Radiators cold unless hot water is on

[Brad44]

This is my first time on the forum.

Radiators will not heat up when central heating only is on. They will only heat up when the hot water is on and I turn up the tank thermostat which in turn switches the pump on. The motorised valve appears to move when I turn on central heating but pump does not switch on. I have a combi boiler.

Any suggestions please?

 

[D_Hailsham]

Which combi boiler?

What tank are you talking about?

Pics would help.

 

[Brad44]

It is an Ideal icos m3080 boiler about 3 years old.
Its the hot water tank I am describing. The motorised solonoid port valve is turning and there is a power supply at the room thermostat.

If this helps the radiators heat up if i turn up the thermastat on the hot water tank and ensure the hot water and central heating up both on constantly.

 

[weareleeds]

The icos ain't a combi if you have a 3 port valve it is most likely that the end switch has failed so new valve reqd (or head if possible)

 

[D_Hailsham]

It is an Ideal icos m3080 boiler about 3 years old.

That's a system boiler, not a combi.

Its the hot water tank I am describing.

Now I know you don't have a combi, that makes more sense.

Your problem will be either a faulty valve actuator or faulty wiring.

You can check the wiring if you have a multimeter set to AC volts.

Turn HW OFF and Heating ON at the programmer
Set the room stat high.
Measure voltage between Honeywell white wire and neutral; it should be 240v.
Measure voltage between Honeywell grey wire and neutral; it should be 240v.
Turn HW ON at programmer and turn HW stat down.
Measure voltage between Honeywell grey wire and neutral; it should be 240v.

If the voltage on the grey wire is not 240v in both cases, there is a wiring fault. Check that there is a wire from the hot water thermostat to the valve grey wire, Also check that there is a wire from the HW OFF terminal of the programmer to the grey valve wire.

If the voltages are OK, then either the actuator is faulty or the valve is sticking.

Remove the actuator to expose the valve spindle. This should rotate easily over about 20° between HW open and heating open. If it is binding a little WD40 should help.

If the spindle is free, the actuator is faulty and should be replaced.

 

[Brad44]

Sorry my mistake it is a condensing boiler.

I will test as suggeted with meter.

Thanks for your her help

Brad

 

[Brad44]

All voltages are okay.
The actuator is a siemens 3PMP-V22 which i believe is equivalent to the new Siemens CMV322. There is movement when the central heating is on and I can hear a micro switch when the motor stops, but the pump will not start unless hot water is on.

Should I now replace the whole unit or just the actuator as they are both priced the same?

 

[D_Hailsham]

The actuator is a siemens 3PMP-V22

Should I now replace the whole unit or just the actuator as they are both priced the same?

Unfortunately you cannot replace the actuator by itself on the 3PMP-V22, you will need to change the complete vale. As that is necessary, spend a few pounds more and get a Honeywell V4073A.

 

[Brad44]

Okay. Thank you for your help.