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mattwnz

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#310818 24-Nov-2023 16:43
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Currently having an issue with a newish home which has two full size dishwashers installed in the kitchen, and it has always had these two dishwashers installed. Normally we don't use the two dishwashers at the same time, but recently we have for cleaning pots, and we have noticed that when they are both running and we then turn on the kettle, the fuse trips, and it knocks out power in one part of the house. I think the circuit is on a 16A circuit breaker.
The power outlets are labeled with the circuit number, and going around that house, I have found 15 double sockets connected to that same circuit, so it has been used in one large part of the house  across different 4 rooms. There are also 2 additional single sockets, one for each dishwasher. There is also an LED kitchen bench strip light on that circuit. There possibly maybe a few more outlets behind cabinets.  So that is a total of 32 individual outlets on that circuit. There are used in areas in the kitchen and living and lounge areas, and used for things like a TV, amplifier, toaster etc, which are all attached to that circuit. I don' think the circuit should be tripping from normal usage like this. Does it sound like the sparky has put too many outlets on the circuit, and is there any standard or best practice guideline in NZ showing what it should be? Is it easy for a sparky to fix this, by putting some of the circuits on a different circuit breaker? TIA


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CYaBro
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  #3163271 24-Nov-2023 16:53
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You sure it's a circuit breaker and not an RCD?

 

Can you get some photos?

 

RCDs usually protect a few circuits.

 

I would hope the sparky didn't put that many power outlets on one circuit!


 
 
 

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frankv
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  #3163323 24-Nov-2023 16:58
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I assume your dishwashers are heating the water themselves, rather than plumbed into hot water? Either way, when they turn on their heater I guess it'll be 1kW or so, so ~5A, and your kettle will also be 2kW ~ 10A, so if they're all on, there's a total of 20A through the 16A circuit breaker. But kettle plus 1 dishwasher is 15A, or 2 dishwashers alone is 10A. 

 

You'll likely run into the same thing if you have a toaster and kettle on at once, or run a heater at the same time as dishwashers. Other stuff like TV and amplifier are low power compared to any kind of heating device. Hopefully your washing machine and drier are on a different circuit.

 

For the time being, plug your kettle into the stove instead. 

 

Should be straightforward for a sparky to fix, assuming all/most wiring goes back to the meter board, and there's room for more CBs on the meter-board. But if all 17 outlets are daisy-chained together, there will be some re-wiring to do.

 

 


Bung
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  #3163340 24-Nov-2023 18:23
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Guess again, I think most dishwashers would be equivalent to a kettle. Ours is 2.3Kw. If the sparky stuck that many outlets on 1 breaker I doubt that they would be separately run back to the board. Even without 2 dishwashers there should probably be 3 circuits available in the kitchen. Don't forget the microwave.




mattwnz

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  #3163345 24-Nov-2023 19:17
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CYaBro:

 

You sure it's a circuit breaker and not an RCD?

 

Can you get some photos?

 

RCDs usually protect a few circuits.

 

I would hope the sparky didn't put that many power outlets on one circuit!

 

 

 

 

Thanks, yes it is the circuit breaker, and I have circled it in red below. The RCD is beside it which hasn't tripped. It is numbered (04), and the numbers quoted above are the number of (04) outlets I have found in the house, and they do all seem to lose power when it trips.  It is not a problem I have ever come across before and wouldn't expect it in a new house.  

 


mattwnz

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  #3163351 24-Nov-2023 19:34
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Bung:

 

Guess again, I think most dishwashers would be equivalent to a kettle. Ours is 2.3Kw. If the sparky stuck that many outlets on 1 breaker I doubt that they would be separately run back to the board. Even without 2 dishwashers there should probably be 3 circuits available in the kitchen. Don't forget the microwave.

 

 

 

 

There is a different circuit on the other side of the kitchen, and luckily microwave is on the different circuit. But they have overhead cupboards above the outlets, so don't want a steam from kettle under the cupboards.  But all of the  living room,  most of the hallway and half the lounge are also on the same circuit, as are almost all outlets in the kitchen. That is why I was wondering if there was any recommended guidelines they should follow on the max number of outlets per circuit.  


timmmay
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  #3163355 24-Nov-2023 19:44
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I've had this kind of thing happen, but in the laundry, with a clothes drier plus a front loading washing machine that heats its own water. Your only real option is to get an electrician in to run more circuits to the kitchen. That'll mean a new circuit breaker as well. If access isn't too difficult it shouldn't be crazy expensive, I guess (as a layman who has used electricians many times) 2-3 hours of work, a breaker, and some mains. cable.


