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Zone valves why and how do they work?

Discussion in 'Electrics UK' started by ericmark, 14 Aug 2019.

  1. ericmark

    ericmark

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    Really looking at the post Hive Wiring but don't want to hijack the post.

    But we have just bought a new house to us, so have just finished visiting house with the idea of moving, and we looked at a few new builds, it seems many now have the heating zoned, dormitory and living area, well I say that, often the bathroom seems to be included in dormitory area, and for us of the 4 bedrooms upstairs only two used as bedrooms, one is an office and one a craft room, so would need moving from dormitory to living area. Seems to be a rather short sighted idea.

    However out of interest how are they plumbed and wired? I can see the idea of a programmer which selects dormitory and living area areas and uses different times, however how does it turn the boiler off when not required? Most motorised valves have micro switches, but switching between two modulating thermostats just can't work out how it is done.

    If using return water to control the boiler modulation, you need some thing to stop it cycling, the traditional method is a thermostat in a room normally kept cool with no outside door or alternative form of heating normally on ground floor as heat rises, so ground floor normally coolest.

    Pre modulating boiler it would have been easy, programmer feeds thermostat, thermostat feeds motorised valve and motorised valve feeds boiler, but since the room temperature is now controlled with a TRV that will no longer work, so how is it done. Do they simply pretend it's not a modulating boiler and keep switching it off/on?
     
  2. stem

    stem

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    The sudden arrival of multiple zones in new builds is down to the arrival of Part L of the building regulations in 2010 that stipulates different zones for the living areas and sleeping areas. But what constitutes a sleeping area? I find myself in the same position as you and use a bedroom as an office. Fortunately my house is much older so just has the one heating zone.

    Honeywell have produced a data sheet that gives a summary and provides details on the wiring; you can find it here.
     
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  3. bernardgreen

    bernardgreen

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    They should live in a old cottage where zoning is nigh on impossible. Many cottages are just a single zone as there is no effective thermal separation between living areas and sleeping areas.

    Part L might work for a convential family living a conventional lifestyle in a conventional new build house.
     
  4. stem

    stem

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    Indeed, quite impractical! like I said:
     
  5. ericmark

    ericmark

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    OK my house is not new, I have 9 potential zones (Not including granny flat) each with it's own programmable TRV head, in real terms 4 of the heads are linked to the wall thermostat so really that is one zone, so in real terms 6 zones, every radiator has a potential of having a TRV fitted with a motor in the head, so it is a motorised valve, with a program that controls what temperature it is set to at different times of day, the heads start at £10, the only down side, is the TRV motorised valve does not have micro switches built in which can in turn tell boiler when to fire up.

    The Honeywell system will work with an oil boiler that is not modulating, however it is clearly not designed for a modulating boiler, it may tick the Part L box, but is not fit for for the job. Honeywell make EvoHome, now that would do the job, and not a single non radiator mounted motorised valve is used, except maybe for DHW.
     
  6. reds42

    reds42

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    Fitted my parents house with the Drayton Wiser system. That has individual motorised radiator heads so each room can be controlled separately with their own timings and temperatures. The original system programmer is replaced with a control unit that communicates with the radiator valves by radio and can turn the boiler on/off - if a radiator valve calls for heat the control unit fires up the boiler.

    Seems to work well and has saved them a lot of money on gas, but radio reception through thick walls or big distances can mean the need for smart plugs to act as repeaters for the radio signals to improve range.
     
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  7. SimonH2

    SimonH2

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    Dragging "plumbers" into the 20th century now we're nearly 19 years into the 21st century :rolleyes:

    It's what my parents have had in their houses since, umm, the 1980s :whistle: One of the first things dad did when we moved into a newbuild in 1969 was to fit a wall stat (so still one zone) - the guy who serviced the oil boiler would comment on how clean it was due to the lack of short cycling.
    And one of our neighbours back then had a custom heating system installed - stat and zone valve in each room. Bet a later owner had that ripped out.

    EDIT:
    Fro Eric, how they work is quite simple (in an S-Plan system, using 2 port valves). "Whatever controls are there" control power to the motor in the valve head, when power is on the motor drives the valve open, when power is off it closes under spring power. When at least partly open (exactly how far varies with make), a microswitch closes. The switches can be paralleled to control the boiler & pump.
    In simple systems, the switches control both the power to the pump and power (or demand input) to the boiler. Often the boiler controls the pump and includes a run-on feature - in which case a bypass valve is needed to avoid dead-heading the pump when all the zone valves are closed (it's also usually needed when TRVs are present but for slightly different reasons).
    Plumbing wise, each valve simply controls the flow through part of the system - as many valves as you want zones. So one valve controls flow to downstairs rads, another to upstairs rads, a third to the hot water cylinder coil. As above, you could have one per room if you wanted - but these days it's easier to use electronic TRV heads for room-by-room control.

