Part P 17th, Smoke Alarms, Existing Circuits

[DJUK]

I've a bit of a dilemna, my building inspector and electrician seem to be in disagreement about what is allowed and what is not.

I'm converting a garage to an office, so I've got the list of requirements from the LABC, and working towards those quite happily. The BI wants a smoke detector in the utility room which is directly adjacent to the garage. The Consumer Unit is also in this room. The BI said he wanted the detector wired into the lighting circuit. The Electrician said this isn't allowed under 17th edition. The building inspector checked his regs and says "yes it is". The BI wants a Part P signoff and the sparkie says what he wants won't comply, not without a whole new CU and various other gubbins. The house is 10 years old, finished December 98.

So.. here's what I have. I have a CU with a mains side and a (single) RCD side. Mains side has a 32A circuit for the cooker, two 6A circuits for lights (upstairs and downstairs), and a dedicated 6A circuit for the smoke alarms. RCD side has two 32A circuits ( for upstairs and downstairs ringmains ). I have two free slots, which I want for two new circuits in the garage, a ringmain and a lighting circuit. The CU is old, an "Ashley & Rock" unit which isn't made anymore, bought out by Hagel I understand.

My question is, how does Part P relate to existing circuits? Can I add an additional smoke detector to the existing dedicated smoke circuit without requiring signoff? Isn't this really just a spur? To the best of my knowledge, the cable for the smoke circuit is not mechanically guarded, and this is why I ask if Part P is required. If it's not, I can just add a new detector to the circuit as a spur, if it is, I may have to get a whole new CU because I don't think I'll be able to find an RCBO for my CU, which would appease Part P.

Then I just need worry about Part P for the two new circuits to be installed in the garage on a single RCD...

 

[sparkyspike]

If the existing smoke alarms are on a dedicated circuit, then there's no point taking the utility smoke detector off the lighting circuit. You'll have to wire it into the existing detector circuit as you suggest.

I would have thought that you could add a smoke detector without notification, but Part P and the electrical regs would still apply. (Part P applies regardless of whether you are notifying). Besides, aren't you already notifying for the rest of the work being done?

You still have to be concerned with how you route the cable, but you needn't have to fit an RCD to the smoke detector circuit if all the cables are in the ceiling.

What is the BCO's reason for requesting a smoke alarm in the utility room?

 

[DJUK]

Basically I'm hoping to avoid a whole new CU just because of a smoke detector.

Building inspector wants a smoke detector in the utility (because the office (nee garage) has no external door). Yes, already notified and had several visits from BCO. The problem will be about getting Part P signoff, not the BCO who just wants the cert at the end.

From what I've read, because the cable is in the walls/ceilings and (probably) isn't guarded, it either needs to be on an RCD or RCBO. It's not recommended to have smoke detectors on RCD and I probably can't get an RCBO for my old CU, this means I'll have to replace the whole CU and get an RCBO for it as well. So maybe an extra £110 odd for the parts, and then fitting costs, just because of a blasted smoke detector.

There's a fair bit of information about installing new stuff to Part P, but precious little info on how Part P applies to existing infrastructure.

So what I need to know is, can you add to existing circuits ( i.e. add smoke detector to existing smoke circuit ) without having to recertify to whole thing? BCO says regs can't make you redo all existing stuff, but sparky is suggesting Part P means you do.

 

[Spark123]

All that "Part P" states is "P1 Reasonable provision shall be made in the design and installation of electrical installations in order to protect persons operating, maintaining or altering the installations from fire or injury. "
It doesn't go into detail of how to go about it.
Your electrician will probably use the IEE regs which goes a long way to showing compliance with P1.

There was a change in the 17th edn regs which means most normal cables need RCD protection if they are concealed in a wall or partition, does the new cable to the smoke detector need to be run concealed in a wall or partition?

 

[DJUK]

The new smoke detector would be about 3ft from the CU

The existing smoke circuit must lead out from the CU, so the proximity should make it relatively easy to add another spur from it, my guess is it would be in the ceiling.

 

[jabuzzard]

Basically I'm hoping to avoid a whole new CU just because of a smoke detector.

Building inspector wants a smoke detector in the utility (because the office (nee garage) has no external door). Yes, already notified and had several visits from BCO. The problem will be about getting Part P signoff, not the BCO who just wants the cert at the end.

Then the building inspector is out of line if you ask me. There is nothing in the regulations that state that a room without an external door needs a smoke detector when I read them.

There are regulations to deal with rooms that don't open onto an exit route, but these are all to do with flats.

As you are making alterations it is my understanding that he can insist that you have mains powered smoke detectors installed, and if these are powered off an RCD protected circuit then they need to have battery backup. You will need a minimum of one downstairs and one upstairs, in the hallway and they must be interlinked, though the interlink can be wireless.

