HW Heating When CH Only Selected

[Deryck Tintagel]

I have an odd problem with the HW.

I have a vented system with tank for the HW and a 3-port valve (Honeywell V4073A) next to the tank. With HW only selected the radiators are cold and the HW heats normally. When CH only is selected (most of the day at the moment) I had noticed that the HW was excessively hot. Just holding the pipes in and out of the 3-port valves tells me that pumped water is passing through the HW tank and adjusting the tank stat it clicks at between 70°C and 80°C!

With CH only selected, I checked the voltages at the wiring centre and found that the grey wire is live permanently (as expected). The orange and white wires change to 0V when the room stat is satisfied and switch to 230V when heat is called.

I powered down and checked the 3-port valve and the lever can be moved across with some resistance and it moves back due to the return spring.

I suspect the 3-port valve is faulty somewhere but not sure whether it is the actuator or the valve body itself. I can take it apart to check but need to know what I looking for.

Any help appreciated!

 

[ericmark]

OK let me explain the three port valve.
1) The lever on the side is to allow the system to be bled, it only moves the valve to central position (HW and CH).
2) Default is HW, the valve is not powered at all for HW, so to turn HW off it is powered, (grey wire) not turning it on.

With CH only selected, I checked the voltages at the wiring centre and found that the grey wire is live permanently (as expected). The orange and white wires change to 0V when the room stat is satisfied and switch to 230V when heat is called.

So since "the grey wire is live permanently" there should be no HW. I seem to remember with many valves the head can be unclipped, and you can likely watch the head move, and also manually move base.

 

[Deryck Tintagel]

Thanks Ericmark, that was my understanding. I watched a YouTube video by John Ward and that explained pretty much everything but I think it missed the situation with HW off and CH on / called specifically. I managed to fill the gaps!

I did have a problem earlier in the year when I had no HW but warm rads even though the heating was off. A sharp tap on the 3-port seemed to sort it. I will disassemble the actuator and valve body to see if there is a particular part that is faulty. If anything, I hope it is the actuator as this will save me draining the system