Electrical Overfuse on Main Disconnect

Hi everyone. I have inspected a Manufacture Home with many modifications on the electrical system. Let me see how I can ask the question by breaking down the findings of the electrical system. First, the house has a 200 amp main disconnect at the main electrical meter panel. In that main panel the Service Wires that come through the Electrical Mast are 2/0 AWG aluminum wire, instead of being 4/0 AWG. Which makes me think that the owner modified the panel and added a larger main disconnect than the original 150 amp. The same with another main disconnect in the breaker panel inside the house, where the wires that reach the panel are 2/0 AWG but the main is 200 amps. In addition, since the house has 3 breaker subpanels, a large one (subpanel 1) where the second main disconnect that I already mentioned is, and another two, where the first (subpanel 2) has 10 breakers and only two breakers have current cables. . The third subpanel (subpanel 3) is on the outside, and has four breakers that do have wires, and only one of the breakers has current. However, I did not notice any type of overheating of the breakers. Taking into consideration that the house is vacant with only the kitchen appliances, the AC, the Water heater, and a well pump, the question is: what is I supposed to report in the 4-point report, as a hazard in the electrical section? I look forward for your reply.

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2 gauge is larger than 4 gauge

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2/0 vs 4/0
image

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If the #2/0 service conductors are aluminum then you’re correct that the OCPD needs to be 150 amps or less. Some photo’s would help.

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Hi, Robert. Yes that correct! Here pictures of: main panel (3), and the rest are for Subpanel1, Subpanel2 (10 breakers), and Subpanel3 (smallest with 4 breakers)










The first pic of the Square D Homeline panel states 100 amp max. If that is the main, you got a mess!

/0 gauge, Marcel.

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5th image down, 'awg 2/0 compact al–triple, Ampacity at 90°C: 150 Amps.

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Yes, this first panel from the POCO (power company) is the service disconnect and, typically, everything downstream should be wired as a distribution (sub) panel.

I agree with David and would recommend a qualified electrician correct the electrical system for safe operation, as needed.

Looks like you have a pedestal with the service disconnect and feed through lugs to the indoor panel. Those #2/0 Al conductors are too small to be protected by the 200 amp OCPD.

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Yes, thats correct Robert. Is what I wanted to confirm/verify. Like I said in the first whole history at the begining, in summary:

  1. Main Panel and Disconnect (outside), have a 200 amp main disconnect and service wires coming in an the ones going to the inside Panel Breakers are 2/0 AWG.
  2. On the inside, we have Subpanel 1: with another 200 amps main disconnect, and a 2nd, Subpanel2 that is been service by an 100 amp breaker from the outside main panel. So, the problem I see on Sub1 is same as main panel, a 200 amp main disc. with coming wires of 2/0 AWG alum. On the Sub2 it only has double tab in one breaker, and another 8 breakers with no wires (no power on them).
  3. The last its a Subpanel3 (Sub3), by the side of the garage, and it has 4 breaker, where only 2 of them has power, ahd the othe 2’s don’t.
    There were modifications in the electrical system that definitetly.

Hi David. Thats a Subpanel, that I called Sub3. The house has 3 Subpanels and a Main Panel. The main panel, by the meter, has a 200 amps Main Disc. and 2/0 AWG Al wires.

I think the answer you are seeking is to mark the 4-Pt “Unsatisfactory” - check “other” under hazards and note “The service is undersized for the load”. If you choose, also add recommend further evaluation by a qualified professional.

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How did you determine that “The service is undersized for the load”?

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Strictly by the 200 Amp disconnect and the 150 Amp service entry. Not our job to calculate the actual load downstream, though helpful to take an educated look. NEC as follows: The minimum ampacity for ungrounded conductors shall not be less than the rating of the service disconnecting means specified in 230.79(A) through (D)."

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Better wording in my opinion would be “service entrance conductors not properly sized to overcurrent protection (main breaker).” Or you could say it the other way, “overcurrent protection (breaker) not properly sized for service entrance conductors.”

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You could also check the box for “Improper Breaker Size” and explain it’s the service disconnect. I usually reserve using that for branch circuit breakers. Though it is also relevant here - more of a personal choice and my $.02 more than anything…