Plumbing/controlling UFH/Rad system

[Besidethewye]

Just plumbing in the heating system.  

 

It's more complicated than I had hoped.  Two separate UFH systems and three radiators via another UFH manifold with three pumps so each can operate independently.  Thermostats brought back to two separate wiring centres.

 

Was recommended to use non return valves in the returns from each manifold to prevent unwanted circulation in any circuit that's not required.  This instead of two port valves to bring each circuit on.  Happy to do away with the two port valves if they are not needed in the interests of simplicity.

 

Two manifolds will use actuators with the inherent delay in opening valves - the plumber is suggesting that we fit a bypass valve so that as the actuators slowly open the pump is not pushing against closed valves but recirculating through the bypass over pressure valve.  The third manifold is always open - no actuators - so pump can switch on immediately and will flow with no problems.

 

Planning to take the always open circuit thermostat back to one wiring centre and use the boiler enable and discussed using the actuator switch to run the pump - talking to the supplier this would work direct but might put in a relay.

 

Just wondering whether it's worth having a time delay relay to hold starting the pumps to manifolds with actuators rather than letting the bypass valve take the strain.  

 

 

[ProDave]

Don't complicate it. Use the proper kit designed for the job.

 

Keep and use the 2 port valves (making the non return valves redundant)

 

Each manifold will be controlled by something presumably, e,g a time switch to say when that UFH system will be on?  So connect that time switch to control the manifold controller that each UFH manifold should have.

 

The manifold controller takes care of switching on the pump and the actuators when each zone calls for heat from it's thermostat and if no zone is calling for heat the pump will stop.  The manifold controller has a relay output contact that you use to energise the 2 port valve for that manifold.

 

Each 2 port valve has a switch contact. Connect all these in parallel to fire the boiler when any 2 port valve is open.

 

That is it.

 

If your heat source is an ASHP it may get more complcated as some ASHP's want to take over control of the 2 port valves so you have to alter the sequence of the wiring a bit.

[Besidethewye]

Dave - thanks for that.

 

It is an ASHP.

 

The wiring centres switch a pump and give the call for heat - but they don't incorporate a time delay to switch the pump on once the actuators have opened.  It was avoiding the pumps working against a closed circuit that was the reason to ask about time delay relays.

 

So the issue is whether a bypass pressure relief valve to allow the pump to circulate in the time that the actuators take to open is ok or whether at time delay relay makes more sense or whether we do both (or neither!).

 

The heat pump supplier recommended the non-return valves rather than the two port valves - apologies if adding the background just confused the issue. 

 

 

[ProDave]

The pump on the manifold will not get bothered by pumping into a short circuit for the time it takes the actuator to open (a couple of minutes usually)

 

An overall bypass as far away from the ASHP will stop the heat pump tripping on low flow while you wait for the actuators.

 

 

[Besidethewye]

Thanks again Dave - sounds like we should be ok!  The heat pump circulates to the buffer tank so should be fine and if the pumps are ok we should be good to go.