Fireangel have advised me that for grade D system, I only need one mains wired alarm and all other can be battery operated. I thought they all needed to be mains wired but they are adamant that this is the case. I informed them:

It's for a single let rental . Kitchen lounge bathroom and 2 beds. 

 

They referred me to:

https://www.fireangel.co.uk/british-standard-bs-5839-6-2019/

 

Grade D1. A system of one or more mains powered detectors, each with a tamper‑ ...

 

Also will one smoke in hall, one in lounge and one heat detector in kitchen suffice for ld2? 

Any help much appreciated. 

 

 

Utter nonsense.

Grade D is mains with battery back up, D1 being tamperproof back up, D2 user replaceable back up. All devices are the same power source and interlinkable.

A battery only system is Grade F and only really suitable for legacy single dwellings and flats and over time would be phased out as new, builds, conversions and rewires see Grade D installed as minimum.

You don't mix Grades other than a HMO or conversion to flats where you may have a Grade A common system and Grade D to individual flats/bedsits

Grade D:LD2 is a system comprising interlinked mains powered with back up smoke & heat alarms with smoke to Alarms in hallways and landings (circulation spaces & escape routes) plus high risk rooms (at least heat to kitchen and smoke to principle habitable room, i.e. living room)

The only situation I could see mixed in place is where the statutory requirement is Grade D:LD3 (new builds, re-wires, etc although LD2 is more common now) and additional voluntary protection is provided to other areas and to save money and ease installation Grade F is used - however unless interlinked the added value is grossly reduced (Grade F are more likely to be removed, flat battery or no battery hence the move towards Grade D)

Thankyou so much Anthony, yes it didn't make sense to me. Glad to have asked you. 

Thanks again!