Three way valve and head - strange behaviour

[Basildon_Bond]

So - I have a Bosch condenser boiler and conventional thermostat, timer etc. I noticed recently that when I selec tcentral heating on the timer control, the hot water also comes on. I started a thread about it here:

Sticking Sunvic 3 Port Valve

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...

www.diynot.com

OK so I removed the valve head unit (Sumvic SD2701) and checked - the valve spindle could still be turned by hand with a little effort. So - I replaced the head with an identical new model from ebay and had an electrician wire it in. The SD2701 has a slider to move between 'Normal Use' and 'Flushing Only' and this is pointing to 'Normal Use'.

Here's the problem. If I select 'hot water' on the timer the boiler fires up immediately. If I select 'central heating' tho, nothing happens, although the timer light comes on to indicate CH 'active'. I've checked the thermostat and the system pressure; both fine. If however I keep the timer on 'CH' and move the slider to 'Flushing Only' the boiler will fire up immediately. If I then move the slider to 'Normal Use' the boiler stays on.

Any idea what is going on here? What does the 'Flushing Only' setting do in terms of the valve - does it open the valve to both CH and HW ? I've read that other valve heads have a slider to move between 'heating' and 'hot water' - what is different about mine ?

TIA

 

[Johntheo5]

Here's the problem. If I select 'hot water' on the timer the boiler fires up immediately. If I select 'central heating' tho, nothing happens, although the timer light comes on to indicate CH 'active'. I've checked the thermostat and the system pressure; both fine. If however I keep the timer on 'CH' and move the slider to 'Flushing Only' the boiler will fire up immediately. If I then move the slider to 'Normal Use' the boiler stays on.

When you select CH, do you mean CH only or CH and HW?? If Ch only then and if wired like the Honeywell (below) 230V should be supplied via the programmer CH on request & the roomstat and the white wire to power the motor via internal switch1, the valve will then start moving across towards mid position and switch1 will then switch to the grey wire and if HW is not requested then the HW OFF contact (on the programmer) will supply 230V to continue driving the valve to fully over and switch2 will then provide 230V to the orange wire to fire the boiler. IF HW is/was also requested on but if the cylinderstat is satisfied then it (cylinderstat) will provide the 230C via its contact2 to drive the valve fully over with switch2 again providing 230V to fire the boiler.

So, above when you move the lever to flushing only (mid position), and the boiler fires up and remains firing when you return the lever to "Normal" does/is the valve then move to the CH only position, hard over, with onl port A (CH) open??.
IF so, it looks like you are not supplying 230V from the CH on request and the roomstat to switch1. You say you have checked the thermostat, I presume this is the roomstat?, and how are you checking it?, do you have a Multimeter that you are actually getting 230V on its contacts?.

Any idea what is going on here? What does the 'Flushing Only' setting do in terms of the valve - does it open the valve to both CH and HW ? I've read that other valve heads have a slider to move between 'heating' and 'hot water' - what is different about mine ?

Flushing only should move the valve to mid position, normally used when draining down or refilling the system, I dont think any mid position valve lever can move the valve fully over to the CH only position but not sure about this, others will advise.

TIA

 

[Madrab]

Cant say I've ever hear of a manual selector for 2 different positions, the lever is purely to allow draining or commissioning therefore on a 3 port, it centralises the valve @ mid position, on a 2 port it locks the valve open.

(edit) sounds like you have either a wiring/programmer issue, if the head has been changed and it's still doing the same. Without going into war and peace on the post as to how a 3 port works, i'll link to an explanation as to how it functions - You already have a diagram for wiring but I'll link to a series of GIF's that graphically show how the wiring works depending on what's calling/satisfied, from that you should be able to circuit test all the components to rule stuff out.

Don't forget it's all 240V so if you are testing then safety first.

https://www.newmrr.co.uk/how-the-3-port-valve-works/

John Turnbull

 

[DP]

Cant say I've ever hear of a manual selector for 2 different positions, the lever is purely to allow draining or commissioning therefore on a 3 port, it centralises the valve @ mid position, on a 2 port it locks the valve open.

(edit) sounds like you have either a wiring/programmer issue, if the head has been changed and it's still doing the same. Without going into war and peace on the post as to how a 3 port works, i'll link to an explanation as to how it functions - You already have a diagram for wiring but I'll link to a series of GIF's that graphically show how the wiring works depending on what's calling/satisfied, from that you should be able to circuit test all the components to rule stuff out.

Don't forget it's all 240V so if you are testing then safety first.

https://www.newmrr.co.uk/how-the-3-port-valve-works/

John Turnbull

Madrab, do you ever get p1553d off and write in anger
Cool dude indeed
Merry Christmas

 

[Madrab]

Madrab, do you ever get p1553d off and write in anger
Cool dude indeed
Merry Christmas

If there's one thing I've learned on this place @DP there's absolutely no point letting anyone get to you, they just aren't worth it.

