spur or own elec supply to boiler

[desrob]

can anyone clear this matter up for me,i was told of an electrician friend that all heating systems should have there own independent supply from consumer unit,i have and i'm sure many others have got the elec supply from a spur or even in some case put a 3 point plug 3amp fuse and away you go ,this is even in some mi i've came across.i can understand the thinking of it's own circuit,but how often is it put into practice,not a lot i think,could be wrong please enlighten me,

 

[GQuigley67]

I would think its fine to use a spur, but then if an electrician is working on the sockets and he's turned the sockets off at the consumer unit then household doenst have any heating, maybe that's the case.

 

[desrob]

yes .thats the logic,but is it necessary

 

[quality]

No it isn`t, it is good practice to have the heating on its own circuit but it is not a regulation must have, a switch fused spur is fine

 

[Mick Helpful]

This more of a health & safety issue than Mode of connection. A boiler should be disconected from the supply when servicing and not be capable of being switched on inadvertently. As an electrical appliance, a gas fired boiler is a low current item so the final sub-circuit is not relevant. For discrimination purposes its best to have a single final subcircuit with a 16A mcb feeding a 20A switch or BS546 15A socket outlet. The 15A socket outlet provides the best isolation (far >6mm} and being a round pin plug it can't be inadvertently connected to a BS1363 13A socket-outlet. With its own sub-circuit any short circuit fault elsewhere doesn't affect the boiler. However there is nothing to prevent a boiler being fed via a fused connection unit off a ring main or radial sub circuit.

If an RCD is fitted to the installation, which it should be, any earth leakage fault will cause loss of supply. This will occur regardless of in which circuit the earth leakage fault occurs.

 

[James.C]

This is quite a confusing issue but basically it is down to interpretation, there are no rights and wrongs, I use a seperate circuit to a switched fused spur and I hasten to add not on the RCD side of the CU, the reason for this is that nuisance tripping does occur which means you could lose the heating and particularly in this cold weather we are experiencing could result in burst popes etc, the same principle is applied to freezers in that an RCD trips whilst you are away and you have lost everything that was in there, so it is for practical and economical reasons these circuits are usually on the non RCD side which is why High Integrity Consumer Units are now on the market.

 

[Reg Man]

If It is not RCD protected, Have you not got to use a permenent wired fused box? ie: should not use 3pin plug, because that could then be used for other household appliances if it were to be removed.

 

[James.C]

If It is not RCD protected, Have you not got to use a permenent wired fused box? ie: should not use 3pin plug, because that could then be used for other household appliances if it were to be removed.

Thanks for getting back, you are absolutely right, which is why I said it's own supply to a 13amp switched fused spur (not socket) obviously with the fuse down rated but because this is hard wired no one else can access the spur without the use of tools so it is perfectly acceptable and within regulation.

The reason for the switched spur is for local isolation where this can be done by the flick of a switch and or removing the fuse, saves going back to the Consumer Unit

hope this is helpful and please feel to contact if you require other electrical info

 

[Mick Helpful]

Reg Man wrote: ie: should not use 3pin plug, because that could then be used for other household appliances if it were to be removed.

Still using 5A and 15A plugs for everything? All appliances by law these days come with a 13A plug fitted You
can get 5A and 15A plugs fitted with a fuse, they're not cheap tho'

 

[quality]

I would like to clear the current view if I could

Fixed equipment i.e boilers requires fixed wiring and had done since 1992 that is that sorted

new circuits as of now or since 2008 have to be RCD protected but that does not mean that the central heating has to have its own circuit. It can be supplied by a ring main which has rcd protection and via a switched fused connection unit SFCU
it only has to be on its own circuit if its new build after 2008 of if rewiring / renovating

The local building inspector will advise the same

 

[Reg Man]

Still using 5A and 15A plugs for everything? All appliances by law these days come with a 13A plug fitted You
can get 5A and 15A plugs fitted with a fuse, they're not cheap tho'

Only if there is no RCD protecting the circuit. There is benefit to using 3pin plugs on an unswitched shuttered socket. Isolation of the boiler when carrying out work is absolute because you have to remove the plug. On a fused spur how many just flip the switch?

 

[James.C]

OK, without trying to get into a heated argument, (RCD's in the application in question) The regulations can be quite confusing, they are not a legal requirement, only guidelines for recommendation. so I would like to clarify something, which is, that whilst it is preferable for all circuits to be protected by an RCD it is not written in stone that they have to be, you have to consider the practical applications of the installation, so in my view, the exemptions to this are Freezers, Smoke Alarms & Boilers because all could be adversly effected by being on an RCD circuit, which again is why there are now High Integrity Consumer Units on the market to allow for this. however, having said that, there is nothing wrong with connecting to an RCD if so desired, you just have to accept the consequences of the end result, i.e smoke alarms not going off in the event of a fire were the batteries to fail, loss of food stuff if the freezer went off whilst away due to the fault of another circuit or burst pipes because the heating went off for the same reason. something to think about!

If I were to do the job for DESROB who asked the question on this, then I would suggest creating a new circuit, supplied by a non RCD protected CB as they are now known (Formerly MCB) of the appropriate size which is dictated by the boiler and cable size and then connect to a local 13amp fused spur, again with the appropriate fuse fitted.

