Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 28

Thread: Evohome - living room slow to heat

  1. #11
    Automated Home Guru
    Join Date
    Jan 2015
    Posts
    102

    Default

    Here's one I've just done on the City Plumbing website:

    LR.jpg

    It's suggesting 5042 BTU/hr, or 1.48kW. I honestly have no idea what the radiator is rated at, can't see a manufacturer on it anywhere. But most 1500 x 300mm rads I've found online are around 5100 BTU.

    http://www.plumbcenter.co.uk/product...s--5179-btu-h/
    Last edited by garmcqui; 8th March 2016 at 10:14 PM.

  2. #12
    Automated Home Legend top brake's Avatar
    Join Date
    Feb 2015
    Location
    the edge of the cloud
    Posts
    827

    Default

    Also worth checking the HR92 adapt or isn't screwed too far down.

  3. #13
    Automated Home Guru
    Join Date
    Jan 2015
    Posts
    102

    Default

    Quote Originally Posted by top brake View Post
    Also worth checking the HR92 adapt or isn't screwed too far down.
    but the radiator is getting up to a good temp, 66C plus as measured at the surface with a cheapo thermocouple thermometer. Water temp inside will be higher I'd imagine. Would it be doing this if the HR92 wasn't opening the valve far enough?

  4. #14
    Automated Home Legend top brake's Avatar
    Join Date
    Feb 2015
    Location
    the edge of the cloud
    Posts
    827

    Default

    What is differential temperature from one end to the other?

  5. #15
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    1,842

    Default

    Using the formulas here:

    http://wiki.diyfaq.org.uk/index.php?...ting_radiators

    If your radiator is a double panel single convector (type 21) then its delta 50 heat output is only about 1197 watts. If it is a double panel double convector (type 22 - thicker with two sets of fins in between) then it will be about 1512 watts.

    However your average panel temperature is only (66-59)/2+59 = 62.5 degrees which assuming the set point is 20 degrees that falls to about 1068 watts and 1350 watts respectively. IMHO that is considerably undersized (especially the lower figure if its a type 21) in terms of wattage for a room that is 3.9 x 4.3 x 2.4 metres.

    By way of comparison our living room is 4.3 x 3.9 x 2.8 metres with a 1 metre deep bay window with brick and plaster interior walls. There are three separate radiators mounted around the bay window piped together (with a single HR92) each 800mm wide by 600mm high - they are old fashioned double panel radiators that do not have fins, so are lower effective wattage than modern convectors would be, however their total delta 50 wattage still works out to about 2800 watts - roughly twice the wattage of your radiator, and visually more than twice the size.

    According to my graphs the room takes about 1 hour 50 minutes to go from 11 degrees up to 21 degrees in current condtions where outdoor temperatures are between 0-5 degrees. However keep in mind that I am measuring the temperature at the HR92 (no separate wall stat) which will tend to give the impression that the room warms up faster than it really does (the far side of the room is not up to temperature that quickly) however a separate thermostat in the middle of the room shows that the room is up to temp (21 degrees) in roughly 2 1/2 hours from 11 degrees.

    So I would say that yes, you are asking too much of your radiator, even just looking at the picture my immediate thought was "too small", but doing a few calculations confirms it.

    You say you don't have much more room but it looks like you could increase the height significantly (bringing it up to just under the window) and if it is only a single convector type 21 you would see a significant increase by going to a full thickness type 22 without increasing the surface area on the wall over a type 21.
    Last edited by DBMandrake; 8th March 2016 at 10:31 PM.

  6. #16
    Automated Home Guru
    Join Date
    Jan 2015
    Posts
    102

    Default

    it looks like it is a type 22 double convector:

    IMG_0650.jpg


    It's just strange because other rooms in the house don't seem to have much bigger rads and heat up much more quickly:

    Kitchen - 6.1m x 3.4m - heated by two 800x600mm type 11 rads.
    Bedrooms - each 3.6m x 3.2m - each heated by one 600x450mm type 11.
    Last edited by garmcqui; 8th March 2016 at 10:46 PM.

