RCD Tripping on AMF switch-over to generator supply

[qwest]

Tony - nothing troll going on. Honestly I'll take a picture with today's newspaper of the whole job if it helps!

 

[qwest]

... OK local electrician contacted. He asked all the right questions but doesn't seem like there is an immediate answer. Should know more later today when they visit.

 

[Darkwood]

I had guessed the earth may not be set up correctly.

What I don't quite understand is what additional risks or benefits are involved in switching the earth system.

Now I could switch out the generator earth but I can't see that being the issue.

Incidentally the earthing system to the gen is on really heavy gauge copper - looks like three core car battery cable - the gen earth was tested by my electrician and they seemed to think it well within spec

I don't have test kit myself beyond a little meter but I have checked if there is any pd between the utility E and the gen E (when the two aren't connected obviously) and there is no pd.

So what would I gain by switching earth systems? I would gain a momentary period where the entire house has no earth at all.

Some of the most dangerous lines ive seen on this forum in a long time regarding the theme here.....although we still lack info to give confident answers their is a risk that this set-up is a death-trap for your family ..... il reiterate that point because of the casual nature of your posts and openess to expressing you don't understand a lot of what you've done .....Advanced DIY it maybe, your enthusiasm to understand what you have done is commendable but you really need to appreciate you are clearly out of your depth with possible deadly consequences ..... we await your pics and will be interested to see what the electrician says....

 

[qwest]

Not sure how to comment the images but looks fairly straight forward to me once you chase the wires back to something you recognise. Probably not so easy from a picture.

Supplies to contactors go in the base and out of the top. The one on the right is connected to the CU and the one on the left is bridged over so the gen supply does the same when switched.

You can see how simple it would be to switch the gen earth. But there is a less obvious issue. There is a 12v circuit for gen battery and power to the computer. So switching out the gen earth would also switch out the DC neg since this is grounded to the gen chassis. This is normal and best practice I have looked at other setups and they all earth the gen battery to the gen chassis. So I don't think there is a way to switch the earth. Maybe I need another control battery which is not earthed to achieve this but again this isn't seen in other gen setups.

 

[Engineer54]

As Darkwood has suggested let's wait until the electrician(s) that are coming today, look over you're system and come up with a solution.

One thing i would suggest to you, is to ask them to re-dress the house and generator supply cables in that ATS. As it stands at the moment it's a bloody abortion of a job.

I don't think a single 1.2m earth rod for a permanent Stand-By Generator is sufficient to be totally honest, especially if it's one of these 3/8'' twigs. If this earth rod has a screwed end it will be a 5/8'' rod that can be extended by use of a coupler... If not then discard the old rod and drive in 2 X 1.2m X 5/8'' rods for the generator earth. Then get the electrician to measure the rods Ra, the lower the value the better!!

Anyway, let's see what this electrician has to say about your problem and the overall installation of this gen-set....

 

[qwest]

Well, an electrician has taken a look but no further forward. Theories now surround faulty RCDs - so it looks like further expertise is needed to get to the bottom of it.

 

[Darkwood]

So independent separate rcd's all suddenly go faulty .... sounds like you got your everyday basic domestic electrician there.... did you question him on his proficiency with back-up supplies and supply arrangements?

 

[Engineer54]

Well, an electrician has taken a look but no further forward. Theories now surround faulty RCDs - so it looks like further expertise is needed to get to the bottom of it.

I'm afraid you're going to have another look for a qualified proficient electrician that knows a lot more, than just domestic wiring.... You may have to call on the services of a bonafide electrical contracting company, that covers among other things, industrial/commercial installations and maintenance....

 

[Engineer54]

Can you post close up's of all the RCD devices you have in place at the moment, preferably with the enclosure covers off?? A photo or two of the gen-set would be nice too showing the connections and earthing and control panel interior...

 

[Aindowsimon]

You've had me thinking . Wot you have with ur common'd you're pme earth with the gen earth witch is also pme'd?? . I understand the earth is pmd! So to speek at both dno side and generator wot you have is maybe as ur contractor lets say gen side cuts out ur rcd may momentarily detecting a foreign current down earth as the contractor has isolated the line and neutral but neutral and earth at equal potential . So I'm thinking you may need to run the earthing conductor via contactor ? I apologise I'm no shakspear absolutely hopless with words ( and spelling a true engineer lol )

 

[qwest]

Still no luck with this. The last engineer walked away from the job by the look of it. Any advice on who to contact that may undertake this sort of work in the Newcastle are would be great.

 

[thebigcheese]

Aggreko have a great team of Generator Engineers who may be able to help. They may cost £££ but they deal with AMF on large scale installations all the time

 

[qwest]

Aggreko would love to do this if I had a sizeable estate of generators but it is just one rather small generator so I can't see that being a route to explore. My last attempt I explained the problem and even said it had eluded the ability of several previous engineers - I don't want to waste time on this any more so hoping to have a better chance of success with a recommendation.