Rcd tripping from new 3hp tablesaw

[Kyanther]

I have a 40amp trip on my main consumer unit feeding my workshop where I have another consumer unit with 1x6 amp 2x16 amp and 1x32amp trips. I've replaced my old 3hp tablesaw that was run from a 13 amp plug on the 32amp ring with a new 3hp one that is plugged into a 16amp socket through a 20amp isolation switch and into its own 16amp trip.
Is there any reason other than a fault with machine why the new machine is tripping the house Rcd?
Hope this makes sense
Thanks

 

[pc1966]

Tripping the RCD is a little worrying, as a new saw should not have any significant earth leakage.

However, you might have a N-E fault that is not normally apparent but now the start-up current of the table saw is enough to cause a current imbalance large enough to trip the house RCD.

So I would advise that you get a professional sparky in to check out your saw and the house wiring to see what the real reason is behind the nuisance tripping.

 

[snowhead]

Was the 16amp plug already on the saw and was the 16amp socket already in the workshop and has previously been used with no issues?

As my guess would be the 16amp plug or socket is wired up wrong, N & E reversed in one of them, if either have recently been fitted.

 

[Kyanther]

Thank you for the replies. N + E checked and not reversed. Yes plug was on machine and welder works fine on socket.
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I've temporarily fitted a 13amp plug and put it into ring main only as a test and it still trips the house rcd.

 

[Baddegg]

Does it trip as soon as you start it up or after some use?

 

[Kyanther]

Straight away. The blade twitches as it trips

 

[westward10]

Can you show a pic of the 40A device which is tripping because a single phase 3hp motor will take between 45 and 50A on start up.

 

[Kyanther]

its not the 40amp trip its the rcd thats tripping but heres the pic of the consumer unit

 

[westward10]

I misread your original post. Is there a hole in the front of the 40A mcb.

 

[pc1966]

Thank you for the replies. N + E checked and not reversed.

You need to check for a N to E short somewhere within the wiring as well.

Normally N & E are essentially at the same 0V potential. But if you get a lot of current going through N (for example, on motor start up) then there will be a voltage drop and if there is an insulation fault to E then it will divert some current, and so trip a RCD.
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Of course, it is also important to check the saw in case it has some fault leading to current going to E.

 

[Andy-1960]

How is the motor being controlled? Can you show us a picture of the motor starter?

 

[Kyanther]

Well spotted but no its the mold mark on the clear door!

 

[Lucien Nunes]

Agree with above, either the saw is faulty or there is a neutral-earth fault one one of the circuits protected by the RCD that trips, that is being revealed by the high starting current of the saw. It is not necessarily the circuit that the saw is plugged into that is faulty. Either way, insulation test results are needed to progress the diagnosis any further.

 

[Kyanther]

Thank you all. I've got an engineer from Axminster tools coming to change the motor at the end of the week. So we'll see if that fixes the problem if not I'll get those earth tests done!