Table Saw trips RCBO

[Bedders]

I have a ring cct (2.5mm ) in my cabin which is protected by a 20amp RCBO. This has been in existence for over 3 years with no issues. I recently bought a table saw and when turned on, on its own all is OK. However the other day I had a heater and a dust extractor on, then turned on the table saw, the RCBO immediately tripped. It only trips when other appliances are on and you turn on the table saw. My question, is there a way to dampen the start up of the tablesaw motor or would I have to upgrade the RCBO to 32amp. The table saw is a Dewalt with a 2000watt motor. It is a bit aggressive on star up. Ideally is there something it can be plugged into to reduce the initial surge it creates.

 

[timhoward]

It's been an interesting thread. It's slowly emerged that there seems to be a well engineered distribution circuit and the fact it was a "ring" got slightly overlooked at first as the very logical reaction was 'that's more than 20 amps so of course it will trip'.

Those commenting at the beginning didn't know there was a 10 sq mm SWA feeding it and it initially sounded like a cheap and nasty job.

To my thinking there are two definite things to check before changing that device:
-Is the Zs low enough for a B32? If not it would rely on RCD technology to turn off in time under fault conditions, and a new certificate needs to state that RCDs are being employed for fault protection. (If moving to a type C then even more reason to check this).
-Do end-to-end tests confirm it's a healthy ring final circuit and is eligible to be protected by a 32 amp device in the first place?

I'd also want to know the OCPD of the distribution circuit, it might be 25 amp MCB for all we know and the problem just moves. Unlikely, but possible!

It comes down to a simple choice
-stick a B32 in and hope all is ok
-get 5 minutes of testing done and be sure all is ok.

 

[mainline]

I would not be putting a 32a rcbo just because its been suggested by someone I don't know on an Internet site

The same could be said about not changing it.

A 32a rcbo may be fine or it may be dangerous.

Can you explain how it could be dangerous ?
Even with a break in the ring ?

There must be a reason why someone has chosen to put a 20a on what seems to be a ring.

Yes because as already said they didn't have a 32.

The 20a type C suggestion is good, assuming you can get an EFLI result low enough.

How can putting an underrated 20amp rcbo on a circuit that requires around 5kw be a good suggestion.

 

[Bedders]

It's been an interesting thread. It's slowly emerged that there seems to be a well engineered distribution circuit and the fact it was a "ring" got slightly overlooked at first as the very logical reaction was 'that's more than 20 amps so of course it will trip'.

Those commenting at the beginning didn't know there was a 10 sq mm SWA feeding it and it initially sounded like a cheap and nasty job.

To my thinking there are two definite things to check before changing that device:
-Is the Zs low enough for a B32? If not it would rely on RCD technology to turn off in time under fault conditions, and a new certificate needs to state that RCDs are being employed for fault protection. (If moving to a type C then even more reason to check this).
-Do end-to-end tests confirm it's a healthy ring final circuit and is eligible to be protected by a 32 amp device in the first place?

I'd also want to know the OCPD of the distribution circuit, it might be 25 amp MCB for all we know and the problem just moves. Unlikely, but possible!

It comes down to a simple choice
-stick a B32 in and hope all is ok
-get 5 minutes of testing done and be sure all is ok.

All the work was carried out by an electrician and certified. FYI THE DISTRIBUTION IS from a Henley block off the main CSU fed into and additional CSU for distribution. A 62amp breaker is fitted in that CSU which then has the 40amp MCB feeding the cabin.

 

[HappyHippyDad]

I'm sure it's 95% likely that a 32A breaker would be fine. Not only fine, but more suitable than the 20A. However, the only times I have ever come across a 20A breaker on a 'ring', is when there has been a fault found on the ring, or a DIYer has added spurs off of spurs and someone has downsized the breaker.

The OP has clearly stated that the 20A breaker was used simply because it was the only one available. If this is correct, then again, 95% likely all will be fine. No offense is meant to anyone (@mainline , or the Op), I would just need to be 100% certain a 32A is suitable rather than 95% and this could only be done by being there and seeing/testing it for yourself.

I would still advise @Bedders to get an electrician in if he intends to start changing the design of the circuit (ie 32A breaker).

He sounds experienced and knowledgeable from his posts, so I expect all will be well.