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Bypass Valve Setting on a Mult-zone setup

Discussion in 'Plumbing and Central Heating' started by da3533, 26 Apr 2021.

  1. da3533

    da3533

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    Hello

    I am installing multi-zones on my central heating. I have a Vaillant Ecotec Pure 830...
    I want to fit in an auto bypass valve in case the pump continues to work after my zone valves are closed. Which setting on the bypass valve do I need to set? It has the following setting: 0.1,0.2,0.3,0.4

    [​IMG]

    I understand that I need to find my minimum flow requirement and pump curves, but I can't seem to find or work it out.

    Thanks
     
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  3. oldbutnotdead

    oldbutnotdead

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    The boiler is the heat generator so the only item requiring a bypass. Check the installation manual for required bypass setting, be warned you usually need a decent length pipe run between boiler and bypass (so that the water circulating can cool down a bit, which is the whole point). 0.2 bar is a common setting.
     
  4. da3533

    da3533

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    ok thanks.
    Instead of connecting the bypass from flow to return, I can just connect it from flow before the valve to after? so at least if the valves one-day breaks, at least the radiators will still operate.
     
  5. oldbutnotdead

    oldbutnotdead

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    Does your boiler require a bypass? How is the pump powered- if it is an oldschool system (thermostat controls motorised valve, pump only powered via microswitches in the valve) then the pump will never run unless 1 or more motorised valves are fully open.
    If your boiler requires a bypass then no, bridging one of the motorised valves is not adequate (if all rads on the circuit are off or trvs are all satisfied then there will be no circulation path). Check your boilers installation manual, note that a radiator without trvs is no longer acceptable as a bypass


    As a footnote, motorised valves are a fairly crude method of controlling your heating- have you considered wireless trvs and a more modern controller?
     
  6. da3533

    da3533

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    it is a new Vaillant Ecotec Pure 830 It is a combi boiler. We are wasting a lot of money heating the whole house during the nights. So kinda need to sort it out.
    I have two hives and two receivers, one for upstairs and one for downstairs. I will install two Drayton valves on both flow pipes connecting this to a wiring centre. The wiring centre will connect up all hive receivers corresponding terminals and off to the boiler. it is quite a straightforward setup. I am just curious to know how the boiler would cope if there are problems with the valves, i.e. not opening when it suppose to... So then figured I would need to install a bypass before all valves just in case.
     
  7. D_Hailsham

    D_Hailsham

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    Do you mean the Ecofit Pure 830?
     
  8. oldbutnotdead

    oldbutnotdead

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    It may not be that straightforward. At the moment (presumably) the Hive controllers are acting as timeclock and thermostat. Why not change the programmed on/off times and reduce the setback temperature initially.
    Second point- because of the circulation issue (and the pump usually being integral with the boiler in a combi) some modern boilers require that motorised zone valves are connected to the boiler so that the integrated controller can manage cool-down circulation (by leaving mvs open and pump running after a firing cycle).

    Do you have any sort of warranty on this boiler- replacing room stats with Hive or whatever is one thing, inserting additional valves into the system could void that warranty if they are not installed and controlled correctly and the system reconfigured to operate safely with them
    EDIT. A reread tells me you haven't installed the Hives yet. Usual setup would be one 2 channel receiver and 2 thermostats, you may struggle to control both Hive bases via the app.
    So currently you have a single channel controller and a room thermostat? As above, change the on/off times and reduce the overnight temperature to start with.
    A much less intrusive setup would involve Wiser or Tado or Honeywell wireless trvs and associated controller. Much lower odds of damaging anything, similar cost to fitting zone valves.
     
    Last edited: 26 Apr 2021
  9. da3533

    da3533

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    i have installed 1 heating hive and it works with the house heating system since 2018. you can control both single hives, my dads house came with both and he controls both single channels. 1 hub -> 2 recievers to 2 thermostats.
     
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  11. D_Hailsham

    D_Hailsham

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    A bypass is not intended as a stand-by, in case a motorized valve fails. Provided you buy a decent valve, e.g Honeywell (not an Asian look-a-like) you should get many years of life out of them.

    Your boiler does have an internal bypass, but it's mainly there to regulate the pump output. (See the installation manual, which should have been left by the installer.)

    An external auto-bypass only needs to operate when the boiler is running at minimum output, which is 6.3kW for the 830. The boiler is designed for a flow/return temperature difference of 20C. This is equivalent to a flow rate of 271 litres/hour. From the graph 30c on page 29 of the manual, this gives a pump head of 250mB which is the default setting.You have a large installation, so you may need to increase the internal bypass setting by turning the internal bypass clockwise, otherwise the ABV my never open.
     
  12. da3533

    da3533

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    I have already bought the Drayton ZA5
     
  13. da3533

    da3533

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    Also, i could run the bypass to my tower rail. TRVs are not needed for Tower rails. This way there is plenty of pipe run
     
  14. da3533

    da3533

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    Hello, Not sure where you had got your facts from but I am afraid you are incorrect. There are no struggles running both thermostats with Hive, this is how everyone sets these up. 1 Hive hub connects to multiple Hive enabled devices. I have just connected my upstairs hive. Now, on my APP, I have two devices, upstairs and downstairs. both can be separately controlled and scheduled independently.
     
  15. oldbutnotdead

    oldbutnotdead

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    That was me confusing receivers with hubs. AFAIK one hub per account, many devices can connect to a hub. Apologies for any confusion caused.
     
  16. oldbutnotdead

    oldbutnotdead

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    Long as there are no valves on the towel rail- or is the rail plumbed before your (to my mind ill-advised) motorised valves, in which case plumb bypass across the towel rail & you'll need a lockshield on the towel rail turned down quite low so you get heat in the rest of the house.
     
  17. ianmcd

    ianmcd

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    No that will just by-pass the valve , the by-pass goes between the flow and reurn pipes before the MVs, or as you ask you can connect your towel rail before any MV and that will do the same thing
     
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