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Bosch GCM 10 S. Trpping CB . (SOLVED. Thanks Everyone.)

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Benchwayze

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Hi Folks,

A puzzling annoyance has developed with my SCMS.

To unlock the plunge mechanism on this saw, it is necessary to pull the locking switch over with the thumb whilst simultaneously switching on the power. This is a most awkward operation, one-handed, and I know it's probably unsafe to do this with both hands. The problem is that for some reason, switching on the motor is tripping one of the switches in my Contact Breaker circuit box. I can only put it down to hesitancy on my part, whilst struggling to operate both switches at once. Again, it's a real awkward operation!

The techie stuff is:

i) The saw didn't do this when I was using another socket, even further from the switch box.
ii) No fuses are blowing. If I reset the CB switch, the saw will start; but not every time. Sometimes it takes two or three attempts.
iii) No other socket in the shop is being affected. No other electrical equipment in the house is being affected. Just the power from the double socket I'm using.

iv) First time I've used the saw from this particular output socket.
v) Never had any problems with this socket before, when I operated my 1hp, lathe from it, using the extension lead.

The location of the saw isn't close enough to the socket, to plug direct into the socket. I have to use a 4 gang extension, with fuse. (Although this didn't present a problem up until now.) So far the machine hasn't cut out under load.

I am still getting used to this saw, and I wonder; am I just being too timid with this switch? It seems to need paws like a Yeti, in order to operate the lock and the power switch together, with one hand.
Finally, do I need a direct pick-up from the switch box, with a higher rated fuse, as I do for my planer, which is a BIG machine?

The only info I can find about the motor is:

230-240 V
50 Hz
Input Power Rated 1800
4600 rpm no load

Puzzled. Any info would be appreciated.
TIA

SOLVED MANY THANKS

:?
 

Eric The Viking

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Dumb question, probably: do you have to spin up the blade in order to unlock the plunge, or is it an electro-mechanical interlock you're triggering (I vaguely remember these new Bosch saws have an interlock for movements, independent of the blade motor)?

It sounds a lot like there's an inductance somewhere, for example a solenoid for an interlock, causing the breaker to trip. It looks from the pictures as though it has a brushed motor - that's unlikely to do it, but if it's an induction motor, it might. There might be suppression on the solenoid that's failed - a new capacitor should be a cheap fix, or a warranty repair.

Assuming nothing is actually faulty, I think the 'standard' fix is to use the 'other' type of circuit breaker (type-C sensitivity), which is less sensitive to this sort of tripping.

If it's any consolation, my 110V site transformer does the same thing a lot of the time. The higher the resistance of the wire back to the fuse box (distance, extension cables, etc.) the less it happens. It actually works fine though (as far as I can tell).

HTH, E. (over to Bob M.!)
 

Benchwayze

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Thanks Eric.

Haven't tried to start up the saw without pulling the plunge lock aside. I'll try tomorrow. The shop is all locked up for the night!

The 'Other-type' of CB sounds expensive. Does this entail a new CB box Eric, or is it just a plug-in gizmo I can put into the socket and plug the saw into it?


Thanks.
 

Eric The Viking

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Nah it's just a plug-in (clip on actually) like-for-like replacement.

The only problem is that, although they're supposed to conform to nominal sizes, sometimes they don't interchange, so, for example, you might not get a Wylex MCB to fit in a "MEM" box, or whatever. It's usually a matter of making sure it's the same brand, but I've got a mixed set of them in the garage box (which is a no-name Chinese thing), and that's fine.

Cheers,

E.
 

Benchwayze

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Thanks again Eric.

The first thing I'll try is to move the four-gang socket to the main outlet, furthest from the CB Box.
If that doesn't work I'll move the saw-bench, so I can plug directly into the ring socket. If that doesn't work I'll try a CB plug.
(We have a similar 'tripping' problem whenever a light-bulb blows, only this is on the lighting circuit of course.)

Maybe my box is too sensitive. Either way it's nuisance and slows thing down considerably!

Thanks again Eric. :D
 

Benchwayze

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Looks like I will have to call in a sparks Eric.
All the CB's I can find are upwards of 60 quid, and I can't see anything that I recognise as a 'plug-in device. All the ones I am looking at are obviously meant to be fixed inside the circuit-box, and I don't think I want to mess with that!
Thanks anyhow Eric. I'll let you know how I get on.

regards.. :)
 

Eric The Viking

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Benchwayze":29dov4ng said:
All the ones I am looking at are obviously meant to be fixed inside the circuit-box, and I don't think I want to mess with that!
Sorry, that's what I meant!

There's a "DIN rail" inside modern 'fuse' boxes, onto which all the breakers clip. It's simply a matter of swapping over your existing breaker (on that circuit only) for one that has a slower trip. It's a fifteen minute job for a sparks, including the cup of tea...

Cheers,

E.
 

misterfish

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Most of the (branded) MCBs that Screwfix sell cost about £5 at the most, but if you are not comfortable working with 'leccy then the major cost will be getting it changed.

Also, when I first got my TS it was fitted with a 13A plug and started OK when plugged in to the ring circuit. But when bolted down in its final place the wire wouldn't reach the socket and I tried an extension block and it just wouldn't 'latch' on. I wired it into its own dedicated 16A circuit and the problem more or less went away but it still tripped the mcb on a regular basis. I changed to a type C and have never had a problem since. The saw obviously draws more current at start up which explains why the fuse in the plug attached when I bought it was bridged with 32A fuse wire.

Mistefish
 

Benchwayze

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As per usual I have to thank everyone for their willing and informative advice.
Thanks one and all.
I have solved the problem by moving the 4-gang socket from the first outlet (From the Consumer unit) to the 4th socket, right by the door. (I.e, the furthest ring-socket from the Consumer Unit).
I have spun the saw a dozen times, and no tripping occurs.
When I put the lead back into the first socket, the switch tripped immediately.
So it seems you were right Eric. The further from the Consumer Unit, the more resistance.. (Obvious!! Why didn't I think of it?)
All I have to do now is move the mitre-saw to the other side of the shop, to avoid electrical leads trailing across the walkway, and I am done. I shall just have to use the other socket for low draw machines like my morticer and drill .

Thanks again everyone for the advice. =D> =D> =D>

Much obliged folks. :D
 
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