Green light not working/no mains power to smoke alarms

[Guest Simpo]

Hi I've just replaced an Ei151TL after the old one started behaving erratically/bleeping etc, but the green light isn't on ie there's no mains power. It's interconnected to two other smoke alarms of different manufacture.

I have checked all the connections to all three and all seems OK, but still no green light! They're all clearly working but from their batteries.

We had new circuitry installed 18 months ago and unlike before there's no separate circuit for smoke alarms, and although I'm not sure which circuit the alarms are on, everything else in the house seems to be working just fine. I'm baffled. Anyone?

[Safelincs]

Hi Simpo

This definitely sounds like a wiring issue, whether a miss-wire on the interconnect from installation or as a result of a power surge, blowing the interconnect and possibly the live in resistor. This would lead to the green mains light not being on, and in quite a few cases (although not all) erratic behaviour such as random beeps or even false alarms.

Our suggestion would be that the wiring is checked by an electrician (continuity, megger test etc.) before the units are replaced. The green light should then be on and all should be OK.

Harry

[green-foam]

It's interconnected to two other smoke alarms of different manufacture.

NEVER interlink mains smoke detectors that are from different makers. Change them ALL to the same make, even the the first two you already had.

When a mains interlinked smoke alarm fails, you should only replace it with one from the same maker.

[Guest Simpo]

Had electricians check it over today..... There is no mains power to the smoke alarms at all. Nor is there any obvious source of any at the fuse b ox.. Now trying to get hold of electrician who installed it, as it's baffling

[Guest Simpo]

NEVER interlink mains smoke detectors that are from different makers. Change them ALL to the same make, even the the first two you already had.

When a mains interlinked smoke alarm fails, you should only replace it with one from the same maker.

when I bought this house two of the interlinked ones were Newlink, the other Ei151. When we had a new fusebox and loft conversion done 18 months ago, the electrician changed the upstairs Newlink one to a Gavern (I think) and changed the wiring, which is different to the downstairs pair.

[green-foam]

I would suggest that there being "no obvious connection in the fuse box" is because they are connected to a light / light circuit.

This is considered a good idea, since if there is a problem with your smoke alarms you can not turn them off at the "fuse box"

By connecting them to a lighting circuit you will not deliberately turn your lights off at "the fuse box" so the smoke alarms are always powered up.

I would guess that if as you say the first two devices have a green light lit then as they are interlinked, the first place to check would be the 2nd of the two smoke alarms.

_________________________________________________________

If it helps, Interlinked smoke alarms are wired as follows.

Mains to first smoke alarm.

Mains and interlink from first smoke alarm to second smoke alarm

Mains and interlink from second smoke alarm to third smoke alarm (etc)

The last smoke alarm only has the mains and interlink.

So if a number of interlinked smoke alarms do not indicate they have mains, but some do indicate they have mains, the first place to check is the last smoke alarm that has mains.

I personally have a "feeling" it is to do with the fact you have 2 different makes of smoke alarm.

[Guest Simpo]

I would suggest that there being "no obvious connection in the fuse box" is because they are connected to a light / light circuit.

This is considered a good idea, since if there is a problem with your smoke alarms you can not turn them off at the "fuse box"

By connecting them to a lighting circuit you will not deliberately turn your lights off at "the fuse box" so the smoke alarms are always powered up.

I would guess that if as you say the first two devices have a green light lit then as they are interlinked, the first place to check would be the 2nd of the two smoke alarms.

_________________________________________________________

If it helps, Interlinked smoke alarms are wired as follows.

Mains to first smoke alarm.

Mains and interlink from first smoke alarm to second smoke alarm

Mains and interlink from second smoke alarm to third smoke alarm (etc)

The last smoke alarm only has the mains and interlink.

So if a number of interlinked smoke alarms do not indicate they have mains, but some do indicate they have mains, the first place to check is the last smoke alarm that has mains.

