Evohome - living room slow to heat

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  • garmcqui
    Automated Home Guru
    • Jan 2015
    • 119

    Evohome - living room slow to heat

    Hi all,

    Had Evohome installed for over a year now, very happy with it. I recently managed to get Python to log my room temperatures (target and actual) and plot graphs on Plotly, which has led me to confirm what I've been feeling for a while now - the living room takes ages to warm up!

    The following graph shows how the set temp (red trace) and actual room temp (blue trace) changed over the last 24h:

    Living Room.jpg

    As you can see, the target temperature changes from 10C to 21C at 5.30 am, but it is 8.30 before the room is nearing 21C, which seems long to me. Other rooms seem to heat up much quicker.

    The radiator seems to get plenty warm, almost too warm to touch. The radiator size is a 300mm x 1500mm double (which according to spec, is rated at about 5000 BTU/h) but is under the window (see pic). The house is a new build and the living room is 3.9m x 4.3m (ceiling standard height)

    IMG_0641.jpg

    What do you think, am I being unreasonable to expect it to heat up quicker?

    Cheers
  • HenGus
    Automated Home Legend
    • May 2014
    • 1001

    #2
    It might be worth deleting the zone and re-building it with the Evohome Controller on a stand as the room sensor to see if local effects around the HR92 are the issue. My other thought, am I not a plumber, is the radiator big enough for that size of room?

    Comment

    • DanD
      Automated Home Ninja
      • Feb 2016
      • 250

      #3
      Hi,

      I see a similar profile for one of my zones, but it's due the fact that I've had to restrict the flow via the lockshield to stop TRV noise when the other zones have hit their setpoints (I'm going to replace the TRV at some point). Although your radiator gets hot, have all radiators been balanced as it could simply be that it's slow to heat due to restricted flow? Otherwise, is the room door open at these times as it could simply be that heat is being lost to the rest of the house.

      Dan

      Comment

      • rotor
        Automated Home Guru
        • Aug 2015
        • 124

        #4
        According to this calculator:

        Use the BestHeating BTU calculator to work out the heat requirements of your room & find a choice of radiators & towel rails to heat your home comfortably


        A room that size with 2.4m ceiling height, with a heated room above it, needs 3,929 BTU. So if your radiator spec is correct, then something is not right (nothing to do with Evohome, in theory).

        Are you heating all the other rooms starting at 5:30 as well? If so, then either the boiler isn't grunty enough for the whole house, or the radiators are badly un-balanced, and the living room rad is getting luke-warm water because the other rads are hogging all the heat. Based on the shape of the graph, I would guess that the rest of the house heating comes on at 6:30 (an hour later), as you can see the graph flattens out, and then around 7:45 the graph gets a lot steeper, which implies the rest of the house is now up to heat, and the TRVs have all mostly closed down, leaving much hotter water for the living room.

        That's my non-expert tuppence anyway.

        Comment

        • top brake
          Automated Home Legend
          • Feb 2015
          • 837

          #5
          Overnight setback to 10 degC is way too low. You're losing all the heat in the fabric of the building. So it has to heat the walls before heating the air.
          I work for Resideo, posts are personal and my own views.

          Comment

          • The EVOHOME Shop
            Site Sponsor
            • Dec 2014
            • 483

            #6
            Originally posted by garmcqui View Post
            Hi all,

            Had Evohome installed for over a year now, very happy with it. I recently managed to get Python to log my room temperatures (target and actual) and plot graphs on Plotly, which has led me to confirm what I've been feeling for a while now - the living room takes ages to warm up!

            The following graph shows how the set temp (red trace) and actual room temp (blue trace) changed over the last 24h:

            [ATTACH=CONFIG]685[/ATTACH]

            As you can see, the target temperature changes from 10C to 21C at 5.30 am, but it is 8.30 before the room is nearing 21C, which seems long to me. Other rooms seem to heat up much quicker.

            The radiator seems to get plenty warm, almost too warm to touch. The radiator size is a 300mm x 1500mm double (which according to spec, is rated at about 5000 BTU/h) but is under the window (see pic). The house is a new build and the living room is 3.9m x 4.3m (ceiling standard height)

            [ATTACH=CONFIG]686[/ATTACH]

            What do you think, am I being unreasonable to expect it to heat up quicker?

