RCD problem

[Michael Walker]

Hi, my names Mick. I live off grid in 7 acres of woodland near Chepstow. I've been here 3 years now and can't imagine life anywhere else. 

I have a spring for water and 640w of solar supplying 3x100w deep cell batteries. 

I also have a 3kw diesel generator to run my washing machine and at this time of year to up my batteries. The genny has been performing perfectly well for 16 months but last week the 16amp RCD kept flipping. 

I checked the extension from the gen and the wiring to the washer(&water pump). All good. After resetting for the 10th time, the RCD stopped working. I have replaced it with a 25amp unit and it was still the same,even with nothing plugged into the gen.

The original RCD unit had the earth and negative wired into the same side of the RCD which I have copied onto the replacement. 

Today I tried it one last time and it is working perfectly. I know these intermittent problems are the worst but winter is the when the batteries, therefore my,for want of a better word 'house's, needs it the most.

Thank you for taking the time to read this, and for any advice you might have to offer.

Mick

 

[Michael Walker]

Hi all, it's happening again. 

Genny ran for 5 hours yesterday, no problem until RCD threw. Wouldn't reset.

Genny housed and dry.

Question: Can I bypass the RCD? The power comes to the dwelling via a jcb extension  with built in breaker. The plugs that go into it all have 13amp fuses. Surely they would protect my devices. 

Thanks for your patience, hoping my idea for a fix will float. Mick

 

[Murdoch]

Unplug all the devices you have. 

Reset rcd

Plug in devices one by one and you may find one device is the culprit

 

[Michael Walker]

Hi Murdoch, thanks for getting back so quickly. 

The RCD throws with nothing plugged into the gen.

It was the same with the original RCD, I can't for the life of me figure why it's happening 

 

[Murdoch]

Disconnect solar and batteries,

please dont start multiple threads

 

[Michael Walker]

I don't understand what effect that would have on the generator. The RCD trips when nothing is connected. The RCD is 25amp, it has replaced the original 16amp unit that was on there when I picked the generator up. 

If the RCD trips at 25amp, why doesn't the 13amp fuse in the plug blow. Or the trip switch on the extension.

Seriously considering bypassing RCD. 

 

[Blue Duck]

Is it actually an RCD? 

Fuse takes longer to blow in an overload situation, lucky dip on a short.

 

[Murdoch]

I don't understand what effect that would have on the generator. The RCD trips when nothing is connected. The RCD is 25amp, it has replaced the original 16amp unit that was on there when I picked the generator up. 

If the RCD trips at 25amp, why doesn't the 13amp fuse in the plug blow. Or the trip switch on the extension.

Seriously considering bypassing RCD. 

ANY load downstream of an RCD, with a fault can and most likely trip the RCD

if you don’t disconnect the solar / battery system you haven’t isolated everything connected.

and by isolating it means switching off live and neutral 

 

[OnOff]

Can you perhaps post a picture of the 16 & 25A units?

You may not have posting rights yet but can post a link to another photo upload site or the mods here can give you posting rights.

 

[OnOff]

I don't understand what effect that would have on the generator. The RCD trips when nothing is connected. The RCD is 25amp, it has replaced the original 16amp unit that was on there when I picked the generator up. 

If the RCD trips at 25amp, why doesn't the 13amp fuse in the plug blow. Or the trip switch on the extension.

Seriously considering bypassing RCD. 

Is the extension lead a reel type and is it unwound? Wound leads can actually melt together in the middle but look perfectly OK from the outside. They will generally have two ratings on them  wound and unwound.

On another note things like cables and generators, motors etc can take time to heat up in use and only then "go down to earth" and "trip" when hot and things have expanded. Photos of what you have would ascertain whether its RCDs or MCBs you have. 

 

[apprentice87]

The RCD is 25amp, it has replaced the original 16amp unit that was on there when I picked the generator up. 

If the RCD trips at 25amp, why doesn't the 13amp fuse in the plug blow. Or the trip switch on the extension.

