3 Port Valve - actuator or valve at fault?

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My 3 port valve (Sunvic valve and 2701 actuator) is not working I think i.e. HW always heats when CH is on. I assume it is functionally stuck at mid-position.

I removed the actuator and it still moves to 3 distinct positions when programmer asks for CH or HW or both.

The spindle of the valve turns smoothly and does not seem corroded etc. It can be twisted 360degrees - not sure if that's normal!

I actually foolishly bought an actuator (SD 2701) from heatingcontrolsonline.com but reluctant to open it as I may need the combined actuator/valve (SD 2211) which actually costs less than actuator alone. D'oh.

I tried shifting the valve around, but difficult to tell where the hot water goes as pipes all stay quite hot.

To complicate, I have a frost-stat which keeps turning on the system as it has been so cold. Can this send the valve to mid-position. I'm sure the problem predates the cold snap anyway.

How can I tell which part is not working? Thanks for any help out there...
 
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My 3 port valve (Sunvic valve and 2701 actuator) is not working I think i.e. HW always heats when CH is on. I assume it is functionally stuck at mid-position.

I removed the actuator and it still moves to 3 distinct positions when programmer asks for CH or HW or both.

The spindle of the valve turns smoothly and does not seem corroded etc. It can be twisted 360degrees - not sure if that's normal!

its not

I actually foolishly bought an actuator (SD 2701) from heatingcontrolsonline.com but reluctant to open it as I may need the combined actuator/valve (SD 2211) which actually costs less than actuator alone. D'oh.

good move dont open it,take it back and get the valve

To complicate, I have a frost-stat which keeps turning on the system as it has been so cold. Can this send the valve to mid-position.

not normally but depends how it has been wired in ie what is the protection for?
boiler protection or ch pipe protection

Matt
 
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A frost stat is normally wired in series with a AT pipe thermostat, this would protect both system & boiler.
 
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Frost stat sits on pipe between boiler (which is in garage) and house hot water system. Not sure how it is wired - not obvious from the wires around it. Think that might be a red herring.

I've established that by twisting the valve spindle I can send new hot water to the HW tank or CH radiators. Since the actuator goes into the 3 necessary positions (when it is unscrewed from the valve at least!) I'm confused where the problem lies.

If the spindle is not supposed to move round and round it sounds like
I needto replace the whole thing? From other threads I see this requires draining the system (to below the valve level at least). Is this a job for a willing amateur?
 
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Friend has potterton valve and spindle turns 360 degrees. It does of course have a flat machined on one side making a 'D' so you can't put the actuator head on in wrong position.
If you can get the 3 positions, your problem will be a faulty micro switch.
The valve moves over two sections. Up to mid point (driven by power on the white wire) and mid point onwards (driven by power on the grey wire)
One micro switch transfers power from white to grey wire.
The second micro switch when triggered puts power to the orange wire which lights the boiler. In HW mode or HW/CH mode the cylinder stat provides the power.
 
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OK, thanks. I'll plan to get the combined part (as it is cheaper) and see if changing only the actuator (in 10 minutes) will save me having to change the valve (a few hours and more sweat!).
 
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