3 PORT SWITCH 4073A NO PIMPLE

[alfier]

Can I replace the sync motor on this item or do I have to drain the system and change the entire 3 port switch with a Siemens 3PMP-V22 which I have.
Fault is some CH rads hot when HW only on, however system is 25 years old, but them I'm 68!
Alfie

 

[Prof.plumb]

I'm afraid you will have to drain system and change the 3 port body. As if you get heat out to the rads when there is no demand for heating then the valve is passing.

 

[ChrisR]

Can I replace the sync motor on this item

You could but it OPENS the valve to CH, so it isn't the problem.

You could also change the head+plate for new Honeywell ones, but you're gonna get wet so you may as well use your new valve.

Might be worth checking that you don't have some other plumbing problem first - reverse flow or similar.
With the sytem cold, first turn all the power off (valve springs shut) put back on with just the HW alone on. Feel the pipe from the valve which goes to the CH. A foot from the valve it should stay cold.

 

[alfier]

Hi Chris R.
Did as you said with all off during the night and all pipes cold. Switched on hot water only 4073A lever remains at the left away from the manual position , both pipes get hot as does 2 upstairs radiators. I await your valued comments.
Alfie

 

[Gasguru]

If the pipework on the radiator side of the valve (Port A) gets hot at a reasonable distance from the valve (ie not conducted heat) then the valve is not fully shutting off.

You can either get a Honeywell ball and plate kit plus the actuator or change the complete valve with the Siemens.

 

[alfier]

Thank you to all who took the time and trouble to help me. I shall change the switch when winter goes away I assume the wiring colour code is the same for the siemens replacement.
Happy Christmas Alfie

 

[ChrisR]

If it's a spring return one the wiring will be the same colours.

There are two O rings on a honeywell valve shaft. Sometimes a squirt with WD 40 , which will get to one of them, makes a difference. Worth a try!