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room stat location

Discussion in 'Plumbing and Central Heating' started by pmx_super, 16 Sep 2010.

  1. pmx_super

    pmx_super

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    The room stat for my CHS is currently in the hall. The hall radiator doesn't have a TRV, but all other rooms do.

    Unfortunately my hall radiator is oversized, so if I want to heat the rooms to a good temperature the stat in the hall has to be set to very high and I have to live with a hall that's like a sauna. Luckily the thermostat is wireless so I can easily reposition it and I was wondering what the best alternative location for it would be.

    I figured either:

    1) The living room - which never seems to warm up at the moment. It has appropriately sized radiators, so if I turn the 2 TRV's to max I'm guessing the room would operate effectively to control the house?

    or

    2) The first floor landing - this has no radiators, so when this is warm it's generally a pretty good sign that the rest of the house is warm. I guess it's primary heat source is the oversized hall rad downstairs though..

    Which sounds best, and what are the pitfalls with the best option?
     
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  3. pmx_super

    pmx_super

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    Of course I just realised that this won't stop my hall getting really hot...
     
  4. Richard C

    Richard C

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    What makes you think the hall rad is oversized, apart from the temperature being very high? Have you checked the rad size against the heat output required for your hall?
    Have you tried ballancing all the radiators in the system?
     
  5. Alfredo

    Alfredo

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    Well I'd probably suggest you put a TRV on the hall rad if its really boiling you, but yes balance the system first.

    I'd have though the common sense thing to do with the wireless stat is to try it in a number of different locations and find the one which suits you best. Its not as if you are going to trip anyone up on the cable is it :LOL:

    Alfredo
     
  6. D_Hailsham

    D_Hailsham

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    I had a similar situation to you. The hall rad was enormous as it was expected to heat the hall, two staircases and two landings of a three storey house. There was a fixed wall sat in the hall and TRVs on all the room rads. I balanced the system, but that did not stop the hall stat shutting the boiler off before the rooms reached temperature.

    I solved the problem by closing down the valve on the flow side of the hall rad a bit at a time, which reduced the rad output, until the required balance was obtained. The TRVs then shut off before the hall stat stopped the boiler.
     
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  7. vulcancontinental

    vulcancontinental

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    Exactly as above except I would turn the hall radiator off then open it a quarter of one rotation and see how you get on. If this is too much another quarter turn etc. You'll get to the same point.

    The top of the radiator will be just as hot as it ever was as hot water rises in the rad so don't be fooled by that; you're reducing the amount of water passing through when balancing not the temperature of the water.

    If there is a room cooler and at a more stable temperature than the hall you could try it there but generally the hall is a good place and site the stat away from the radiator, kitchen door, sunlight, and not on an external or garage wall.

    Do not put a radiator thermostat in the same room with the room thermostat.
     
  8. D_Hailsham

    D_Hailsham

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    ;)

    Reminds me of the family who go lost in a village. So they stopped the car and asked a passer-by for directions to their destination. He scratched his head, thought a minute and eventually said: "Well, if I was going there, I wouldn't start from here."
     
  9. vulcancontinental

    vulcancontinental

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    You're right. It may be idiosincratic but I know where 'off' is while fully open can be many places.

    I find some rad valves will turn two complete rotations and some four or five. All the useful effect I find when balancing is in the first turn and a half as they're not proportionate (well domestic ones usually aren't). You could therefore be turning the rad valve down many quarter turns before you get to the point of effect if you start from fully open.

    Like the man said "Lady, I just don't have the time."

    :)
     
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  11. DP

    DP

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    My answer to the dilemma would be fit the transmitter in a room that is always cold and remove the TRV head. instal TRV on hall rad. Now you will have an installation where the 'warm' room rads shut down when ambient temperature reached, and cold room when heated, shuts the boiler down
     
  12. pmx_super

    pmx_super

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    That's interesting, I didn't know I could do that. I take it the flow side is the "in" side?
     
  13. Richard C

    Richard C

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    Rather than doing it hit & miss, get yourself a couple of cheap digital thermometers & balance the whole system properly;
    http://www.diyfixit.co.uk/central-heating/balancing-a-central-heating-system.html

    You will be amazed at the difference it makes, your heating system will actually work as it’s supposed to & be more efficient.
     
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  14. pmx_super

    pmx_super

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    You read my mind - I was about to ask for a how-to guide on balancing a system!
     
  15. D_Hailsham

    D_Hailsham

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    I agree. I've seen balancing instructions, on this site, saying that all you have to do is turn the LS valve down two turns on the ones nearest the boiler, one turn for the intermediates and leave the furthest rads full open!

    Balancing will not help if the rad is oversized for the area in which it is installed.

    Also see How to balance a CH system. It's more detailed than the link you were given earlier.
     
  16. pmx_super

    pmx_super

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    That is better, thanks. Just one clarification - should I aim to get the drop across each rad equal to the manufacturer specified drop at the boiler or the actual drop at the boiler that I've achieved?

    (PS - Closing the inlet valve on the hall rad has already helped considerably, so thanks again for that tip. I expect diminishing returns the colder it is outside though and hence the longer I need the rads on to bring house up to temp.)
     
  17. D_Hailsham

    D_Hailsham

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    It's best if all drops are the same. The drops quoted by boiler and rad manufacturers are achieved in ideal conditions in laboratories. The drop across a boiler will depend on many factors, including pump speed setting. As most pumps only have three fixed speeds, it's virtually impossible to achieve exactly the drop that the manufacturer quotes. In any case the drop is also influenced by the weather - the colder it is outside the more heat the rad will give out, so the greater the drop, and vice versa.

    If you fit a thermostat with "Optimum Start", it automatically adjusts the on time according to overnight drop in temperature. Instead of setting the time you want the boiler to come on, you set the time you want to be up to temperature, e.g when you get up.

    There has been speculation whether this actually worked, so I rigged up a timing device to check. It only came into operation last Friday, when we put the heating on. So far the results have been:

    Sat - 48 minutes early
    Sun - 40 minutes early
    Mon - 30 minutes later (house was already up to temperature).

    I'm going to monitor it for the whole heating season.
     
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