I personally have a "feeling" it is to do with the fact you have 2 different makes of smoke alarm.

this all sounds good - thanks. Yes, from what you've said it sounds like the connection to the mains may be from the first smoke alarm (the new one upstairs) to the lighting circuit. The curveball is that the lights are all working perfectly, but the electricians that came yesterday couldn't find any mains power to any of the three alarms. I've now disconnected all three alarms because they've been going off at all hours and we have a young child. Do you think I should get a second opinion/another electrician in to have a look and see if they can get to the bottom of it? Or maybe try just connecting one alarm to the upstairs connection to see if that yields anything? Appreciate your advice - this is a great forum

[green-foam]

A second opinion is always a good idea.

I would suggest you ask before you commit yourself "Are you familiar with mains interlinked smoke alarms"

Although it may sound a bit condescending, I have found that some companies will say yes, but the bod who turns up at your place says otherwise. Emphasise the point you want some one who has worked on them before.

[Guest Simpo]

hi, prior to getting anyone else in, I've had another quick look at the connections to the first alarm. They are:

MAINS - live, neutral and earth coming from mains

ALARM - live, neutral, earth (going into and) coming out of the first alarm and then interlink wire to second alarm

these connections relate to a Garvan smoke alarm,which may be faulty and hence causing the problem

However, I have a different smoke alarm (Ei151TL alarm 3 in the chain) which clearly states no earth should be used.

Am now a bit confused!

[Guest Simpo]

adding to the above... I had a look at the second alarm in the chain and there's no earth, just live, neutral and interlink. Which seems to suggest the earth disappears/is terminated somewhere between alarms 1 and 2. I think that's all in order/correct??

[green-foam]

All mains devices require an earth / earth termination point, UNLESS it is double insulated, which I doubt the smoke detectors are.

It has to be there, but you don't use it, it is if some one should sever the cable, instead of the electricity flowing through the person who cut the cable, with possible lethal results, it flows to earth. (yes it will go bang, but its better that than to be.............

Also as I first said, you should

NEVER interlink mains smoke detectors that are from different makers.

You do not know what damage may occur.

[Guest Simpo]

I checked it again tonight and there's definitely no mains power to the alarms. I've contacted the firm that installed the wiring and asked them to come and look at it. They also replaced an old upstairs Newlec with a Garvan, meaning we now have a Garvan, a Newlec and an EI151. Once the wiring/power is sorted I'll change the alarms, probably to three E151s. Thanks for your advice: hopefully there will be no more curveballs.

[Guest Ggg]

Had the exact same issue today replaced 3 old alarms with new ones (loft,middle and ground floor) left the kitchen as it is brand new only a year old.   The loft has the green light but the others dont.   my thinking is the alarm circuit was put in when the loft extension was built and runs off its own loop on a separate electric box installed for the loft meaning mains runs directly to that one first ie first device on the circuit explaining why there is no fault but all the rest are not receiving mains power so believe there is an issue with the wiring onwards from there.         Any other ideas ?

[green-foam]

Were the previous detectors working before you changed them?

Also how many cables do these detectors have? The reason is, if they have two cables that will be loop in and loop out, which in turn means they are all fed from the same supply, if however they have just one cable that probably means they are all fed from the nearest supply. (A light fitting?)

If they have two cables, I would check at the last known working detector (loft in your case)

[Guest Only one green light]

I have changed the smoke alarm with the same make before replacing  there was only one alarm  that had a green light on  but the rest of them had no green light on .in the boiler room someone  took it out  alarm due to keeping them awake  would this make the rest of the smoke detectors green light not work .they are wired the same as the old one  they are all the same kidde just changed them to new ones  same wiring set up  two brown and two grey with blue sleeves and two black  and two eath. They are all the same model  just updated with new model as the old ones was out of date  and just needed  replacement. Can anyone  tell me what's  this problem  o have checked the wiring they all correctly wired as the same as the old units .thanks .

[green-foam]

Mains smoke alarms are wired in parallel, and are "independent" The only common thing they have is alarm indication, so the green "power on" light on one device will NOT affect the others.

If all devices have no green light I would suspect a supply problem. If one does have a green light and the others do not I would suspect a wiring error.

You can of course swap them all (On a just to find out basis) with the one with the green light to see do they work.