Travel Distance Query

[Midland Retty]

Agreed 

Sorry Tom I didn't want to make you cry!

Regarding grade A and D systems

In simple terms Grade A has a control panel, and manual call points on the system as well as other enhancements over a Grade D system

[CivvyFSO]

the level of detector coverage however is usually constant (Category LD2 - LD3 in shared houses) the increase being the grade of system (normally from Grade D to a Grade A).

The detector coverage is the more salient point in this discussion as an LD2 Grade A won't protect a staircase any more than a Grade LD2 D system would for example.

Based on the above what would be the advantages of upgrading from an interlinked grade D to a grade A?

Identification of faults, the ability to silence/reset, more robust wiring, possiblity of zoning. And then some.

You could probably manage to chop the interlinking wire off a grade D system without any indication anywhere that such a thing has occurred.

[Tom Sutton]

I understand the extra reliability and addition facilities of a grade A over a grade D but why in the Lacors guide is a shared accommodation over four floors need grade A and a HMO over two floors require grade A? Is it the extra number of people or the additional time required to evacuate I am just trying to understand their reasoning.

[Midland Retty]

Hi Tom

Its to do with several things. Shared houses are supposed to be akin to a normal domestic dwelling containing a family unit, and are considered less of a risk than a "normal" HMO where strangers share accomodation under one roof (I think that is debatable but thats for another discussion another time)

Increase the size of the property, and you increase the time to escape meaning greater reliance is required on the fire alarm system to work when it should, hence the CIE as you already mentioned to identify faults etc.

A Grade A system also requires manual call points and therefore if someone on an upper floor discovers fire there will ordinarily be a call point close by to activate and raise the alarm as soon as possible.

The CIE will assist the fire service in pinpointing the zone or detector head rather than having to search the whole building.

[Tom Sutton]

As I have said before I understand the advantages of a Grade A over Grade D but its relevance to exiting houses I have problems with. The increased the size of the property is the only one that comes to my mind, the so called alternate escape (escape windows) where people are supposed to bale out of windows from the 1st floor (not in my experience) and can be rescued from the 4th floor by the first turn using their ladders, therefore less reliance can be placed on the fire alarm. Maybe!