Reliable 3-Port valve actuator?

[spamlet]

Is there such a thing? If so, does anyone have one they know to have run trouble free for say 3 years: if so what make is it?

Our current one is a Honeywell, and is very rickety inside. I recently had to look at the micro-switches and even found that one of them had even been assembled with the contacts twisted! Even after straightening the contacts getting the thing to balance properly again was very fiddly, as all the springs and cams and the like are thin and wobbly, and it even changes as the mounting screws are tightened. Thus it is now stuck in the mid position again. This is the third actuator we have had. The first was a Potterton and quite sturdily made, but its backing plate was brittle and broke when I went to replace the contacts. The replacement newer Potterton only lasted about a year, before needing new contacts. Next time I went for the Honeywell, which has, as above proven to be expensive rubbish.

Are there any good ones out there?

S

[spamlet]

Oops sorry: looking again, the second one we had was a Danfoss.

S

[<me9]

IME no. I've ended up changing to two port valves. They seem much more reliable (10+years rather than 6 months)

[spamlet]

Sadly I don't feel up to any substantial replumbing at the mo: especially as plumber has recently tapped the system with some new pipes for an upstairs shower and routed them right in front of the pipes I'd need to get at...

S

[Harry Bloomfield]

Nothing at all wrong with the actual valve, just the actuator design which lets it so badly down. It simply needs someone to design something more robust, which has the motor move the valve to the correct position then stop - rather than the motor constantly oscillating on the microswitches against the spring. Surprisingly, I have not seen a DIY replacement actuator yet, but it doesn't look at all difficult to do.

[spamlet]

There's a job for you Harry: sign me up for one when you've sussed it! I would imagine that while they have us over a barrel knowing we have to buy new every other year, there is not much incentive to come up with a different design.

S

[Harry Bloomfield]

There is a rather good web site somewhere which explains their principle of operation and how to repair them.

It needs something like a tiny DC motor (to provide forward and reverse motion), geared down to provide the torque, a two lobe cam to trigger the two micro-switches - then a timer circuit to run it back to the default position.

Even an electrically operated brake, which held the position and turned off the motor - would be a major improvement on the existing botch of a continual rocking motion.

Food for thought.

[Harry Bloomfield]

Harry Bloomfield laid this down on his screen :

More food here...

[Harry Bloomfield]

spamlet laid this down on his screen :

It seems they may have...

[mick]

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.

[geoff]

In message , Harry Bloomfield writes

They used to manufacture 3 port valve actuator heads which would drive to the correct position and then stop as the respective microswitch opened, but they don't seem to be available any more

however, the synchron motors are quite cheap (I can get them for about £7 locally or I could get them at £3 each if I bought 1000)

[Andrew Gabriel]

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.

[Andrew Gabriel]

If it's doing that, it's wired in wrongly, or the internal diode has gone open circuit. The motor is stopped in mid position by having DC applied to the coil to lock the rotor. It's locked in the far position by keeping the motor powered but stalled. For spring return from mid position, there's a resistor to leak a tiny AC current through the motor to degauss the yoke after it's been locked with a DC field.

Actually, it's quite an amasingly simple design to achieve what it does with so little supplementary controls.

[<me9]

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.

[spamlet]

Yes: its on one of the UK-DIY faq pages and I've linked to it in earlier threads.

S

[spamlet]

Yes, I've changed one before, but it is usually the microswitches that go first, and then cause the motor to be on all the time, so just changing a burnt out motor is quite likely to disappoint if the switches are not done at the same time. The motors are quite similar to the ones on microwave turntables.

S

[spamlet]

Cheers Harry, I had forgotten about Sunvic - although part of our control system is made by them.

Looks like the momo equivalent of the Danfoss is:

SDM 1901 - 3 Port Actuator £77.28

Pricey. but possibly worth it if it avoids all the hassle.

Cheers, S

[spamlet]

Thanks: I've not come across those types yet.

Cheers, S

[Harry Bloomfield]

[e-mail] 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.

[Andrew Gabriel]

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.