Reliable 3-Port valve actuator?

On 21 May, snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

Is that a new thing, using diodes? The ones I've used have used a resistor to put just enough power onto the motor to stall it, but not enough to let it run back. I gave up on them about 15 years ago and converted the system using (then) the same make of 2 port valve. I recently had to change the downstairs valve due to leakage round the stem and took the opportunity to change the upstairs one whilst the system was drained. I think they were about 15 years old. The 3 port ones gave trouble from about a year old (just out of warranty) for about 3 years (changing micro switches regularly) for the last two years. One remained in service for the hot water, but as a divertor, reliable in that mode, for another 10 years, only changed after SWMBO complained enough about cold radiators after she'd drained the cylinder for a bath, diverting all heating to the cylinder.
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snipped-for-privacy@privacy.net explained :

Now the diode has been mentioned, I do remember having seen one fitted to one of our actuators in the past. The one I took off when it failed about 12months ago, after just 12 months use, was installed when the boiler was replaced with a new one. That actuator had no diodes and no resistors - just the microswitches and the motor.
The present one fitted is/was a new Sunvic which was bought as spare for when our old one died, prior to the new boiler. I had refurbed that one several times and knew it was beyond being refurbed again.
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Harry (M1BYT) (L)
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On Fri, 21 May 2010 22:01:55 +0000, Andrew Gabriel wrote:

Ah! is that what it's for?!
I always wondered.
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John Stumbles -- http://yaph.co.uk

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On Fri, 21 May 2010 15:48:02 +0100, spamlet wrote:

When we were doing boilerhouse panels we provided a lot of Landis & Staefa (previously Landis & Gyr) and Sunvic valve actuators. We didn't often get any problems. Mind you, the 3-port ones were often of the true "proportional" type, with a feedback pot, and didn't use a motor-against- spring system. I've no experience of current designs as we stopped doing boilerhouse controls some years ago.
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Mick (Working in a M$-free zone!)
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Of the heating systems I maintain in various family members' homes, I've never had one fail. (They're all mid position values.)
GBMVSP-23 (British Gas - don't know who makes it): Somewhere between 10 and 20 years old.
Lifestyle (is that Drayton?): 11 years old.
Landis and Staefa: 7 years old.
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Andrew Gabriel
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writes:

Thanks: I've not come across those types yet.
Cheers, S
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Actually that's wrong, must be 8-9 years old.

Go to a heating/plumbers merchant. B&Q did keep the Lifestyle range, although that was in the days before they made way for the cushions, but will still be much cheaper from a plumbers merchant.
Landis and Staefa - I think they were bought by Siemens. That's the only one I actually bought, and as I am controlling it by a computer rather than conventional boiler/thermostat controls, I had to work out exactly how to drive it. I had a chat with someone in Landis and Staefa (or may have been whoever bought them) who was incredible helpful and explained in detail how to drive it. It's used as a zone valve to switch between upstairs and downstairs heating zones.
I don't use the end-stop microswitch, so if that died, I wouldn't notice. I did use it as a feedback control to confirm to the computer that the valve was working initially, but I ran out of spare computer inputs for other things so that extra test got dropped.
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Andrew Gabriel
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writes:

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> Andrew Gabriel

Phew! It's really impressive the things some of you guys are able to take
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