Hot Water but no Central Heating

27 Nov 2008
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United Kingdom
Hi all,

I'm new here and needs some advice. Here goes...the Hot Water system works fine but the Central Heating will not come on :rolleyes:

The boiler is a Potterton Suprima 50, and the digital controller is a Potterton EP2002. I know problems with the Suprima boilers are well documented but I'm not sure this is the problem this time. Showing on the bolier is an Amber LED not the Red, so I suspect it is not 'lockout'. The info I have says this most likely 'no external call for heat'. When you run hot water for a while the LED goes green and the boiler fires up okay until the water is heated again.

I have checked the thermostat is switching okay and the is 240V present on both sides of the switch when moved.

The Red LEDs are both on on the EP2002 digital controller.

When the Hot Water is on and boiler running, the pump near the tank in the airing cupboard runs.

I measured the voltage at the boiler and on the Hot Water side there is 240V

I measure the voltage between the SwL and the terminal mark Pump and there is 38V :confused:

I suspect this could be the controller at fault? Any other ideas or places to check before buying replacement parts I may not need?

Please help........we're cold!!! :LOL: :evil: :LOL: :evil: :LOL:
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That kind of problem sounds like a motorised valve problem.
I had a 3 port mid position valve problem (well I've had two).
On one the valve moved across as it should but boiler did not light due to faulty micro switch. On the other the valve would not go beyond the mid position.
So do you have a 3 port or two 2 ports.
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Just after the pump it will split HW from CH. Have a look at FAQs you'll see a picture
Yes I have what looks like a 3way v/v. 1 pipe goes to the pump, 1 pipe goes to the centre of the HW tank and the other goes through the floor boards to what I suspect to the boiler.

Its a 'Myson Power Extra', although obscured by the door frame it looks to have 2 indicator LEDs? 1 for HW and the other for CH. Should they illuminate? Neither are on at the minute. :rolleyes:

Thanks for your help so far guys!! Just need to get the heating on for when the wife comes home!!:cool:
Don`t know about that make of valve, but would think if the heating or hot water is called for, on or the other should light. I would do as FAQ 3 and see if it works.
Okay I followed the FAQ guide. The 3way v/v now has the little Orange LED's on when I move the manual lever on the underside. I have set the 'Temperature' control on the boiler to just on, the thermostat on the tank set set to 60 but won't move either way so that is the original setting. I have had to cable tie the manual lever on the 3 way v/v to the CH position and the amber CH LED is light brightly.

The rads are warming up slowly.

What would be the next course of action. Is it the 3 way v/v that is the problem or the controller? I assume the controller makes the 3way v/v move to it's positions?
You've got it! ' myson power extra' thats what I used.
It will most likely be a ACT 322. ACT means actuator.the 3 is 3 ports and the 22 is size of pipe ie 22mm. You need to comfirm that.
I think ours came from boilersonline I think about £42.
Right its a complicated bit of kit, not easy to understand how it works for many.
Briefly it works over two stages, starting with HW only which is the 'rest'. position from here the options are either HW/CH (end of stage 1 at midposition) or only continues to CH only positon (end of stage 2)
You need to find out what positions can be achieved.
There is a small geared motor drives a geared quadrant against a spring.
The motor only turns a few revolutions and is constantly energised, that is until power is removed and the spring unwinds the quadrant and motor back to the rest position.
There a few things that could be the cause of your problem.
Best thing is to remove the actuator head off the valve spindle. this will allow you to test the spindle for stiffness between finger and thumb should be easy.
By noting the flat on the spindle you can leave it about mid point.
Now turn the actuator head over so you can see the 'D' shaped hole and note its position.
Turn both HW and CH off If not already at the rest position it will move there within secs (time to unwind)
Next turn on HW boiler will light but quadrant will not move.
Now turn on CH (so both are on) question here does valve move to mid position (we will assume it does).
Next turn HW off. what should happen is boiler will stop (cylinder stat gone off) momentarily. valve should now move across further to CH only position.
I suspect everything is ok whilst HW is cold and in demand and its set in mid position but it closes down because HW has become satisfied. You can prove this by either running some hot water off and creating a demand, boiler will relight giving heat to HW and some to CH but not for long.
What you can do to get some heat is to have HW only on the actuator but set the spindle to the CH position. of course the room stat will have no effect.
The controller only supplies power. three outputs.
HW ON a wire from this terminal goes to cylinder stat (via 10 terminal box), then from cylinder stat to boiler, but when satisfied the power is diverted to the 'grey' wire of valve (needed to power motor over second stage)
CH ON a wire from this terminal goes to room stat (via box) and then to the 'white' wire of valve (via box). This required to drive motor over first stage.
HW OFF a wire from this terminal is required to join up with the grey mentioned earlier. This is required in case the HW is off and is still needed to drive motor over second stage.
Your problem could be either micro switches or motor or stiff spindle. If the spindle is free a replacement head is the easiest option
9 times out of 10 the syncron motor has warn out.

Easy replacement and only costs about £7 from part no. 11025
Well hopefully replacing the actuator has worked!! I got a Myson ACT322 from Plumbase today and fitted it. The heating now controls automatically and the house is warm again.

We'll see how it performs over the weekend, but so far so good!! Thanks for all the people that helped with advice etc.

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