- Reaction score
- 17,016
Fault finding. Good to systematically and logically investigate the problem, then the culprit has been staring you in the face...
phone call from new customer- no power.
get there, split rcd board. “It’s that big switch that won’t stay up”, says the woman
Ok, the rcd. Unplugged everything I could find, did some initial dead tests... everything seems ok. Powered up RCD, it holds... turn on each mcb in turn... all holding... Great!
Two minutes pass, then click! First mcb trips, downstairs sockets. Damnit.
Wasn’t the rcd at all, was the mcb!
She’s on the phone to her husband, “try this, try that!” It’s ok.... I’ll find it!
Split the ring, still everything is ok. Can’t find a fault, but there must be one.
Changed the the mcb, just to rule that out.
clamp ammeter on the outgoing legs.... wildly fluctuating between .5, 1, 5, 7A.... keeps jumping up and down.... not a steady rise.
The husband comes home at about 4pm.... he’s an industrial boiler engineer, but hell he needs to stay away from electrics!
“hmm, I’ll have to run an extension into the garage for the freezers.“
“Freezers!?!” As in plural?
Turns out there’s a single socket in the garage, looks like it’s spurred from a double in the kitchen, back to back.
From this socket is an 8! Way extension lead with a fridge freezer, a chest freezer, a tumblr dryer, a couple of battery chargers and.... wait for it.....
a 3kW immersion heater!!
Seriously!
So all these appliances turning on at once is stretching the 13A fuse in the extension lead, but something still has a fault to take out a 32A breaker at random.
I’m going back tomorrow. It’s fixed and working just now. I’ve told him to try each freezer in turn in the socket, but I’ll have to do something else with the immersion, it’s own radial circuit.
phone call from new customer- no power.
get there, split rcd board. “It’s that big switch that won’t stay up”, says the woman
Ok, the rcd. Unplugged everything I could find, did some initial dead tests... everything seems ok. Powered up RCD, it holds... turn on each mcb in turn... all holding... Great!
Two minutes pass, then click! First mcb trips, downstairs sockets. Damnit.
Wasn’t the rcd at all, was the mcb!
She’s on the phone to her husband, “try this, try that!” It’s ok.... I’ll find it!
Split the ring, still everything is ok. Can’t find a fault, but there must be one.
Changed the the mcb, just to rule that out.
clamp ammeter on the outgoing legs.... wildly fluctuating between .5, 1, 5, 7A.... keeps jumping up and down.... not a steady rise.
The husband comes home at about 4pm.... he’s an industrial boiler engineer, but hell he needs to stay away from electrics!
“hmm, I’ll have to run an extension into the garage for the freezers.“
“Freezers!?!” As in plural?
Turns out there’s a single socket in the garage, looks like it’s spurred from a double in the kitchen, back to back.
From this socket is an 8! Way extension lead with a fridge freezer, a chest freezer, a tumblr dryer, a couple of battery chargers and.... wait for it.....
a 3kW immersion heater!!
Seriously!
So all these appliances turning on at once is stretching the 13A fuse in the extension lead, but something still has a fault to take out a 32A breaker at random.
I’m going back tomorrow. It’s fixed and working just now. I’ve told him to try each freezer in turn in the socket, but I’ll have to do something else with the immersion, it’s own radial circuit.