UFH must valves open before pump runs?

[gcc9876]

The (rather sparse) manual with the controller that was supplied with my UFH (Hettaj describes the start sequence as - when demanded by the stat - valves open then pump runs.

As the programmability of the stat is very basic, I’d like to replace it with a smart controller the same as I use on rest of CH rads, (Netatmo) which “learns” how quickly the area or building heats up and turns on the heating in advance of the programmed time so that the desired temp is achieved by that time, also compensating for external temperature.

the only problem is that it is basically just a make/break switch so if I installed this then the UFH pump would start before the valves had opened. (Triple circuit in one open plan room, all 3 run or none, so they are wired in parallel.Is there a bypass in the pump (Grundfoss) or is it harmless for pump to run against valves for short while that they take to open?

the other option is to wire valves so they remain open when pump is off - bad idea?

or a different controller altogeth…

advice and suggestions welcomed. Thanks

 

[Pedro2859]

What sort of valve do you have? A standard Honeywell V4043H 2 port valve has 5 wires and 2 are connected to a switch that only closes/powers when the valve fully opens so is ideal for connection to a circluation pump.

Alternatively Broyce Controls make a range of DIN rail mounted relays including delayed ON or delayed OFF that you could use to give a short delay between the valves receiving power and the pump receiving power - I recently fitted one with a delayed OFF to a circulation pump to enable a 5 minute pump overrun to dissipate heat away from a very large boiler. I did this at the same time as installing a Netatmo Thermostat to replace an ancient Honeywell Aquatrol 2000 controller that had packed up.

 

[gcc9876]

What sort of valve do you have? A standard Honeywell V4043H 2 port valve has 5 wires and 2 are connected to a switch that only closes/powers when the valve fully opens so is ideal for connection to a circluation pump.

Alternatively Broyce Controls make a range of DIN rail mounted relays including delayed ON or delayed OFF that you could use to give a short delay between the valves receiving power and the pump receiving power - I recently fitted one with a delayed OFF to a circulation pump to enable a 5 minute pump overrun to dissipate heat away from a very large boiler. I did this at the same time as installing a Netatmo Thermostat to replace an ancient Honeywell Aquatrol 2000 controller that had packed up.

just to make sure I’m following you correctly: so you’re saying connect the stat to the valve and let the valve trigger the circulation pump?

 

[milgo123]

I think that the op is talking about the actuators on the manifold (op please correct if I've got this wrong)

OP if you have 3 circuits in 1 zone (being controlled by 1 room stat) then I don't believe that you even need to be using actuators.