Circuit breaker vows

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KellyP

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#272585 3-Jul-2020 12:56

I just came home to find my heat pump wasn't operating, sure enough the circuit has been tripped.

I switched the CB back on. No issues. After 20 minutes, same thing.

This time it won't come on. The heat pump was installed on an existing circuit - unfortunately it's my fault for not quering this with the installer at the time. This was done in August 2016.

I've also isolated the heatpump by turning off the outdoor switch and yet the rest of the circuit will not come on. I'm hoping it's just the MCD that is gone?

MCD: https://www.hagerelectro.com.au/e-catalogue/energy-distribution/modular-protection-devices/mcbs/mcbs-residential-6ka-c-curve/msn120/18994.htm

Heat pump: https://www.mitsubishi-electric.co.nz/heatpump/i/69108B/rapidheat-kj50-floor-console-heat-pump

My biggest question is why did it happen?

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#2516753 3-Jul-2020 13:18

Maybe wiring has been damaged. Melted?

Get the electrician around.

MikeAqua

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#2516793 3-Jul-2020 14:21

When this happened to us two houses ago, it turned out that wiring had melted inside the outdoor unit, which had caused a short circuit. The electrician classified it as fusion and our insurance policy covered this. So ... two new heat pumps

Mike

gregmcc

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#2516904 3-Jul-2020 17:20

You ask why it didn't want to reset right away, Overload protection on circuit breakers are thermal based, that is the heat rise on the bi-metal strip inside the circuit breaker has to cool down in order to reset, the more severe the overload the greater the heat generated and contained within the circuit breaker, and if it does reset the time before it trips will be shorter. It's kind of like boiling your electric jug, if it's just boiled and you flick the switch again it turns right off as it is already at it's "turn off point or trip point"

Most likely your heat pump has had a failure that has caused an overload condition in the wiring, the circuit breaker has done it's job, not so much a factor that the heat pump is on a shared circuit with power outlets, it's just a bit more inconvenient.

muppet

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#2516919 3-Jul-2020 18:01

I would suggest something like:

"I Circuit Breaker A, Take You, Circuit Breaker B, to be my lawfully wedded husband/wife. Through voltage spikes and dips, blackouts and brownouts I will always be by your side. You switch me on. With you, my circuit is finally completed"

Good luck with your vows.

MadEngineer

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#2516927 3-Jul-2020 18:17

^ what a muppet.

You're not on Atlantis anymore, Duncan Idaho.

KellyP

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#2516974 3-Jul-2020 18:46

Thanks for the replies. I'll get in touch with the heat pump sparky on monday.

gregmcc:

You ask why it didn't want to reset right away, Overload protection on circuit breakers are thermal based, that is the heat rise on the bi-metal strip inside the circuit breaker has to cool down in order to reset, the more severe the overload the greater the heat generated and contained within the circuit breaker, and if it does reset the time before it trips will be shorter. It's kind of like boiling your electric jug, if it's just boiled and you flick the switch again it turns right off as it is already at it's "turn off point or trip point"

Most likely your heat pump has had a failure that has caused an overload condition in the wiring, the circuit breaker has done it's job, not so much a factor that the heat pump is on a shared circuit with power outlets, it's just a bit more inconvenient.

Thanks - should this breaker have been a RCD considering its on the same circuit as other outlets (4 doubles and a single)?

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KellyP

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#2516975 3-Jul-2020 18:47

muppet:

I would suggest something like:

"I Circuit Breaker A, Take You, Circuit Breaker B, to be my lawfully wedded husband/wife. Through voltage spikes and dips, blackouts and brownouts I will always be by your side. You switch me on. With you, my circuit is finally completed"

Good luck with your vows.

haha - it's been a long week

gregmcc

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#2516978 3-Jul-2020 19:04

James Bond:

Thanks for the replies. I'll get in touch with the heat pump sparky on monday.

gregmcc:

You ask why it didn't want to reset right away, Overload protection on circuit breakers are thermal based, that is the heat rise on the bi-metal strip inside the circuit breaker has to cool down in order to reset, the more severe the overload the greater the heat generated and contained within the circuit breaker, and if it does reset the time before it trips will be shorter. It's kind of like boiling your electric jug, if it's just boiled and you flick the switch again it turns right off as it is already at it's "turn off point or trip point"

Most likely your heat pump has had a failure that has caused an overload condition in the wiring, the circuit breaker has done it's job, not so much a factor that the heat pump is on a shared circuit with power outlets, it's just a bit more inconvenient.

