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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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    • CommentAuthorNRDigger
    • CommentTimeSep 6th 2020
     
    Hi all,
    As noted in another thread we are refurbishing our large 3 bed house.

    I have a specific question about zoning in central heating.

    Our proposed plan currently is to either relocate our existing boiler or replace it whilst we are at it.

    Currently all rads are on the same zone - main runs are 22mm with 15mm branches.

    Based on the current rads (some of which I've upgraded to make a larger system to allow a future ASHP), in total I estimated a 21kw heating demand/output at 50'c and approx 27-28kw heating demand at 60'c flow temp.

    Currently all rads have standard TRVs on. We have a single main thermostat in the living room.

    I would like to have a system whereby upstairs rads are heated in the morning to a lower temperature and downstairs to a higher temperature for more of the day. COVID has meant changes to working practices that will likely become long term and so the house will be largely daytime occupied.

    I have looked at this thread: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16213&page=1#Item_0 and note the recommendation for Radbots. These seem an excellent idea except I'm concerned my main thermostat will cause issues, i.e. the Radbots will turn the radiator on when there is no call to heat from the boiler.

    I would have the option, given the current access to floorboards (!) to physically separate the upstairs/downstairs radiator runs and create two physically separate zones, but clearly if I can get a system whereby TRVs, central thermostat and boiler all talk to each other, that would be a lot simpler. Does such a system exist?

    All of this, of course, with the view that at some point after we have worked through 'Project Insulation', an ASHP is likely to be going in...
    •  
      CommentAuthorDamonHD
    • CommentTimeSep 6th 2020
     
    Radbots can't cause any new issues over your existing TRVs in the form they are currently being sold: either could want to call for heat but without direct boiler control nothing will happen if the boiler is not already running.

    (You shouldn't have any form of TRV, eg not mechanical nor Radbot, in the space that you have your house stat.)

    Rgds

    Damon
    • CommentAuthorNRDigger
    • CommentTimeSep 6th 2020
     
    Posted By: DamonHDRadbots can't cause any new issues over your existing TRVs in the form they are currently being sold: either could want to call for heat but without direct boiler control nothing will happen if the boiler is not already running.

    (You shouldn't have any form of TRV, eg not mechanical nor Radbot, in the space that you have your house stat.)

    Rgds

    Damon


    Thanks Damon, yes, that makes sense! So I guess if I asked the question is there a way to use a Radbot or similar device that worked together with a central thermostat or controller so that the demand for heat was directed by the individual rads/radbots directly?

    (And good point about the TRVs in the room with the central stat :) )
  1.  
    Posted By: DamonHD
    (You shouldn't have any form of TRV, eg not mechanical nor Radbot, in the space that you have your house stat.)


    Posted By: NRDigger(And good point about the TRVs in the room with the central stat :) )

    If you do have a TRV in the room with the central stat, turn the TRV up to max.
    •  
      CommentAuthordjh
    • CommentTimeSep 6th 2020
     
    Thankfully, I no longer have to worry about such things as radiators, but since you already have the option to separate the upper and lower floor's circulation, I would tend to do that and add controllable zone valves. I think you'll find that more than one zone is 'encouraged' by current building regs, though whether you can claim any useful brownie points is beyond my expertise.
    • CommentAuthorphiledge
    • CommentTimeSep 6th 2020
     
    We have a hard zoned set up with the upstairs split from downstairs and the downstairs in 2 separate zones. Each zone has its own programable stat switching a 2 port zone valve. Any zone valve open fires up the boiler if the WBS isnt hot, otherwise WBS does the heating . Bathroom towel rails are piped on a separate zone without any control so they're on if any zone is being heated.

    Had a quick look at Radbots and Im not sure they would be suitable for upstairs heating where you want the heating on before you get up or go to bed and not likely to be switching lights on to trigger the Radbots. Maybe Im not understanding how they work??
    •  
      CommentAuthorDamonHD
    • CommentTimeSep 7th 2020 edited
     
    (Mods, if you feel this is commercial, please just bin it.)

    In my home I run Radbot with a boiler control and we no longer use the house stat, so the boiler runs if one or more Radbots call for heat. That Radbot boiler control is not available for domestic sale however, because Radbot's message is all about keeping things very simple.

    So it can be done, and works nicely, but that doesn't necessarily help you much.

    Feel free to follow up with a whisper or in email if you wish.

    Rgds

    Damon

    PS. A relatively smart modern boiler or HP should (I would hope!) monitor return temperatures and stop trying to heat if there is little or no actual demand, eg because all valves (mechanical TRVs, Radbots, whatever) outside the area with your house stat are closed.
    • CommentAuthorrevor
    • CommentTimeSep 7th 2020
     
    How are you heating DHW? if you are also doing DHW from the boiler I would do 3 zones GF 1st floor and DHW
    Get a programmer that you can programme different times from each zone. Gives you a very flexible system. Think they must exist in 1982 I did 4 zones with 4 channel Sangamo timer, 3 stats 2 room and one cylinder stat. On the cylinder if you go to control DHW this zone valve actuator is a different one cant recall exact detail but has an extra wire for the micro switch forget exactly how it is wired but it is a conventional tried and trusted simple logic.You can keep the rad valves as they are but fit a bypass between the flow and the return at the boiler and a pressure relief valve in case all rad valve shut off before room stat senses to close zone valve and boiler. Very simple and cheap to do timer likely to be the most costly single item.
    If you want to do a real good job plumb the cylinder in 28 mm pipe and the central heating also in 28 mm to where it splits between the GF and 1st floor.
  2.  
    In the morning we use all the rooms, except the lounge, but in the evening we use the lounge as well. So it makes sense to have the lounge on a separate zone to the rest of the house.

    The plumbers don't lay it out that way, so we tried a cheaper wireless system (Conrad fht) to program a separate time/temperature profile in the lounge radiators. It was fairly successful, perhaps a bit too noisy for bedrooms.
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