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Help ! How does an actuator work?

Postby Jaynecasey70 » Mon Nov 07, 2011 5:50 pm

Decided to put my heating on the weekend and normally control it by moving the thermostat in the hall and normally the central heating comes on. But it wont! You have to press the advance hot water then advance heating for it to come on.

We had a new actuator fitted in April this year a bgmvsp 23 by British Gas because we had no hot water, and the engineer fixed it by replacing the actuator. We havent had the heating on since then because it wasnt needed.

So is there something I can try ? Ive wobbled the slider thing at the front of the actuator and that wiggles about freely is that right ? There is a slider on the left of it that i cannot seem to move what does this do and how do you move it(it wont budge). The one on the right hand side removes it from the valve if you lift it doesnt it?

Do I need to phone British Gas and wait in all day for them or is there someting i can try first?


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Postby plumbbob » Tue Nov 08, 2011 8:23 am

If the heating works by pressing the advanced button on the timer then the actuator is working fine.

Have you checked that the time is set correctly and that the heating is actually programmed to come on? If you have had a power cut during the summer it is possible all the timer settings have been lost and the unit needs to be re-programmed with the correct times.
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Postby Jaynecasey70 » Tue Nov 08, 2011 9:19 am

Hi plumbob

Thanx for your reply

The heating advance button only works if you press the water advance button first its the only way the heating will come on on demand, but we used to just turn the thermostat up and it would click.

The heating is timed to come on in the morning at 6 till 8 with the water and you can hear the thermostat click if you move it during this time.

It something stupid thats wrong i know it is i dont think its major but just dont know what

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Postby sparx » Tue Nov 08, 2011 7:23 pm

Hi, I think Plumbob missed the bit about advancing the HW to get heating to operate.
I think the actuator valve is stuck, 3 port valves are by design a 'bodge-up'!
They work by powering a motor against a spring, for one position full power is provided to open one port fully; for mid position the power is reduced to the motor via a resistor which means near the mid point the motor stalls. with power off the spring wins and drives the valve the other way. Horrible for an electrician to contemplate.
At each position switches inside the actuator send a 'call' signal to the boiler.
It seems your valve is stuck in mid position so requires both CH & HW to be demanded to call boiler.
(Bet you wish you hadn't asked how they work now Hi)
Did BG change whole valve body or just removable actuator head?
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