Extending existing linked smoke alarm system

[marchant]

Extending existing linked smoke alarm system

I have an existing mains powered [battery backup]smoke alarm system with 3 alarms linked.

They are powered from one supply from the consumer unit.

My question

I want to add two more mains [battery backup] smoke alarms. I can link in the mains power but can I just link in the links - although the new alarms are different manufacturer to the existing which were fitted a few years ago [not by me]

All are battery backed up.

I was thinking of just adding the two new ones and just linking those but it would be great to link all 5 together. I have the 4 wire mains cable ready to install.

Any help would be appreciated.

Thanks

Marchant

 

[breezer]

might not work, differnt makers, try two and see first

 

[marchant]

might not work, differnt makers, try two and see first

Hi

Thanks for the reply.

I don't want the new alarms to destroy the existing alarms.

How does this link wire work? What voltage are we talking about?

Thanks

Marchant

 

[breezer]

I don't want the new alarms to destroy the existing alarms.

yes, i can understand / agree with that

How does this link wire work?

if a voltage is present on the link terminal the detector will make its noise. the first one to detect something puts out a voltage that the others then "see"

What voltage are we talking about?

Thats the question. dont know. it may vary from one brand to the other, it may not. never tried it.

it may be mains, since there is 240 supplying each, but if thats so, what will the signal voltage be since it should work when they are running on batteries.

safest thing is to change all the existing, unless you can find the info

 

[marchant]

hi

Thanks for the reply.

Think I will leave i it as two separate linked systems.

Marchant

Yes I agree it must be 9v or less. I could test the voltage when on and see if they happen to be 9v! or all the same.

 

[breezer]

i cant see it being 9v

if it is how do you send 9v down 1 core? the other 2 are carrying 240, no you cant use the earth

 

[marchant]

i cant see it being 9v

if it is how do you send 9v down 1 core? the other 2 are carrying 240, no you cant use the earth

But with mains failure it would be not be mains. Or AC, so must be DC, the earth could be used - why not? I will have a few experiments tomorrow.

Thanks

Marchant

 

[breezer]

the earth is earth, nothing else. if you did send a voltage down it you could trip any rcd.

yes it could be 9v dc when no mains, but what if there is mains, perhaps in a powercut they do not signal each other , that solves all the problems.

yes to test it would be very interesting. please post what you find

 

[marchant]

the earth is earth, nothing else. if you did send a voltage down it you could trip any rcd.

yes it could be 9v dc when no mains, but what if there is mains, perhaps in a powercut they do not signal each other , that solves all the problems.

yes to test it would be very interesting. please post what you find

If they do not link during power cut, this would be stated on the instructions - surely. I have the instructions for one of the existing and the new alarms and both say not to link with other manufacturers but they may say that anyway!

One quick test last night was to look on the link wire with a voltmeter on AC, the alarms were set off, did not think to check for DC. Need more time to investigate unless someone knows?

Thanks

Marchant

 

[bernardgreen]

I no longer have the full notes of the project to interface smoke alarms to a paging so some of this is from memory.

The interconnection method did vary between makers but I believe a common method was being proposed.

In the majority we looked at the neutral of the 230 volts was also the 0 volt of the electronics, the 9 volt battery negative ( 0 volt ) connected to the neutral. The signal interconnect was fed with 9 volts or less via a resistor in every alarm so the "NO SMOKE" condition was a DC voltage on the interconnect signal wire. Any unit that went into SMOKE mode shorted the interconnect to neutral removing the DC voltage. Other units detected the voltage had gone and went in REMOTE SMOKE mode.

There was one make where in SMOKE mode the unit would put 230 AC onto the interconnect to indicate SMOKE detected. This had the advantage that passive sounders could be added to the system.

One system has all the alarms connected in series along the signal wire ( mains in parallel to all units ) End of line units fed a current along the signal wire, Any unit in SMOKE mode would open circuit the signal line and the removal of current would trip all others into REMOTE SMOKE mode. This was a fail safe system in that a cut interconnect put all alarms into REMOTE SMOKE mode (on battery if the cut had removed mains )

 

[marchant]

I
In the majority we looked at the neutral of the 230 volts was also the 0 volt of the electronics, the 9 volt battery negative ( 0 volt ) connected to the neutral. The signal interconnect was fed with 9 volts or less via a resistor in every alarm so the "NO SMOKE" condition was a DC voltage on the interconnect signal wire. Any unit that went into SMOKE mode shorted the interconnect to neutral removing the DC voltage. Other units detected the voltage had gone and went in REMOTE SMOKE mode.
/quote]
Hi

Thanks for the reply.

Yes this seems to be the case. The voltage does vary on the link but say between 8-9volts when in alarm status. It is not recommended that different manufacturers are mixed. So I intend to have two links , one the existing with 3 units and the two new ones on another link, till I replace the existing 3 smoke alarms. I see it is recommended that they are changed every 10 years.

Thanks for all the help.

Marchant

 

[Lectrician]

You should not mix makes.

The interlink is not standardised.

The interlink is an ELV signal to allow interlink to work during a mains failure.

What make are your original ones? If they are a good make, I would add identical ones to them. If they are crap I would replace them as part of your expansion.

 

[marchant]

You should not mix makes.

The interlink is not standardised.

The interlink is an ELV signal to allow interlink to work during a mains failure.

What make are your original ones? If they are a good make, I would add identical ones to them. If they are rubbish I would replace them as part of your expansion.

Hi

Thanks - bit late I have ordered my two new ones Dicon and will replace the others at the 10 year mark. I have not yet taken the existing down to check for makes. They were put in by the builders.

Thanks

Marchant