No Bypass Loop

Discussion in 'Plumbers' Talk' started by Andrew McConnell, Jan 5, 2018.

  1. Andrew McConnell

    Andrew McConnell New Member

    Good morning

    I have recently moved into a new property that was built in 2010. It has a Worcester Camry 25/32 Utility oil fired boiler fitted with external water storage.
    The configuration is S-plan (however the wiring is imaginative to say the least).

    The boiler is not wired for pump overrun. There is no separate feed to the pump - it is linked from the call for boiler 'Live' within the Worcester electronics box

    Recently I noticed the internal pump would continue to run after the programmer (Hive) would switch off.
    This turned out to be a faulty microswitch on the Honeywell 272848 2-port valve (CH).

    Looking at the pipework - the discharge from the pump is connected directly to the two port valves (CH & HW) with no bypass valve fitted in between, neither can I locate a bypass loop (For info the port valves are about 1mtr from the discharge of pump)

    Maybe Im missing something -

    Queries -
    1.When the pump remained on (due to micro switch) port valve shut, no return loop - should the pump not have tripped due to dead heading/overload?

    2.Should I have a bypass valve fitted after the pump and before the port valves?

    3.If I need to fit a bypass should I wire in a stat and run a cable to the pump for overrun ?


  2. nigel willson

    nigel willson Screwfix Select

    1/2 . It may have an internal bypass! I don’t know if it has . Look up ur boiler ,that will tell you.
    3. Pump overrun is controlled by the boiler, if it is equipped for that . Again look at boiler wiring diagrams.
  3. Andrew McConnell

    Andrew McConnell New Member

    Thanks for the reply Nigel
    I have checked my boiler Commissioning and Operation manual - noting about an internal bypass. However does state that an automatic bypass valve with at least 3mtr loop should be fitted - I guess that answers question 2 for me!

    No overrun facility within boiler or wiring centre. I was wondering if I should buy a timer and wire it in?
    I suppose there is no point until I get a a resolution on the bypass issue.
    Still confused how the pump was running with nowhere to pump it?
  4. nigel willson

    nigel willson Screwfix Select

    Does it show wiring of a pump overrun. If not ,it’s not required.
  5. Andrew McConnell

    Andrew McConnell New Member

    No wiring for over run - does state though if wiring centre (external JB) is fitted with overrun facility remove link and run a new cable in.
    NB Boiler Wiring is very basic. There are no PLC or PCB's associated with this boiler.
  6. nigel willson

    nigel willson Screwfix Select

    In which case you don’t need one for that reason. However if you have TRVs fitted you should have a bypass cos of all the trvs shut , no circulation.

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