Calling All Solar Heating Experts
Discussion
Murph7355 said:
Ours does (if I'm reading you correctly).
The max temp on the solar thermal seems to be the thermostat for that "circuit". There's also one for the boiler "circuit" I believe.
So if I set the max temp on the solar system to, say, 90degC, if sunny enough for long enough, the water in the tank will get much hotter than the 'stat the boiler is set for (say 50degC). Which matches experience of running a hot tap in very sunny weather.
On our system there's actually no other way for this to work. The system either keeps circulating to bleed off the heat in the panels to the hot water tank, but hence getting the water hotter and hotter. Or it keeps the tank sensible but then the panels get too hot (and potentially boil the fluid).
The challenge I have in understanding the logic of the system is that it only works to any useful degree when it's really sunny. Which is also when most people don't need anywhere near as much hot water anyway
It is no doubt doing "something", but how much difference it's making fiscally is very difficult to ascertain - for me anyway, as the system has always been here and it is not possible to isolate it without causing issues with the system itself.
This year's decent weather is all but gone. For next year I may try better insulation on the tank and isolate the boiler when it starts to get sunny. See if it can cope. I guess another alternative would be to shower etc in the evening...but that's not ideal.
Edited to add - the system pump starts when panel to tank diff is 10degC, and goes off again when it drops to 5degC.
That looks as if it's working.The max temp on the solar thermal seems to be the thermostat for that "circuit". There's also one for the boiler "circuit" I believe.
So if I set the max temp on the solar system to, say, 90degC, if sunny enough for long enough, the water in the tank will get much hotter than the 'stat the boiler is set for (say 50degC). Which matches experience of running a hot tap in very sunny weather.
On our system there's actually no other way for this to work. The system either keeps circulating to bleed off the heat in the panels to the hot water tank, but hence getting the water hotter and hotter. Or it keeps the tank sensible but then the panels get too hot (and potentially boil the fluid).
The challenge I have in understanding the logic of the system is that it only works to any useful degree when it's really sunny. Which is also when most people don't need anywhere near as much hot water anyway
It is no doubt doing "something", but how much difference it's making fiscally is very difficult to ascertain - for me anyway, as the system has always been here and it is not possible to isolate it without causing issues with the system itself.
This year's decent weather is all but gone. For next year I may try better insulation on the tank and isolate the boiler when it starts to get sunny. See if it can cope. I guess another alternative would be to shower etc in the evening...but that's not ideal.
Edited to add - the system pump starts when panel to tank diff is 10degC, and goes off again when it drops to 5degC.
When do you use most of your hot water? our main use is in the morning.
It does only produce hot water during a reasonable day (it doesn't have to be full sun all day) these are much more efficient than solar PV. Your tank should be capable af storing that heat until you want to use it. If you have a cylinder top temp reading - how much is it losing over night?
If you keep drawing hot water off during the day, you will get a lot of warm water but no hot. We do not use much domestic hot water during the day.
Paul Drawmer said:
That looks as if it's working.
When do you use most of your hot water? our main use is in the morning.
It does only produce hot water during a reasonable day (it doesn't have to be full sun all day) these are much more efficient than solar PV. Your tank should be capable af storing that heat until you want to use it. If you have a cylinder top temp reading - how much is it losing over night?
If you keep drawing hot water off during the day, you will get a lot of warm water but no hot. We do not use much domestic hot water during the day.
Good idea on taking the tank readings (it needs a data logger When do you use most of your hot water? our main use is in the morning.
It does only produce hot water during a reasonable day (it doesn't have to be full sun all day) these are much more efficient than solar PV. Your tank should be capable af storing that heat until you want to use it. If you have a cylinder top temp reading - how much is it losing over night?
If you keep drawing hot water off during the day, you will get a lot of warm water but no hot. We do not use much domestic hot water during the day.
). Most use is in the morning. Couple of 38degC showers. And a little in the evening (warm shallow bath for a small child).
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