Trying to choose between 2 towel rads - which one should I go for?
trying to choose between 2 towel rads. one is smaller has 25mm pipes 4.07L of water content and apparently chucks out 670W @50c. the next one is more expensive is taller but has 22mm pipes holds 6.2L of water and apparently outputs 493W @50c. why the descrepancy in output? surely a larger overall rad with more water content outputs more heat? i will be running it on a system designed for 40c at -3.1c outside so will likely see a lower than design temp in the room but its the biggest rad i can fit.
Possibly 25mm Vs 22 mm pipes. Output depends on surface area principally, but also on form factor. A rad that is twice as tall as another will emit less than twice as much.
Plus measurement margin of course
Output typically varies proportionally to DT^1.3 where DT is the temp diff between the average radiator temp and the room temp. If the 50C you quote is actually DT, output will be 25%. If the 50 you quote is the input flow temp then output will be 55%. Both assuming room temp of 20 and flow-return dt of 5
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
Posted by: @jamespaPosted by: @adamktrying to choose between 2 towel rads. one is smaller has 25mm pipes 4.07L of water content and apparently chucks out 670W @50c. the next one is more expensive is taller but has 22mm pipes holds 6.2L of water and apparently outputs 493W @50c. why the descrepancy in output? surely a larger overall rad with more water content outputs more heat? i will be running it on a system designed for 40c at -3.1c outside so will likely see a lower than design temp in the room but its the biggest rad i can fit.
Possibly 25mm Vs 22 mm pipes. Output depends on surface area principally, but also on form factor. A rad that is twice as tall as another will emit less than twice as much.
Plus measurement margin of course
Output typically varies proportionally to DT^1.3 where DT is the temp diff between the average radiator temp and the room temp. If the 50C you quote is actually DT, output will be 25%. If the 50 you quote is the input flow temp then output will be 55%. Both assuming room temp of 20 and flow-return dt of 5
both are delta T50 apparently, one is recalculated from a higher flow temp to be more realistic it says on the site.
Posted by: @adamkboth are delta T50 apparently, one is recalculated from a higher flow temp to be more realistic it says on the site.
In that case output at 40C will be 25% of quoted value, ie not a lot.
Towel rails appear to be like this, options if not enough are
- add an electric element
- fit a standard radiator and a rail over (they exist)
- ignore the problem and allow heat from other rooms to make up the difference (the one I chose)
- fit a standard radiator in addition to the towel rail
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
Posted by: @jamespaPosted by: @adamkboth are delta T50 apparently, one is recalculated from a higher flow temp to be more realistic it says on the site.
In that case output at 40C will be 25% of quoted value, ie not a lot.
Towel rails appear to be like this, options if not enough are
- add an electric element
- fit a standard radiator and a rail over (they exist)
- ignore the problem and allow heat from other rooms to make up the difference (the one I chose)
- fit a standard radiator in addition to the towel rail
im thinking of going for the taller one and letting the heat from the plant room plus the flow/return 28mm and the primary 28mm's that are in the ceiling all do there bit, as ive had a rad in a bathroom before and they tend to rust quickly. also the room is insulated on all sides including the floor and ceiling.
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