I was planning to hard wire the interconnect. Presumably the radio link bases wont be required in that case?
Also, can you please confirm that these meet the Grade D LD2 standard as I couldn't find this info anywhere.
Grade D of the standard basically means mains powered with backup battery.
As of the
2019 BS 5839 standard there are now two levels though -
- Grade D1: the stand-by supply must be tamper-proof and last the full life of the alarm
- Grade D2: the stand-by supply is user-replaceable and will not last the full life of the alarm
So the one you've linked with a 9V battery would be Grade D2. Grade D1 is the type with a tamper proof lithium rechargeable battery installed.
Part B of the building Regulations suggests that Grade D2 is acceptable, so you would be covered.
LD2 then refers to where the alarms cover...
- LD2 – A system incorporating detectors in all circulation spaces that form part of the escape routes from the premises, and in all rooms or areas that present a high risk of fire to occupants.
As I understand it that means staircases or hallways (circulation spaces - one per level unless the hallways are long), with a heat alarm in the kitchen. Some guidance suggests the main lounge as well, but I don't believe that is set in stone - if there was an open fire in there then it could be said it presents a high risk of fire....
Optical or Ionisation are the different types of methods of detection, and each work better for certain types of fires (smouldering/flaming, etc). In general, optical is less prone to false alarms and are now the recommended option. They are less sensitive to smoke from toast, or steam from a shower room, though they are not recommended for use in a kitchen - a heat alarm is the preferred option there)
Ionisation alarms might be suitable for upstairs landings or stairwell - they are faster to react to fast flaming fires from paper, wood etc.
As previously mentioned, if you run the wiring in trunking, then you should use fire-rated cable clips to ensure against premature collapse of the wiring in the event of a fire. This applies to all trunking and cabling, not specifically ones supplying fire alarms though.
There is no specific 'right' way to run trunking on the ceiling - as long as the cabling within it is protected against premature collapse. It may be easier/neater to run around the edges, or the shorter direct route may be preferred.
3 Core and Earth is what you'll need for hard-wiring between then, though 1mm would be fine too.