3 Port Valve

[mobily]

Hello all,

I have a problem where when hot water and heating is called for the heating doesn't work, however when heating is called for on it's own there is no problem.

I checked the actuator and it was hot even though heating and hot water were off.... is this normal?

 

[D_Hailsham]

I have a problem where when hot water and heating is called for the heating doesn't work, however when heating is called for on it's own there is no problem.

Do the tests in How a mid-position valve works

I checked the actuator and it was hot even though heating and hot water were off.... is this normal?

Yes that can happen. The link above explains why.

 

[mobily]

Thanks for that.

I have taken off the actuator and there is a spindle on the valve, do I just need t try and see if it will turn to establish if it is sticking or not?

 

[D_Hailsham]

I have taken off the actuator and there is a spindle on the valve, do I just need to try and see if it will turn to establish if it is sticking or not?

Read the link then ask the questions!

 

[45yearsagasman]

Is it a mid position or a diverter on a priority system?

 

[mobily]

It is a mid-position valve. There is a lever on the side of the actuator that seems stuck solid in a certain position at the top. Unfortunately the HW CH indicator has been taken off so I am not sure which section this is! *Edit* having looked at similar models it would appear it is stuck on 'B' and I can't move the lever at all whether the actuator is on or off the valve.

I did read the article but was a little technical for me, that is by no means a criticism of your article but more of a criticism of my lack of knowledge in that area.

I am surprised with the problem I have as all other 3 port valve issues seem to be about heating coming on when only hot water is called for!

 

[MANDATE]

The problem as described is interesting!
When heating is called for alone there is no problem!
So for this to happen the room stat powers up the 'white wire', this in turn moves the actuator/valve to mid position. Micro switch operates. power on 'white' is dropped and replaced with power on the 'grey' (from programmer).
2nd micro switch triggered and allows power out from actuator to operate boiler/pump.

Now when hot water and heating is called for the heating does not work.
The room stat functions, the actuator/valve is not stuck so there seems to be no reason why it should not work.

If the actuator/valve is at mid position, with pump working heating should work. Unless of course, there is too much resistance on the heating side and water finds it easier to go through the hot water route or back to boiler via a by-pass valve.
Sometime a gate valve is used on the hot water side to restrict the flow giving more flow to the heating side.

On the other hand the 'hot water' and 'heating' setting is not permanent.
It only operates until one of them becomes satisfied. This is usually the 'hot water' and when this occurs the actuator is supposed to move to 'heating only' by powering up the 'grey' wire again.
There is however a subtle difference this time.
The power to the 'grey' does not come from programmer, it comes from the cylinder stats 'satisfied' terminal.
If that power supply is not there, due to faulty connection or contacts in cylinder stat then the valve can't move on to heating. Boiler can't operate because hot water is satisfied.
I can't think of any other explanations that would apply

 

[D_Hailsham]

When heating is called for alone there is no problem! So for this to happen the room stat powers up the 'white wire', this in turn moves the actuator/valve to mid position. Micro switch operates. power on 'white' is dropped and replaced with power on the 'grey' (from programmer).
2nd micro switch triggered and allows power out from actuator to operate boiler/pump.

In heating only the boiler is switched on by the valve orange wire.

Now when hot water and heating is called for the heating does not work.

In this case the boiler is turned on by the HW thermostat (same as HW only).

The OP has CH only - so the valve is moving over OK and orange has 240V. But what has happened to the voltage from the HW stat when in mid position? Presumably HW only works OK, thought the OP hasn't said so.