Geekzone: technology news, blogs, forums
Guest
Welcome Guest.
You haven't logged in yet. If you don't have an account you can register now.


UsernameNotAllowed

20 posts

Geek


#272795 16-Jul-2020 13:10
Send private message

Hi

 

Our switchboard has a two pole main circuit breaker with one larger and one smaller cable coming into it. I'm wondering what this smaller cable is for. Both cables are 235V as I measured. Is this smaller cable like a 'supplementary' cable as the larger one is not enough?

 

I have attached a picture below:

 

 

Any ideas on this smaller cable's purpose? Thanks 


Filter this topic showing only the reply marked as answer Create new topic
mdooher
Hmm, what to write...
1424 posts

Uber Geek

ID Verified
Trusted
Lifetime subscriber

  #2524137 16-Jul-2020 13:15
Send private message

probably for the ripple (controlled hot water)

 

 





Matthew




Tracer
343 posts

Ultimate Geek


  #2524973 17-Jul-2020 20:27
Send private message

That's your hot water supply. It's controlled by a ripple relay so the network can switch it off at peak times and goes through a separate meter (usually combined into one unit on modern meters) so it can be billed at a different rate. As the ripple relay and meter are in the meter board you need a separate wire coming into the switchboard, and since you still want the main switch to turn everything off, you have the two separate poles on the main switch. The cable is smaller because it's only 16 or 20 A for the hot water only, whereas the main is likely sized for 63 A to feed everything else in your house.


UsernameNotAllowed

20 posts

Geek


  #2525132 18-Jul-2020 11:16
Send private message

Thanks for the information. I found the ripple control receiver in the power meter box.




petermcg
77 posts

Master Geek


  #3352847 11-Mar-2025 21:14
Send private message

I have one of this type of 2 pole main switch. My mains cable from the street enters on the right side top terminal 3, my house load exits from terminal 4 bottom right, I have my ripple wire connected to terminal 1 top left,, now there is a spare terminal, not used bottom left labelled terminal 2,

 

Its the same as this one pictured, but just using top instead of bottom terminals, I understand that this is not the style of 2 pole switch that will isolate Live and neutral.

 

My question is this, Can I use spare terminal 2 to feed a 10mm mains out to my garage?


tweake
2391 posts

Uber Geek


  #3352861 11-Mar-2025 21:52
Send private message

no.

 

the hot water feed is 16 or 20 amp while garage submain is 30 amp so the wiring is undersized to start with. edit: also there is the ripple control to deal with.

 

also that main breaker is 63 amp and you need a 30 amp. so if the garage overloads it will cook the garage feed before tripping that breaker. 

 

you need to put in a separate breaker wired to the bus bar etc. 

 

also none of the above your allowed to do. its sparky only job.


Handle9
11390 posts

Uber Geek

Trusted
Lifetime subscriber

  #3352919 11-Mar-2025 22:29
Send private message

To reinforce above: A homeowner may not work in a switchboard. Only appropriately registered electrical workers may do this kind of work.

 

Don't do it. If you have to ask on here you don't know what you are doing.

 

If you want to save some money find a sparky who will let you do the donkey work and then come and charge you for testing and terminating, don't take the risk of winging it.


petermcg
77 posts

Master Geek


  #3352926 11-Mar-2025 22:56
Send private message

Thanks guys, an electrition is going to do the work, I was just trying to satisfy in my own mind how this switch works. Still a bit unsure its quite technical, It appears that the 2 poles are connected together within the switch itself.


 
 
 

Move to New Zealand's best fibre broadband service (affiliate link). Note that to use Quic Broadband you must be comfortable with configuring your own router.
tweake
2391 posts

Uber Geek


  #3353255 12-Mar-2025 17:07
Send private message

petermcg:

 

Thanks guys, an electrition is going to do the work, I was just trying to satisfy in my own mind how this switch works. Still a bit unsure its quite technical, It appears that the 2 poles are connected together within the switch itself.