            Cheers
            Looking at the graph, your actual temp didn't drop below 16.5 degrees. Are those curtains closed at night? Does the radiator have convector fins on the inside? I would personally say the radiator is undersized for a condensing boiler (assuming new build it would have one), especially if you have reduced the boiler flow temp. Remember that radiator is probably 5000 BTU per hour at 82 degrees Celsius - 82 is holy mother fugger to the touch, 60 ish is ooohhh thats hot to the touch, so would be interesting to see what the temp at the radiator surface is.

            Comment

            • garmcqui
              Automated Home Guru
              • Jan 2015
              • 119

              #7
              HenGus - forgot to mention, a Y87RF thermostat is acting as sensor, the HR92 is simply an actuator. Yes, I have suspicion about the size of the rad. Problem is, I'm limited as to what size can be fitted in the current position. If needed, I reckon I would be able to upgrade it to a 1600mm x 400mm, at a push.

              DanD - just checked the living room radiator with a digital thermometer. It's reading 66C and one end and 59C at the other, I presume this is warm enough?

              rotor - Only three rooms are heated at 5.30, along with hot water cylinder. The boiler is an 18kW condensing unit, only 18 months old - before I fitted Evohome it would comfortably heat the entire house at once, so I doubt it's not enough.

              top brake - I just set the temp to 10C so there's no boiler demand overnight, but temperatures never get anywhere near that low. The lowest I've seen rooms get to overnight is about 15C. What do people generally keep their Evohome set to overnight?

              Cheers for replies

              Comment

              • garmcqui
                Automated Home Guru
                • Jan 2015
                • 119

                #8
                Originally posted by The EVOHOME Shop View Post
                Looking at the graph, your actual temp didn't drop below 16.5 degrees. Are those curtains closed at night? Does the radiator have convector fins on the inside? I would personally say the radiator is undersized for a condensing boiler (assuming new build it would have one), especially if you have reduced the boiler flow temp. Remember that radiator is probably 5000 BTU per hour at 82 degrees Celsius - 82 is holy mother fugger to the touch, 60 ish is ooohhh thats hot to the touch, so would be interesting to see what the temp at the radiator surface is.
                Curtains are never closed, so as not to impede the radiator. Yup, convector fins present. Boiler is an 18kW condensing unit, boiler temp is set to the "e" (which is about 75% of max) as the engineer who serviced it recommended. Just measured the rad temp with a cheapo thermocouple thermometer, probably nowhere near accurate but it's reading 66C at one end and 59C at the other.

                IMG_0649.jpg
                (no idea why it's upside down, won't let me rotate)
                Last edited by garmcqui; 8 March 2016, 09:52 PM.

                Comment

                • The EVOHOME Shop
                  Site Sponsor
                  • Dec 2014
                  • 483

                  #9
                  Originally posted by garmcqui View Post
                  Curtains are never closed, so as not to impede the radiator. Yup, convector fins present. Boiler is an 18kW condensing unit, boiler temp is set to the "e" (which is about 75% of max) as the engineer who serviced it recommended. Just measured the rad temp with a cheapo thermocouple thermometer, probably nowhere near accurate but it's reading 66C at one end and 59C at the other.
                  Radiators can never be oversized (as you can then reduce boiler flow temp which improves condensing) but always hate seeing them undersized. They just don't seem to 'look' right when they are not 600mm high lol - maybe just me?

                  Comment

                  • top brake
                    Automated Home Legend
                    • Feb 2015
                    • 837

                    #10
                    Can't tell if that rad is undersized from that pic need to do heat loss calcs for the room
                    I work for Resideo, posts are personal and my own views.

                    Comment

                    • garmcqui
                      Automated Home Guru
                      • Jan 2015
                      • 119

                      #11
                      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.

                      Last edited by garmcqui; 8 March 2016, 10:14 PM.

                      Comment

                      • top brake
                        Automated Home Legend
                        • Feb 2015
                        • 837

                        #12
                        Also worth checking the HR92 adapt or isn't screwed too far down.
                        I work for Resideo, posts are personal and my own views.

                        Comment

                        • garmcqui
                          Automated Home Guru
                          • Jan 2015
                          • 119

                          #13
                          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?

                          Comment

                          • top brake
                            Automated Home Legend
                            • Feb 2015
                            • 837

                            #14
                            What is differential temperature from one end to the other?
                            I work for Resideo, posts are personal and my own views.

                            Comment

                            • DBMandrake
                              Automated Home Legend
                              • Sep 2014
                              • 2361

                              #15
                              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.
                              Last edited by DBMandrake; 8 March 2016, 10:31 PM.

                              Comment

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