My research indicates that in Scotland you also have to have a heat detector in the kitchen as well.

 

[Spark123]

The new smoke detector would be about 3ft from the CU

The existing smoke circuit must lead out from the CU, so the proximity should make it relatively easy to add another spur from it, my guess is it would be in the ceiling.

I'm pretty sure the electrician can find a method of complying with the 17th edn regs and installing a smoke detector without RCD protection.

 

[RF Lighting]

I'm certain I could...

Besides, you new smoke alarm will probably need to be connected to one of the existing units, and NOT the CU, as you will need to interconnect the new smoke alarm to the existing one.

It is very unusual to find the interconnect wire has been taken to the CU.

 

[mikric]

Do you have a window in there that could be used as means of escape ? Assume you have created what is known as an inner room.

 

[DJUK]

Yes, the new window in the garage has two fire escape opening windows in it, and there is an outside door in the utility room adjoining the garage ( where the CU is located, and where the BCO wants the smoke detector ).

 

[ebee]

Smoke detectors may be wired on their own dedicated circuit or an existing (well used) light circuit.
The latter is often prefferable because loss of that circuit should prompt immediate attention by the user.

If the existing smoke detectors are hard wired with interlink than your new one if hard wired should be connected to the same circuit.

They may be wired on different circuits if the interlink is via radio.

You wouldn`t need to change consumer unit and/or provide RCD protection to existing circuits (you might decide you want to though).
only new wiring would need either RCD protection or buried in wall more than 50mm deep or surface run on wall or earthed sheave protection .
If you can avoid new wiring in walls you will not need this protection but you might decide you still want it.

If you decide you are best giving RCD protection to the existing smoke detection circuit you need not change the Consumer Unit to one that takes RCBOs you could add a RCD to the circuit as it leaves the fuseway at the consumer unit.

 

[Zambezi]

Replace your current "damaged" light fitting with one of these and be done with it...
http://www.tlc-direct.co.uk/Main_Index/Fire_and_Smoke/Housesafe/index.html

I have just noticed that TLC has discontinued them but other places should sell them.

 

[holmslaw]

..

 

[DJUK]

If the existing smoke detectors are hard wired with interlink than your new one if hard wired should be connected to the same circuit.

I don't believe the old ones are interlinked. Not sure what this means in relation to the new one.

only new wiring would need either RCD protection or buried in wall more than 50mm deep or surface run on wall or earthed sheave protection. If you can avoid new wiring in walls you will not need this protection but you might decide you still want it.

You've hit the nail on the head, this is the bit which is catching me. The new smoke detector will be directly next to the CU, less than 3ft between them, and the cable would run in the ceiling. Does it have to be protected? And if so, would it be possible to put shielded cable in there ( without ripping out the ceiling ) to satisfy? If not, it means an RCBO which in turn means a whole new CU.

If you decide you are best giving RCD protection to the existing smoke detection circuit you need not change the Consumer Unit to one that takes RCBOs you could add a RCD to the circuit as it leaves the fuseway at the consumer unit.

No room, only two slots free on the CU, which are needed for the new ringmain and lighting circuit in the garage.

 

[ebee]

If the existing smoke detectors are hard wired with interlink than your new one if hard wired should be connected to the same circuit.

I don't believe the old ones are interlinked. Not sure what this means in relation to the new one.

only new wiring would need either RCD protection or buried in wall more than 50mm deep or surface run on wall or earthed sheave protection. If you can avoid new wiring in walls you will not need this protection but you might decide you still want it.

You've hit the nail on the head, this is the bit which is catching me. The new smoke detector will be directly next to the CU, less than 3ft between them, and the cable would run in the ceiling. Does it have to be protected? And if so, would it be possible to put shielded cable in there ( without ripping out the ceiling ) to satisfy? If not, it means an RCBO which in turn means a whole new CU.

If you decide you are best giving RCD protection to the existing smoke detection circuit you need not change the Consumer Unit to one that takes RCBOs you could add a RCD to the circuit as it leaves the fuseway at the consumer unit.

No room, only two slots free on the CU, which are needed for the new ringmain and lighting circuit in the garage.

If the existing are not interlinked then have a word with the building inspector, he would probably want you to end up with at least one per floor.
Example (Leave existing in they are not doing any harm).
Then create a new run providing one as he has asked for and at least one per floor all to be interlinked, if hardwired.
or changed at least some of the existing to radio versions and add the one he has asked for , again acheiving the one per floor as a minimum using a radio interlink.

If the new cable is surface run in trunking or if it exceeds the 50mm min run above the ceiling then no need to RCD it or earth sheath it. Personally I don`t think 50mm is enough but the rules say it is.

You don`t need any spare ways on the consumer unit if running from an already existing circuit as you can place the RCD adjacent to it not inside it thus ensuring either just the new portion or alternatively the whole circuit is RCD protected.

Hope that helps