    I di find myself wondering what the inspector would say if presented with a system with no zones valves, no bypass valve, but a system with a fully modulating pump and electronic TRV heads on every radiator to give individual room control of temperature/time ? System far better than Part L requires, but not actually in compliance with what is on that fact sheet :whistle:
     
    Last edited: 16 Aug 2019
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  8. ericmark

    ericmark

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    This was what I expected to happen, but does not actually work, as to why is a big question. I have a box full of TRV's waiting to be fitted, that may improve the situation, but as it stands when the boiler fires to heat the domestic hot water, some times I find radiators warm. Theory they should not get warm, the pump is not used with DHW and the TRV should be closed, but they do get warm, to test turned off the maintenance valve on the pump, with it closed the radiators don't get warm, so I have two motorised valves wired up ready for plumber to fit. Main reason for the motorised valve is to stop radiators getting warm in the summer.

    If the same radiator always got warm, I would blame the TRV, I would assume not shutting fully, but it is random which radiator gets warm, the valves open fully at 12 noon Saturday, that is when the TRV's exercise, however not at this time or day when the got warm.

    All the electronic TRV's you hear from time to time adjusting, but at moment set to 16°C at night and 17°C in the day and in last month the temperature in house has never dropped below 20°C so they should have only opened when scheduled to exercise.

    I suppose which an electronic head a TRV is a zone valve or a motorised valve, but with a wax head, or actuator using heat rather than a motor then technically it's not a motorised valve as it does not have a motor. However the TRV is gradual as it opens or closes, so it modulates the heat output from a radiator, but the traditional motorised valve has two or three set positions, I know in theory one could send pulses to the valve to part open it, but as far as I am aware they are used either open or closed with a S plan.

    So I can see how a motorised valve is turned on/off at different times of the day. But can't see how the motorised valve can be controlled by a thermostat, as no way will every room will be at the same temperature unless the TRV can take control.
     
  9. JohnW2

    JohnW2

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    Just as Part P of the Building Regs is just one sentence that says nothing specific, Part L of the regs is very brief and extremely vague, leaving almost all detail interpretation to the discretion of the reader (e.g. as regards what is "reasonable provision", "energy efficient", "effective controls", "reasonable in the circumstances" etc.). It certainly says nothing as specific as the requirement for zoning such as you mention. I presume you are talking about Approved Document L, which is, of course, 'guidance' - not 'requirements'/'law'.

    As you presumably know, this (and only this) is Part L (i.e. 'the Law) ...

    upload_2019-8-17_0-53-23.png

    Kind Regards, John
     
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  10. SimonH2

    SimonH2

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    The motorised valves are no different to a "whole house" system - placement of the stat is always a compromise.
    With electronic TRVs, you could use feedback from the heads to opetate the zone valves - though you might find that you havecthe same problem. Ie, if a head is calling for heat (by not shutting the valve) then is equally likely to call for the valve to be open.
    As to why ... maybe they have a PID algorithm and the rate of change is such that they occasionally open a little. Also, while you say "the temp has never dropped below ...", is that measured at the TRV head ? I know there's been some cool periods lately, and TRVs are typically close to the floor where they'd be affected by cold drafts.
     
  11. ericmark

    ericmark

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    The Energenie thermostat reports both the target and current temperature quick check today entry level floor is 18 and 19 deg C and target 17 deg C. However the cheaper Bluetooth TRV's don't report current temperature, 61dmtMm13BL.jpg there is a display on the valve, however hard to read in place, 510VC3xAYwL.jpg so phone it what I use to set valve, Screenshot_20190725-112626_calor BT.jpg so the valve in real terms is set then forgot, once the motorised valve is fitted I will set higher temperatures but set low so I do not get thermo syphon when the DHW is heated. Away from house I can access far less, however don't really need to access anything when not home so this MiHome_all.jpg is the away from home report, not sure why I would ever switch off top one My Devices, the next Hallway is the Nest thermostat on the wall, next 4 are the 3 entry floor rooms, two radiators in living room, and they are set to auto follow Nest, flat heating is no more, it was a socket that supplied the pump in flat as with next 2 the sockets and light switch have not been fitted in this house, sockets built into an extension lead. The last one Plug in Swit is a switch and monitor which has the portable air conditioner plugged into it only a small one as you can see only uses 639 watts when running, this is about the only item on the list which I will access when not at home, and get the room cool for when I arrive home, and it is in fire place venting up the chimney so well away from the radiators, so although radiators show 23 degs C the centre of room far cooler.

    Although I am able to turn central heating off/on away from home, I have never done so, I will look to see temperatures of the three rooms, but only to see if I need to switch on the AC before returning, not the heating, the 5 bluetooth TRV heads are set and forgotten, and since never done a winter with bluetooth heads don't know how good or bad they are, I have run a couple of winters with the wifi controls.
     
  12. reds42

    reds42

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    Maybe the valves arn't quite pushing the pin on your radiator valves all the way down to achieve turning the radiator off completely?

    Could be a fitting issue rather than control system.

    The wiser ones I fitted had a selection of different collars to use for different valves, and after fitting they had a calibration process to run on each valve.
     
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