I wonder if any of you guys would have any idea of the electrical demand for the pumps for a water mist sprinkler system? Five floors, with the ceiling of the top floor being about 25m above the tank in the basement. Each storey is around 400m2. I know that it is a bit of a daft question but we are on our limit with maximum demand and will probably have to put the pumps on a priority arrangement. I just want to get a heads up An inkling would do.
My neighbour has a water mist system in his house. The same firm that installed it does an annual service. After 3 or four years of servicing the firm failed the system because the MCB of the pump circuit was a B-type and it needed to be C-type. So if it needed to work at any time prior to this, it probably wouldn't have.
Some years ago I went on an IET Local Group visit to the waterworks museum at Hereford where they have an old fire water pump from one of the wartime munitions factories that were around Hereford.
Pump power isn't that high as you are only delivering a small water quantity albeit as a high "volume" mist - but it is a high pressure system so expect pumps in the region of 10 - 30kW
If power is genuinely a problem (and possibly back up may not be available), then you might consider gas pump variations - basically cylinders of distilled water, driven by a cylinder or two of argon or nitrogen - completely mains free essentially. Typically a single "unit" will do about 250m3 based on a oil fire load (big genset for example) - you can have variants of tank town water supply and a gas driver pump fed from the 80kg, 300 bar inert gas system
Alternatively, if you can't run electric pumps, how about compressed air driven pumps from a small compressor and big receiver - basically trading instantaneous demand for long term low level energy input
Speak with a supplier, based on the hazard class being protected, they will usually be able to give you a pump power rating based on selected system pressure and flow rate - or just apply mass flow rate x pressure to give kW and add a bit for motor and pump efficiency
My neighbour has a water mist system in his house. The same firm that installed it does an annual service. After 3 or four years of servicing the firm failed the system because the MCB of the pump circuit was a B-type and it needed to be C-type. So if it needed to work at any time prior to this, it probably wouldn't have.
Typically the domestic systems are basically a pressure washer in the cupboard under the sink connected to a spray head under the kitchen tap and/ or connected to a wall outlet with some Aico heat alarms to trigger it. They can also be connected to a tank of water stood in a hallway or similar with a decorative cover over them.
Like any sprinkler they should only wet the area they are installed in and where there is a fire, they are a lot less destructive than a sprinkler system and if they are supplied from a tank there is not an infinite supply of water, so are time limited. I would expect the system to be zoned may be with multiple pumps.
I installed the cables and supply for a domestic version that is in a TT system and had to install a RCD, there's a discussion about it on the old forum. Before I installed it I ended up having discussions with a couple of consumer unit manufacturers about RCD and MCB protective devices as you don't want those devices disconnecting the pump prematurely.
One of the commercial gas versions killed a guy in South Wales stealing scrap metal.
