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Kity Bestcombi 2000 tripping MCB

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javerre

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Hi,

I've got a Scheppach/Kity Bestcombi and its tripping the MCB (rated 32A) whenever I turn on the saw or the planer. Spindle moulder is fine.
Any ideas anyone?

Interestingly if I disconnect the spindle motor inside the base (at the 6-pin in-line connector) it stops tripping the MCB and the saw / planer starts fine. Reconnect the spindle motor and it trips again.

Anyone got a circuit diagram to help me understand what's going on?
 

Pete Maddex

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Hi

I have a Bestcombi and the manuel PDF I can send you.

If you PM me your email address I will send it to you.

Pete
 

guineafowl21

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javerre":xhs1bf3u said:
Hi,

I've got a Scheppach/Kity Bestcombi and its tripping the MCB (rated 32A) whenever I turn on the saw or the planer. Spindle moulder is fine.
Any ideas anyone?

Interestingly if I disconnect the spindle motor inside the base (at the 6-pin in-line connector) it stops tripping the MCB and the saw / planer starts fine. Reconnect the spindle motor and it trips again.

Anyone got a circuit diagram to help me understand what's going on?
Is it definitely an MCB, and not an RCBO?
 

javerre

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Pete Maddex":1p4sr0ik said:
Hi

I have a Bestcombi and the manuel PDF I can send you.

If you PM me your email address I will send it to you.

Pete
I tried but because I’m a noob it appears I don’t have PM privileges yet :(
Hopefully will get these soon :)
 

javerre

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guineafowl21":1zu760jh said:
Is it definitely an MCB, and not an RCBO?
@guineafowl21 I’m tripping everything: the 20A MCB and the RCD on the spur and the 32A MCB on the main consumer unit.

Been fine for the last 5 years and then suddenly it’s all blowing :(
 

javerre

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GrahamF":2dmooha3 said:
What's the mcb, is it a type "C"? If not, try replacing with one.
@GrahamF It’s a 32A type B but I don’t think it’s the startup surge because after disconnecting the spindle motor (which should have no affect because the selector switch is in the saw position so it’s not powered up) the saw starts fine.
 

guineafowl21

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javerre":2hqjjv7z said:
guineafowl21":2hqjjv7z said:
Is it definitely an MCB, and not an RCBO?
@guineafowl21 I’m tripping everything: the 20A MCB and the RCD on the spur and the 32A MCB on the main consumer unit.

Been fine for the last 5 years and then suddenly it’s all blowing :(
:shock: The machine socket is protected by a 32A MCB, then 20A + RCD, and they’re all tripping? And yet each individual motor works?

I apologise in advance for this, but seeing as you’ve just joined to ask this question - is this a wind-up? I’ve seen it before. Someone joins a forum to pose an impossible question, as a kind of trolling. Each genuine answer was countered with increasingly unlikely statements, then the user disappeared.

With that out of the way, I would be looking for a chafed wire or faulty switch. A good visual inspection.
 

javerre

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@guineafowl21 I’m not winding you up or trolling, this was a genuine issue.

Relative to the wiring diagram @petemaddex supplied, the live and neutral were definitely swapped in my unit. Somewhat disconcerting, but it’s clear from the way the starter is wired. Not a big deal given it’s AC but meant the emergency cutoff was on the neutral, which was not ideal. However, that was not the cause of the MCB blowing.

The unit is *supposed* to be wired like this:

29132FBC-ABC8-4245-9C1E-8CC107350C67.jpeg


However my unit was wired like this:

287476E9-A219-45DE-9BB1-2206ED205776.jpeg


As you can see, the two on/off latching relays (m1 for the saw and planer, m2 for the spindle) were wired oppositely!

I carefully traced all the wires and checked with a meter and it was definitely like this. Now, in principle the machine should still operate when wired like this because the selector switch will only allow one if the relays to latch, but it’s not ideal - if even momentarily both switches are active the live and neutral circuits will be directly connected together!

By swapping live & neutral at M2 I fixed my problem and the unit now operates as expected. I also and swapped live and neutral where the mains cable comes into the main connector block for good measure as I wanted the emergency cutoff to be on the live circuit (and to match the original wiring diagram better).

I purchased the unit brand new from DMA but it’s one of the later models that was made in China so maybe the quality control was not the same as for the original french units.

Hopefully this may help anyone else with this issue.
 

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guineafowl21

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If it was miswired from the factory, I’m at a loss to explain this:

“Been fine for the last 5 years and then suddenly it’s all blowing :(

... and also why both MCBs and RCDs were tripping, when they trip for different fault types. Particularly the RCD, since even the fault you have found should not cause a L/N imbalance.

It sounds to me like you have an intermittent fault, and the miswiring might be unrelated. Keep us posted (hammer)
 
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