InterNACHI teaches to take into account the meter and meter casing when determining service amperage. I’ve heard some even on these forums say that only the SE, main panel and breaker matter. But by that logic wouldn’t only the main breaker/fuse count? As many amps will flow as possible given a load until the breaker/fuse steps in.
So can somebody explain why either way to consider the meter and meter casing or not?
Older meters and their housings were a “clue” (and may still be for an old installation (I have seen houses that still hed 3 individual separated wires providing the service from the pole)). But this is no longer particularly relevant. Gauge of the SE cables is what you want to use.
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If you had a split bus panel there is no singular main as there can be up to 6 service disconnects. That leaves you with only the size of the service conductors and panel ampacity to determine the service size.
Using the meter to size a service can be of little value. A 200 amp, 5 jaw meter will fit in a 100 amp meter enclosure and vice versa. The utility company can install whatever meter they want so it is a poor indicator of the actual service size. Also something like a 125 or 150 amp service will likely have a 200 amp meter.
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But should we not use the meter casing or box as part of it? It’s terminals are only rated for a certain ampacity just like the main panel and SE correct?
Good question. If every other component of the service is say 200 amps then it’s a 200 amp service. If the meter enclosure is only 100 amps then you have a serious defect. IMO calling it 100 amp service due to the 100 amp meter enclosure would not be correct.
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Does that not contradict the “weakest link” thoerum that we have been taught for decades?
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That’s what I was asking thanks. I saw a round meter base with 100 or maybe 150 amp aluminum SE feeding a 200 amp panel and breaker home a few months back. The home had bootleg grounds. It was a mess.
I’ve also seen round meter bases on 100 amp panels. It seems that some of these were made for 100 amps and others for 60. I’ve heard it both ways. If the panel and SE cables look original I would lean towards it being 100.
Weakest links what can/should be provided and should be the stated service amperage in my opinion. If there is a substantial difference between service disconnect and other components (say a 200 amp main breaker with a new box but the feeders are only sized for 100) then that is called out in the report. The layman looking at the new box with a 220 amp main would likely assume he has plenty of power for his new Tesla charger and the phone will begin to ring. Older homes and upgrades are often piecemeal and an explanation is warranted.