Garage and house breaker Tripping

[morpheus83uk]

Hello,

I have purchased a new thicknesser (1500W) and have plugged it in for the first time and it tripped the electric breaker in the garage. I reset the breaker and pressed the reset circuit breaker button on the machine and it happened again. I did get it going eventually but when I turned it off again and then about 5 minutes later turned it on it tripped again! I have other power tools in the sockets I tried to try and rule out sockets and they all work perfectly fine so I think its something to do with the machine itself. I trips the breaker sometimes in the garage and sometimes in the house.

The house has a 16A B type breaker labelled as garage.
The garage has a 16A B type breaker for the sockets in the garage

I have been advised by the company that they can take it back or it could need a 16A C type breaker installing due to the high inrush current and the C type breaker will deal with that and stop it from tripping. So as I didnt have any of them in the main consumer unit I tried on one of the sockets in the house which has a 32A B type breaker. The machine fired up, I did this a further 4 times to replicate the issues in the garage and the machine fired up every single time. So the machine has been ruled out as being faulty.

So I contact an electrician and he told me to purchase a 16A or 20A type C breaker for the garage and he will come and install it. I send him the link to one I find on Screwfix he gives me a thumbs up. I think I will go for the 20A to cover the current of running the machine and like an extractor to collect the dust chips etc and maybe the radio etc would probably be better and bear better under the load. But inside the main house on the consumer unit the breaker in there is 16A B type breaker as mentioned I asked the question if I needed one or two because the main consumer using is rocking 16A B type and the garage sockets will be connected to 20A C type or 16A C type, i'm thinking I would need to replace the one in the house as well to cope. As 20A > 16A or the inrush current would be fine on the C type 16A and would trip in the house as it would exceed that load of the 16A B type breaker.

The electrician says I only need one for the garage. Obviously I am not an electrician but I can't get my head around how that would work. Can anyone explain this or how it would work or if its even correct? Google seems to suggest it would trip the main house and a video I just watched of how to do it, the amperage shown in the house was 40A and there was 32A for the sockets and 6A for the lights on the garage consumer unit... so am I just going mad or am I just missing something really obvious?

Thanks

 

[pete01]

Yes the B type will still probably trip in the house.

What size cable is feeding the garage?

 

[EFLImpudence]

I would say you are correct.

You don't actually need the second breaker in the garage at all.

 

[securespark]

Yes, there won't be any discrimination or selectivity, whatever it is they call it these days.

 

[morpheus83uk]

Thank you for the replies.

I would say you are correct.

You don't actually need the second breaker in the garage at all.

When you say I probably don't need the second breaker in the garage I am not sure how that would work?

Yes the B type will still probably trip in the house.

What size cable is feeding the garage?

As for the size cable feeding the garage I am not sure?

What would be the recommendation for the house breaker be and what would the recommendation be for the garage in my situation?

Thanks

James

 

[ericmark]

A MCB is two devices in one, the thermal trip will take time to work, and the magnet part is B (3 to 5 times thermal) C (5 - 10 times thermal) and D (10 - 20 times thermal) the magnetic part is required, so the supply will open within the required time, should there be a direct short, so with a 16 amp MCB type B the magnetic part will trip with 16 x 5 = 180 amps, so for it to work a direct short must allow more than that to flow, we also add 5% to allow for volt drop, so 230/(16x5)x95% = 0.273125 Ω this is called the loop impedance, or 230/(16x10)x95% = 1.365625 Ω and before one can swap a B16 for a C16 the loop impedance to earth and neutral needs to be measured, until this is done, we have no idea if the MCB can be swapped, with a RCD the earth loop is not so important, but to suggest one can simply swap a B16 for a C16 without first testing is irresponsible, you may be able to do it, but not without testing first.