Central Heating Motorised Valve

Hi
We have a problem with the central heating. I think we have narrowed it down to the motorised valve which is a Myson 3-Port valve.
The problem is that although we have hot water the heating doesn't come on unless you use the manual override lever. We can see from the lights on the actuator that the timer control is passing the right 'signals' to it, but it isn't opening the valve.
I had a look on the Myson website and it is possible to buy the 'actuator' bit seperately and its 4 screws and some simple wiring to replace which having taken the current one off to have a look I think I could manage. The alternative would be to buy a complete new valve but I understand that would require draining the system and would be beyond my capabilities and expensive to have done (a quote to replace it with a Honeywell valve is 150+VAT).
Can anyone tell me whether it would be false econonmy simply to replace the actuator - is it like replacing the disks in a car and not getting new pads at the same time for example?
Any suggestions gratefully accepted.
Thanks
Christine
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xtinexoop wrote:

Provided that the valve is moves freely just changing the motor should do the trick. make a sketch of which wire goes where and then take the old motor with you when you buy the replacement just in cas eit is a bit different or there is a choice of motors.
Good luck
Bob
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As others have said, as long as the spindle of the valve rotates freely, and as long as there are no obvious leaks from the valve, it is perfectly reasonable to replace just the actuator. The simplest thing is to replace the whole actuator assembly - but make a careful note of where each of the (probably 4) wires connects before disconnecting the old one.
If you're slightly more ambitious, you may get away with just replacing whichever of the internal components of the actuator are shot. It contains a motor, a resistor, a diode (I think) and a couple of change-over micro-switches. It can be done, but it's a bit fiddly - and requires reasonable soldering skills.
Roger
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Hi Christine,
You can buy the individual parts which sit inside the valve head at a fraction of the cost of buying the whole thing, and they are very easily replaced.
Test the microswitches to see if they are passing the voltage signal along to the other parts of the system.
example of a microswitches here: http://tinyurl.com/opo0
Make sure that the synchron motor is running when you make a call for heating (switch the system on) and is opening the valve.
example of synchron motor here: http://tinyurl.com/opoc
The parts used inside these valve heads are pretty universal, mainly because they all come from the same manufacturers, and they only cost pennies compared to buying the whole head part. Try looking around your local repair shops for them and save yourself a good few pounds.
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Thanks for taking the time to reply
I am going to go and check that the spindle bit is spinning freely and if it is then I will replace the actuator.
Although I like the idea of only replacing the bits I wouldn't know where to start...
The actuator is about 45 + VAT which is a still a lot cheaper than getting the whole thing replaced, as I can do the wiring myself. I will get the same make to save worrying about the 'fit'.
Anyone recommend a good online source for the actuator? Its an ACT322.
Christine
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http://www.hav.co.uk/products/potterton_myson.htm 41.34 + vat, you need to swipe the whole page with the mouse to see the prices, they're black on black. or http://www.onlineboilerspares.com/acatalog/BOILER_CONTROLS.html 45.00 + vat
but best of all: http://www.discountedheating.co.uk/shop/acatalog/Online_Catalogue_Myson_277.html do the whole valve for 42.50 (if it's the 22mm one, pls chk) so you could buy the whole thing & swap the head or replace the valve if needs be. If the latter, tell the plumber you're supplying the parts :-)
--
fred

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Sorry, not an online supplier

Also, this lot may do the head on its own, try calling them, they're always busy, but I've found them to be a good bunch.
--
fred

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On 26 Sep 2003 03:22:23 -0700, snipped-for-privacy@totalise.co.uk (xtinexoop) wrote:

I've been buying bits from MJT Controls. This looks like the page you need: http://www.mjtcontrols.co.uk/Controls_Type3.aspx?Manufacture_ID=6&Appliance_Type=VALVES+%2f+ACTUATORS
Appears to be 31.03+VAT+delivery, which I think is a mere 2.50
I found them very helpful on the phone (went and got a fan off the shelf to confirm whether or not a gasket was included) and delivery was very fast indeed.
--
John
Mail john rather than nospam...
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That's a shame. Synchron motors are about a tenner! Most manufacturer's parts are interchangeable. Don't know specifically about Myson.
You can get a whole valve for 35 quid, so don't pay 45 for just the head.
Christian.
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Thanks for all the help guys!
I have bookmarked the supplier pages.
The tenant we have in the house has now told us its all working again! (maybe it was just 'stuck' after being off over the summer?)
I guess its gonna go at some point though so I might get the part now and hold it 'in stock' ready for when we need to get it done!
Christine
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