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- 13 Dec 2023
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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:
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
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