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 Post subject: Boiler Isolation
PostPosted: Tue Sep 12, 2017 12:29 am 
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A comment in an EICR: "No means of isolating the permanent live wire into the boiler in the garage" which is strange since it has never been flagged before.

So I queried it over the phone. "Doesn't flicking the RCD do that?" Seems not since the RCD is located in a different building. Fair enough.

"So I'll get a FCU fitted. Pull the fuse and perm live isolated". Nope. Apparently, according to him, it should be double pole to isolate the perm live.

Before I call his boss, is he right? Boiler isolation should be double pole, not single?

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 Post subject: Re: Boiler Isolation
PostPosted: Tue Sep 12, 2017 7:37 am 
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Sometimes the boiler can be fed from a remote point eg cylinder cupboard in the house. Some boilers have a live neutral and permanent live and in these circumstances a triple pole isolator is recommended.


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 Post subject: Re: Boiler Isolation
PostPosted: Tue Sep 12, 2017 8:44 am 
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:withstupid:

Double pole switched fused spur by the boiler if it's a combi and a triple pole fan isolator if it's a system boiler :thumbright:

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 Post subject: Re: Boiler Isolation
PostPosted: Tue Sep 12, 2017 9:00 am 
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552.1.2 Every electric motor having a rating exceeding 0.37 kW shall be provided with control equipment incorporating means of protection against overload of the motor. This requirement does not apply to a motor incorporated in an item of current-using equipment complying as a whole with an appropriate British Standard.

537.2.1.1 Every circuit shall be capable of being isolated from each of the live supply conductors. In a TN-S or TN-C-S system, it is not necessary to isolate or switch the neutral conductor where it is regarded as being reliable connected to Earth by a suitably low impedance.
Provision may be made for isolation of a group of circuits by a common means. if the service conditions allow this.

Circuit. An assembly of electrical equipment supplied from the same origin and protected against overcurrent by
the same protective device(s).

Reading above it would seem if you have a TT supply maybe he is correct in that you need something to disconnect the neutral, there has been so talk about TT supplies and use of RCBO's which really need to have the neutral switched. And some makes of consumer unit do have single width RBCO's which have double pole switching. But in the main a FCU is not considered in the same way, although you can get double pole switches in a FCU often they are not considered as forming a circuit so you don't need to inform the LABC when fitting one.

Since the motors inside a boiler don't exceed 370 watt then no need for local isolator to comply with regulations. The HSE say you have to isolate else where before opening a panel etc. So for example before removing the cover from a consumer unit you should either switch off the isolator feeding the consumer unit or if there is no isolator withdraw the fuse, however you also should not break the seals on the suppliers fuse, so either way you are normally breaking a rule so in the main we do remove the front from a live consumer unit even if really it should be isolated first. In all other cases however we do need to isolate.

If to isolate also means switching off the lights then we get to a very basic regulation.

314.1 Every installation shall be divided into circuits, as necessary, to:
(i) avoid hazards and minimize inconvenience in the event of a fault
(ii) facilitate safe inspection, testing and maintenance (see also Section 537)
(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
(iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced by equipment in normal operation
(v) mitigate the effects of electromagnetic interferences (EMI)
(vi) prevent the indirect energizing of a circuit intended to be isolated.

Even that go to any caravan or narrow boat and you have two RCD's both 30 mA one feeding the other, however the lights are also battery operated, so fit a battery light in the outbuilding then you have removed the problem of no lights after isolating.

In mothers kitchen the electrician insisted in fitting isolators for the hob and oven which were useless really since you need to reach over the hob to operate them, but there is a mini consumer unit in the kitchen right by the door so it did not need an isolator anyway. This happens a lot, some one says correctly you need a double pole isolator because it was a TT supply, but then the person being told does not realise it was because of the TT supply and says you need a double pole isolator even with a TN supply.

I think it's called Chinese whispers?

Personally I would either fit a plug and socket, or a switched FCU but I can't find a regulations saying you must.


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 Post subject: Re: Boiler Isolation
PostPosted: Tue Sep 12, 2017 9:12 am 
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Razor wrote:
:withstupid:

Double pole switched fused spur by the boiler if it's a combi and a triple pole fan isolator if it's a system boiler :thumbright:

I think the point is if that isolator has to be LOCAL and although I think local isolation would be nice, I can't find anything saying you MUST have local isolation in this case, it seems there is an isolator the RCD but it's not local. I have never used a triple pole isolator for domestic central heating, it has always been placed before lines are split.

If we are saying you must have a local isolator then also there should be a local isolator with every remote motorised valve, that would require four pole isolators which I have never seen used.


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 Post subject: Re: Boiler Isolation
PostPosted: Tue Sep 12, 2017 11:10 am 
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Thanks all. That corrects my understanding.

I think I'll have a double pole FCU or switch fitted before the perm live spurs off and be done with it.

It's a bit of a puzzle why it hasn't been raised in previous EICRs, but I guess some of these things can be subjective.

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