Hi can any one tell me if pre heated water (from solar panel) can be routed into the cold feed on the above boiler thus using less gas for domestic hot water.
Thanks Paul
Thanks Paul
Vaillant Eco tec Exclusive 838 help
- Thread starter friday2002
- Start date
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In practice it can but I dont think vaillant approve of it.
Preheated water has to be supplied from a blender at a temperature of about 20-25 C thus enabling the boiler to provide a greater flow rate or to save gas.
However, doing that means the boiler has less headway to properly control the output temperature.
Normal control is by modulation of the boiler input power. Thats from full power down to about 35% in most models.
In practice the main problem effect is that it will not be able to control the temperature properly at lower flow rates.
Tony Glazier
Preheated water has to be supplied from a blender at a temperature of about 20-25 C thus enabling the boiler to provide a greater flow rate or to save gas.
However, doing that means the boiler has less headway to properly control the output temperature.
Normal control is by modulation of the boiler input power. Thats from full power down to about 35% in most models.
In practice the main problem effect is that it will not be able to control the temperature properly at lower flow rates.
Tony Glazier
Most boiler manufacturers now manufacture a Control Valve assembly for linking Solar thermal to a Combi boiler as Vaillant market Solar Thermal products I expect that they can provide a Valve set for your application! 
There are many companies offering a possible solution to your question. On the closed forum here, they are discussing one possibilty.
http://www.altecnic.co.uk/images/stories/pricelists/AltecnicSolar_PriceList2011.pdf
Scroll down to solar combi valves
http://www.altecnic.co.uk/images/stories/pricelists/AltecnicSolar_PriceList2011.pdf
Scroll down to solar combi valves
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The inlet water must be below the set outlet temperature.
At low differentials between inlet and set outlet temperatures the only control the boiler has is on/off modulation. So the outlet temperature will vary. No problem for a bath but not good for a shower.
Tony
At low differentials between inlet and set outlet temperatures the only control the boiler has is on/off modulation. So the outlet temperature will vary. No problem for a bath but not good for a shower.
Tony
Hi
Thanks all of you that’s given me plenty to think about and to work out if it’s worth it or not.
Thanks Paul
Thanks all of you that’s given me plenty to think about and to work out if it’s worth it or not.
Thanks Paul
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