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Thread: Evohome - comfortable temperature

  1. #11
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    That sounds strange, even if the radiators were piped in series they should both open up...

    I assume you'll have done the obvious of not having a TRV at all on the 2nd rad, and swapped around the HR92 between the 2 rads. The only other thing I can think of (short of gunk) would be the lock shield valve is too shut off on the dodgy rad.

  2. #12
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    Both lockshields are fully open, I've tried taking the trv off and it does sometimes get warm but haven't established a pattern yet.

    When I talked about it being in series I meant with a radiator in another room (and zone) that meant it the living room wasn't getting any hot water when (for example) the kitchen gets up to temperature and closes the hr92s. At the weekend I may take off all the hr92s in the whole house and see if it gets up to temperature.

  3. #13
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    Quote Originally Posted by mjombly View Post
    The radiators in our house are column style radiators which I think are primarily radiating rather than convection so the Hr92s seem to read about 2 degrees higher than other thermometers. (at least whilst they're on!). I'll keep an eye out for some cheap dts92e units on ebay but for now I'll calibrate them down by a couple of degrees.
    Yes a column style radiator relies more on direct infrared radiation and less on convection, so will tend to give a less accurate (higher) reading on the HR92 than a modern convector, because it won't draw as much cold air from the floor up past the HR92.

    While I don't have any column radiators I do have a mix of modern convectors and older style dual panel radiators without convector fins and I notice that the old panels without convectors do not give as accurate a reading as the convectors - one reason I have a DTS92 in the living room as it has three old style dual panels without convectors.
    That aside the system seems to be working OK except for one room that the system just can't get up to temperature (the living room with the evohome controller in). I'm wondering if the radiator is linked in series with one of the other radiators and is therefore not getting any hot water. It does seem to get hot but not constantly which I'd expect when it's 3-4 degrees below the set temperature.
    Unless you have a very old or oddball installation it's very unlikely that two radiators that aren't beside each other are piped in series. We have three panels side by side in a bay window in our living room and they are piped in series but you can clearly see the pipes going between them and there is only one TRV controlling them - they are effectively just one large panel.

    But for separated panels it seems very unlikely, and if they were piped in series with individual TRV's then that's just plain wrong.
    Will the system keep trying (i.e boiler on constantly) or does it eventually learn that it's futile and give up? It's showing as 100% heat demand in the installer menu and I've opened the lockshield valve as far as I can. Could just be gunked up I guess.
    No it won't learn that it can't heat the room enough - it will just keep trying.

  4. #14
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    Quote Originally Posted by mjombly View Post
    Both lockshields are fully open, I've tried taking the trv off and it does sometimes get warm but haven't established a pattern yet.
    Could be a faulty TRV valve body on the radiator.

    Try turning one other room up quite high, say 25C to ensure the boiler runs at 100%, then on the suspect radiator remove the HR92 and turn the black wheel fully anti-clockwise to see if the radiator heats up fully.

    If it does not, try removing the white and black base completely. See if the radiator gets piping hot now. If it does, it could be an incompatibility between the HR92 base and the valve body such as the pin being too long.

    If it still doesn't there is something wrong with either the TRV valve body (needs replacing) or some issue with the pipework that is preventing flow to the radiator.
    Last edited by DBMandrake; 19th December 2018 at 11:45 AM.

  5. #15
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    I am now thoroughly confused, I removed the living room hr92 (and the screw on part too) and the radiator has been piping hot and also cold tonight with seemingly no correlation with system demand (which has been 100% all evening) or temperature in other rooms. I think I'll have to try removing all the trvs in the house and see if the living room warms up. The previous owner was a bit of a "handyman" so it's possible he did something creative with the pipework but I just don't know.

  6. #16
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    I think you need to do a good old fashioned radiator rebalancing.

    My assumption at this stage is that there's another room that's calling for heat, and this cold radiator is being starved because the water is finding a path of less resistance (as it will always do).

  7. #17
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    You might be onto something there, prior to investing in Evohome my daughters room was colder than the rest of the house (3 external walls) so I opened the lockshield up fully, thinking this would make her room hotter. The 2 living room radiators and the hallway radiator are all struggling to get warm and I'm wondering if it's because my daughters radiator (which is always set higher in Evohome than the rest of the house) is starving them of flow.

  8. #18
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    I closed the lockshield down this morning for that room and the landing as both were very warm but no extra heat in the living room. Looks like I'll have to do a proper balancing to see if that helps. I feel like even unbalanced once the other rooms reach the right temperature they would be closed off and the living room should warm up?

    I also turned the boiler up to 5 which gives a flow temperature of about 65 degrees (was previously on 4) but that hasn't helped either.

    Could boiler pump speed have anything to do with it? I haven't seen a setting for that though. I may have to resort to getting a plumber in if I can't troubleshoot the problem myself.

  9. #19
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    It's probably a pressure problem, or lack of. Before you blame the pump, check also to see if the boiler's system pressure is 'in the zone' (usually between 1 and 2 bar, i.e. around 1.4 to 1.6 bar).

    If it is the pump, this is strictly engineer territory. Messing with them can do a lot more harm than good, so get a chap in to check the rad balances, pump and pressure, but build a nice list of things for him to work through before you stump up the call-out.

  10. #20
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    I run my condensing Worcester boiler at 70C flow temp (sometimes 72C when it's colder outside), so you could increase yours a tad.

    Also, is the sitting room one of the furthest rooms from the boiler? I had a similar issue and decided to increase the pump speed to maximum.

    Also, have you ruled out airlocks in the feed pipes (depending how the pipe network was installed).

    Just my two penneth if it helps.

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