Sizing a fan

[Fatboise]

Hi,

I was watching that program on BBC2 "It's not easy been green" and saw that they piped the warm air from the kitchen where the wood burne is, up stairs to the bedrooms and I was thinking that I wouldn't mind bit of that. I have a large kitchen/dining/living room with a wood/coa burner in it. This room is 8m x 5m and is at the side of the house an is single storey. What I'd like help with is sizing a fan/hosing to move the warm ai from the kichen to two of the bedrooms upstairs. I should have n problem routing the hosing.

Any help/tips greatly appreciate

-- Fatboise

[dom]

I was looking at a friends rural cottage in Brittany and suggesting they do this by changing the bedroom (it's a single bedroom cottage) into a galleried bedroom, immediately above the wooodburner.

If one of the bedrooms to be heated is directly above the kitchen, then I'd suggest floor vents on the appropriate side of the room (as many as possible, passive, no fans). For getting the warm air from room to room on the same floor, vents - bigger the better (and least number of bends) - then you only need slow moving/quiet fans.

There may be building control issues here, due to the possibility of smoke/fumes spilling from the stove (and any other heating appliances) rather than going up the chimney/flue - due to the pressure differences introduced by the fans.

Fatboise wrote:

[TheScullster]

"Fatboise" wrote

Look at Vent-Axia web site. They have their "system calculator" document which gives info on duct and fan sizes etc. One thing to be aware of is the huge reduction in performance you will get using concertina-type hose rather than smooth duct. It may be far easier to route, but, size for size, it adds far more resistance to air flow.

Phil

[Fatboise]

Look at Vent-Axia web site.

They have their "system calculator" document which gives info on duc and fan sizes etc. One thing to be aware of is the huge reduction in performance you wil get using concertina-type hose rather than smooth duct. It may be far easier to route, but, size for size, it adds far more resistance to air flow.

Phil

Phil, Thanks for the advice about the ducting. I had a look at th Vent-Axia website and it's just what I'm looking for don't know why didn't find this when googling??

-- Fatboise

[robert]

Also remember if you want quiet operation choose a larger fan and run it slower.

Robert Robert

[Aidan]

I thought they'd used a heat recovery unit with a cross-flow plate heat exchanger ( but I wasn't paying much attention). Their intended use is to pre-heat supply air from outside with an extracted air stream. The air from the kitchen would usually be moisture-laden and exporting it to elsewhere in the house would not be a good idea. If it's cooker extract, then trying to recover heat from it would also not be a good idea too. I think they'd do better with a air heater coil supplied with LTHW from the heating system. The one they used seem to have electric heaters which would undermine the green intent. I'm sure they know what they're doing. ;-)

Both air streams entering the PHX should be filtered and a significant part of the system resistance will be internal to the air handler, from the filters & the PHX. The recovered heat would be a nuisance in summer, unless you have a ducted by-pass around the heat recovery device(s).

[Aidan]

And the heat transfer depends on the temperature difference.

If used to heat re-cycled (warm) room air with an extract air stream, the efficiency will drop sharply, to the extent where the payback achieved by the device (heat recovered v power consumed by the fans) becomes dubious. Efficiency will be highest with cold incoming air.

[normanwisdom]

Have same plan. Intend to blow the air from living room into the ensuite shower cubicle in the bedroom. Whats best for duct - grey rainwater goods or what?

cheers Jacob

[Fatboise]

Aidan, Thanks for your inputs. I looked at the vent-axia site and sa that they supply the heat recovery units which I had looked int somewhat when I thought of this project. The thing with my house is have a solid fuel "pot belly" stove in the Kitchen/living room which i used during the winter. What I was planning was using the fan to mov the heat to the bedroom late in the evening just before we go to bed s the remaining heat fromt he stove isn't lost in the Kitchen/living roo when there is nobody there. At this stage of the evening there shoul be no cooking moisture or smells left in the room and if there is som late cooking I can put up with that the few times that it happens. Th fan would be on for 1 hour at the most so I thought it wouldn't b worthwhile investing in the heat exchanger unit

-- Fatboise

[TheScullster]

do some lightweight duct 100 and 125 dia IIRC I used the 100 recently for a toilet fan duct through loft space.

Phil

[normanwisdom]

Thanks for that. Not much in it for price - some screwfix grey rainwater goods a bit cheaper.

cheers Jacob

[normanwisdom]

Thanks for that. Not much in it for price - some screwfix grey rainwater goods a bit cheaper.

cheers Jacob