3 port valve - help diagnosing problem please

[gsf600y]

Hi,

My Hot water is working fine.
My Central heating is not

I've got a 3 port valve. I turn on the hot water, I can hear and feel the 3 port valve doing its thing, and boiler kicks in, and all is fine.

I turn on central heating, and nothing.
I've manually moved the slider on the 3-port valve, and the boiler kicks in, and hot water is flowing to the rads, which is good.

So, could anyone suggest what's broken here?

The valve is working for the hot water, and manually can open for the central heating.
Is the motor partially broken?
Is it the gearing on the valve?
Or something else?

Thanks in advance

3 port valve

• gsf600y
• 17 Sep 2013
• 1

 

[gsf600y]

Hmmm...actually, I'm not sure if the controller box is working.
The downstairs rads are not heating.

The pump only appears to emit a slight noise and small vibration when I turn the hot water on - perhaps just from water flowing through it rather than it working?? When it's just the central heating, it makes no noise, and no vibration.

I'm wondering if the problem is the control box not firing up the pump or valve for the central heating, but it does for the hot water.

Or maybe the pumps bust.
Urrgh.. Confused.....

 

[Armo74]

Sounds like the motor has had it.
You can buy replacement synchron motors.

 

[gsf600y]

That's what I initially thought....but when I realised the 2 downstairs rads were not heating, but the upstairs 4 did, I thought maybe it's something else.

 

[Armo74]

Turn the working rads off and see if the bad rads heat up.
It may be a balancing issue.
Do the rads that don't work have thermostatic valves?

 

[gsf600y]

Well, 2 upstairs have TRVs. I've now set these to off.
The other two upstairs don't have TRVs, one of which is not heating I've just realised.

The two that are cold downstairs do have TRVs, set to 5.

EDIT: The cold one upstairs needed bleeding.....maybe that will cause downstairs two to heat now......

 

[MANDATE]

The pump is used for both HW and CH so thats not the problem.
The valve does not need to be moved from the rest position. HW position is the rest position.
Could be no power from room stat to valves 'white' wire.
Its more likely to be a faulty motor. replaceable for about £20.
Or if the motor is ok and the valve is moving, then it will be faulty contacts on micro switch, which prevents power leaving the valves 'orange' wire.
Remember boiler gets power from cylinder stat when HW is called for, but it has to come from valve when CH only

 

[gsf600y]

Mandate, I thought the micro switch on the valve, which I manually turn on, is what's kicking the boiler in? It's when I slide the slider to manual that the boiler kicks in, which I assume is because the micro-switch is being pressed in?

UPDATE: ONE of the downstairs rads is now heating....... just waiting for other.

 

[Armo74]

Have a look on FAQ's on balancing.
You may also need to remove some TRV heads on the rads that are not heating.