Sunvic Zone valves

[Doctor Drivel]

guy has whole a piece on the faliures of these valves. He explains in detail of the electrical failures. Some valves are worse than others.

Maybe Maxie would comment.

[YAPH]

I've became aware of that site and its author's warnings regarding these devices a couple of years ago, having been installing these Sunvic valves for some years to date without problems. I've carried on using them and must have installed a few dozen (both 2 and 3-port) and have so far had only one failure, of a 3-port almost immediately after I installed it. (I've still got the actuator head - must get round to finding out what's wrong with it.)

So, from my small sample size I'm not seeing the sort of level of problems one might expect from SeeRed's site, though I'll carry on keeping my eyes open for any.

[Doctor Drivel]

Similar with me. I have been aware of the site for a number of years. Usually the installer does not get to see any failures down the line. He does point out that after he contacted Sunvic they did increase the value of the capacitor and insert a diode.

He does mention that the 230v input is dropped to 24v to energise a 24v relay that switches 230v. He can't figure out why they did this. It can't be difficult to insert a small 230v coil relay from Maplin and make it all

230v and much more reliable, especially in the mo-mo valves.

I have used two Sunvic mo-mo's in a recent job where the CH was run on gravity and no pump. I like the point that the valves do not have a ball or paddle not restricting flow.

could have used commercial mo-mo valves, but they are much more expensive and a little more difficult to get - not that Sunvic mo-mos are everywhere. I know of a mo-mo valve, I think Honeywell, that is still going after 37 years. It only activates twice a day and consume no electricity when open or closed. On a gravity system this mean no electricity is used. People underestimate the electricity some gas and oil CH systems can use.

If water gets inside the actuator they can "explode", so positioning of the valve is important to prevent water ingress. As with all pumps and zone valves it is best to have them as cool as possible preferably on the return - possibly more essential with Sunvic.

[YAPH]

I think Sunvic still do 'traditional' Mo-Mo actuators (the sort I've written about in the wiki page) which you can use with full change-over switching: the types with the electronics in them only have that so they can be a drop-in replacement for spring-return types.

But as you say getting hold of Sunvics is a challenge now since B&Q dropped them. My local PTS can get the 22mm 2-port and 3-port ones but other types (e.g. 28mm) are a bit of a pain (not that B&Q used to do those anyway).

[Doctor Drivel]

Sunvic still do. Here you mention the Honeywell 3-port valve, under the heading Mo-Mo and sub heading 3-port, not mentioning if this is a mo-mo version. To my knowledge, Sunvic are the only maker left making domestic Mo-Mo valves. Are any other companies making them?

But as you say getting hold of Sunvics is a challenge now since B&Q

All the main suppliers can get them, but few stock them. It is probably easier in mail order on the web and cheaper.

[Andy Wade]

I've nothing to add about Sunvic valves, but the name Steve Wozniak on the website (also the domain registrant) rings a bell. Someone of that name used to work (and possibly still does) for the BRE. He wrote a definitive study on the UK use of solar thermal water heating in 1979 - a copy of which I've still got.

If it's the same person - scientist, academic background - the material on that site might well be worth noting.

[Doctor Drivel]

He does give credit where it is due. He also says that the repairs are better and more durable than what fit Sunvic in the standard product and make the actuator far more reliable. After the guarantee has expired it may be worth soldering in the zenner diode he mentions to give longevity and to avoid an inconvenient breakdown.

[Man at B&Q]

Do ACL/Drayton badge their valves for other people? The ones in the pic on that site look identical to the two in my system which are causing problems. They are Ikon brand from Travis Perkins, approx 9 years old.

MBQ

[Steve Firth]

It should, it's a relatively famous name.

[Doctor Drivel]

It appears Sunvic upgraded the troublesome components in the 2-port MoMo, and all is OK.

[Andrew Gabriel]

I can't tell how big they are from the pictures, but you can make a LV DC relay much smaller than it's possible to make a 240V AC mains relay, even allowing for the voltage drop components. Also, it will be lower power consumption.

I would comment that they've made a mistake in the design of the voltage dropper. There should be a resistor in series with the dropper capacitor to limit the inrush current when power is applied to the circuit. As it stands, if power is applied anytime other than the mains zero crossing point, the two capacitors will initially look like a short circuit, with the inrush current limited only by the diodes, capacitor ESRs, and wiring impedance. The resulting voltage pulse across the reverse biased diodes and the electrolytic capacitor could well exceed 24V momentarily (and the relay coil too, but that won't care due to its inductance). His circuit diagram doesn't give the voltage rating of the bridge rectifier or the electrolytic capacitor.

[Doctor Drivel]

Sunvic probably used 24VDC relays as they were ready availability and small in size. They would fit inside the existing casing. This makes the actuator unit an easy swop for existing designs. 240v AC relays do tend to be larger. But I have seen some quite small 240v relays these days. Maybe Sunvic should revisit and rethink. I assume that 24v relays are also cheaper.

The unit still has a capacitor problem because of the design, but it will take many years for it to blow. It is easy to replace using a soldering iron, or replace every 5 years to ensure no breakdown and downtime.

It is possible to fit 240v relays externally in a wall mounted box as they were in some models over 30 years ago. Then only the motor and end micro-switches are inside the actuator case with no chance of an explosion either if there is water ingress, as is the case with the current version.

Get in touch with him. He is eager for feedback. [e-mail] And report back. :-)

[YAPH]

In that case it's more than likely that they are the same. The Drayton ones are quite distinctive and I doubt anyone would get away (or want to get away) with making a something that would so obviously be a knock-off of anything other than the market leader, Honeywell (which there is at least one me-too version off).