Don't get me wrong there's a few that have had me close to it, especially one at the moment but hey, if they're that intractable, what's the point.

Merry Christmas to you too bud

 

[Basildon_Bond]

Ah - unfortunately I haven't been able to inspect how the valve moves - I'll check that. When I say I 'check the thermostat' - and yes I mean roomstat- I only mean it's turned up - I haven't checked the output from it.

Many thanks for your help John

Thanks Madrab - I'll have a look at the link.

 

[Basildon_Bond]

Question - Is the wiring and operation the same for a Honeywell and a Sumvic (I have a Sumvic SD2701).

Thanks

 

[Madrab]

Question - Is the wiring and operation the same for a Honeywell and a Sumvic (I have a Sumvic SD2701).

Thanks

All wiring for a Y plan or an S plan would be standard regardless of the make of valve, as long as the number/colours of wires from the valves and the function are the same.

 

[Johntheo5]

 

[Johntheo5]

Comparing it with the Honeywell it does look the "same"

Re your original post, when you get it to operate like below, is it just CH that comes/stays on and is that with CH ONLY selected? or is it with HW selected as well and the cylinderstat calling?.

"Here's the problem. If I select 'hot water' on the timer the boiler fires up immediately. If I select 'central heating' tho, nothing happens, although the timer light comes on to indicate CH 'active'. I've checked the thermostat and the system pressure; both fine. If however I keep the timer on 'CH' and move the slider to 'Flushing Only' the boiler will fire up immediately. If I then move the slider to 'Normal Use' the boiler stays on."

 

[ianmcd]

Cant say I've ever hear of a manual selector for 2 different positions, the lever is purely to allow draining or commissioning therefore on a 3 port

I think he is referring to a 3 port 3 wire diverter valve rather than a mid position valve, not very common but have seen a few, along with the old manual diverter valves that had a manual lever between HW and CH think they were a servowarm idea many years ago

V4044C1288 Diverter valve 22mm 3 wire 3 port. Honeywell. Motorized Valve.

V4044C1288 Diverter valve 22mm 3 wire 3 port Honeywell Motorized Valve V4044C Motorised Diverter Valve The V4044 Motorised Diverter Valve has been

terrybookers.co.uk

 

[Madrab]

Is that like the ones that connect directly to a boiler and then controlled by it for HW cylinder control, like in the older CDI's etc? Would that not still just have a single position 'mid position' lever for servicing? Never used one TBH

 

[ianmcd]

Is that like the ones that connect directly to a boiler and then controlled by it for HW cylinder control, like in the older CDI's etc? Would that not still just have a single position 'mid position' lever for servicing? Never used one TBH

They were the origional W plan priority HW, only 3 wires and live for the motor was supplied from cyl thermostat satisfied, when power applied to the valve it motors into CH position, have only seen a few not very common, but are common in boilers with a small thermal store

 

[Johntheo5]

Came across this some time ago, installing this NO relay should ensure that the valve returns to the HW unpowered position even if CH was its last port of call.

 

[Basildon_Bond]

Comparing it with the Honeywell it does look the "same"

Re your original post, when you get it to operate like below, is it just CH that comes/stays on and is that with CH ONLY selected? or is it with HW selected as well and the cylinderstat calling?.

"Here's the problem. If I select 'hot water' on the timer the boiler fires up immediately. If I select 'central heating' tho, nothing happens, although the timer light comes on to indicate CH 'active'. I've checked the thermostat and the system pressure; both fine. If however I keep the timer on 'CH' and move the slider to 'Flushing Only' the boiler will fire up immediately. If I then move the slider to 'Normal Use' the boiler stays on."

Yes - so if the Sumvic is in the 'normal' position and neither CH nor HW are currently active on the timer - and I then press HW ONLY on the timer, the HW light on the timer comes on and the boiler immediately fires up. I've noticed at the same time that both the HW in the taps and radiators gradually get warm.

If I then cancel HW - boiler goes off and HW light goes off. no problem.

If then as before with nothing active, I select CH ONLY on the timer, the CH timer light comes on - but the boiler DOES NOT fire up. zilch! If however I move the Sumvic slider to 'Flushing Only' and then back to normal, and try again , the boiler fires up. I've noticed that again, altho only CH selected in thi case, both the HW tank and radiators get warm.

I'm wondering whether the three-way valve is too stiff to be moved properly by the motor. I did take the head off and turn the valve spindle by hand - - and I could - but there was some resistance - it wasnt completely easy to turn, if you see what I mean.

Thanks