Is this the programmer or the motorised valve.

8 Oct 2005
Reaction score
United Kingdom
I have a pumped c/h and hot-water system. Worked fine for years, suddenly I get hot water but not c/h.

The boiler, pump and the motorised valve for the c/h are not switching on, even though the programmer is set to have c/h on and the hall thermostat is turned up and has "clicked" to make the connection.

Well firstly I thought it must be the programmer. However in manually moving the motorised valve to open (using small lever on valve) it feels odd (I'll describe below), I wondered if there was a electrical circuit that needed to be completed by the valve opening to switch on the boiler and pump, whereby if the valve was faulty it also could stop the pump and boiler starting up - or are they all independent of each other?

The hot-water valve has a different feel to the suspected c/h valve when using the small lever to manually open it. When the hot-water valve is off, you can feel the "gears/motor" being turned as you move across the lever to open it, I sort of remember that also being the case with the c/h valve. However with the c/h valve currently, when you move the lever it is clearly moving against a spring, but I can't fell the same "gears/motor" tuning effect.

Programmer: Danfoss FP75
Valve: Honeywell

Sorry this is so long.
Sponsored Links
Yes it is a 2-port valve. I just didn't know if the programmer sent out a signal individually to each of the pump, valve, boiler, or if it needed the motorised valve to be working for the pump and boiler to also switch on.

I know if the valve wasn't working, that it wouldn't allow hot water to circulate, but would the boiler and pump have come on anyway?
the valve controls the pump/boiler.

when calling for heat is the lever floppy or has resistance on it ?
Sponsored Links
Yes, valve has to be calling for heat before the supply is passed to boiler.

As you have 2 valves, if the h/w is satisfied and c/h is calling for heat but c/h valve (switch unit head) not operating, then there is no call to boiler.
The valve lever isn't floppy (as it would be if the valve was on), it is in the default off position. But when moved manually to "on" it is moved against what feels like a spring (if released it springs back to off position).

But it doesn't have the same feel of moving the actual motor valve as the hot-water valve has. It's just like pushing against a spring, with no mechanical action seeming to happen.

If you are saying that even if the programmer correctly calls for c/h to go on and so sends the signal to pump + boiler + valve to operate - but the valve isn't working it stops the pump + boiler to start up, then it may be the valve at fault.

I just wasn't sure that the valve had a "electrical" function to allow all the rest to switch on, other than the "mechanical" function of opening or closing the water flow.

Perhaps you are saying that there is a "flow switch" which has to trip to also switch on the boiler + pump?
The valve has a microswitch in it that is activated by valve motor when the thermostat calls for heat, and which then passes current to the boiler and fires up the boiler. Usually the valve head can be replaced seperately from the valve body and this makes it a simple job.

You can check the electrics at the c/h wiring centre if you understand the circuitry and are competent.
With the head off the valve you can check the water valve manually.
If the valve lever is not 'floppy' and there is 240VAC on the brown wire to it, then the motor in it has had it.

A lot of people will just replace the synchron motor, but I always replace the valve head, so everything is new and under warranty.
Well the valve I had was quite old and I wasn't sure that just the head could be replaced, so I replaced the whole valve.

That did it. It's all working again now. So it wasn't the programmer, but the motorised valve.

The key clues were that it didn't feel right, when using the manual lever and once I knew that unless the valve was working properly, the pump and boiler wouldn't come on, I was sure it was the valve (just for others who may have the same question).

Many thanks to those experts who guided me.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links