Thanks - should this breaker have been a RCD considering its on the same circuit as other outlets (4 doubles and a single)?

No as a heat pump is not a socket outlet, it is classed as a fixed wired appliance even though in your case it is wired to the same circuit as socket outlets

andrewNZ

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#2516985 3-Jul-2020 19:29

My money is on rodents.

I haven't seen a circuit breaker fail, but I've seen them do their job plenty of times.

This doesn't necessarily need to be a heat pump electrician, in fact it sounds like the heat pump isn't the issue. Any competent sparky should be able to sort this out for you.

KellyP

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#2516998 3-Jul-2020 20:07

andrewNZ: My money is on rodents.

I haven't seen a circuit breaker fail, but I've seen them do their job plenty of times.

This doesn't necessarily need to be a heat pump electrician, in fact it sounds like the heat pump isn't the issue. Any competent sparky should be able to sort this out for you.

This did cross my mind. The house is from 1908 (wiring is early 1990s). I also did wonder if the 10 days of rain we've had recently in Christchurch has had anything to do with it (i.e. water in the outdoor unit).

Danite

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#2517070 3-Jul-2020 22:30

I agree, if you have turned off the AC isolator and the CB is still tripping then its something else in the circuit (or water in the isolator if its outside). Next step would be go round those outlets that are not working and unplug everything then try again, if that works start plugging back in. If there is a fridge on the circuit my money is on that for the defrost element.

Agree with the CB failure comment, im an electrician and I dont think I have ever seen a CB fail in that it just starts tripping.

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KellyP

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#2517453 5-Jul-2020 07:57

Danite:

I agree, if you have turned off the AC isolator and the CB is still tripping then its something else in the circuit (or water in the isolator if its outside). Next step would be go round those outlets that are not working and unplug everything then try again, if that works start plugging back in. If there is a fridge on the circuit my money is on that for the defrost element.

Agree with the CB failure comment, im an electrician and I dont think I have ever seen a CB fail in that it just starts tripping.

Thanks for the reply - I have a sparky coming tomorrow.

Small update: the CB is definetely working as I unplugged everything as you mentioned and see what worked. Fridge not on the circuit.

Items such as an espresso machine and Google Home Speaker wouldn't come on however I managed to get one of these going (the LED lit up) and a touch lamp did turn on - however it's almost as the isn't enough voltage in the circuit as the lamp wouldn't go as bright as usual and was slow to get to level (not very stable either).

I was able to replicate this with two touch lamps on two different power outlets on the same circuit. I left it at that and switched the circuit back off.

andrewNZ

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#2517553 5-Jul-2020 14:38

Definitely stop trying to reset it, leave the breaker OFF.

A few reasons I say this:
- At some point the short might be blown clear, this could make the fault harder to find.
- Resetting the breaker might be creating a spark. Sparks are bad for obvious reasons.
- A partially cleared fault may allow the breaker to be reset, but still generate significant amounts of heat. Bad for obvious reasons.

Electricity is great, but faults are a significant hazard.

KellyP

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#2517847 6-Jul-2020 09:42

andrewNZ: Definitely stop trying to reset it, leave the breaker OFF.

A few reasons I say this:
- At some point the short might be blown clear, this could make the fault harder to find.
- Resetting the breaker might be creating a spark. Sparks are bad for obvious reasons.
- A partially cleared fault may allow the breaker to be reset, but still generate significant amounts of heat. Bad for obvious reasons.

Electricity is great, but faults are a significant hazard.

Thanks - yes I won't be touching it again. Will report back when the sparky has had a look at it.

KellyP

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#2520133 9-Jul-2020 15:09

Sparky found the problem in the spare bedroom:

We've done a partial renovation but unfortunately we never got to this socket. Sparky said we're lucky and I'd have to agree.

I'll probably get them all replaced soon.

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