Alarm Feed

[davelx]

What do the manufacturer's instructions say? If it specifies a fused spur at 3A then that is what you must use to comply with the regs.

Do you think that feeding it with a 3A MCB would be compliant, or do you think that it's necessary to comply with the every word of the MIs?

I don't know for certain but I would not think the MIs actually call for a 'fused spur' as such.

Wouldn't they just specify the fuse rating and perhaps a means of isolation, possibly stating a double pole and the usual 3mm. separation?

The Galaxy M.I.s say EXACTLY what I typed - hence my use of quotation marks:

View media item 62351
As far as slavish adherence to MI's is concerned, I prefer not to stir up that wasps' nest.

 

[JohnW2]

However as pointed out most require a point of isolation and isolation requirements vary with the supply type. With a TT supply likely you will require a switched FCU to be able to isolate but with a TN supply a un-switched FCU or single pole MCB would be fine to isolate. ...So to recap the main point is what is the supply type. With a TT that's with an earth rod then you need an isolator with a TN that's where the supply company supply the earth then not really required.

Is that strictly true? Unlike the implication of what the OSG says (and we know that the OSG often 'makes things up', or condradicts the regs), I don't think that anything in the regs (BS7671 itself) says that individual items of equipment or circuits necessarily require a dedicated means of isolation - as far as I can see, there is merely a requirement for A means of isolation. That means of isolation could therefore probably be a (double-pole) Main Switch or RCD in the CU, which would, I think, satisfy BS7671 with both TT and TN installations. After all, I've never seen, for example, anyone suggesting that a lighting or sockets circuit in a TT installation requires a dedicated DP isolator.

Being pedantic if the manufacturer says it needs a switched FCU then you should use one to comply with rules. But with common sense with a TN system not really required.

... and, as above, probably also 'not really required' with TT. As you say, strict compliance with the MIs requires that if they ask for a 'switch', then there has to be one, but I have to say that I personally regard the presence of an easily operated (maybe unintentionally) means of switching off a fire alarm system as being contrary to safety consdierations - so one may have to balance one's opinion about safety with considerations of compliance with MIs.

Kind Regards, John

 

[JohnW2]

The Galaxy M.I.s say EXACTLY what I typed - hence my use of quotation marks:

"...in accordance with the current IEE and local wiring regulations .... Where live and neutral circuits cannot be reliably identified, 3A fuses must be fitted to both circuits...."

Good grief !!!! (on all sorts of levels!)

Kind Regards, John

 

[davelx]

The Galaxy M.I.s say EXACTLY what I typed - hence my use of quotation marks:

"...in accordance with the current IEE and local wiring regulations .... Where live and neutral circuits cannot be reliably identified, 3A fuses must be fitted to both circuits...."

Good grief !!!! (on all sorts of levels!)

Kind Regards, John

That was my reaction!

 

[JohnW2]

The Galaxy M.I.s say EXACTLY what I typed - hence my use of quotation marks:

"...in accordance with the current IEE and local wiring regulations .... Where live and neutral circuits cannot be reliably identified, 3A fuses must be fitted to both circuits...."

Good grief !!!! (on all sorts of levels!)

That was my reaction!

I really think that, even for those who are usually obsessed with the need to follow the letter of any MIs, following those ones would be totally irresponsible! ... and, in any event, someone who 'cannot reliably identify the live and neutral circuits' probably should not be working on either of them in the first place!

Kind Regards, John

 

[ban-all-sheds]

The Galaxy M.I.s say EXACTLY what I typed - hence my use of quotation marks:

"...in accordance with the current IEE and local wiring regulations .... Where live and neutral circuits cannot be reliably identified, 3A fuses must be fitted to both circuits...."

Oh please write to them and ask them to explain how they can say it must be installed in accordance with the IEE regulations when those prohibit fuses in neutral conductors.

 

[bernardgreen]

It does say "" Where the live and neutral cannor be reliably identified ""

I read that as "" if there is a supply conductor that cannot be reliably identified to be neutral then that supply conductor must be fused ""

I do not read it as saying a known neutral must be fused.

While a fuse in the neutral is frowned upon one has to give consideration to the possiblity of the conductor may be live ( not at ground potential ). If there is fault that puts that conductor in contact with earth then a fuse would be essential in that conductor.

 

[JohnW2]

I read that as "" if there is a supply conductor that cannot be reliably identified to be neutral then that supply conductor must be fused ""

Yes, that (together with also putting a fuse in 'the other one') seems to be what it's saying - but isn't it a ridiculous statement? We're not talking about anything complex or esoteric, merely the connection of power to an alarm! Under what circumstances would it not be possible 'to idenify the live and neutral circuits reliably'????

Kind Regards, John

 

[bernardgreen]

Under what circumstances would it not be possible 'to idenify the live and neutral circuits reliably'????

Ik the UK probably no such circumstance exists. But maybe the manufacturer's instructions are written for countries where there is no neutral. ( as in a conductor tied to ground )

 

[JohnW2]

Under what circumstances would it not be possible 'to idenify the live and neutral circuits reliably'????

Ik the UK probably no such circumstance exists.

Quite.

But maybe the manufacturer's instructions are written for countries where there is no neutral.

I think you're probably being over-generous in trying to find excuses for them but, if that were the case, I rather doubt they would be calling for compliance with the 'IEE' wiring regs, would they?

Kind Regards, John