 

[desrob]

thank you james.c.it's seems everyone has an opinion which is fair enough but i'm with you on this one. i am gas engineer/plumber by trade and have recently done the 17th edition wiring regs and a full scope part p course. would it be possible to tap into your un-doubted knowledge thanks again.derek

 

[Billy Bob Bob]

personally a 3 amp 3 pin plug is the safest way to work on a boiler you just pull the plug out total isolation

 

[Reg Man]

OK, without trying to get into a heated argument, (RCD's in the application in question) The regulations can be quite confusing, they are not a legal requirement, only guidelines for recommendation. so I would like to clarify something, which is, that whilst it is preferable for all circuits to be protected by an RCD it is not written in stone that they have to be, you have to consider the practical applications of the installation, so in my view, the exemptions to this are Freezers, Smoke Alarms & Boilers because all could be adversly effected by being on an RCD circuit, which again is why there are now High Integrity Consumer Units on the market to allow for this. however, having said that, there is nothing wrong with connecting to an RCD if so desired, you just have to accept the consequences of the end result, i.e smoke alarms not going off in the event of a fire were the batteries to fail, loss of food stuff if the freezer went off whilst away due to the fault of another circuit or burst pipes because the heating went off for the same reason. something to think about!

If I were to do the job for DESROB who asked the question on this, then I would suggest creating a new circuit, supplied by a non RCD protected CB as they are now known (Formerly MCB) of the appropriate size which is dictated by the boiler and cable size and then connect to a local 13amp fused spur, again with the appropriate fuse fitted.

Agree with you too. Common sense. Deviation from the reg's is a little doggy unless you can prove you have done better.

 

[Puddle]

personally a 3 amp 3 pin plug is the safest way to work on a boiler you just pull the plug out total isolation

Seconded,some have a hang up about having a plug not a fused spare,I can not see why,the fact I got a shock from a system the other week (posted pic) when fused spare wired by passing switch just added to my view

 

[Reg Man]

Seconded,some have a hang up about having a plug not a fused spare,I can not see why,the fact I got a shock from a system the other week (posted pic) when fused spare wired by passing switch just added to my view

I prefer a plug too. Too often though their fitted into a switched socket, not so good. Alway try to practice safe isolation, with volt meter, Check test meter from known source, turn appliance off, check appliance case and terminals, check test meter once more. A bit of a chore, but better than getting bitten.

 

[James.C]

thank you james.c.it's seems everyone has an opinion which is fair enough but i'm with you on this one. i am gas engineer/plumber by trade and have recently done the 17th edition wiring regs and a full scope part p course. would it be possible to tap into your un-doubted knowledge thanks again.derek

No problem a all, please feel free and I will try my best

Regards

Jim

 

[clydey]

17th edition appendix 15 (informative)
ring and radial final circuit arrangements
reg 433.1.5
The load current in any part of the circuit should be unlikely to exceed for long periods the current carrying capacity of the cable
this can generally be achieved by
reg 433.1.5 (ii) not supplying immersion heaters, comprehensive electric space heating or loads of similar profile from the ring circuit
(iii)connecting cookers, ovens and hobs with a rated power exceeding 2kw on their own dedicated radial circuit
--------------------------------------------
2kw is approx 8 amps odds
appendix 15 shows a nice diagram of a ring final circuit where at the bottom of the circuit
it shows the fused connection unit labeled [ Fused connection unit (FCU) supplying fixed equipment
hope this helps

 

[Eddie Charlton]

1. this is a fixed appliance so should be connected to a fused spur.
2. does not need a separate circuit to boiler as long as correct spuring rules are abided by.
3. will need a 3 amp fuse applied to the switched fuse unit for appliance protection.

if the spur is going to be aqn add on to an exisiting cirucuit then best practice as per 17th edition in that (only) the added part of circuit to the spur needs to be RDC protected. if it is just a replacement of , say a single socket to a switched fuse unit, then no RCD is required.

 

[Billy Bob Bob]

1. this is a fixed appliance so should be connected to a fused spur.
2. does not need a separate circuit to boiler as long as correct spuring rules are abided by.
3. will need a 3 amp fuse applied to the switched fuse unit for appliance protection.

if the spur is going to be aqn add on to an exisiting cirucuit then best practice as per 17th edition in that (only) the added part of circuit to the spur needs to be RDC protected. if it is just a replacement of , say a single socket to a switched fuse unit, then no RCD is required.

spur must be double pole for safety,you can still get killed trough the neutral

 

[Jeff Armstrong]

I agree with QUALITY as the IEE Regs [electrician's bible] 17th Edition was issued in 2008 and all new installations must adhere to it's rules so that is that indeed .

 

[Reg Man]

Fused spur is great. The installation requirements: Top level is Electrictiy at work regs, second level is manufacturer instructions, thrid level is British standards. If the manufacturer instruction say the appliance can be fitted with a 3 pin plug on an unshuttered socket (as they generaly do) its ok. The manufacturer instructions come above British Standards.