Changed Room Stat - Is It Now Holding the 3 Port Valve Open?

[DAMONREAD]

Changed my room stat on the central heating yesterday. Thought I had matched the wiring right, but now think maybe I didnt.

I can hear that the stat is controlling the pump correctly.

However I noticed last night that even when the pump was off some of the rads were red hot and others were cold. Some rads heat up and cool down in synch with the pump, but these ones upstairs stay hot.

I am thinking the 3 port valve is not operating correctly.

Is it possible that I have missed wired the thermostat and that this is causing it to hold the valve open?

Or

Is it likely to be completely unrelated problem and I am just noticing it now because I was looking for any problems?

There were 3 wires to the stat, not just 2.

 

[kevplumb]

y plan

• kevplumb
• 19 Sep 2009
• 22

 

[DAMONREAD]

Trying to think this through from the wiring diagram.

I guess that the permanent live and the switched live leading to the pump are the wrong way round?

When below heat the circuit to the pump completes and when up to heat the circuit to the pump breaks, thus operating correctly. However at that point the connection is switched live to switched live, so the valve does not close.

 

[D_Hailsham]

I guess that the permanent live and the switched live leading to the pump are the wrong way round?

I thought you just changed the room thermostat. Have you also made changes to the pump wiring?

Which permanent and switched lives are you talking about? Use the diagram to explain.

When below heat the circuit to the pump completes and when up to heat the circuit to the pump breaks, thus operating correctly. However at that point the connection is switched live to switched live, so the valve does not close.

Don't understand what you are talking about Which switched lives?

As long as you have got the neutral right (terminal 2 of the stat), terminals 1 and 3 of the stat are interchangeable. All that will happen is that the temperature control of the stat will not be quite so accurate as the anticipator resistor between 1 and 3 will be permanently in circuit.