Seriously considering bypassing RCD.

Ok, from this it can be seen that you have no idea at all about the function of RCD's or MCB's.. You need an electrician..

You seem to think that the 13A fuses in your BS1363 plugs will protect your devices, maybe they will, but they will NOT protect you..

Photos would help..

john..

 

[kerching]

Not wishing to urinate on your fried potato products BUT a 25 A RCD will not trip at 25A or even 50 it may possibly melt BUT it won't TRIP whereas it WILL TRIP as it senses an earth fault approaching 30mA

you seriously need to,get someone in who knows what they are doing AND how to,test when completed

 

[apprentice87]

you seriously need to,get someone in who knows what they are doing AND how to,test when completed

Definitely.. especially as your setup is powered with a generator, bypassing the RCD would be a lunatic thing to do.. You say you are near Chepstow?? I understand the burns unit closed down some time ago.. Shame that, you may be needing them soon..

Please listen to Kerching.. [above..]

john...

 

[apprentice87]

Hi all,

As in interesting point that just popped into my little brain.. Say you have a setup powered by a small generator. Presumably the ONLY earth fault protection you have will be an RCD, as, i would imagine, if you relied on an OCPD to provide fault protection, the generator would be physically incapable of providing a PEFC high enough to provide ADS within the required disconnection time????

john..

 

[Michael Walker]

Hi. Yes, extension lead is real type completely unwound. RCD original unit and the one used now both have RCD printed on them. Genny trips, or doesn't with nothing plugged into it. 

It's ex-army from a surplus outlet. Very basic 3kw,diesel Lambordini. It is pull start and simply has the RCD and the blue, 3 pin outlet. Nothing has been fiddled with and the replacement RCD is wired identically as the previous unit.

I'm a mile from the nearest car,across farmland, including 3 streams. 

The problem with it being intermittent, as I'm sure you're aware, is that unless the problem shows its face to a professional, it remains a mystery. 

It has run trouble free for over a year.

Not being a fan of burns of any kind  I will heed the advice to leave the unit in place.

Many thanks to all for your input. M

 

[kerching]

Get elctrical work wrong and at the least it will not work correctly....at the worst it will kill you and possibly others and whilst you are  dying it will hurt a lot

just saying 

 

[Michael Walker]

Anyone live near Chepstow looking for a job? I can deliver. M

 

[Phoenix]

Hi all,

As in interesting point that just popped into my little brain.. Say you have a setup powered by a small generator. Presumably the ONLY earth fault protection you have will be an RCD, as, i would imagine, if you relied on an OCPD to provide fault protection, the generator would be physically incapable of providing a PEFC high enough to provide ADS within the required disconnection time????

john..

While undoubtly true, I think for a small machine like this, it wont be as bad as it looks on paper. The lack of PEFC is going to be down to two reasons:

a) the high impedance of the generator winding, as compared to the grid, we can, at least measure one with this with a loop tester, the saving grace with high proportion of the impedance in the source windings, is that under fault conditions the output voltage will collaspse down quite a lot.

b)The ability of the machine to actually produce enough energy to feed into the fault, you can't generally measure this, and a loop test won't show any hint of it, unless you test with quite a high test current, it does again have its advantages that under a hard short the machine is likely to stall.

So I would expect if the RCD providing fault protection was inoperative, then under a fault that wasn't sufficent to operate the OCPD then the volatage would likely dip  down to whats probably a safe level, the machine would slow right down, it would try and ramp up to compensate, but that could just cause even more current to be drawn and it would soon stop. Probably wouldn't want to be holding a class 1 appliance at the time becuase you cant guarentee it'll be under 50v, but I don't think the fault would be able to persist for ages until it got someone, in quite the same manner that a fault on a TT system with a failed RCD / VOELCB can

 

[apprentice87]

Great answer!!

john..

 

[Michael Walker]

In layman's terms please. I'm a retired tree surgeon. Mick