oil fired boiler tripping ring main


Postby groobydoo » Sat Nov 24, 2007 1:47 pm

Hi guys,

My oil fired combi boiler is occasionally tripping the ring main. the first time it happened it blew the control box for the CH about 4 weeks ago. I've since replaced it but the RCD has tripped twice since- I,m pretty sure it is the boiler- it's just happened again this afternoon with very few appliances running when the wife ran the hot water. I've had no work done recently that could have caused this. I'm not sure where to start to fault the system :? , I'm a pretty competent DIYr. Can anyone give me some pointers or suggestions please?

Thanks in advance.
groobydoo
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Postby TCSC » Sat Nov 24, 2007 6:35 pm

This has to be a "if you need to ask, should you be doing it?". Bite the bullet and get in a professional who has experience of these things. It could easily be a matter of life or death. I don't mean this as an admonishment, but hopefully to make you feel better about spending the money.
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Postby BLAKEY1963 » Sat Nov 24, 2007 11:40 pm

GROOBYDOO
boiler circuits have earth leakage on an excessive level
and if a TT SYSTEM with an earth rod for your earthing
facility, then rcd should be on a split load board and
upgraded to 100 milliamp trip , rather than 30 milliamp.
secondly an electrician should be called in to check and
test wiring.
with these two eliminated u can look at possible fault on boiler. THEN call in corgi reg plumber gas fitter

BLAKEY1963
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Postby groobydoo » Sun Nov 25, 2007 10:07 am

Thanks Blakey, now pretty sure this is boiler problem. Pump has now blown. Electric feed is spur off ring main. I have an external oil fired boiler- its a corgi free zone here- the joys of living in the middle of nowhere. I'll report back when we get to the bottom of it.
groobydoo
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Joined: Sat Nov 24, 2007 1:33 pm


Postby TCSC » Sun Nov 25, 2007 5:06 pm

If the system is TT then the RCD will be on the whole system and will already be 100mA sensitivity. Without knowing what you are doing, it could contravene the 16th regs and dangerous to reduce its sensitivity further. An S type RCD could possibly be used, but again that should only be a call made by a fully qualified sparky.

If the RCD that tripped is the one giving supplimentary protection to the ring main as well as the boiler, then it can not be changed for a less sensitive one. The 16th ed regs require RCD protection for any socket that can possibly be used to supply electrical equipment outside. This effectively means any socket within a few metres of a window which in turn means any socket down stairs. The 16th regs requires this RCD to be 30mA sensitivity. Besides which, the whole point about 30mA is that it is just below the current that would be lethal if it flowed through your body. 100mA is just above the lethal current.

Look, -- you have something wrong with your system. It involves some sort of earth leakage path. Your bath tub is connected through lovely conducting copper pipes to your boiler and you emerse yourself in hot water to make the most effective conductive connection between your body and the hot water system. I assume you have not had a bath since the fault first showed itself. I certainly wouldn't have! If I did, I would be lying in the bath wondering if the faulty earth leakage path was through the bath and me or a member of my family.

And don't bother hoping that it is nuisance tripping. It has taken out your control unit and it has gone several times recently. I presume it wasn't tripping this time last year?
TCSC
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Joined: Fri Oct 19, 2007 1:23 pm


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