Smoke detector help please

Personally I think this has been the most worrying and confusing thread I read up to date.
And a read of the BS5839 sounds well over due as professional sparks.
Posts have mixed up Part6, Part 1 , Grade A, Grade D, and Grade F which all have their own standards, and places. So lets look at it.


1. Supply isolation is grade A (Fire control panel)
2. Grade D does not require a separate dedicated supply (due to battery backup)
3. Grade E does require a dedicated supply circuit (due to no battery backup) Grade F battery only detection, can only be used in private dwellings, being customers choice. A variation agreement maybe reach to fit Grade F (such as listed building)
4. Building control are there for a reason, and actually hand it to you on a plate...or drawings in this case.
Dont follow their instructions...and you will get burnt.[/QUOTE]


I'm not sure where the confusing parts are but yes lets look at it.


OP starts by saying he has forgotten wiring for smokes on a rewire and building control is involved in some fashion.
Members then say he can have wireless smokes wired off the lighting.


So we have no cables for a "Grade E system" and when using lighting circuit for mains that's a "Grade D system".
So as already stated a "Grade D system" has an independent circuit (dedicated) OR regularly used lighting circuit (not any old circuit is it).
A member then posts a link to some battery only radio smokes as a "get out of jail", so I click on link and
then read the data sheet regarding the said smokes (yes I'm sad) where it states they will only satisfy to a "Grade F" system.
It appears some people failed to click on link and then read the spec. But ha ho


I don't have my copies of BS 5839-1 & 6 on this computer (they're on work computer) but I do have a copy of
"Electrician's Guide To Fire Detection And Alarm Systems" on my shelf (for quick ref) where right or wrong as I said "I believe" where it says
for dwellings power supplies approved document systems we have "single independent circuit" blah blah "regularly used lighting" blah blah "jump through hoops about RCD's" blah blah
we then get to the line saying "The Approved Document requires a means of isolation for
the fire system supply so that it can be isolated with the lights on. This will need to be labelled so that its purpose is clear."


Now with out checking BS 5839-6 until tomorrow (if I can be assed) that statement whether true or not is basically saying it needs isolation for testing and maintenance.
I know Approved Documents have been updated/changed the same as other documents.
But I would imagine this guide (yes guide) is probably correct and can see no reason for its removal (could be wrong).


Not sure where BS 5839 -1 comes into thread.
Not sure where "Grade A" system comes into thread.


If your still confused get yourself a beer/glass of wine and turn computer off, life's to short.

A Grade A system part 6 requests your revert to Part 1. As this will now be your standard to install a full fire alarm system.
Local isolation is only required on a control panel...Grade A/part 1.
Now time for my beer, As I have given the specs..where to look, and what is required.

Well in dwellings you should be working to "Approved Document B Volume 1"
Where on page 14 it states under power supplies "There should be a means of isolating power to the smoke alarms without isolating the lighting"

Now where is my lighter for my cigar lol

so bung a keyswitch in the feed.

I looking through document B..can you shed some light on isolation issue, read page 14 no mention of isolation. but fire alarm recommendations only start at page 20....need to get my pipe out.

Thank you for the lastest copy mine was out of date.....As Document B be suggests smoke detection should be taken from dwellings db direct or grade D from lighting circuit. Smoke detection POWER SUPPLIES should be taken from the main db with isolation. ie the fire alarm control panel, as mains smoke detection is not supplied from a POWER SUPPLY.....I admit, it is misleading, but is aimed at a control panel not a mains smoke detector.

I'm sure it says smoke alarms... not fire system control panel.

I have seen this phrase used alot recently "smoke power supplies" basically the control panel which supplies the smoke detection. I think it very misleading, but if you read the section you mentioned on page 14, you can see it applies to Grade A/part 1 of using double pole isolation.

Mains powered smoke alarms have an integrated what...

Grade A must have a dedicated supply yes.

And a control panel with its own power supply...........you dont connect mains powered smoke detectors to a power supply..?

tazz said:

And a control panel with its own power supply...........you dont connect mains powered smoke detectors to a power supply..?

Click to expand...

No because they have an integrated one.. and are called smoke alarms.
They are a self contained power supply, backup supply, detection and sounder all in one.

Exactly...hence in document B it states in 1.19 power supplies for a smoke alarm system

I give up.. read it how you will lol