Correct size radiator for room

Discussion in 'Plumbers' Talk' started by DIY_Has123, Oct 6, 2021.

  1. DIY_Has123

    DIY_Has123 Member

    Good with most DIY and electrical but plumbing is not really my forte.

    Recently refurbished my upstairs first floor bedroom/office 3.35 metres x 3.85 metres and height of 2.65 metres.

    Used BTU calculators online but they're giving me varied results. Will this radiator be suitable for the room:

    -Living room below (heated)
    -Exterior solid brick wall 3.35m by 2.65m with double glazed window (0.85m wide x 1.67m high)
    -Insulation put between wood floor joists and in ceiling (loft bedroom above)
    -Previous radiator was standard white approx 1.25 metres wide x 0.6m high

    Also after the plumber (or heating engineer ??) fits the radiator and tests, can I remove it straight after to paint behind and fit flooring and skirting boards and fit it back on myslef?
    Will I need to flush the system after I do this?

    Heard something like this and really not sure what it is sorry.
  2. andy48

    andy48 Screwfix Select

    Assuming the existing radiator heats the room adequately:
    1. Work out the BTU capacity of your existing radiator:
    1a. Determine construction. Single or double panel, with single or double set of fins or no fins.
    1b. Look up Myson web site, select radiator nearest size and construction and get BTU figure for temperature difference of delta T50.
    2. If BTU figure from 1b is:
    2a. Greater than 2701, you will need a bigger new radiator.
    2b. If equal to or slightly less than 2701 (say up to 2500 BTU) I'd advise you to get a slightly bigger new radiator.
    2c. Otherwise the one you have picked should do.
    3. You can remove it after the plumber has finished and fit it back yourself with fairly basic DIY skills and a couple of decent adjustable spanners.
    4. There is no need to flush the system after replacing the new radiator, although it wouldn't hurt. The flush would be better done before it is fitted.
    5. Make sure the flow and return connections are properly made in relation to the position of the air vent.
  3. DIY_Has123

    DIY_Has123 Member

    Great thanks. I think this should do based on calculations and new insulation install in floors and ceiling, even though its about half the size as previous radiator.

    Plumber quoted me £150 to install, based in London. Is this reasonable btw?
  4. Jimbo

    Jimbo Screwfix Select

    If the rooms above and below are heated, there is basically no loss through the floor and ceiling so the insulation will likely not make any difference to the radiator size.
  5. andy48

    andy48 Screwfix Select

    1. Its not the physical size of the radiator that's important, its the heating capacity. If you put in a radiator with a lower capacity you may find the room never gets warm or heats up very slowly. The key heat loss factor in your case will be the external wall and windows.
    2. If its half the size of the existing radiator, expect trouble.
    3. £150 sounds a little on the low side to me for London. Two hours work? - should be enough but makes no allowance for problems.
    4. I trust you have noted that under radiator supports may be necessary if the walls are not suitable for wall mounting.
  6. kiaora

    kiaora Guest

    In my view, the position of the radiator is the most important consideration,
    A radiator opposite wall from a window v a radiator under a window,

    under the window every time,
    Just consider the cycle of warm air rising and cool air falling ?

    the radiators opposite wall of window, will draw cool air across the room at low level ……

  7. Severntrent

    Severntrent Screwfix Select

    Certainly a factor to be considered in the old days of single pane windows but not so much an issue with modern double glazing
    kiaora likes this.
  8. kiaora

    kiaora Guest

    I agree, it’s just my age, I still think of coal fires etc…
  9. DIY_Has123

    DIY_Has123 Member

    I think the insulation has made a difference regardless. Upgraded the ceiling insulation from sparse fibreglass to thick rockwool.

    Currently have no heating in the room and on average cold days it only feels cold if the window is open for ventilation whereas before it was cold even with window closed.

    The double glazing is new thermally broken modern aluminium, before I had basically metal framed aluminium windows.

    Also worth mentioning is I put Wallrock KV600 thermal liner paper on the solid exterior wall which should make some difference.
  10. DIY_Has123

    DIY_Has123 Member

    Regarding 4, its an old Victorian terraced property with solid double brick walls so I'm guessing should be strong enough to mount on wall with no feet support? Radiator is about 18kg I think.
  11. DIY_Has123

    DIY_Has123 Member

    This Acova radiator may be small but its triple column, I believe previous was s
    Thanks Andy. When the central heating was upgraded about 20 years ago now in my house, I belive a single panel 600x1300mm radiator was installed in this bedroom, but this was before the loft conversion which came years later.

    A Myson select compact single panel radiator 600x1300 has BTU output of 3000-4000 I believe but now that a loft bedroom has been built above, I believe the BTU requirement should be lower.

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