn paper is from removing my own label), but there is a label affixed to the inside vertical wall. This is a very bad location for a label because it is obscured by the wiring in the panel's gutter. I apologize for the bad photos, but they are the best I could do in the overcrowded, live panel.

Because of the bad angle, here is my transcription of the photo's text regarding breakers: Cat. No. TM2010E Model 1 Use with GE Type TQL. TQL-AC. TQAL. TQAL-AC. THQL-AC or THQAL-AC Breakers

Panel Front Panel Front Inside Breakers Cover Removed UL Label Obscured Panel Info Label Info Label 1 Info Label 2 Info Label 3 Info Label 4 Info Label 5 Main Breaker 1 Main Breaker 2 Main Breaker #2 AL Wire

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  • Can you post photos of the labeling on the door of the existing loadcenter, or is that labeling completely gone?
    – ThreePhaseEel
    Commented Aug 8, 2021 at 23:42
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    I've added a photo. Sorry about the poor quality.
    – stmp945
    Commented Aug 9, 2021 at 1:12
  • Can you post photos showing the rest of the labeling for that matter?
    – ThreePhaseEel
    Commented Aug 9, 2021 at 1:17
  • I just added more photos - thanks!
    – stmp945
    Commented Aug 9, 2021 at 1:47
  • The Square D breakers are not viable or safe for a GE panel. Use THQL, or if they don't fit, Eaton CL. (CL not BR).
    – Harper - Reinstate Monica
    Commented Aug 9, 2021 at 2:38

1 Answer 1

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Yes, that will be fine - except - this will convert your inside panel from a main panel to a subpanel.

  • Neutrals and grounds must be entirely separated on the panel, with additional ground bars added as needed.
  • The neutral-ground equipotential bond (green screw or strap) must be removed since that bond will be in the meter-main now.
  • The feeder cable from meter-main to "main breaker" panel must have a separate neutral and ground (e.g. either 4-wire, or 3-wire inside metal conduit).

Now, the way I would handle that is by asking for a 2" metal conduit passage to be installed between new meter-main and old panel. It should be large enough for the triple 4/0 aluminum wire you'll need as service feeder, plus a ground wire. However for now you could just use #2 aluminum wire.

It should be alright to have a functionally unfused service feeder for such a short distance, for the same reason it's OK right now to have unfused service entrance wires - the distance is short.

However if the AHJ really stands on it, it's possible to obtain a 100A breaker for that panel.

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  • @stmp945 -- yeah, with a QN(R)2100 in the main panel, that should work just fine.
    – ThreePhaseEel
    Commented Aug 9, 2021 at 2:23
  • Thanks! To clarify: when the electrician replaces the meter main, he can re-use the existing #2 aluminum wire that is currently feeding the existing 100A panel. I can then convert the existing main panel to a subpanel by removing the bonding screw and ensuring the neutrals and grounds are separated. Then, I can replace this panel with a new 200A subpanel at my leisure and replace the #2 aluminum wire with 4/0 aluminum. Is that all correct?
    – stmp945
    Commented Aug 9, 2021 at 2:25
  • Additionally, will you please clarify what you mean by a "functionally unfused" service feeder? I think this just means that the 200A breaker in the meter main is larger than the 100A in the subpanel. Is that correct?
    – stmp945
    Commented Aug 9, 2021 at 2:25
  • I mean that the 200A breaker is too large to give meaningful protection to the #2(?) service entrance wires from meter to panel. So they need to comply with the rules for that. Unfortunately with these photos it looks like the wiring there is an SE cable running direct inside walls. That lacks ground, so that would need to be retrofit. The electrician and AHJ have a right to balk at that.
    – Harper - Reinstate Monica
    Commented Aug 9, 2021 at 2:37
  • +1 this is almost the exact procedure I used last when I upgraded my 100A service to 200 amp and replacing the meter socket with a meter main.
    – whatsisname
    Commented Aug 9, 2021 at 3:49

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