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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorShevek
    • CommentTimeMar 5th 2015 edited
     
    What do you think is the best way to control radiators in bedrooms?

    A Nest thermostat in each room? (I really hate the user interfaces of standard thermostats)

    And what's the easiest to install and most cost effective while still offering reasonably good control? I've seen this TRV mentioned (what's that green button do?):
    http://www.honeywelluk.com/products/Thermostatic-Radiator-Valves/RadPlan-TRV-Pack/VTL120/

    House is very well insulated, airtight retrofit with underfloor heating to ground floor level and radiators in the bedroom to the upper floors, run of a combi. We tend not to heat the bedrooms very much, only in the evenings at the height of winter to take any chill off. We may well have tenants in the future who use and heat their rooms than we do though.
  1.  
    Trv
    • CommentAuthorringi
    • CommentTimeMar 5th 2015
     
    honeywell evohome is one option, but you have to control the system from a central location not each bedroom themselves. So no good for HMOs.
    • CommentAuthorShevek
    • CommentTimeMar 5th 2015
     
    I do really like the simplicity of a TRV. What are their disadvantages?

    (we're not an HMO, just have lodgers)
    • CommentAuthortony
    • CommentTimeMar 5th 2015
     
    Switch em off!
    • CommentAuthorShevek
    • CommentTimeMar 5th 2015
     
    Tony, you always have the most straight forward answers. :bigsmile:
    • CommentAuthorgravelld
    • CommentTimeMar 5th 2015
     
    What do you mean by 'control'?

    We use Heat Genius, works very well.
    • CommentAuthorShevek
    • CommentTimeMar 5th 2015
     
    One of the following:
    1. On and off
    2. Thermostatic control
    3. Thermostatic control with timer
    • CommentAuthorgravelld
    • CommentTimeMar 5th 2015 edited
     
    Well if it's just one bedroom rad you want to control and you want other rads off AND you want the boiler interlock to shutdown the boiler once your bedroom is to temp then it had to be one of the zoned systems like HG or Evohome.

    Nest allows a small number of zones but is very expensive to zone the house.

    If you don't care about other rads turning on or the boiler running you can just get a timer TRV e.g. the Pegler TRVs.
    • CommentAuthorShevek
    • CommentTimeMar 5th 2015
     
    Okay, I realise now there's a lot more I need to learn about CH controls! Thanks.
  2.  
    Would it be wise to just run the rads off a central manifold along with the Ufh and just use a simple on/off actuator?
  3.  
    Trv s do seem a bit unresponsive sometime. do they work on flow or air temp. Or a bit of both? I thought air but then remember reading way back that flow temp. had something to do with it.
  4.  
    Would have to be air temperature surely, otherwise they'd shut off with traditional flow temps.
    • CommentAuthorEd Davies
    • CommentTimeMar 8th 2015 edited
     
  5.  
    ''do they work on flow or air temp? ''

    Air.

    AIUI that's why some of them were designed to be fitted horizontally. Vertical takes them too close to the rad.
  6.  
    I've come to the conclusion that there are two basic approaches to heating control -

    - "micro-manage" with a large number of zones. The full extent of this is room stat and timer control on a room by room basis, whether with manifolds and actuators or electronic radiator valves. Requires lots of wiring and actuators so a fair bit of cost. In a large leaky, poorly insulated, house where some rooms are used infrequently this will give you the lowest heating bills as you only heat the areas you are using, when you're using them.

    - macro control with the whole house at the same temperature or a small number of zones. This was the traditional UK radiator based approach. If set up properly TRVs compensate for a poorly balanced system, oversized radiators in some rooms, or rooms that have a higher heat loss. They also give a way of isolating individual rooms manually.

    In our poorly insulated Victorian house with some time spent balancing and using a min/max thermometer over a number of weeks to work out the TRV setting for each room (which I then marked on the TRV as visitors/lodgers had a habit of turning up the TRV if they were cold) I managed to get the house to heat evenly to a uniform temp.

    My reading is that all this changes when you've got a highly insulated airtight house as in theory it becomes easy, and not costly, to heat the house evenly. Run the system constantly at a low temperature and it becomes self regulating and the cost savings of controlling on a room by room basis are negligible (and outweighed by the savings on the control equipment that is required to do room by room control). If you're running rad's hot you might still want to use TRVs to limit the output but if you're running large cool rads you might not need them. You can still turn radiators off manually with the lockvalves if you're not using some rooms.
  7.  
    Its been a recent realisation to me that the rooms where the TRV's are on the return rather than the flow hold their temperatures more accurately.

    This peaked my curiosity and I came across this article:

    http://heating.danfoss.co.uk/xxnewsx/759716fc-82db-4be4-bc4a-0e18ab022edb.html

    So actually it turns out that most of my TRV's and pretty much every one i've ever seen in somebodies house is actually mounted wrong, horizontal is better, worst case is vertical on the flow.

    I'm getting a remote sensor head TRV from eBay to have a play with.
    • CommentAuthorSimon Still
    • CommentTimeMar 8th 2015 edited
     
    Posted By: danielbroadIts been a recent realisation to me that the rooms where the TRV's are on the return rather than the flow hold their temperatures more accurately.