 

 

its actually 2 separate breakers joined together. in the photo its actually the gray bit linking them. i'm not a huge fan of this because i have had it where one will trip but it hasn't got the strength to fully trip the other. however there is purpose made duals (afaik) so it depends on what you have. 

 

an option is to delink the two breaker and replace one with a 30 amp for the garage feed (assuming board is full).


  #3353261 12-Mar-2025 17:30
Send private message

You will find that it is 2 switches joined together with the link in the handle, they aren't circuit breakers. There will be separate circuit breakers to provide the protection. 


tweake
2391 posts

Uber Geek


  #3353263 12-Mar-2025 17:46
Send private message

larknz:

 

You will find that it is 2 switches joined together with the link in the handle, they aren't circuit breakers. There will be separate circuit breakers to provide the protection. 

 

 

doubt it.

 

pretty common to use the circuit breakers as a switch. 


  #3353264 12-Mar-2025 17:49
Send private message

The symbol shows a switch, not a circuit breaker and there is no Type number.


Daynger
435 posts

Ultimate Geek


  #3353752 13-Mar-2025 20:30
Send private message

tweake:

 

doubt it.

 

pretty common to use the circuit breakers as a switch. 

 

 

 

 

You can doubt all you like but that is a main switch, not an MCB, as larknz said.

 

 


petermcg
77 posts

Master Geek


  #3353755 13-Mar-2025 20:52
Send private message

My one is a dual pole like this one, one side has the main in cable and feeds the rcd and circuit breakers but there is nothing coming from the other end of the switch that has the ripple wire, in fact I dont have an electric hot water heater I have gas. I was thinking that these 2 switches were linked inside the unit, but maybe not.


  #3353757 13-Mar-2025 20:55
Send private message

Definitely not linked internally. Maybe your house had an electric water heater in the past.


John19612
68 posts

Master Geek


  #3353872 14-Mar-2025 07:04
Send private message

larknz:

 

The symbol shows a switch, not a circuit breaker and there is no Type number.

 

 

To be specific, it is the symbol for a double pole on-load isolator.

 

Some (most) of the unqualified advice in threads like this is more than enough reason for Section 79 of the Electricity Act to be repealed ASAP.


Filter this topic showing only the reply marked as answer Create new topic





News and reviews »

Air New Zealand Starts AI adoption with OpenAI
Posted 24-Jul-2025 16:00


eero Pro 7 Review
Posted 23-Jul-2025 12:07


BeeStation Plus Review
Posted 21-Jul-2025 14:21


eero Unveils New Wi-Fi 7 Products in New Zealand
Posted 21-Jul-2025 00:01


WiZ Introduces HDMI Sync Box and other Light Devices
Posted 20-Jul-2025 17:32


RedShield Enhances DDoS and Bot Attack Protection
Posted 20-Jul-2025 17:26


Seagate Ships 30TB Drives
Posted 17-Jul-2025 11:24


Oclean AirPump A10 Water Flosser Review
Posted 13-Jul-2025 11:05


Samsung Galaxy Z Fold7: Raising the Bar for Smartphones
Posted 10-Jul-2025 02:01


Samsung Galaxy Z Flip7 Brings New Edge-To-Edge FlexWindow
Posted 10-Jul-2025 02:01


Epson Launches New AM-C550Z WorkForce Enterprise printer
Posted 9-Jul-2025 18:22


Samsung Releases Smart Monitor M9
Posted 9-Jul-2025 17:46


Nearly Half of Older Kiwis Still Write their Passwords on Paper
Posted 9-Jul-2025 08:42


D-Link 4G+ Cat6 Wi-Fi 6 DWR-933M Mobile Hotspot Review
Posted 1-Jul-2025 11:34


Oppo A5 Series Launches With New Levels of Durability
Posted 30-Jun-2025 10:15









Geekzone Live »

Try automatic live updates from Geekzone directly in your browser, without refreshing the page, with Geekzone Live now.



Are you subscribed to our RSS feed? You can download the latest headlines and summaries from our stories directly to your computer or smartphone by using a feed reader.