Strange Bell Activations

[samnaffy]

I installed a menveir ts690 last year all ok, no problems whatsoever!

A year later a new tenant moved into the house and soon after he was complaing that the external bell (cqr) was activating randomly. Strange it was fine till he moved in. so i linked the bell tamper out! It was still activating mostly in the middle of the night and then sometimes early in the mornin but obviously if it did go off during the day he couldnt tell me! He was a right dumb wierdo! Didnt have a clue

He explained that there was nothing showing on the screen, no tampers, checked the log entered hes code in and that done nothing so he had to wait for the timer to cut out. He said the strobe didnt flash either. I didnt have my ladders at the time, they were stolen but disconected it in the end and put a speech dialer on as he didnt want a new bell!

Does anyone have any sugestions wot could of caused it? Thanks!

[lawandorder]

I installed a menveir ts690 last year all ok, no problems whatsoever!

A year later a new tenant moved into the house and soon after he was complaing that the external bell (cqr) was activating randomly. Strange it was fine till he moved in. so i linked the bell tamper out! It was still activating mostly in the middle of the night and then sometimes early in the mornin but obviously if it did go off during the day he couldnt tell me! He was a right dumb wierdo! Didnt have a clue

He explained that there was nothing showing on the screen, no tampers, checked the log entered hes code in and that done nothing so he had to wait for the timer to cut out. He said the strobe didnt flash either. I didnt have my ladders at the time, they were stolen but disconected it in the end and put a speech dialer on as he didnt want a new bell!

Does anyone have any sugestions wot could of caused it? Thanks!

Yes, an intermittent cable fault on the positive hold off will cause the external to activate without showing a tamper and without triggering the strobe.

An intermittent short between negative hold off and switched negative will also do the same.

Faulty sounder can also present with the same symptoms.

There won't be any consistency but more likely to occur during damp weather.

The fact that it was fine until your tenant moved in unlikely to be relevant.

Hope this helps.

[james.wilson]

faulty bell id say

[camerabloke]

sure its the bell? dozens of times been called to a smoke detector

[motco]

Yes, an intermittent cable fault on the positive hold off will cause the external to activate without showing a tamper and without triggering the strobe.

An intermittent short between negative hold off and switched negative will also do the same.

Faulty sounder can also present with the same symptoms.

There won't be any consistency but more likely to occur during damp weather.

The fact that it was fine until your tenant moved in unlikely to be relevant.

Hope this helps.

As a bell/sounder maker of some years standing (up till 2003) as far as I recall lifting the positive HO should also cause a tamper signal. Ours certainly did/do (new owner of Co.).

[lawandorder]

As a bell/sounder maker of some years standing (up till 2003) as far as I recall lifting the positive HO should also cause a tamper signal. Ours certainly did/do (new owner of Co.).

I agree, some do but I don't think it was ever a requirement of BS4737 so I'm not sure that it "should".

Certainly some universal SAB modules that I have worked on on the past fed the the tamper return (either negative or posttive) through the contacts of a relay which was kept energised by the hold offs passing through the SAB tamper switch.

With these modules dropping either hold off would de-energise the relay and remove the tamper return.

Conversly I have worked on many bell boxes where the tamper switch is in series with the negative hold off and removal of the pos hold off would sound the external but would have no effect on the tamper return.

To be honest I have fitted lots of CQR sounders but can't say I have ever tested one in this way.

I seem to recall a batch of cheapish sounders that Gardiner used to sell under their own brand back in the mid 90s, thse were prone to problems similar to the one the OP describes.