Grade D vs F smoke sensors

[Martyn]

We run sheltered housing for the elderly and need to upgrade our current detection system.  At present we have hardwired D2 sensors externally monitored, but only a single one inside the front door lobbies.  The system is old and when we replace it, we will need to be installing sensors throughout the living spaces. This will be hugely disruptive and costly, as it will mean running hardwires in roof voids, and putting trunking all over the place. 

The regs seem to insist we can only have D2 in this type of housing, but I don't understand why F2 sensors are not as good.  We have found a supplier who will provide radio interlinked sensors, and if they are faulty, or the battery power runs low, the external monitoring centre will be alerted to the fault. There is no hardwiring at all.

Can anyone explain the benefits of D2 over F2, if they can do the same thing as each other?

Thx  

[green-foam]

In short:

A D2 system is mains powered with user changeable standby batteries.

An F2 system is only battery powered. (with user changeable batteries)

 

I would suggest you get another quote as although "wireless" systems are quicker to install and the installation process is less disruptive they can be more expensive than a wired system, also there is the ongoing cost of batteries which will need to be changed.

[AnthonyB]

On 10/03/2022 at 14:47, Martyn said:

We run sheltered housing for the elderly and need to upgrade our current detection system.  At present we have hardwired D2 sensors externally monitored, but only a single one inside the front door lobbies.  The system is old and when we replace it, we will need to be installing sensors throughout the living spaces. This will be hugely disruptive and costly, as it will mean running hardwires in roof voids, and putting trunking all over the place. 

The regs seem to insist we can only have D2 in this type of housing, but I don't understand why F2 sensors are not as good.  We have found a supplier who will provide radio interlinked sensors, and if they are faulty, or the battery power runs low, the external monitoring centre will be alerted to the fault. There is no hardwiring at all.

Can anyone explain the benefits of D2 over F2, if they can do the same thing as each other?

Thx  

Grade F systems only have a single power supply and are more prone to removal and failure. The robust nature of a Grade D system is why it is now the norm and the use of Grade F equipment is being phased out slowly as legislation requires more and more places to have Grade D (or higher) when built, rewired or altered.

Wireless linked systems are the norm and the old need for linking physically with bell cable is long gone