I'm a new joiner to the group so Hi everybody.
I am carrying out some research as to the feasibilty of using a solar water heater to preheat the mains pressure DHW supply to a combi boiler. The reason is obvious but if you getn avergae temperature lift averaged out over the year the savings are worth having provided the simple remain simple. This is the main aim.
The system will have a seperate loop for the solar water heater heating a tank which is mains fed and linked directly to the boiler. Thats the easy bit.
As far as I can make out most combi boilers work on a feed water temperature of around 10 degrees. They achieve delivery temperature by restricting flow through the heat exchanger so increasing the time that the water is in the heat exchanger and so allowing the temperature to be rasied sufficiently. As such, most combi's will not recognise the fact that the DHW feed water is at an elevated temperature ( say 50 degrees) this will mean that the boiler will fire regardless of water temperature so leading to the possibility of dangerously high tap temperatures being delivered.
The idea is to keep the system simple utilising a bog standard solar panel with a glycol mix heating a mains fed tank running directly to the boiler. This does away with the usual gismos that get bolted on to such systems adding expense and making it more complicated than it need be. After all, it is not rocket science. What is difficult is getting the answer as to whether general combi boilers will regulate depending on the temperature of the inlet water. I suspect they do not.
The question is then do combis recognise pre heated water or am I going to need to scope out specific combi boiler that do.
All comments very much appreciated.
Dee