disabling (switching off) main panel won't trigger the bellboxes

[ross94]

Hi all, I have the above issue ( well not really an issue) but I would like to try and sort it out. I have an alarm system with 2 live bellboxes all on SAB mode and a slave sounder which are all fed by a (elmdene) 2 amp psu, the main control panel feeds everything else on the system, keypads,pirs internal sounder dailler, trigger and tamper relays ect. The alarm works fine btw.

Anyway without boring you all I will get to the point. If the main control panel is disconnected the bellboxes will not self activate as it does not power them the panel only triggers them via the relays. However there is a double pole relay mounted in the panel which is for the tamper from both bellboxes, the panel feeds this relay The panel has an 8 core running to the psu this contains the supplies the bell and strobe trigger relays mounted inside the psu, the negative reference point and finally the 2 tamper returns from the bellboxes (one of the tamper returns loops via the slave sounder cable then via the psu tamper switch then to negative input on tamper relay inside the panel).There are 2 unused cores (brown and orange) from this cable.

My plan is to use the spare contacts from the tamper relay in the panel as its a double pole, I would connect the negative from the panel to the common and connect one of the extra cores say the brown to the NO terminal on the relay and inside the psu I would connect this brown with the bell trigger wires in the NO terminals on the trigger relay.

So hopefully this setup will mean if the panel is disconnected it will trigger the bellboxes as the tamper relay in the panel will lose power and trigger the sounders. sound good? one last thing will this damage the panel due to the negative being linked to the psu negative?

Hope this is clear. Iv'e tried to explain the set up as best as I can in absence of a picture.
Any help would be great cheers

 

[sparkymarka]

There should be a negative linked anyway ! Sounds a bit of a bodge ?

 

[ross94]

Well I am stuck with what I have i'm afraid. rewiring would cause major disruption and hassle the gf would not approve. The psu is mounted in an upstairs cupboard and the main panel is mounted near the fuseboard under the stairs. would this setup I described work? ta

 

[sparkymarka]

What panel is it ?

 

[EightyTwo]

As sparkymarka says, there should be a link between the negative of the psu and the negative of the panel already. I'm not sure what you are trying to achieve - do you want an activation if the cable between the psu and the panel is cut/damaged? If so, (a) the bell tamper should cover that and (b) you could use the tamper switch in the psu (via the brown and orange) to generate a tamper at the panel (connect it in series with something).

Alternatively, if you want the bells to sound when this cable is cut, run the bell power from the psu down the brown to the panel and then back up the orange to the bells. This way, if the cable is cut (and the brown and orange aren't left permanently shorted), the bells will self-actuate. Finally, you could link the brown and orange with the C/NO contacts of a relay powered by the panel. Thus, if the panel's power died, the relay contacts would open and the bells would sound.

 

[ross94]

Its a scantronic 9751 should of mentioned that at start, Yes there is a negative link between the psu and panel. My concern was the load from the sounders flowing back on the panel as its negative is linked to the psu negative if that makes any sense?.Yep eightytwo your last sentence is what I am trying to achieve which is basically making the bells sound if the panel lost power.
thanks

 

[EightyTwo]

The power from the bells won't "flow back" to the panel - it'll stop at the PSU!! The negative link is only there to make sure that 0V (a.k.a. Common) is common to both the panel and the PSU. This means that when the panel "applies negative" to the bell trigger, it is the same negative as the PSU.

I've seen systems where this has been cocked up and (say) the panel's 12V has been connected to the PSU's 0V. This makes the PSU's positive 24V w.r.t the panel! Most of the system will work but when the panel applies the bell trigger, the bell sees -12V rather than 0V!!