extending a Y plan

Discussion in 'Electricians' Talk' started by steve CF, Jan 13, 2010.

  1. steve CF

    steve CF New Member

    Existing heating system is a standard Y plan

    plumber wants to add under floor heating so it can be controlled independently of the central heating.

    he has installed a standard 2 port valve and room thermostat and a separate pump just for the floor heating.

    problem im faced with is getting the floor heating to operate without the central heating, obviously i cant just connect the output from the two port valve to the to the boiler as its also bringing the central heating on . it obviously back feeding through the orange wire to the 3 port valve and operating the central heating,

    any ideas ?
     
  2. ashtreefarm

    ashtreefarm New Member

    Hi, speak to the plumber and change the system to an S plan by removing the 3 way valve and use individual zone valves (each zone valve will have its own thermostat).
    This will provide greater control of the system, you could even separtate the upstairs circuit with a separate timer, therefore reducing heating costs further.
    Zone 1 Cylinger, Zone 2 Downstairs Heating, Zone 3 Upsatirs Heating, Zone 4 Underfloor Heating etc.
    This way would have removed the need for the extra pump. Cheers
     
  3. oscar21

    oscar21 New Member

    I dont see why connecting the new valve to the old one would operate the central heating as the orange wire only connects to the micro switch in the valve and not the actuator. The problem I see doing it this was is with the original pump as it is probably connected to the pump connections in the boiler and would operate every time the boiler was on.

    I concur about changing the 3 port to 2 two ports, but also fitting an extra pump so each zone valve has its own pump. So you would end up with 3 two ports and 3 pumps, one for each zone, the pumps would be connected to the brown of each valve and not the orange/grey.

    The only other way would be to use a relay or two to keep the original single pump.
     
  4. Star-Delta

    Star-Delta Member

    steve CF

    Install enclosure and SPDT relay :-

    Connect boiler feed to common terminal.
    Connect central heating switchwire ( orange ) to N/C terminal.
    Connect underfloor heating switchwire ( orange ) to N/O terminal.
    Use underfloor heating switchwire ( orange ) to power relay coil.

     
  5. Lectrician

    Lectrician Screwfix Select

    You cannot use a mid position valve and a two port valve.

    The mid position valve does not spring return to CH off all the time depending on which turned off first. This can mean if you then turn the new 2 port on, water will still be able to flow through the open rad port on the mid.
     
  6. steve CF

    steve CF New Member

    Lectrician your spot on mate.

    as you say when the boiler is running the 3 port valve will not close so water will flow either to central heating or cylinder tank.

    told plumber he needs to convert the system to a s plan with 3 separate 2 port valves.

    only problem i have now is the underfloor heating came as a kit witch has a built in pump. how do two pumps you use the pump feed from the boiler which has pump over run facility to power 2 separate pumps whiout having them both running.
     
  7. Stoday

    Stoday New Member

    Yes, Lectrician's spot on.

    The underfloor heating pump pumps it's own water circuit, which operates at a lower temperature (~35°C) than the water circuit through the radiators and HW cylinder.

    UFH water circuit comprises the coils, wax operated valves and manifold. The feed into the manifold is via a modulating valve that maintains the (lower) manifold temperature. The UFH pump operates only when one or more of the wax valves is open.
     
  8. Lectrician

    Lectrician Screwfix Select

    The UFH will have a control centre for the pump, wax capsules, room stats and time control. This control will run the UFH heating pump as required.

    There will be a pari of volt free contacts on the UFH controller which is used to fire the boiler. When used in an existing system you use this pair of volt free contacts to open the new UFH valve, the valve then firing the boiler.
     
  9. oscar21

    oscar21 New Member

    I think the problem is, the original single pump will be wired to the pump connections on the boiler and whenever the boiler is fired this pump will start, even if the CH and DHW zone valves are in the shut position.

    I think the only way to do it properly is to replace the 3 way valve with 2 x 2 ports and have a pump for each valve, wired to the brown of the zone valve so the pump starts whenever the valve starts to open. The orange and grey pair are connected together along with the boiler terminals on the UHF control panel. The only down side I can see to this is there would no longer be a pump overun.
     
  10. oscar21

    oscar21 New Member

    Thinking about it, it shouldn't matter that the original pump runs as it will just pump round the UFH instead.
     
  11. oscar21

    oscar21 New Member

    Lec, I undrstand what you have said, but on the UFH systems I have connected up there was a separate terminal on the UFH control panel for the zone valve connections, including the grey and orange. If the zone valve did not open then the boiler contacts would not fire the boiler. Why not just connect the valve up as it should be and wire the volt free contacts across the gray/orange pairs of the other valves.

    On a side note I thought a 3 port valve was always open to the DHW and when the white wire was energized it opened to the CH as well, operating the microswitch to turn the boiler on.
    I appreciate the older 6 wire ones were able to shut off completely.
     
  12. oscar21

    oscar21 New Member

  13. Stoday

    Stoday New Member

    No, no no. You do not need a pump for each valve.

    The DHW stat controls the 2-port cylinder valve; the room thermostat controls the 2-port valve to the radiators, the UFH controller the 2-port valve to the UFH manifold (via the modulating valve).

    The boiler and its pump are turned on when any one or more of the three 2-port valves opens. The boiler turns off when all three 2-port valves start to close, the pump turns off after all three 2-port valves have closed.

    The thermostats in the UFH zones control the wax valves on the UFH manifold. The pump operates when one or more of the wax valves is open. The modulating valve allows hot water from the main circuit to flow into the manifold to maintain a temperature of ~35°C. The UFH controller opens the 2-port valve for the UFH.



    items: 1) the DHW stat, 2) the room stat for the radiators and 3) the UFH controller.

    On operation
     
  14. Stoday

    Stoday New Member

    That lot got mixed up somehow. I was replying to oscar21's 6.55 post. Mine should read:

    You do not need a pump for each valve.

    The DHW stat controls the 2-port cylinder valve; the room thermostat controls the 2-port valve to the radiators, the UFH controller the 2-port valve to the UFH manifold (via the modulating valve).

    The boiler and its pump are turned on when any one or more of the three 2-port valves open. The boiler turns off when all three 2-port valves start to close, the pump turns off after all three 2-port valves have closed.

    The thermostats in the UFH zones control the wax valves on the UFH manifold. The pump operates when one or more of the wax valves is open. The modulating valve allows hot water from the main circuit to flow into the manifold to maintain a temperature of ~35°C. The UFH controller opens the 2-port valve for the UFH.

    You can see from the Y-plan schematic that it can't be used for UFH and rads and DHW.
     
  15. oscar21

    oscar21 New Member

    No, no no. You do not need a pump for each valve.i>

    Correct, thats why I posted again right away, I was just thinking that the UFH has its own pump and the original one was not needed.
     
  16. Lectrician

    Lectrician Screwfix Select

    What I said.... ;)

    1 Boiler pump is fine for the three 'cicuits'. It needs to run when any of the 3 zone valves open (with boiler too).

    UF heating pump is completely seperate and switched via the UF heating wiring centre. The UF heating pump circulates the UF water, but the boiler pump still needs to pump to get the water to the manifold.
     

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