    This peaked my curiosity and I came across this article:

    http://heating.danfoss.co.uk/xxnewsx/759716fc-82db-4be4-bc4a-0e18ab022edb.html" rel="nofollow" >http://heating.danfoss.co.uk/xxnewsx/759716fc-82db-4be4-bc4a-0e18ab022edb.html

    So actually it turns out that most of my TRV's and pretty much every one i've ever seen in somebodies house is actually mounted wrong, horizontal is better, worst case is vertical on the flow.

    I'm getting a remote sensor head TRV from eBay to have a play with.


    That makes a lot of sense but that article says "Today’s most popular TRVs for fully-pumped (2-pipe) domestic systems are 15mm bi-directional, reversible, angle types with built-in (integral) sensors. These allow total installation flexibility, i.e. sensor mounted vertically or horizontally in either flow or return."
    • CommentAuthorringi
    • CommentTimeMar 8th 2015
     
    Yes, but you want the TRV to measure the air temp in the room, not just above a hot pipe.
    • CommentAuthorPaul_B
    • CommentTimeMar 8th 2015
     
    Would this not suggest a better method, although more expensive, is a wireless room temperature stat connected to a wireless eTRV head? Thereby you are getting a much better indication of room temperature and the TRV is probably better controlled with an electronic head than the standard "mechanical" wax system with the arbitrary 1 - 5 scale?

    Paqul
    • CommentAuthorgravelld
    • CommentTimeMar 8th 2015 edited
     
    In the case of Heat Genius the boiler interlock is controlled by the room thermostats but the TRVs are 'autonomous'; they will shut down themselves if they feel they are too hot and stay open otherwise. This leads to a couple of downsides. If there is not decent air flow they will shut down early and the room won't reach temp. If the room has reached temp but the TRV disagrees and other rads are calling for heat, the rad will still get it.

    I think that's because they are reusing Danfoss TRVs and it might be a limitation of the integration rather than by design.

    They are mechanical rather than wax.

    Did OpenTRV ever go anywhere?
    • CommentAuthorringi
    • CommentTimeMar 8th 2015
     
    The first thing to do as run the boiler flow as cool as you can, therefore it takes longer for the rooms to heat up and the system is a lot more stable.
    • CommentAuthorEd Davies
    • CommentTimeMar 8th 2015
     
    The OpenTRV wiki looks a bit cobwebby but Damon's page has minor updates for earlier this year so there's clearly still some life in the project.
    • CommentAuthorSeret
    • CommentTimeMar 9th 2015
     
    I looked at OpenTRV, but their system is a bit idiosyncratic and won't be a good fit for everybody IMO. Looks like a case of some people scratching their own itch rather than trying to produce a product for the general market.
    •  
      CommentAuthorDamonHD
    • CommentTimeMar 9th 2015 edited
     
    OK, you lure me in for a short comment.

    Yes, we're still alive and trying to get a production engineered item ready for the market this coming winter; should have been 6 months ago but that's life.

    Intrigued to know what is "idiosyncratic" about it!

    Rgds

    Damon
    • CommentAuthorSeret
    • CommentTimeMar 9th 2015
     
    Posted By: DamonHD
    Intrigued to know what is "idiosyncratic" about it!


    Welcome back! Last time I looked at it wasn't time-based, and instead it tried to detect occupancy by measuring the level of lighting in the room (the assumption being lights on = people in room). If I've got that right that's a pretty unusual approach, you have to admit.
    •  
      CommentAuthorDamonHD
    • CommentTimeMar 9th 2015 edited
     
    It is possible in the current version to set two simple timed programmes per device: I use them to ensure that my kids' bedrooms are warm at night and that the kitchen is warm first thing in the morning, but yes this device is primarily meant to be hands off and occupancy driven. We happen to use ambient light levels as one way of detecting occupancy.

    If you don't get fixated on the current mechanism for detecting occupancy then what we are attempting to achieve is pretty standard in modern commercial buildings; occupancy and zoning, with up to 50% energy savings.

    Rgds

    Damon
    •  
      CommentAuthorSteamyTea
    • CommentTimeMar 9th 2015
     
    If you sense occupancy by any mean, and assuming that occupancy changes relatively frequently e.g. sometimes 1 person, sometimes 3, sometimes for 7 hours, sometimes for 18 hours, and sometimes for an hour or less, then will this not change the power that has to be delivered to the room.
    By this I mean that if a room is unoccupied and therefore unheated for say 15 hours, then you need to get it up to temperature pretty quickly, so you need a large heater, then say that same room is unoccupied for 6 hours and occupied for 18 hours, then a smaller heater.
    Won't this start to affect the overall efficiency of the system? Especially in old and leaky houses.
    •  
      CommentAuthorDamonHD
    • CommentTimeMar 9th 2015 edited
     
    With OpenTRV there is nothing to stop you manually adjusting the target temperature at the valve in the way that a small proportion of householders willingly do: that will give the best results with some thought.

    But the vast majority want to switch the heating on in October and off in April and not touch it otherwise.

    It's when rooms are left unoccupied for many hours at a time that occupancy sensing can help, setting back the target temperature a limited amount depending on user's desired comfort level and expected near-future occupancy.

    We're NOT targeting UFH or anything else with a very long thermal time constant.

    Rgds

    Damon
    • CommentAuthorSeret
    • CommentTimeMar 9th 2015
     
    Given that we're specifically talking about bedrooms Damon how would OpenTRV work? Presumably during the daytime the occupancy sensing isn't active? So would the bedroom be heated during the day by default? Any way to override that automatically?
   
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