Comment by Kirby64
7 hours ago
> Imagine someone buys 5 panels that can each supply 5amps. They plug them into outlets on a 40 amp circuit. They then proceed to run their toaster, microwave, vacuum, and hair dryer. They can draw 65 amps through the wires before the circuit breaker trips. (40 from mains, 25 from the panels)
Circuit breakers trip bidirectionally, so the circuit breaker itself would protect if too much current is drawn through to the mains panel.
How, precisely, would you get 65A through the wiring on this 40A circuit, if I drew 40A of consumption and had 25A of supply?
The 25A cancels out the 40A, so the upstream feed would only see 15A total. You do get 65A of total current drawn through the breaker panel, which is a concern, but the supply wiring would not see 65A. Subpanels (which, this would be a subpanel if it only had 40A capacity) are typically going to be just fine.
Are you in the UK, perchance?
In the UK you typically make a ring circuit. In the US you make branching circuits.
In the US you get: Mains -> Breaker -> Outlet 1 -> Outlet 2 -> Outlet 3.
In the UK you get: Mains -> Breaker -> all outlets -> Breaker
In the US, assume I had 65A of load on outlet 3 -- I've plugged in too many things into a surge protector. Assume a bunch of solar panels are on outlet 1.
The the diagram looks like: Mains -40A-> Breaker -40A-> Outlet 1 -65A-> Outlet 2 -65A-> Outlet 3
Now, the breaker won't trip because only 40A are crossing the breaker. But 65A are on the wire between outlet 1 and 2 and between 2 and 3.
No, I’m in the US. What you’re describing does not exist in that capacity in the US. No multi outlet branch circuit exists that is backed by a 40A breaker. At most you’re going to see 20 amps for a regular outlet.
Either way, your scenario of a multi outlet branch circuit on a 20A outlet would also not be correct. Let’s just make it simple: 20 amps of solar gen and 20 amps of power gen, connected as follows:
Panel -> Breaker -> Solar outlet -> hairdryer outlet
The current would flow from the solar outlet to the hairdryer outlet fully, and the measured current through the breaker would be 0. All wires would be at 20 amps and therefore safe. (Lets ignore that 20 amp wire is only rated for that temporarily… continuous draw would be 16a…) No violation of any current limits and no danger.
Now, you could go crazy and connect 30 amps of solar and 30 amps of hairdryers and that would be dangerous, but we’re rapidly getting into the realm of incredulity. As soon as you removed the load/hairdryers you would pop the breaker.