Ok, I admit it, I'm stumped......

[andyb]

Is that a fudge or should the head be swapped to the SZ 2351?

The home owner knows her house was built by bodgit and scarper so its the latest of her money swallowing her money...

I think it's a fudge Murdoch, though it should work.
The actuator is for a gravity fed system but if you wire it as the drawing and ignore the CH side of things it should work ok.
SL to brown, orange to boiler. There's no need to worry about the grey, that just brings on the pump for the CH in a gravity system. You've got another 2 port valve for that.

 

[bigspark17]

So, if it's a 2 port valve then it looks like the feed from the tank stat (S/L) goes to the brown, and orange to the boiler. You do not connect the grey.

Definatly not. Orange becomes live from the permanent live of the grey which should come from pl from boilers pcb. But from murdoch op it hasnt been wired with a 5c to boiler L,N, PL, SL, cpc. So it may be an older boiler which may not specify sl fed off pl on pcb so may have grey linked to pl in wc. It does sound like a Dodgy head apart from you say "wetpants" has changed the valve twice. Are you sure you werent getting back feed off ch orange.? Maybe fresh look at it will serve you well next visit, not a nice job last call of day!

 

[Leesparkykent]

I've just googled the valve and Andyb looks like he has it spot on. The valves not a conventional valve where grey is permanent live. Brown of the valve connects to normally closed of the cylinder thermostat and orange switched live to boiler/pump. The orange of this valve will also be commoned with the orange of the other valve. As this valve is usually for Gravity HW and pumped central heating I'm not sure if having the oranges from both valves together will affect by back feeding the valve if it does then it would be easier to replace the sunvic with a standard Honeywell two port.

 

[andyb]

Definatly not. Orange becomes live from the permanent live of the grey which should come from pl from boilers pcb. But from murdoch op it hasnt been wired with a 5c to boiler L,N, PL, SL, cpc. So it may be an older boiler which may not specify sl fed off pl on pcb so may have grey linked to pl in wc. It does sound like a Dodgy head apart from you say "wetpants" has changed the valve twice. Are you sure you werent getting back feed off ch orange.? Maybe fresh look at it will serve you well next visit, not a nice job last call of day!

It doesn't have a permanent live, it's the wrong valve.
You are correct in what you say if it was the correct valve, but there is no grey/orange S/l P/L for that valve.
Look at the drawing Murdoch posted in picture 3.

If you look you will see that when you put the switch live to brown the orange becomes live to feed the boiler. Like I said it's for a gravity system.

 

[davesparks]

Well that's a bit of an interesting one!
Those valves are a bot of a pita sometimes, I've encountered them before and nearly lost the plot trying to work them out. Assuming it's the one I tikka it is!

I've had a bit much cider to be any help now, but I'll have a proper look at it tomorrow and consult my notes on boilers.

 

[andyb]

Having slept on it Murdoch I think you should change the actuator or complete valve. Any demand for heating will open HW valve by backfeeding through the boiler.
If you use a Sunvic actuator it should be a straight swap with no plumbing involved.

 

[snowhead]

The Sunvic SZ2302 is a spring return valve, supplied with the Megaflow unvented cylinder and must be fitted.
It's a safety device to cut off the heat source if the cylinder goes overtemp.

The Gas /Boiler man should be G3 qualified to fit an unvented cylinder and should know not to replace the valve with anything other than a 2 port spring return.

 

[Octopus]

The Sunvic SZ2302 is a spring return valve, supplied with the Megaflow unvented cylinder and must be fitted.
It's a safety device to cut off the heat source if the cylinder goes overtemp.

The Gas /Boiler man should be G3 qualified to fit an unvented cylinder and should know not to replace the valve with anything other than a 2 port spring return.

Not sure I understand this comment!

 

[Leesparkykent]

Not sure I understand this comment!

The valve can be replaced with any normally closed Spring return valve. Doesn't have to be sunvic but might be easier as the body won't have to be changed and that means no draining down.

 

[andyb]

The Sunvic SZ2302 is a spring return valve, supplied with the Megaflow unvented cylinder and must be fitted.
It's a safety device to cut off the heat source if the cylinder goes overtemp.

The Gas /Boiler man should be G3 qualified to fit an unvented cylinder and should know not to replace the valve with anything other than a 2 port spring return.

The Megaflo thermal cutout is the safety device Snow, not the valve which is fed through the cut out. It can be any 2 port spring return valve but it needs a nc switch which the SZ2302 does not have.
It's the wrong valve and should be replaced.

Looking at the 3rd picture in Murdoch's op it's the Sunvic SZ2351 that's needed if you want to stick with Sunvic, though as I said, any spring return valve with a switch will do.

 

[Octopus]

The valve can be replaced with any normally closed Spring return valve. Doesn't have to be sunvic but might be easier as the body won't have to be changed and that means no draining down.

I'm going to call Sunvic this morning so will post what they recommend.

Thanks for all the input so far - I'm glad it wasn't straight forward after all.

I did get a call off a member who spotted the issue pretty much straight away - I won't name them unless they want to come clean....

 

[Leesparkykent]

I'm going to call Sunvic this morning so will post what they recommend.

Thanks for all the input so far - I'm glad it wasn't straight forward after all.

I did get a call off a member who spotted the issue pretty much straight away - I won't name them unless they want to come clean....

lol I think his name starts with H....

 

[Octopus]

lol I think his name starts with H....

Is this going to turn into a game of hang man?

 

[Leesparkykent]

Is this going to turn into a game of hang man?

I wish it could but haven't the time today

 

[Octopus]

UPDATE:

Sunvic Technical : 01698 810945 (who were excellent)

Have confirmed that the valve in place isn't correct (I think I knew that) and that it needs to be swapped for the SZ 2301 (valve normally closed, switch normally open). The body is the same so just a "simple" case of swapping the head.

Happy days!