Are Hall radiators too large?

Discussion in 'Plumbers' Talk' started by Granfernewtown20, Jan 22, 2023.

  1. Granfernewtown20

    Granfernewtown20 Active Member

    When I moved into my current house I found that I couldn't get some of my TRV controlled rooms up to the required temperature. Eventually I realised that this was because the non- TRV radiator in the hall (plus stairs and landing) where the wall thermostat was fitted was much too large and was turning off the heating too soon. So when I overhauled the heating system (changing from a back boiler to a modern condensing one) I took the opportunity to replace the radiators with modern ones. This meant I was able to use double radiators in the problem rooms, sometimes smaller than before, but I DECREASED the output of the one in the hall so that it would take LONGER to heat that volume and allow the other room radiators to do their job properly before the thermostat turned the heating off.
    Since I did that I've come across a number of instances where the same problem occurs in even modern installations. I get the impression that TOO LARGE radiators are being specified for wall thermostat controlled areas because of their volume. My solution of replacing them with lower output ones will solve the problem.....it doesn't cost any more to heat a volume slower with a lower heat output rad than quickly with a higher one but it gives the other rads time to do their work and control properly with their TRVs.
    Am I alone in thinking this.....or have others had this problem and solved it the same way?
    Incidentally, I am not a plumber or a heating engineer, just a competent DIYer.
     
  2. Muzungu

    Muzungu Screwfix Select

    Have you balanced the system? In your situation reduced the flow through the hall radiator using the lockshield valve.
     
  3. halalooyer

    halalooyer New Member

    Your logic is correct, but it used to be achieved slightly differently, the room stat would always be located in the hallway and that room would have the lowest heat demand in the house
     
  4. The Happy Builder

    The Happy Builder Screwfix Select

    Move the room thermostat to the main living room, swap the TRV in that room for the valve in the hall or simply turn the TRV on full in the living room and turn the valve in the hall to reduce the flow.

    Either way move the thermostat, I’d recommend a battery powered thermostat on a stand that is moveable.
     
    Tilt likes this.
  5. Tilt

    Tilt Screwfix Select

    Makes no sense to me to have a thermostat in the hallway

    Unless you live in a house that you like to keep all the rooms like an oven, and have very deep pockets ........ and you don't care about the planet, either.

    Room thermostat in the Living Room with one of these (or this) radiator(s) without a TRV.

    Control all other room radiators with a TRV
     
  6. halalooyer

    halalooyer New Member

    Because you don't understand the principle behind the design
     
  7. Tilt

    Tilt Screwfix Select

    Then educate me ........ please.
     
  8. Alan22

    Alan22 Screwfix Select

    My thermostat is in the hall, if you close the livingroom door and watch Senegeti in your pants it's like actually being there.
     
    Tilt likes this.
  9. fred812

    fred812 Screwfix Select

    Used to have the same problem at our previous place where the stat was in the hall. Because the hall was so well protected ie storm porch (effectively two front doors) and no other outside walls, it was a warm area, we could turn the hall rad off and it would still remain warm. The only way to warm the rest of the house up was to crank the stat in the hall up to 22 or more.
    In our current house we have the stat in the lounge, the TRV in the lounge is set to max, and TRV's on all other rads set to whatever. The lounge in this house is a cooler room and lags the rest of the house slightly in warm up time (but is still satisfactory) which actually works really well, in that the rest of the house warms up nicely to the TRV setting and the lounge is regulated by the room stat.
     
  10. Granfernewtown20

    Granfernewtown20 Active Member

    Thanks for all input. Yes, I could have moved the stat to the Sitting Room and fitted a TRV in the hall. I opted for reducing the speed at which the hall heated simply because I didn't want to have to move the thermostat which would have involved a new run of cable and either wall chasing or surface ducting. Lazy, perhaps, but I was 83 at the time and wanted to keep the work down to a minimum...changing rads (had to because the ancient ones were sludged and wrong sizes) and pipework was a pain. At least all that was under floor or hidden in existing voids.
    On a happier note....all my new rads came from Screwfix with FREE TRVs and locksheilds, so got all my valves replaced with new as well.
     
    Last edited: Jan 22, 2023
  11. MGW

    MGW Screwfix Select

    The instructions say put the wall thermostat in a room kept cool (so it will not switch on heating when the day is likely a warm one) on the lower floor (as heat raises) where there is no alternative heating or door to outside.

    If your house has such a room great, but most homes don't, so if we put the wall thermostat in the hall, we have a problem, if the front door is opened we want a large radiator to recover, and if not opened a small radiator so it does not heat up too fast, we can to some extent adjust with the lock shield valve, but only real way around the problem is to fit a TRV in the hall.

    OK temperatures need carefully adjusting, specially since likely the TRV is lower than the wall thermostat, but aim is the TRV has at least started to close before the wall thermostat is activated.

    It does depend on the boiler to some extent, I know my mothers house worked spot on with TRV's and a modulating boiler (gas) but this house they do not work as well with a non modulating boiler (oil) but the whole idea with a modulating boiler is it only turns off on warm days, when less than the minimum output is required, normally less than 10 kW, on cooler days the TRV's control room temperature.

    But unless linked the TRV can't turn off the boiler on a warm day, so we use a wall thermostat to turn off boiler on a warm day.

    OK often we also use it to turn off heating at night and when we are not home, but if the rooms are not to set temperature then it does not really matter.

    I find the wall thermostat needs to be about 1 to 2 degrees higher than the TRV, and by carefully selecting the schedule of both the TRV and wall thermostat we can allow it to reheat better. So when I was not retired I would set first kitchen, then dinning room, then living room, then hall to heat up with around 10 minutes between each, then around 10 pm the wall thermostat would switch down in temperature then back up at 10:30 pm and the bedroom TRV's were set to higher temperature, the dip ensured the boiler ran to heat bedrooms.

    There are some rooms without programmable TRV heads, the bathroom, shower room and four rooms in the flat under the house, but the 9 programmable TRV's ensure the rooms are warm when required, the last lot fitted 2019 cost £15 each, so only real expense is I fit a new set of batteries every year, they will normally last two years, but I don't take the chance, 18 x AA batteries is not that much.

    Theory is open door and hall cools, both the TRV opens and wall thermostat turns on, but before the wall thermostat set point the TRV starts to close, so extending the time the boiler runs for.

    If you don't want to mess around setting the temperatures then get linked TRV heads, but I simple set the TRV and wall thermostat to work with each other.
     
  12. MGW

    MGW Screwfix Select

    You are correct, there is no real reason to have any wall thermostat, in an ideal world all the TRV's will be linked to a hub, which will tell the boiler to run if any room is cool, these EVO-home1.jpg for example, but we don't live in an ideal world, most central heating works with near enough engineering, we could put a wall thermostat in every room all wired in parallel, but that is a lot of wiring, and linked TRV heads are around £50 plus each, where you can get unlinked but still programmable for £15 each, and a programmable wall thermostat is around £35 where as a thermostat to link to TRV's is around £200, so to get a perfect system costs a lot of money.

    In theory plumbing fan assisted radiators in series instead of parallel would be best option, as they can heat the rooms far faster, and whole idea today is only to heat as and when required, also things like the iVector can be used to cool the room as well, using a reversible heat pump.

    But I did look at the building management system for the 5 speed iVector fan assisted radiator, and very quickly decided what I have is near enough.
     
  13. Tilt

    Tilt Screwfix Select

    Yes, typical flippant comment from a new 'member' ..........
     

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