  #3163358 24-Nov-2023 20:02
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Determination of maximum demand via limitation (the breaker will trip before damage occurs) is legal from the point of view of electrical safety.

 

The standards do include guidelines in Appendix C that suggest the initial twenty sockets should be assessed as 10A, and 5A for each additional twenty or part thereof - that would imply up to forty sockets counts as 15A, within the 16A MCB. Note that for the purposes of that clause, a double socket counts twice, so your situation calculates as 15A per the standard. As noted though, these are guidelines and subject to quite a lot of interpretation. Doubling the number of sockets doesn't really double the connected load; it's more about the floor space and the use of the space. 

 

 

 

However, the CGA and other consumer protection can come into play, especially given that you explicitly asked for accommodation for a second dishwasher, unless they were told they wouldn't be used simultaneously. 

 

I'd be curious to know how many socket circuits they ended up with and how large the house is. Was this just terrible planning or were they trying to skimp on circuits? If it's all daisy chained rather than a tee early on, there could also be fault current/volt drop issues, especially if it's all wired in 2.5mm^2.

 

When I was house-bashing we tried to avoid going past 10 doubles, especially for anything serving the kitchen, and get the kitchen loads pretty evenly split onto at least two circuits. Smaller houses with fixed heating can easily fit on four socket circuits without issues.




mattwnz

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  #3163366 24-Nov-2023 20:39
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timmmay:

I've had this kind of thing happen, but in the laundry, with a clothes drier plus a front loading washing machine that heats its own water. Your only real option is to get an electrician in to run more circuits to the kitchen. That'll mean a new circuit breaker as well. If access isn't too difficult it shouldn't be crazy expensive, I guess (as a layman who has used electricians many times) 2-3 hours of work, a breaker, and some mains. cable.



Unfortunately that isn't an option because it is a skillion roof with no accessible roof space. So they're is no accessibility to services without cutting into gib.

Daynger
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  #3163375 24-Nov-2023 21:06
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How many power points in the entire house?

 

How many power circuits at the board?

 

Could be an easyish fix if there are multiple cables run into the one circuit breaker or a nightmare if they have used one cable from the board and strung out from there.

 

I would be getting in contact with the builder and or the electrician that wired the place and get them figuring it out, new build should have a workmanship guarantee.

 

20 outlets on one breaker is shithouse, especially when including kitchen outlets, I limit to 7 usually and kitchens will have at least two circuits to combat nuisance tripping.

 

At least they havnt used the chinesiest of chinesuim circuit breakers.


mattwnz

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  #3163383 24-Nov-2023 22:17
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Thanks. The house is multigenerational and is over 300sqm. There are 21 breakers for lights and power circuits combined. Not sure how many double outlets but quite a lot, at least 2 or 3 each room. But the most are in the kitchen and living areas and that circuit seems to have a lot more on it than any other circuit. We will be contacting the builder to see if there is an easy solution.

  #3163394 24-Nov-2023 23:37
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Count the C16s on an RCD - that'll be your socket circuits.

 

21 sounds like a lot, but it might not be if you're including RCDs, lights, water heaters etc. in that list. 

 

 

 

One would expect that a large house like that would have a correspondingly large kitchen justifying 3+ circuits. 


mattwnz

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  #3163397 25-Nov-2023 00:12
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There are 7 RCDs, so 3 circuit breakers per RCD. The do include power and lights.  The are also extra breakers for the heatpumps and 2 HWCs. It is also on triple phase power. But it means there are only about 3 spare slots available for any additional breakers. 


  #3163398 25-Nov-2023 00:21
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3 circuits per RCD is the legal maximum. I would assume there are roughly 14-16 socket circuits as they tend to end up about 3:1 sockets:lights.

 

 

 

Unless you have somewhere upwards of 200 double sockets, someone has seriously screwed up on their circuit planning. Your circuits serving the kitchen should generally have the fewest total sockets, not the most.

 

 

 

Perhaps someone's spec called for stuff like garage door openers, fridges, gas heaters to have dedicated circuits but omitted the kitchen?


Daynger
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  #3163647 25-Nov-2023 15:07
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mattwnz:

 

There are 7 RCDs, so 3 circuit breakers per RCD. The do include power and lights.  The are also extra breakers for the heatpumps and 2 HWCs. It is also on triple phase power. But it means there are only about 3 spare slots available for any additional breakers. 

 

 

 

 

Post up a pic of your entire switchboard please.

 

Also count up how many power points in the house.

 

 


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