I have a Wet System which was working last in April. We also have normal radiators in the house which are working fine.

The thermostat is doing its job and kicks the boiler in. The system temperature gauge next to the pipework shows an increase to 45 Deg. However, there is no flow on the flowmeters and the system shuts down. Obviously the pump is not coming on for some reason. Are there any simple gotchas/things to check that I could check before calling an expert?

Bump for the evening.

Is the power to the pump separately isolated?

What turns the pump on? a wire from the boiler or from a control unit?

Is the pump definitely NOT running?

If it actually is running, but there is no flow then there are different solutions.

The pump is wired into a junction box that also takes feed from an H series valve.

Thanks for the reply, I will take a photo of the system and post it up.

Ideally you need to check for power going into the box from the closed valve switch and again coming out to the pump. If live, then its possible that the pump is seized and needs a bit of encouragement to get going again after a lazy summer sat still.

If the pump is running but v quietly, there may be airlocks v near the pump in the UFH loops or the pump itself needs bleeding.

Pic here I hope Pic

why do you have three zones but only one with a motorised valve on it when the pump and valve wire both seems to come from the same supply source?

Anyway, as I suggest above, check that when the thermostat is calling for heat (Im assuming the controller is the white box in bottom left out of which comes the black live supply?) that you have live in the black cable. Again, I assume that the junction box is just taking power from black to the two white cables (pump and valve).

Stoner thanks for your input. We bought the house 6 months ago so were assuming it had 2 zones, as there are 2 thermostats.

I am afraid checking power for live supplies is a bit beyond my DIY skills. Assuming it is a sticky pump is there any way to encourage it without flooding the house?

2 thermostats might make sense if you had one that turned the pump on (i.e. hot water ran around the two right hand circuits whenever pump on – 2 and 3 of 3) and then a second thermostat only opened the valve port to the left hand circuit (number 1 of 3) when that thermostat told it to.

But Id expect to see wires from different controllers. But its hard to tell from a photo.

Have you definitely got both thermostats calling for heat? Maybe one is firing the boiler but the other one is not sending power to the pump? You really need to check that there’s no power at the pump before you introduce the workshop persuader to it,

I would guess that the 3 port (if it is 3 port) is measuring the return temp and is used to ruen the pump on/off? Difficult to say from a photo. I would give the pump a light love tap as it might be a bit sticky after months of non use.

Thanks for all the help. Unfortunately the light tap yielded no result even with both termostats turned right up. I think it might be time to throw in the towel.

If checking for live feed is beyond you you need some help. But my guess is 2 port valve faulty

You could take the head off and move the spindle on the valve whilst demand from radiators. You should feel hot water coming in on one of the pipes

If the motor has been stuck with power going to it for some time this may have burnt out the windings unfortunately, so a suck pump may be the correct diagnosis, but the pump power staying on may have burnt it out unfortunately!