Evohome - living room slow to heat

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  • garmcqui
    Automated Home Guru
    • Jan 2015
    • 119

    #16
    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; 8 March 2016, 10:46 PM.

    Comment

    • The EVOHOME Shop
      Site Sponsor
      • Dec 2014
      • 483

      #17
      Originally posted by DBMandrake View Post
      Using the formulas here:



      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.

      Comment

      • garmcqui
        Automated Home Guru
        • Jan 2015
        • 119

        #18
        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?

        Comment

        • DBMandrake
          Automated Home Legend
          • Sep 2014
          • 2361

          #19
          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.

          Comment

          • garmcqui
            Automated Home Guru
            • Jan 2015
            • 119

            #20
            ok, cheers.

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

            Comment

            • top brake
              Automated Home Legend
              • Feb 2015
              • 837

              #21
              Originally posted by garmcqui View Post
              ok, cheers.

              How difficult would it be to extend the 10mm plastic pipe? Can it be joined?
              If you're not confident I would encourage you to get an installer in to replace the radiator. Will also need balancing.
              I work for Resideo, posts are personal and my own views.

              Comment

              • garmcqui
                Automated Home Guru
                • Jan 2015
                • 119

                #22
                Originally posted by top brake View Post
                If you're not confident I would encourage you to get an installer in to replace the radiator. Will also need balancing.
                Should be fine, I've hung plenty of radiators before, just never worked with this plastic microbore pipe. I did replace rads in both bathrooms with towel rails earlier this year, no problems.

                Regarding balancing - is it as important now that Evohome is controlling all the radiators independently? There is never a time when over half the radiators in the house are on at once, therefore one would think the system would cope with all the lockshields fully open?

                Comment

                • The EVOHOME Shop
                  Site Sponsor
                  • Dec 2014
                  • 483

                  #23
                  Originally posted by garmcqui View Post
                  Regarding balancing - is it as important now that Evohome is controlling all the radiators independently? There is never a time when over half the radiators in the house are on at once, therefore one would think the system would cope with all the lockshields fully open?
                  Balancing is critical in all heating systems and evohome system are no exception.

                  Comment

                  • top brake
                    Automated Home Legend
                    • Feb 2015
                    • 837

                    #24
                    Originally posted by The EVOHOME Shop View Post
                    Balancing is critical in all heating systems and evohome system are no exception.
                    Amen brother

                    And Happy Birthday
                    I work for Resideo, posts are personal and my own views.

                    Comment

                    • The EVOHOME Shop
                      Site Sponsor
                      • Dec 2014
                      • 483

                      #25
                      Originally posted by top brake View Post
                      Amen brother

                      And Happy Birthday
                      Thanks TB!

                      Comment

                      • garmcqui
                        Automated Home Guru
                        • Jan 2015
                        • 119

                        #26
                        Originally posted by The EVOHOME Shop View Post
                        Balancing is critical in all heating systems and evohome system are no exception.
                        Obviously with this being your trade, I accept what you say as correct. However, I'm a sucker for knowing "why"! (sorry!)

                        My question is this... Evohome completely changes the dynamics of a central heating system from one which all the radiators are often heated together (and which has a relatively predictable pattern etc), to one where individual rooms are heated at different times and rarely all at once. Obviously balancing is vital if there are soom radiators which are heating up much more quickly than others, but with Evohome there are only usually one or two radiators calling for heat at the same time, so surely a poorly balanced system will still perform well?

                        Not wanting to be awkward, please do explain why it's still critical. Cheers

                        Comment

                        • Midori
                          Automated Home Jr Member
                          • Aug 2015
                          • 24

                          #27
                          1) It's winter, so expect room warm up temperatures to approach 2 hours if you let night room temp drop to 16.5C.
                          2) It depends where you put the sensor as to what actual room comfort temperature actually is.
                          3) Eliminate the Evohome control by putting the radiator full on and seeing how long it takes to get comfort in your room. (eliminate cycling for this test).
                          4) Radiators are designed to give rated output when mean water temperature is 70C. Mean water tem is half way between inlet and out let temperatures.
                          5) If your boiler is set at "almost cannot touch" temperature then it is not anywhere near 80 C at the radiator.
                          6) Even if set at 80C the water entering radiator may be considerably lower. So measure both rad in and out temps and calculate the mean temperature.
                          +
                          7) Radiators give up their heat 30% by radiation + 70% by convection. Curtains, Furniture and Laundry can grossly decrease efficiency.
                          8) You only get what you pay for when water velocity maintains 60C return water temp at the radiator, and if radiator has no air in it.
                          9) 80 C boiler temperature is way too high for most UK locations / seasons, and also to be avoided if HWS is not independently controlled, or if kids are around.
                          10) regardless of what the controller says, health, activity and clothing affect comfort and fuel bills!
                          Last edited by Midori; 14 March 2016, 10:12 AM.
                          Assoc IHVE; Matthew Hall Satchwell MW Kellogg CompAir; posts are personal and my own view

                          Comment

                          • The EVOHOME Shop
                            Site Sponsor
                            • Dec 2014
                            • 483

                            #28
                            Originally posted by garmcqui View Post
                            Obviously with this being your trade, I accept what you say as correct. However, I'm a sucker for knowing "why"! (sorry!)

                            My question is this... Evohome completely changes the dynamics of a central heating system from one which all the radiators are often heated together (and which has a relatively predictable pattern etc), to one where individual rooms are heated at different times and rarely all at once. Obviously balancing is vital if there are soom radiators which are heating up much more quickly than others, but with Evohome there are only usually one or two radiators calling for heat at the same time, so surely a poorly balanced system will still perform well?

                            Not wanting to be awkward, please do explain why it's still critical. Cheers
                            From you questioning, what do you think 'radiator balancing' means? Why do you think evohome makes this less important for a heating system?

                            All central heating boilers require a temperature drop from the flow to the return pipe. The 'designed' temperature drop for a condensing boiler heating system for example is normally 20 deg C (75 deg C flow and 55 deg C return). If radiator valves are just left fully open, the central heating water going in the flow pipe of the radiator might 'exit' the return pipe too quickly, hence we 'temperature balance' the heating system at each radiator by restricting the 'lockshield' valve to obtain the correct temperature differential. This is started at the nearest radiator and finished at the 'index' radiator (furthest radiator).

                            A quick Google search will give you some basic 'how to' guides, but radiator balancing is very difficult when radiators are not designed with the correct temperature differential in mind - normally the case when a condensing boiler (requiring a 20 deg C drop) is fitted to an existing radiator system that was designed for a standard efficiency boiler (requiring a 11 deg C drop).

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