3 amp fuse in FCU for boiler

[JohnW2]

The WIRING regulations are not applicable to ANY connected equipment, because they are the WIRING regulations. They are not the equipment connection regulations.

That was my point - that BS7671 is of very little relevance to the matter under discussion.

The one grey area, at least in my mind, is equipment hard-wired into the installation, whether through an FCU or otherwise, since I think that some would say that such constitutes 'fixed wiring' and therefore comes within the scope of BS7671. That view is perhaps supported by the fact that (as has been pointed out by EFLI) 'the Wiring Regulations' allow omission of overload protection for cables which are undeniably 'part of the installation' given certain characteristics of the load supplied - so it cannot be said that those regulations do not ever include consideration of the connected equipment.

Kind Regards, John

 

[mwatsonxx]

That was my point

Really interestizzzzzzzzzzzzzzzzz.

 

[ericmark]

I did look up the installation instructions for mothers boiler, mine is too old to find instructions on line, electric supply 140 watt requires an external 3A fuse to BS1362. It also states that if there is no mechanical timer fitted it can be fitted in zone 2 of a bathroom, seems the mechanical timer changes the IP rating from IPX4D to IP20.

The programmer, roomstat and froststat are all supplied from the boiler, it has three internal fuses, a 2.5A, (T2.5H) a 1.6A (T1.6L) and a 0.5A (T500L) all 250 volt rating, the fault chart says if either 2.5A or 0.5A blows it will show as no power to boiler. They even supply a spare fuse clipped to cover.

It would seem the boiler manufacturer may stipulate a 3A BS1362 fuse, but they do not rely on it for protection, it also seems they do not expect motorised valves to be fitted, I do have two fitted but they are battery operated 2 x AA batteries in each, there are further batteries in the room thermostats, and a 5 volt USB supply to the hub, and separate mains supply to the router. Also separate supplies to PC, tablet and phone, all used to work the heating.

It states the supply must be either from a fused double pole isolator or a plug and non switched socket, can use supplied 2 meter cable or another, it does not stipulate type so clearly does not need to be gas tight.

I was surprised that a switched FCU was required when it states the socket must be non switched, I would think a power failure would cause a strain on the boiler being switched off without being allowed to cool, but reading the instructions it would seem the 3A BS1362 fuse is to protect the supply flex, which is quite reasonable.

As to BS7671 this was not referred to, it did refer to IEE regulations which would I assume also cover the inspection and testing of in-service electrical appliances, (PAT testing) and the old Book 3 which covered installation testing as well as BS7671 I do remember a continual debate as to who should test items like hand driers are they part of the old PIR (EICR) or portable appliance testing as not portable or part of the installation, they are an appliance which is in-service.

I would not want to use a 500 volt insulation tester on my boiler. And I suppose being on a plug and socket does make the testing easier, I personally hated testing a hand drier, required locking off and removing to workshop to follow all the rules, can't remove the FCU without isolating elsewhere and once isolated nothing to power the PAT tester.

I remember when boiler fitted the plumber plugged it in to commission then the electrician came around latter and removed plug and connected to a FCU.

 

[JohnW2]

It also states that if there is no mechanical timer fitted it can be fitted in zone 2 of a bathroom, seems the mechanical timer changes the IP rating from IPX4D to IP20.

I'm not sure that it's related to IP rating. Wouldn't a 'mechanical timer' usual have a means of manual switching, in which case it would not be allowed in Zone 2?

I was surprised that a switched FCU was required when it states the socket must be non switched ....

Are they not just presenting common sense? A switch (on a socket) which can be accidentally switched off is not ideal for a boiler/heating system, and the fact that the plug can be pulled out for local isolation means that a switch is not required - so 'best' not to have one. With an FCU, there is no plug to be pulled out, so they may think that it makes sense that it should have a switch for 'local isolation'. I know that BS7671 does not require such 'local isolation', but the boiler manufacturers (or even possibly some unidentified 'gas regulation'!) may feel that a boiler should have it.

Kind Regards, John

 

[ban-all-sheds]

That was my point - that BS7671 is of very little relevance to the matter under discussion.

The one grey area, at least in my mind, is equipment hard-wired into the installation, whether through an FCU or otherwise, since I think that some would say that such constitutes 'fixed wiring' and therefore comes within the scope of BS7671.

If you read the definitions of Electrical Installation and then Electrical Equipment in Part 2, and then Chapter 11 does the grey-ness go away?

Equipment is in scope, but the requirements of the regulations apply only to its selection and use.

HOWEVER...

I do not see why a manufacturer may not require things of the installation which do not contravene the regulations.

There is no argument which can ever be made which says that the Wiring Regulations forbid the use of an FCU with a 3A fuse to supply an item of equipment.

There is no argument which can ever be made which says that the Wiring Regulations (or indeed any others) forbid the use of a 3A fuse in the plug which an item of equipment.

Ib ≤ In ≤ Iz is required.

Ib ≤ In << Iz is not forbidden.

We don't know if they do, but it cannot be argued that gas regulations (or indeed any others) may not require things of the installation which do not contravene the Wiring Regulations, such as a 3A fuse.

And I don't think that it can be argued that a maker may not require a 3A fuse. No matter how much you say they should not, no matter how many times you ask them to justify the requirement, no matter how many times you ask them to explain how their equipment is used in places where such fusing cannot be provided, ATEOTD they may make that stipulation.

The Wiring Regulations require one to "take account" of the manufacturer's instructions, so it can be argued that any MI imposed requirement for a 3A fuse is not mandatory.

I leave it as an exercise for the reader to decide whether ignoring a manufacturer-required provision of a BS 7671 compliant safety device just because you don't think they ought to require it and/or just because you don't think their equipment needs it, qualifies as good workmanship and demonstrates an appropriate level of skill.

 

[mwatsonxx]

is perhaps supported by the fact that (as has been pointed out by EFLI) 'the Wiring Regulations' allow omission of overload protection for cables which are undeniably 'part of the installation' given certain characteristics of the load supplied

With three conditions that he chooses to ignore, and ignoring them will lead to fires in domestic premises, all caused by people believing EFL's judgement as supported and endorsed by JohnW2

 

[ban-all-sheds]

With three conditions that he chooses to ignore

Which are?

 

[winston1]

no matter how many times you ask them to explain how their equipment is used in places where such fusing cannot be provided, ATEOTD they may make that stipulation.

But if I was installing their boiler in, say Croatia, I would still want to know how to comply with that stipulation.

 

[ban-all-sheds]

If you were installing their boiler in Croatia you would be advised by them on how to install it there, and any work which you did on the electrical installation would be bound by the Croatian wiring regulations.

Maybe the Croatian wiring regulations forbid makers from requiring that compliant things be done because they "have no right" to require them.

And maybe they don't.

 

[mwatsonxx]

Which are?

You know what they are, and they have'nt changed in the past 40 years.

 

[ban-all-sheds]

Please show which requirements EFLI has chosen to ignore.

 

[mwatsonxx]

Please show which requirements EFLI has chosen to ignore.

see above

 

[ban-all-sheds]

An unacceptable response.

You said "With three conditions that he chooses to ignore".

Will you please have the decency to show what those are, instead of repeatedly evading the question.

 

[securespark]

Don't bother, Ban, he's loving every minute of it, waiting with glee for the next response to his drivel.

 

[THRIPSTER]

If you consider that the FCU to a boiler is meant to be the single point of isolation for the central heating system which includes the boiler, ancillary wiring, pump, room thermostat etc - often wired in 0.75mm² or 1mm² then perhaps this argument can go away.

Regards