Trip Switch

DIY Stew · 12 Mar 2012

I have put a separate electrical circuit in the garage/workshop but whenever I try to use my sliding mitre saw it trips out, I have been told I will need to fit a commercial trip but have no idea what that is. Any help would be appreciated as the only other supply is from the ground floor ring main (which is fused) and I have to plug into that via an extension cable. The tripped circuit is ok for the radio, hoover and trailer lamp.
Alternatively I thought about changing the trip over with the fused downstairs ring main but I would rather have the garage circuit on a trip for safety reasons.

Stew

Chems · 12 Mar 2012

A normal little saw shouldn't trip the fuse. How did you wire in the new circuit, is it a ring that goes back to the fuse box or is it a radial? If its a radial then thats perhaps your problem. I had a similar problem with my 3hp TS, it was because it was on a ring which apparently halfs the available amount of amps, but by going back to the fuse box properly in a ring main you don't get this.

Lons · 12 Mar 2012

Stew

What size is the fuse?
Is there an RCD in the consumer unit and is this ok or does it trip also?
Does your mitre saw work ok from your other extension? (Just to eliminate any possible earth leakage fault)

If the sizing of MCBs and wiring are correct there shouldn't be a problem with your saw.

Bob

Phil Pascoe · 12 Mar 2012

Take your saw indoors and see if it trips a circuit -eliminate a possible fault in the saw first.

misterfish · 13 Mar 2012

I assume the 'commercial' trip refers to a type 'C' MCB. These are designed for use with high initial current draw surge equipment like larger motors. With a 'normal' type 'B' MCB my table saw regularly tripped its 16 amp MCB, but changed to a type 'C' tripping is no longer a problem. But as others have stated it is surprising that you have this problem with a SCMS.

You say you have put a separate circuit to the garage/workshop - what rating is the MCB/fuse for this? Is it a dedicated circuit or a spur from a ring circuit.

Misterfish

DIY Stew · 13 Mar 2012

Chems
It is a radial circuit.

Phil.p
The SCMS works ok on downstairs ring circuit.

Bob/misterfish
The garage has a single socket which is part of the downstairs ring main this is fused at the consumer unit, if I use this socket for my SCMS I have no problems. I installed another 4 sockets which are connected to the consumer unit vai a B16 trip, this is radial ie the wiring does not go back to the consumer unit.
What I have been told is very similar to what misterfish has said (fit a C16 trip), but I may have a problem sourcing one as this consumer unit is discontinued (MEM 2000) so I am now thinking of having a dedicated garage consumer unit and a ring main as it may be easier in the long run.

Stew