Good Afternoon, I’m hoping that someone can help me with regards to the below scenario that I am faced with. Customer has a Worcester Greenstar 30 CDi Classic system gas fired condensing boiler this has a facia mounted programmer and a wireless thermostat. Plumber has installed underfloor heating in new extension – wiring for this add on straight forward enough until the connection of the switch wire feed to boiler. Spoke to Worcester technical who informed me that the system would have to be zoned (i.e. changed to an s-plan). Plumber has now fitted a 2 port valve to the existing heating system. I have wired S-plan systems before and understand that the orange wire from the existing 2 port valve would join with my switch wire from the underfloor heating controls to fire up the boiler. What I need to know is with this arrangement can the facia mounted programmer still be used to control the existing system with the wireless stat or do I have to install an external programmer and room stat? New underfloor heating zone has its own programmer and room stat wired into its control panel. Hot water is controlled as before via facia mounted programmer and cylinder stat and unaffected. Thanks in Advance
yes you could retain it, but you'll have to ensure that a call for heat from the UFH isn't reliant on the existing programmer/stat also calling - if it's a built in controller that's plugged directly into the control PCB you might have some practical issues ensuring that - so it might be easier just to use any external control connections that should be available within the boiler or at the wiring centre - you need a logical OR control a call for heat from zone one OR zone two will fire the boiler
this might help - it's for a single programmer and 3 valves but you'll get the gist if you have a separate UFH prog/stat and 2 valves, just common oranges which is the call, brown to your UFH stat/programmer output
Thanks for the reply, the esisting controller is plugged directly into the PCB - so can't see how I can utilise this other than leaving this to just control the DHW? The only external control outputs on the boiler are Ls & Ns which I take it would be my feeds to the wiring centre and the Lr which would be my return to fire up the boiler. This then would mean that i would need to fit a external programmer, would that be correct?
that's right, but find the WB circuit diagram in the maintenance manual (near the back) as you might find they provide the external connection on the correct side of the controls for this application I.E. after the timer edit: it's on page 29, but not the entire circuit diagram just a schematic showing LrLsLnLN PCB connections
Thanks for all your help on this one - am i then right in saying that if i leave the L & N supply as is - this will control DHW via cylinder stat and facia timer (there has been no altrations to this part of the system) and use external controls Lr Ls Ln to feed to an S-Plan Plus system as per your drawing (minus DHW Bit) and install external programmer to control both heating zones?
that would work - don't forget to take your L&N for the external controls from the boiler - so you keep the single point of isolation where did the plumber install the valve, was it just the one valve ? and is there a manifold with it's own pump ?
the 2 port valve was fitted to the existing system (currently on manual open) the underfloor heating has it's manifold, pump & thermostat wired into own wiring centre hence taking the switch wire from this to fire up the boiler to join with the orange wire from the new valve to go to Lr on the boiler?
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