RCD tripping

[Dannychop9]

Hi everyone,

I started to use my chop saw on the down stairs ring main an it instantly tripped the RCD on the board. I tried different sockets and the same thing happened. Tried it on the upstairs ring and it worked fine.

So I turned off my tumble dryer off and then used the chop saw down stairs and it worked fine. The dryer runs fine otherwise.

Would this be an overload fault? It's and 80A RCD and all I have turned on for it to trip is the fridge/freezer, tumble dryer, security cameras, WiFi router and chop saw.

I've never had this issue before and nothing has changed, it's just started randomly.

Thanks.

 

[newfutile]

I doubt its an overload on a 32A ring circuit , most likely to be excess earth leakage adding up , an RCD rated at 30 ma can trip around 20ma in some cases . Best to PAT test the equipment especially if its kept in a damp area

 

[SparkyChick]

I'll just add this as from what you've said regarding overload and the device being an 80A device it appears you are under the impression that RCDs protect against overload... typically they don't. The 80A is the maximum current carrying capacity of the device. This applies to all devices that meet standard BS EN 61008. Devices meeting the BS EN 61009 standard are combined RCD and circuit breakers, so they will provide overload protection.

RCDs (BS EN 61008) only trip when they detect excessive earth leakage, which as @newfutile says can be a bit variable when compared to their rated trip current. Those typically used in domestic will be either 30mA for providing the required additional protection on nearly all circuits, or 100mA for providing things like earth fault protection in TT earthing (this is where you have an earth rod).

As @newfutile has said, it's not uncommon for 30mA RCDs to trip anywhere between 20-30mA, and this can cause problems if there is excessive leakage from multiple devices.

 

[i=p/u]

As above it's your leads or equipment.

 

[radiohead]

As above it's your leads or equipment.

I would suggest a N-E fault somewhere on the installation may be the cause. Possibly the starting surge current of the chopsaw motor is enough to result in sufficient current to divert through a high resistance N-E fault to cause the RCDto operate. Most power tools are class 11, in which case a tool fault is not going to trip an RCD on its own. To the OP I would engage an established local electrician to carry out an insulation resistance test on your installation. Shouldnt cost more than an hours labour for a test to verify if any insulation faults are present.

 

[i=p/u]

Plug a kettle in and if doesn't trip, well you know it's your chopsaw. What's point on telling ordinary people all that muc??

 

[pc1966]

It is possible the chop saw start-up current peaks at a few tens of amps so a 13A kettle might not be quite the same test. But in principle it is a sound way to check for that.

 

[radiohead]

Plug a kettle in and if doesn't trip, well you know it's your chopsaw. What's point on telling ordinary people all that muc??

Clearly you don't understand N-E faults.
For a start read the OP. He said the chopsaw does not trip the same circuit when the tumble dryer is off, but does when its on. He also said it does not trip when plugged in upstairs, presumably on a different RCD.
All of which suggests the chopsaw is not necessarily the problem. It may be, but plugging a kettle in will not confirm anything.
The evidence the OP has posted suggests to me a strong possibility of a N-E fault. It may not be, but I think a test would be worthwhile to eliminate it as a cause.
It would also be worth us knowing whether the saw is class 1 or class 11. Most are class11 and should not be tripping an RCD if faulty.

 

[Deleted account]

Clearly you don't understand N-E faults.
For a start read the OP. He said the chopsaw does not trip the same circuit when the tumble dryer is off, but does when its on. He also said it does not trip when plugged in upstairs, presumably on a different RCD.
All of which suggests the chopsaw is not necessarily the problem. It may be, but plugging a kettle in will not confirm anything.
The evidence the OP has posted suggests to me a strong possibility of a N-E fault. It may not be, but I think a test would be worthwhile to eliminate it as a cause.
It would also be worth us knowing whether the saw is class 1 or class 11. Most are class11 and should not be tripping an RCD if faulty.

The chop saw may still be at fault. Maybe just 15-18mA earth leakage and when wash machine is on it has another few mA of earth leakage tripping the device.

my money is on the chop saw being damp.

 

[pc1966]

The only real way to check if for them to get an electrician in to check it. We seem to have the options of:

• Very leaky chop-saw, or
• Too much else on the single RCD, or
• RCD is a bit out of specification and trip-happy, or
• N-E fault being revealed by the chop saw start-up current, or
• more than one of the above

Finding out what it is needs to be done first, and a quick N-E insulation test would allow that sort of fault to be ruled out, and then a suitable clamp ammeter to see if the whole install is leaky, etc, etc.

 

[radiohead]

The chop saw may still be at fault. Maybe just 15-18mA earth leakage and when wash machine is on it has another few mA of earth leakage tripping the device.

my money is on the chop saw being damp.

Perhaps, but that would still depend on it being a class1 appliance. Damp wont make any difference if its class11.

 

[i=p/u]

Il fix it by cutting the plug off it , I bet..

 

[Dannychop9]

Thanks for all the replies!

To all who think it's the chopsaw then I'm afraid you're wrong.

I have just turned the oven on and that's tripped it too.

 

[pc1966]

Thanks for all the replies!

To all who think it's the chopsaw then I'm afraid you're wrong.

I have just turned the oven on and that's tripped it too.

OK, that is convincing there is a N-E fault somewhere.

If you can post your town or post code, you might find there is someone on here that is close and can investigate for you.

 

[i=p/u]

Thx for letting me know , whole handling now , I guess fridge and its kicking in coincidentally