More questions about subpanels

[Copperthief]

Well here's another ... I was talking with my cousin ... And a friend of his service /panel caught on fire !!! It was a 100 amp panel. At the panel it fed a sort of subpanel to the house... 100 amp breaker at the house .... But at the panel at the service it had the 100 amp subpanel breaker and the hot water heater breaker which was 30 amps... I said it was too much there at the service ... Which was why it caught on fire ... I thought at the very least he need 125 amp panel for the sub panel and the water heater ... I there was something about 125% of something ... But how is that done ??you got 20 to 30 breakers all 20 amp and the service is 150 that doesn't add up...

 

[augie47]

The number of breakers and the size of them is of little importance compared to the primary factor of determining the load. The sum of the breaker amperages in a panel is often 5 or 10 times the main.

 

[GoldDigger]

You cannot just add up the breaker sizes instead of actually calculating the loads. But a total of possibly 130A on a 100A service is not a good sign, especially with a reduced size service wire set.
On the other hand it is at least as likely that the culprit was a loose wire connection.
Any aluminum by chance?