New (outdoor) boiler

[Martin Carroll]

I have bought a Grant external boiler for the renovation.

I have a couple of questions re the electrical connection.

As regards supplementary bonding to the oil feed pipe, is this required if the boiler is outside? The internal plumbing will be all plastic after the first metre.

The manual states that "The electrical supply to the boiler and control system should be fed from a single separate 5 Amp circuit breaker with earth leakage protection providing complete electrical isolation". Also a fused double pole switch should be used. I was planning to just use a FCU on the downstairs ring to provide power. Is the separate circuit breaker (MCB?) really necessary?

Cheers

Martin

[John Rumm]

If its all plastic in the house, then I can't see the need.

Not required, but perhaps desirable. Boilers and appliances outside are good candidates for nuisance trip problems, so not sharing a RCD with your socket circuit could have advantages.

[robgraham]

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"good candidates for nuisance trip" Hmm - interesting. I've three external circuits - outside boiler, outside workshop and outside garage/greenhouse/storage shed and in 25 years I've never had a problem. Perhaps as an amateur I do a good job of wiring !!!

Of course having just said that, they will now all give me hell!

Rob

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Martin Carroll saying something like:

Do like 99% of installers do and take a spur from the protected ring to a switched double socket at the boiler with the boiler and pump plugged in with 5A fuses in the plugs. Does all you need and safely, too, for servicing.

[John Rumm]

As with all these things, you can only go with probabilities. There is no guarantee that any setup will cause a problem and none that it won't. So its just a case of working out what is possible or likely, and deciding on how important the implications of it are. Circuits that potentially involve dampness, water, high humidity etc are more likely to cause problems (as are ones with copious mains IF filters or mineral insulated heating elements). Then again in reality they may work faultlessly.

[ARWadsworth]

"good candidates for nuisance trip" Hmm - interesting. I've three external circuits - outside boiler, outside workshop and outside garage/greenhouse/storage shed and in 25 years I've never had a problem. Perhaps as an amateur I do a good job of wiring !!!

Of course having just said that, they will now all give me hell!

Rob

This is not a comment on any of your work Rob but a serious question, but have you tested the RCD in the last 25 years?

I have come across several RCDs that will not trip when they are supposed to.

Adam

[David Hansen]

On Sat, 31 Jan 2009 15:08:56 +0000 someone who may be Martin Carroll wrote this:-

They appear to be confused, or need to introduce some commas. Earth leakage protection is not designed to provide complete electrical isolation, although a suitable double-pole RCD will do so.

There is something to be said for a dedicated radial circuit to a boiler, with a fuse or MCB in the consumer unit. What else is desirable or necessary depends on where the boiler is located. An outbuilding, a separate boiler house, a separate building, outdoors (unlikely, but possible) and so on. Then there is a similar question with regard to the oil tank. The answers to the questions will help with answers to questions on things like bonding.

[Martin Carroll]

In article , David Hansen writes

The boiler is indeed an outdoor model,