Sticking Sunvic 3 Port Valve

[Alfie25]

I noticed yesterday my CH was coming on even though I'd just called for HW and on inspection sure enough the 3 port valve was directing the water to both CH and HW.

I turned the system off and in the absence of anything else to try, I slid the 'slider' lever towards flushing then back to normal again, then fired it up and it seems to be working fine since. If it fails completely I'll get a tradesman in to replace it, but is there anything I can do to stop it sticking again? I see the head/actuator can be removed (2 screws) - is thre anyting in there to lubricate? I take it this can be removed without water coming out?! What is the usual reason for failure/sticking with these?

 

[Hugh Jaleak]

Sunvic valves are common for failing. Best course of action is to replace entire valve for a Honeywell version, will far outlast the Sunvic. The chap behind this website offers a repair service, and has a guide to why Sunvic valves fail.... http://www.seered.co.uk/sunvic.htm

 

[Alfie25]

Well it's worked fine for a couple of months but is now making a clicking noise so I guess its days are numbered. I take it it's a case of just replacing the head with no need to drain down? If fitting a Honeywell, would it need a drain down? Presume you cant put a Honeywell on a sunvic valve?

I've just done some more searching on the topic. With my sunvic valve, when only CH is being called for and this is satisfied, the valve opens back to the mid way and for the 2 minute pump overrun, water is pumped to both CH and HW. Is this normal or has it been wired this way on purpose to avoid the problem being referred to here:

//www.diynot.com/forums/viewtopic.php?t=152124

 

[45yearsagasman]

Remove the head by removing the 2 screws. The D shaped spindle should be free enough to move by hand. If not, then the valve body needs replacing. They can be refurbished, however it would be better to fit a better quality valve, say Honeywell. That would require a drain down. You cannot fit a Honeywell head to a Sunvic body.

 

[Alfie25]

Is it safe to remove the head myself? Any pointers? I presume once you've removed the head and turned the D shaped spindle, in order to get it to fit back together you just put the D shaped spindle back in the same position it was in originally?

And if I'm understanding this right... if I can spin the spindle freely with my fingers, then just the actuator (head) is bad, but if I can't spin it freely then the whole valve assembly needs changing?

 

[D_Hailsham]

Is it safe to remove the head myself? Any pointers? I presume once you've removed the head and turned the D shaped spindle, in order to get it to fit back together you just put the D shaped spindle back in the same position it was in originally?

And if I'm understanding this right... if I can spin the spindle freely with my fingers, then just the actuator (head) is bad, but if I can't spin it freely then the whole valve assembly needs changing?

Yes you can remove the head; no water will escape. Just remember to turn the power off first.

Use the lever at the end to lock the valve in the MAN position before removing/replacing the head.

The spindle will not spin through a full circle, only about 20 degrees, between end stops.

If it's sticky, a little silicon lubricant on the seals may free the spindle.

 

[Alfie25]

Ok thanks, by turn off the power, you mean the boiler? And even with the valve locked to Manual, the spindle should still be able to turn?

If it needs silicon spray, where am I spraying this?

For a bit of further info, the clicking sound it makes is only when it's in the mid position. The sound is like a relay clicking on and off.

 

[D_Hailsham]

Ok thanks, by turn off the power, you mean the boiler?

There should be a switch, usually near the boiler, which turns off the power to the boiler and all associated components, e.g the valve/

And even with the valve locked to Manual, the spindle should still be able to turn?

You lock in manual to remove the head. The spindle is in the valve body, so it is free to move.

If it needs silicon spray, where am I spraying this?

Round the base of the spindle, where the 'O' ring seals are which prevent any water escaping.

For a bit of further info, the clicking sound it makes is only when it's in the mid position. The sound is like a relay clicking on and off.

Can you get heating on its own?

 

[Alfie25]

It's wired for priority hot water so when heating only is selected on the programmer, CH and HW come on, until the cylinder stat is satisfied then the 3 port valve shifts to CH only.

 

[Alfie25]

I've just got round to checking this after a couple of days away. The spindle can be turned by hand although it's not exactly what you'd call smooth. You can feel a bit of resistance as it moves round, and almost as if it "clicks" between positions.
Is this what you'd call normal? Oh, and it was was possible to move it through a lot more than just 20 degrees between the end stops.

Would be grateful for any further advice.

 

[Hugh Jaleak]

From memory the Sunvic valves work on a diferent principle to other e.g. Honeywell. The Sunvic uses a hollow tube, with the flow from the boiler entering at the base. It then rotates according to requirements to align ports cut into the tube with the appropriate outlet(s), so I believe it may be capable of 360 ° rotation.

I found at least one, that whilst it would happily work as expected when removed from the system, once refitted and the system refilled, decided it wished to malfunction and do it's own thing once again..... replaced it with the Honeywell equivalent. No further problems since.

 

[Alfie25]

Thanks for that and I'm glad your Honeywell has proved a better option. To be honest I'm looking to replace my whole CH system at some point in the next 12 months so I'm ideally looking to replace as little as possible on this system. With that in mind I'd be grateful if 45yearsgasman/D Hailsham or anyone else could comment on how 'sticky' the spindle is meant to be when rotated by hand.

 

[Alfie25]

Is it easy enough to fit a new head myself? It's basically 4 wires going into a connector (which is wired to the junction box). Is it just a case of power off, remove head, disconnect 4 wires then reverse the procedure with a new head? Or is there more to it?

The connection block looks like this. Don't know why the 3 port valve isn't wired directly into the junction box.

Untitled

• Alfie25
• 11 Nov 2013
• 1

 

[Alfie25]

Sorry to bump this but would be really grateful for advice.

 

[Hugh Jaleak]

Basically as you have described. Just make sure each wire is replaced in the correct position, (swap one at a time if need be to ensure), otherwise it wont work!