mylesau wrote:
I would have thought those tubes would have performed a bit better, but it is a fair lump of water.
Typical evac tube water heaters do perform much better... but do so with large header tanks and copper heat exchangers... to raise the temperatures to a higher temperature
These units have no copper components... and no internal heat exchanger... they rely solely on heat absorption from the stainless header... and the energy absorption (light) of the evac tubes....
I intend to standardise on a thirty tube system... as opposed to the 24 tube test unit... a 25% additional capacity....
Coupled with the addition of "back" reflectors that have tested by the manufacturer and found to give a further 10-15% efficiency...
So that's a potential 35-40% increase in efficiency... plus a few other tweaks I have in m ind...
Myles wrote:
Issues I can think of:
1. using plastic piping could be an issue if the pump fails or if you reach a max. water temperature - is there a way to dump heat?
Not completely sure what you mean Myles...
If the pump fails the unit will merely thermocycle through the header and tubes.... and they're rated beyond boiling point... and there's a relief valve incorporated..
The controller also has both a tank high temp protection (setable)... so that if exceeded the solar controller will not pump to the tank...
The controller also has an anit-freeze protection ability... if incorporated with the electric/gas heater ability... and the tubes themselves are rated to about -20 degrees...
Controller can be manually over-ridden to activate or shut off the pump at any time...
And the temperature differential setting that controls the pump cycle can be adjusted at any time...
Myles wrote:
2. I guess this is probably best solved with some insulation but temperature fluctuations are the killer - if you get a few days of bad weather your still going to have to have a backup heating source or bye bye fishies.
As noted Myles... the unit has the capability to interface to any heat source... and switch it on/off via controller set points... are for programmable timer periods...
The actual heat devices can/will control themselves according to any thermostat settings... or can be controlled by similar set points on the solar controller...
So you could quite happily wire in a 300w aquarium heater... or activate a gas heater etc..
They're settings/thermostats are mutually exclusive...[/quote]