Hello All,
We installed a solar hot water system for my wife's mother in WI in 2006. For two winters it has displayed a peculiar action. It will turn on and pump water up to a certain point, then drain back into the tank. There is a boiler that heats the pre-heated water from the solar hot water tank before sending it to the in-floor pipes. This failure corresponds with the boiler breaking down. The tank was holding what I would believe was some very hot water for about 4 days until the boiler was fixed. When turned on last winter the system worked fine until the boiler broke down again and then displayed the same problem. The system has been left throughout this summer and is just now about to be visited by the gentleman who helped install the in-floor system and is familiar with the solar system (Jeff). I am interested in learning anyone's thoughts on why this may have occurred. Is it possible that when the water was at its peak heat for 4 days because it was not having its heat pulled off by the in-floor system that a lot of steam was generated that could have frozen at the top preventing the pumps from pumping water to the top? Should we try some heated tape on the attic pipe elbows or something like that?
Does anyone have a thought about what may be going on?
General info on the system:
Water from large solar tank is the pre-heated water that is fed to the boiler for the in floor heating system.
~30ft drop from 6 panels on roof to ~300 gallon tank.
Drain back with at least 1/4" drop per foot
The panels are SolarGenix Winston Series CPCs
Two taco pumps, one 009 and one 006
At one point the service folks for the in-floor system removed a pump in our system, believing it to be bad, they later found it to be OK and re-installed it.
It worked fine until the boiler went down for four days. After this our system ceased to pump water to the top. This has happened for two consecutive winters. The system is working fine-the boiler goes down - thermal system is shut off - when turned back on will not pump water though the system. After the first winter the system was turned back on in the fall and worked fine until the boiler went down again this past winter.
We are not near the system and will know more when visited by Jeff.
Another question is what I should ask Jeff to do while he is there. I will ask him to pressure test the loop, fill the tank, and check the settings on the differential controller. It is a drain-back system that operated normally for 2-3 months for both winters.
We used this post in the design and pre-installation phase and appreciate the wonderful response and help we received then.
Thanks for you insight!
Mike Dooraghi