  7. #17
    Site Sponsor The EVOHOME Shop's Avatar
    Join Date
    Dec 2014
    Location
    Powys, Mid Wales
    Posts
    479

    Default

    Quote Originally Posted by DBMandrake View Post
    Using the formulas here:

    http://wiki.diyfaq.org.uk/index.php?...ting_radiators

    If your radiator is a double panel single convector (type 21) then its delta 50 heat output is only about 1197 watts. If it is a double panel double convector (type 22 - thicker with two sets of fins in between) then it will be about 1512 watts.

    However your average panel temperature is only (66-59)/2+59 = 62.5 degrees which assuming the set point is 20 degrees that falls to about 1068 watts and 1350 watts respectively. IMHO that is considerably undersized (especially the lower figure if its a type 21) in terms of wattage for a room that is 3.9 x 4.3 x 2.4 metres.

    By way of comparison our living room is 4.3 x 3.9 x 2.8 metres with a 1 metre deep bay window with brick and plaster interior walls. There are three separate radiators mounted around the bay window piped together (with a single HR92) each 800mm wide by 600mm high - they are old fashioned double panel radiators that do not have fins, so are lower effective wattage than modern convectors would be, however their total delta 50 wattage still works out to about 2800 watts - roughly twice the wattage of your radiator, and visually more than twice the size.

    According to my graphs the room takes about 1 hour 50 minutes to go from 11 degrees up to 21 degrees in current condtions where outdoor temperatures are between 0-5 degrees. However keep in mind that I am measuring the temperature at the HR92 (no separate wall stat) which will tend to give the impression that the room warms up faster than it really does (the far side of the room is not up to temperature that quickly) however a separate thermostat in the middle of the room shows that the room is up to temp (21 degrees) in roughly 2 1/2 hours from 11 degrees.

    So I would say that yes, you are asking too much of your radiator, even just looking at the picture my immediate thought was "too small", but doing a few calculations confirms it.

    You say you don't have much more room but it looks like you could increase the height significantly (bringing it up to just under the window) and if it is only a single convector type 21 you would see a significant increase by going to a full thickness type 22 without increasing the surface area on the wall over a type 21.
    Like I said, the radiators undersized lol! I was going to do the calcs, but my immediate gut feeling was that it was undersized based on the room size. If you do change the rad, go for Stelrad or 'Henrad' (made by Stelrad) as they are slightly higher on the outputs than equivalent sized rivals.

  8. #18
    Automated Home Guru
    Join Date
    Jan 2015
    Posts
    102

    Default

    one thing I am slightly worried about is the ability of the small pipes supplying the rad to cope with the increased output of a larger rad. They are (as is typical in new build houses) 10mm plastic microbore pipes. Will they cope?

  9. #19
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    1,842

    Default

    Quote Originally Posted by garmcqui View Post
    one thing I am slightly worried about is the ability of the small pipes supplying the rad to cope with the increased output of a larger rad. They are (as is typical in new build houses) 10mm plastic microbore pipes. Will they cope?
    With a larger radiator do you mean ? Yes I don't see why not. The same page I linked to has rule of thumb maximum KW output for different pipe sizes and lists 2.5KW for 10mm.

    That table is actually pretty conservative I think - most of my radiators are 8mm microbore which according to that table is limited to around 1.5KW, however I have one radiator that is a 2000x600mm double panel single convector with a theoretical output of 2736 watts, and it is fed by 8mm microbore, and it has no trouble heating up quickly and maintaining a normal 11 degree differential... (if the flow was excessively restricted it would have an unusually large differential between input and output sides of the radiator and/or take a long time to heat up)

    So for 10mm and the likely size of radiator you can fit there I think you'll be absolutely fine.

  10. #20
    Automated Home Guru
    Join Date
    Jan 2015
    Posts
    102

    Default

    ok, cheers.

    How difficult would it be to extend the 10mm plastic pipe? Can it be joined?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •