Three port valves again

[Surefire]

Hi folks.

Following on from a previous post about mid position diverter valves, I was wondering if there are any which are better than others. By better I mean longer lasting. I've been using Potterton/Myson MPE322’s but they only seem to be lasting 18 months or so (the electrical actuator part that is). I’ve seen other brands like Honeywell, Drayton, Horstman, Worcester Bosch, Eco, Sunvic. The main problem I can see is that they overheat which reduces their lifespan. Mine is currently located in a nice warm airing cupboard so it’s gonna get hot anyway and it would be difficult to improve the cooling. Any opinions on brand longevity?

 

[Gasguru]

Convert to 2 x 2 Ports (and maybe bypass)...no more valve sitting in the HTG position.
Honeywell were always the best but even they have dropped to mediocre...there's little quality left in the heating industry.

 

[ianmcd]

I would go for genuine Honeywell, not Honewell compatible Chinese copies

 

[fixitflav]

I'd consider changing to an either/or diverter valve (Honeywell W-plan). The actuator is simpler and more reliable. I've had a Honeywell for years with no problem. The valve body is the same for both (on the Honeywell, probably same for other makes). I don't think there's significant advantage with mid-position.
Also if in future you get a boiler with weather compensation it must be either/or, as the boiler flow temperature via the controls could be below the cylinder stat setting (weather compensation disabled when HW calling).

 

[Harry Bloomfield]

I would suggest MOMO types, simply because the actuator mechanism is under much less stress.

 

[ChrisR]

They should ALL last "several" years, though the Chinese copies and some motors are dreadful. Momo's don't seem to be any more reliable, sadly.




edited for typos

 

[Harry Bloomfield]

Momo's don't seem to be any more reliable, sadly.

To be honest, I based my opinion on nothing more than studying the design. The spring return type are under constant and massive stress, with the motor powered constantly while ever there is a need for central heating or hot water.

The MOMO type uses a similar motor, but the motor only runs for the few seconds to change the valve position, then it is turned off. It is only powered for the brief need change in position, so there is almost zero heat generated and power wasted inside the actuator. With no stress from a very powerful spring, there is much less wear on the mechanism itself.

Both types do suffer microswitch failures and both can suffer water damage. The MOMO's more complex electrical design, maybe making it more susceptible to water damage, but that is easy to mitigate - just ensure it doesn't get wet.

My personal experience has been of almost annual issues with the spring return valve failing or jamming and as the most troublesome part of my heating system, always keeping a spare actuator to hand, ready to swap in. By contrast, I have not had even the slightest actuator issue, since swapping to a MOMO - though I do keep a second one to hand, ready to quickly swap in.

 

[ChrisR]

I theorized along similar lines but it wasn't borne out in practice, having fitted or replaced something in the hundreds, and found most failure modes.
The elastic stress doesn't cause apparent extra wear. Even the ones which hunt in the mid position due to mismatched resistor and motor can do it for 10 years. Others lasted 30 years +. I fitted maybe 50 new momos, finding no advantage. Some unusual momos are a complete pain because they're hard to find, the wiring's non standard, etc.
IME only Chinese copies and poor motors fail in a year or two.