Thread: Breaker trip

Originally Posted by Treecycle

I'm not sure if this is the correct place for this thread but I know there are quite a few members on here who have extensive electrical knowledge.
I have a Carbatec 2hp dust extractor which I am trying to run off one of those remote control switches so that I can turn it on/off without having to go to the unit and switch it. The problem is that every now and again when I switch it off, it trips the earth leakage breaker on the house. It switches on and off fine, but as the motor slows down, the centrifugal switch drops out and that is when the breaker trips.
Does anyone know why this happens and if there is a way around it?

Thanks,
Dallas

Dallas,

If you plug the Dusty directly into the power point, rather than into the remote controlled outlet, does the dusty still trip the earth leakage unit ? If the Dusty doesn't trip the Earth Leakage Unit when it's plugged directly into an ordinary power point, then I'd try another remote control power outlet.

I've got a Clipsal brand remote control outlet that I use to control a 2HP Dusty and it's worked OK for about a year so far.

Some of the Asian branded remote control outlets are only rated at 7 amps, and burn out quickly when asked to run a 2HP dusty. Both Clipsal and HPM make remote control outlets that are rated at 10 amps, and so far (touch wood) I haven't managed to burn out a 10 amp remote control outlet.

Also note that those remote control outlets seem to be easily damaged by power surges, so if you've had any thunder storms or power surges recently, you could also have a surge damaged remote control power outlet.

Regards,

Roy

Definitely do what Aussie roy suggests, but if the DC starts OK on the remote then it's unlikely to be the remote as its during the "on" part of the operation where the greatest currents are drawn.

Originally Posted by Treecycle

It switches on and off fine, but as the motor slows down, the centrifugal switch drops out and that is when the breaker trips.
Does anyone know why this happens and if there is a way around it?

Let me get this straight.

When connected to the remote, the DC turns on and runs fine?

When you turn it off, the motor slows down and its just before the CS kicks in (yes it switches "on" at slow speed or rest and switches off at high speed) that it drops the RCD?

This is weird because the mains supply has been disconnected and so the RCD should not know what is happening back at the motor.

The RCD measures a difference between current in the active and neutral lines and if there is a difference between them the RCD switches the active line off.

Has the switch on the DC been modified?
My understanding is that if the DC has a latching or "no Volt" switch, to use a remote the remote has to be placed between the DC switch and the motor.
This means the DC switch is always on.
I wonder of the remote is of the type that only disconnects the active line leaving the neutral line connected to the motor. Then when the CS kicks back ON it sends a small current pulse back through the neutral line which the RCD senses.

If this is the case then you need to use a Remote that switches both the active and neutral lines off.

Yes you have it correct Bob. The breaker trips just when you hear the switch change state on slowing down.
I was of the same thought that how does it trip if the power has been removed from the outgoing side of the remote.
No modifications have been done to the switch, and it is the latching type not a no volt switch.
You suggest that I may need to use a remote that switches both active & neutral. Do you have any recommendations here?

Originally Posted by Treecycle

Yes you have it correct Bob. The breaker trips just when you hear the switch change state on slowing down.
I was of the same thought that how does it trip if the power has been removed from the outgoing side of the remote.
No modifications have been done to the switch, and it is the latching type not a no volt switch.

Latching and no volt are usually the same thing.

If you have the remote between the mains and the latching DC switch, how does the DC switch remained latched if there is no power to it when you turn off the power to the remote?

You suggest that I may need to use a remote that switches both active & neutral. Do you have any recommendations here?

Sorry I Don't know of any that do this.

Originally Posted by BobL

Latching and no volt are usually the same thing.

If you have the remote between the mains and the latching DC switch, how does the DC switch remained latched if there is no power to it when you turn off the power to the remote?

I may be using incorrect terminology here. When I say it is latching I meant that you push the start button in and it stays in even when you remove the power from it.
I did some testing on the remote and from my limited knowledge on testing, it appears to only remove power from the active terminal when deactivated. I checked the resistance across the neutral and earth and it remained the same whether activated or off.

Originally Posted by Treecycle

I may be using incorrect terminology here. When I say it is latching I meant that you push the start button in and it stays in even when you remove the power from it.

OK I understand what you mean.

I did some testing on the remote and from my limited knowledge on testing, it appears to only remove power from the active terminal when deactivated. I checked the resistance across the neutral and earth and it remained the same whether activated or off.

The way to check is to remove the remote switch from the mains and DC and measure the resistance between the input and output neutrals. If the resistance is near zero it's a straight thru connection and may contribute to the effect I described previously.

Does the DC trip the RCD when not using the remote?

I have only ever turned it on and off using the switch on the DC, and doing it that way it never trips. I have never tried turning it off at the power outlet. Will have to give that a go and see what happens.

Hi,
Back emfs (electro motive forces) along the neutral often trip elcbs, you get them with cheap power packs and lap top and phone chargers if you switch them off at the single pole switch on the GPO, and have to avoid them by pulling the plug out quickly while still switched on. Your starter may be double pole, try switching off at the GPO without the remote in circuit, and see if it still happens. Another possibility is that you are getting a momentary earth fault on the centrifical switch as it disengages.
Not much help fixing it but it may help understand the mysteries.
Best of luck

Just to help my understanding a little more, what does the centrifical switch actually do?

Originally Posted by Treecycle

Just to help my understanding a little more, what does the centrifical switch actually do?

The CS engages a secondary stator coil which is needed to help a single phase induction motor start. Once the motor gets to sufficient RPM to keep itself spinning so the CS opens and this prevents current going to that coil. When the motor is turned off as the RPMs drop off the CS closes again to engage the secondary coil to be ready for the next start. This may make the motor act like a sort of generator for a brief period generating sufficient V/A on the neutral line to trigger the RCD.

Hi,
It is probably the capacitor discharging causing the problem, the problem with the power packs is whether they have full wave rectification or not. The big mystery for me is why we have not had anyone else with this problem before as quite a few claim to be switching their dusties remotely but then again it can not be a common problem as many single phase induction motors are switched with single pole switches.
Regards

Originally Posted by A Duke

Hi,
It is probably the capacitor discharging causing the problem, the problem with the power packs is whether they have full wave rectification or not. The big mystery for me is why we have not had anyone else with this problem before as quite a few claim to be switching their dusties remotely but then again it can not be a common problem as many single phase induction motors are switched with single pole switches.
Regards

It might just be an overly sensitive RCD.

Treecycle, Do you have another circuit at your place that is is not on the same RCD?

I think we do. I will check when I get home.

BobL is exactly right in post 11. This is exactly what was happening to me.

I used a brand of remote from bunnings (can't remember) and it blew the switches up mercilessly. Snap crackle pop.

Then I moved to the Kambrook remotes and the RCD and unit-draw-on explosions stopped. Those dusty motors sure do draw the amps on start.

I suspected as BobL said, that a partially, or mostly, spinning motor on the dusty was generating a current when off, but when turned back on in the spinning position perhaps dumped it back into earth, however momentarily. RCD clicked, zero power to the shed

Very bloody frustrating. The Kambrook units must switch off both active and neutral. Problem solved.

As for the Zero volt switch, I opened the box and bypassed it. It used to be forced closed with a small dice and vigorous taping