Thread: Table Saw tripping circuit breaker

Changing the breaker is not the answer.

Is it the RCD breaker that is tripping?

If yes, then the saw is leaking (electrically speaking) which is lucky you have a new house with an RCD breaker otherwise you might not have made your post.

Either way I'd be getting the saw tested by an electrician before you turn it on again. This happens occasionally when machinery is moved, something gets knocked or bumped resulting in something connecting where it shouldn't.

Also, can you tell us what the rating is on the breaker that is popping?
I may be under rated for the start current that the saw is dragging.
Have you tried it on another circuit?

What Cliff said is the starting point, but any c/b should be able to carry 8 amps. It is less than the rating of a normal 10A GPO (power point).

you have two possible problems:

1. An electrical fault. If your earth leakage circuit breaker ( or residual c/b) has tripped , then you have a fault. Don't use the saw until you locate the fault !

2. Most likely the starting current of the motor is too much for the circuit breaker, especially if you have other applicances on that circuit. Typically it can be 5 to 6 times the rated current of the motor, and can last for quite a few seconds. In this case you will need to get the c/b changed to one that will handle motor starting currents. Not necessarily a higher rated one, but one that has a bit less sensitive tripping characteristics for overloads

If your earth leakage circuit breaker ( or residucal c/b) has not tripped , you could try it on the air con circuit which will have a higher rating, and provided the circuit is not already heavily loaded, and see how that goes. Remember that the air con may have very high starting currents too, so the circuit could trip if both your woodworker and the aircon are going

Thanks for the quick replies. Before I read Bob's post I tried it again and about 2 inches into cutting a piece of wood it stopped, sort of as the motor would have been under a bit of load.

Bob,
I've attached a pic of which one is tripping, not sure which one is the RCD breaker sorry.

Cliff,
The info on the switch says 4.5kpa C16, 240v-16A, Power N/L.....

You are going to need an electrician to change the C/b or even put in a new circuit for your shed. Get him/her to measure the currents on the circuit before and after operating the saw. My guess is that you have a fair bit of load on that circuit already, as you have only two power circuits for the whole house, and the saw starting up or when under load with cutting just pushes it over the tripping edge.

RCD Residual current device = Safety Switch = ELCB Earth leakage circuit breaker, are all the same, designed to trip the circuit instantly the live mains touches earth, either through a wiring fault, or through a person. They trip at about 30milliamps flowing, and trip quickly, to prevent electrocution. Needs a good earthing connection at your switchboard, ands at the point of the fault, to operate properly.

Usually all houses are required to have one monitoring their power circuits.

Every building site is required to have one.

They should be tested each month by pushing the test button on them.

Originally Posted by Sam

Thanks for the quick replies. Before I read Bob's post I tried it again and about 2 inches into cutting a piece of wood it stopped, sort of as the motor would have been under a bit of load.

Bob,
I've attached a pic of which one is tripping, not sure which one is the RCD breaker sorry.

Cliff,
The info on the switch says 4.5kpa C16, 240v-16A, Power N/L.....

Your RCD is the big breaker that says 40A on it - the fact that it is not tripping is a good sign.

When you say the saw stopped - did it trip the breaker or was it just the saw itself stopping?

If the latter then the saw's internal temperature overload switch has kicked in - another sign to get it looked at.

if it's still the 20A breaker tripping it concerns me that it trips at just 2" into the wood. I would turn off everything else on that circuit and try again - if it works, as jill said you need a dedicated circuit.

The next question is now what size was the piece of wood (What depth of cut) and what's the blade look like - perhaps a close up picture of both would answer those questions. Is the blade on teh correct way around - don't laugh it's happened many times.

I can get my TS to trip my 20A breaker if I push it too hard while ripping bone dry Aussie hardwood with a depth of cut greater than about 3". I also have a current meter that allows me to monitors what is going on and when 3" deep ripping in dry aussie hardwood the saw is pulling 12A. If I start pushing the wood too hard the current jumps up to 17-18 A and can trip the breaker.

If I keep ripping even slowly at those depths for some time eg 10 continuous minute the saw itself can overheat and trip out. I then have to wait for it to cool down before I can cut some more. A critical thing here is blade sharpness and correct blade profile for the task - ripping, cross cutting etc.

BobL, I think it is the 16 Amp c/b that is tripping

If that's the one that's tripping it's not the RCD, it's the circiut breaker. This means you are drawing too much current from that particular circiut which could be for one of two reasons, 1) you have too many other appliances operating the same time as you're using the saw, 2) the saw motor is faulty and is drawing too much current.

It's a 16A breaker and an 8A motor so it shouldn't trip if nothing else is running off the circiut.

Jill,
We built with a volume builder so I'm not surprised that you say only two power circuits, 2 must be the absolute minimum allowed !! That said it is only a small house.

Bob,
Not sure which one goes off first. I was only ripping a 19 thick piece of pine very slowly. When I bought the saw the seller ripped a 50 thick bit of hardwood easily so before I moved it the motor and blade were ok.

Sounds like I need to get the meterbox AND the saw looked at ! Either way I'm still happy with the purchase, the fence is unmoveable and the cast-iron top is deadflat.

Thanks heaps,

Sam

Yeah - sorry its a 16A circuit breaker that breaking.

Originally Posted by nihilism

It's a 16A breaker and an 8A motor so it shouldn't trip if nothing else is running off the circiut.

An 8A rating for a motor means very little. The motor will pull much more current than this when it's under high loads. If the saw is pushed it could even pull 16A. The fact that it first tripped the breaker when turned on and then eventually started (probably some other device was turned off on the same line) and that it barely cuts pine for 2" suggests the breaker is too lowly rated.

Sam - when they change the breaker make sure the electrician checks the wiring coming out of the breaker box is up to spec - if the lower rated wiring has been used then the wiring may overheat - it's unlikely but worth asking about.

My 3HP compressor (and 3HP saw) both blew 10 Amp fuses at the wall. I replaced it (with professional advice) with a 15 Amp slow-burn motor fuse. But by way of further information, the saw also had a 13Amp fuse in the plug and that would blow regularly on startup. It seems it pulls about 14 Amps on startup but once that weakpoint was eliminated it runs forever without a hiccup.

Hi Sam,
Things are a lot more complicated than just putting in a bigger breaker. As there are only 2 breakers it means it is on a house circuit The regs say at least one third of the GPOs must be on the lesser circuit. Each circuit is usually protected by a 16A Fuse or 20A Breaker but as yours are only 16A they have probably been de-rated because of insulation covering some of the wiring.
Switch off the breaker then run round your dwelling and find out which GPOs are live and which dead then you will know which ones share the shed circuit.
Your ultimate answer will be to have an electrician install a dedicated circuit to the shed bearing in mind you will eventually want to run a dusty etc at the same time.
Of course there could just be something wrong with saw.

Thanks for all the replies and suggestions. I've got an electrician coming in the next few weeks to look at the house and also the saw just incase. As I said we built with a volume builder so no doubt the house wiring will be the bare minimum. I'll report back with what the electrician says.

I'd like to publicly acknowledge and thank the seller for his concern and offer of a refund. While it was certainly not required I really appreciate it.

Cheers,
Sam