Reuse existing circuit

[bobred]

I have recently moved into a property that was used as a small care facility. It has a fire alarm system and hochiki low voltage sensors in every room. For me this is overkill and the control panel is in the hallway and ugly, so I want to get rid of it.

My question is can I reuse the the existing circuit for domestic mains alarms? The interconnecting cables for the sensors are red twin and earth, would need to check the cable for rating. The control panel has a dedicated connection to the consumer unit, if I remove all the exsisting sensors can I connect this to the mains mains supply?

Thanks

 

[ericmark]

Pictures are good, one would need to inspect and test, to ensure no faults, but most domestic alarms are not low voltage (230 volts) but extra low voltage (12 volts) and normally 4 wires used to each sensor, two to detect someone in the room and two anti-tamper, so it seems unlikely you have enough wires?

 

[bobred]

Hi. I will supply some photos. The sensors are analogue addressable Hochiki sensors and have a +ve and -ve and an earth and rated at 17V-40V DC. They are daisychained throughout the house. I will check for ratings on the cabling.

 

[Harry Bloomfield]

My question is can I reuse the the existing circuit for domestic mains alarms?

Domestic mains, interlinked fire alarm? Yes you can.

 

[JohnW2]

Pictures are good, one would need to inspect and test, to ensure no faults, but most domestic alarms are not low voltage (230 volts) but extra low voltage (12 volts) and normally 4 wires used to each sensor, two to detect someone in the room and two anti-tamper, so it seems unlikely you have enough wires?

I think that information is a bit out-of-date and in some senses not completely correct.

The OP is talking about 'fire alarms', and they rarely, if ever, have any 'anti-tamper' facility (or wires).

I think the increasing tendency (and what is recommended, actually 'required' in some situations) for fire alarms (smoke/heat) to be mains powered with battery backup, and to be wired with 3-core (3 functional cores) cable two the mains (LV) supply, and the third an ELV 'interconnect' wire (referenced to the LV neutral) - hence, if one wants to also run a 'not-required' CPC, 3C+earth 'flat' cable or 4-core flex.

 

[plugwash]

hence, if one wants to also run a 'not-required' CPC, 3C+earth 'flat' cable or 4-core flex.

Even if we didn't care about the BS7671 requirement to run a CPC, there is the slight problem that 3 core mains-rated cable/flex without an earth core seems to be very difficult, if-not impossible to obtain.

 

[JohnW2]

Even if we didn't care about the BS7671 requirement to run a CPC, there is the slight problem that 3 core mains-rated cable/flex without an earth core seems to be very difficult, if-not impossible to obtain.

Agreed- which is why I implied that, in practice, one would us 3C+E or 4-core flex.

To be clear, when I wrote "a 'not required CPC" I meant 'not required by the alarms'. As you imply, there remains a BS7671 requirement to run a CPC to 'every point', although the reason they give for that is presumably never actually going to apply to the circuit we're talking about, since I cannot believe that anyone is ever going to replace the fire alarms with ones which require an earth connection However, that does not alter the fact that 'regs are regs' (even if 'non-mandatory' ones!).