RCD and boiler circuit

[studentspark]

A central heating circuit has a lot of individual items that can trip an RCD
Any advice on fault finding. i.e isolating individual parts to test insulation resistance.

Insulation resistance continuity testing of motors is something I have little experience of.
Knowing if a valve or pump is faulty is difficult as I not really sure what results I should get, and how you can test them with out having to take the thing apart.such as a valve.

Also disconnecting items

For example if I disconnected the pump to see if that stopped the tripping.
But would that remove a link in the chain of operation and stop the system working as it should so not give useful results. ( and the issue of the boiler being powered with no pump to circulate water concerns me)


Thanks .

 

[Taylortwocities]

You will need an Insulation Resistance tester, the knowledge of how to use it, understanding of what damage it could do and how to interpret the results.

Got all, or any of that?

 

[EFLImpudence]

Clamp meter ?

 

[GaryGarden]

Wouldn't touch it myself and would refer it to a heating engineer /
GSR man/woman

 

[JohnW2]

Wouldn't touch it myself and would refer it to a heating engineer / GSR man/woman

Not an electrician?

Kind Regards, John

 

[PBC_1966]

If you can pick up any (maybe eBay), the little testing guides Megger used to publish and distribute with its equipment in the 1950's/1960's are a good introduction to insulation testing and how to interpret the results. Obviously there's more in the way of electronics to complicate matters these days, but the basic principles with regard to motors and similar devices are the same now as they were 50 years ago.

 

[ericmark]

I would tend to use 250 volt rather than 500 volt on the insulation tester.

 

[AndyPRK]

yes you can disconnect a pump and see if it stops tripping. (don't run the boiler for more than a few seconds though if water isn't circulating). You could also connect the pump to a 13A plug.

Disconnecting motor Valves will stop the system working in most cases.
You could remove the lid and inspect these, or again put a plug on the brown/blue/green&yellow wires. (insulate the others)

 

[Lectrician]

I'm not a fan of disconnecting things and turning back on "to see if it still trips".

You use an insulation tester to pin point the fault by disconnecting sections until the fault is found. With central heating, you still split the circuit down as you would any other circuit, just be sure you know how to connect it all back together

 

[studentspark]

Thanks for the reply.
To answer some earlier points.
Yes I do have the correct testing equipment, and I do know how to use it.
What I don't have is the experience of working with heating systems.
I am very happy and confident in all of the domestic work that I do, otherwise I would not do it.
But heating systems I always refuse to work on, but if I want to start considering myself an electrician I need to crack this.

I know all the theory about how it all works and is connected together.
I have built test rigs so I can play around and test different scenarios.
I have been on the Honeywell and Danfloss courses, I know how it works
The wiring of them really is quite straight forward, just a bunch of switches, all doing there job, passing on calls for heat, switching off when not needed.
Its really easy on your test board.

Its when you go to a job and the system is all over the place

I understand its a methodical procedure , working out what does what (usually seems to be a mess of wires) and I suppose thats the catch 22, I can't properly fault find until I have the experience, and I can't get the experience because I back away from it.

Then you have the issue of should I even be touching this.

An unvented system, for example, do you need to be G3 qualified to even touch the electrics on pressurised systems, Ive asked heating engineers this, and they don't know, a very experienced plumber I know didn't know what G3 was.

Its easy in my shed, not so easy when you are asked to find an intermittent RCD fault on a heating system, and, because you have worked for them before, and they trust you, and you want to help them out, you get involved, when really you don't want to..
Or you are there putting a new light in and they ask you about a problem with their heating.....

I have not got any particular issue at the moment, just wanted to know how you test things and interpret the results.
Any guidance is welcome.


Thanks

 

[EFLImpudence]

An unvented system, for example, do you need to be G3 qualified to even touch the electrics on pressurised systems

I do not know the definitive answer but -

even if you just replace something electrical you would be leaving yourself open if something else went wrong so I would leave well alone.