Hi,
we've just bought a 'standard' three bed semi...
fully double-glazed (not sure when it was installed),
cavity walls insulated (again, not sure when),
about 200mm glass-fibre in the roof done about four years ago (certificates stapled to beams).
There's a 'standard' gas fire in each of the two main rooms downstairs, no immersion heater but a combi boiler in the kitchen.
While I've been working there I've had the two fires running on a low setting and with the internal doors open they heat the whole house within an hour, so I reckon the insulation is pretty good all round.
Doing a full re-wire before we move into a house...
There's no central heating so while I have the floor-boards up I thought I could drop some pipes in ready to install CH later in the summer.
My plan is to install eight rads under the windows and an emersion heater (remove the combi and replace with a CH boiler), do the rads, pipes / water plumbing myself and then pay a gas fitter to install the boiler and commision the system.
So I wanted to know the pipe sizes for the main 'run', front to back...
then I can cut the floor-boards to allow one section to be lifted at each end so I can finish off the installation without having to lift the carpets and the whole length of floor-boards.
I found a tutorial on the internet and there's a set of calcs to decide on radiator sizes for each room. This will tell me if 22mm is OK front to back of the house (I guess it will be but I want to check).
I added the calcs into an Excel spreadsheet but some of the BTU / Watts figures output seem a bit low to me, taking one room as an example:
back bedroom (the mid-sized of the three):
for the room Volume, length: 2.86m
width: 3.38m
height: 2.37m
air change per hour: 1
'U' value: 0.33
Multiplied out, sub-total = 7.56
Window size: 1.78m x 1.04m
double glazed, 'U' value 2.9
Multiplied out, sub-total = 5.37
external wall, width: 2.37m
height: 2.37m
'U' value: 0.6 (they suggested 0.3 for 'heavily insulated', I've allowed a bit extra)
Multiplied out, sub-total = 4.82
ceiling length: 2.86m
width: 3.38.
'U' value: 0.6 (they suggest 0.3, and there's around 200mm of insulation above)
Multiplied out, sub-total = 5.8
floor length: 2.8m
width: 3.38.
'U' value: 0.7 (they suggest 1 but it's a carpeted wood floor with heating in the room below)
Multiplied out, sub-total = 6.77
Total 30.32
multiplied by 20 (19 degrees room temp and -1 outside)
= 606.33 Watts
multiplied by 3.45 = 2092 BTU
Does that sound OK to the experts on here please?
As a check I found an on-line calculator that didn't consider window size, ceiling or floor areas. and that gave a rating of 3600 BTU (that seems too high to me!) for the same room, so I'm not so sure now!
These calcs I used give a total for the rads (excluding immersion heater) of 20224 BTU or 5862 watts.
Again that seems a bit low, what do you think please?
What sort of BTU / watts would an immesrion heater come out at please?
I guess I'll be using a fairly 'standard' 28k BTU non-condensing boiler, if I slightly over-specc'd the rads then I could limit the flow through each and I'd have some in reserve for extra cold days, but again does this sound reasonable or have I got it all completely wrong?
Regards
Peter
we've just bought a 'standard' three bed semi...
fully double-glazed (not sure when it was installed),
cavity walls insulated (again, not sure when),
about 200mm glass-fibre in the roof done about four years ago (certificates stapled to beams).
There's a 'standard' gas fire in each of the two main rooms downstairs, no immersion heater but a combi boiler in the kitchen.
While I've been working there I've had the two fires running on a low setting and with the internal doors open they heat the whole house within an hour, so I reckon the insulation is pretty good all round.
Doing a full re-wire before we move into a house...
There's no central heating so while I have the floor-boards up I thought I could drop some pipes in ready to install CH later in the summer.
My plan is to install eight rads under the windows and an emersion heater (remove the combi and replace with a CH boiler), do the rads, pipes / water plumbing myself and then pay a gas fitter to install the boiler and commision the system.
So I wanted to know the pipe sizes for the main 'run', front to back...
then I can cut the floor-boards to allow one section to be lifted at each end so I can finish off the installation without having to lift the carpets and the whole length of floor-boards.
I found a tutorial on the internet and there's a set of calcs to decide on radiator sizes for each room. This will tell me if 22mm is OK front to back of the house (I guess it will be but I want to check).
I added the calcs into an Excel spreadsheet but some of the BTU / Watts figures output seem a bit low to me, taking one room as an example:
back bedroom (the mid-sized of the three):
for the room Volume, length: 2.86m
width: 3.38m
height: 2.37m
air change per hour: 1
'U' value: 0.33
Multiplied out, sub-total = 7.56
Window size: 1.78m x 1.04m
double glazed, 'U' value 2.9
Multiplied out, sub-total = 5.37
external wall, width: 2.37m
height: 2.37m
'U' value: 0.6 (they suggested 0.3 for 'heavily insulated', I've allowed a bit extra)
Multiplied out, sub-total = 4.82
ceiling length: 2.86m
width: 3.38.
'U' value: 0.6 (they suggest 0.3, and there's around 200mm of insulation above)
Multiplied out, sub-total = 5.8
floor length: 2.8m
width: 3.38.
'U' value: 0.7 (they suggest 1 but it's a carpeted wood floor with heating in the room below)
Multiplied out, sub-total = 6.77
Total 30.32
multiplied by 20 (19 degrees room temp and -1 outside)
= 606.33 Watts
multiplied by 3.45 = 2092 BTU
Does that sound OK to the experts on here please?
As a check I found an on-line calculator that didn't consider window size, ceiling or floor areas. and that gave a rating of 3600 BTU (that seems too high to me!) for the same room, so I'm not so sure now!
These calcs I used give a total for the rads (excluding immersion heater) of 20224 BTU or 5862 watts.
Again that seems a bit low, what do you think please?
What sort of BTU / watts would an immesrion heater come out at please?
I guess I'll be using a fairly 'standard' 28k BTU non-condensing boiler, if I slightly over-specc'd the rads then I could limit the flow through each and I'd have some in reserve for extra cold days, but again does this sound reasonable or have I got it all completely wrong?
Regards
Peter
