To me it looks like he's got 100A for the whole house, 40A breaker for the garage and 80A for the rest of the house. Wouldn't that allow up to 40A (9,200Watts) in the garage (if at full load, that would leave 60A for the rest of the house) or 80A for the rest of the house (leaving 20A for the garage). If it goes over 100A for both then shouldn't the main 100A breaker flip? So he should be able to use up to 40A in the garage, as long as his rest of the house load isn't over 60A? If it goes over, shouldn't the main 100A breaker flip and then no the house wouldn't theoretically burn down? (whooper, that's a question mark there just in case you're not sure I'm asking a question).
Yes. That's basically correct. He's limited by the 100 A service (fuse, not circuit breaker).
His "in house" consumption is limited by the 80A rating of the RCD. However, if he is drawing substantial power in the garage, then it will be limited by the total load on the 100A main switch and fuse.
So, if he exceeds 100A, he will blow out the sealed service fuse, and then have to call the power company to come out, unseal it and replace the fuse and reseal.
The big problem he has in his house is the electric shower. As this has a 50 A dedicated circuit, this suggests that it is a 10.8 kW shower (45A operating load). That is a big load, and once you add lighting loads, kitchen loads, etc. a 40A mining load is starting to look infeasible.
One option is to upgrade the supply from a 230V (23 kW) supply to a 230/400V (70 kW) supply. If he asks his electricity supplier they will quote on the price of an upgrade (usually it's around £2000-£3000), and it'll be another £500-800 for an electrician to replace the fusebox with a 400 V one + another £few hundred for additional circuit installation. In reality, this probably isn't an economically viable option.
I agree. I would have considered the upgrade as a longer term investment in mining equipment, but the noise alone of having all those miner humming away may upset the neighbours. With the 4TH currently running (Avalon4 and S3's) it is already noticeable.
I think my basic understanding still holds. I am limited by the 100A across the whole house. The fuse rating are essentially peak values, and not what you can throw at the all simultaneously.
BTW there is another RCD on the right hand side of the panel rated at 63Amps (with another 50amp shower supply) - not that we use both showers at the same time, due to water pressure issues.
It's probably safer to invest the £2k in more miners and a dedicated remote hosting solution.
