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Thread: Evohome - living room slow to heat

  1. #1
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    Default 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

  2. #2
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    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?

  3. #3
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    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

  4. #4
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    According to this calculator:

    http://www.bestheating.com/btu-calculator

    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.

  5. #5
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    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.

  6. #6
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    Quote 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:

    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
    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.

  7. #7
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    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

  8. #8
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    Quote 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; 8th March 2016 at 09:52 PM.

  9. #9
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    Quote 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?

  10. #10
    Automated Home Legend top brake's Avatar
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    Can't tell if that rad is undersized from that pic need to do heat loss calcs for the room

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