Note: This system features a mismatched boiler,
solar pump station, DHW storage tanks — and
lots of controls trying to make something work.I know that these days we’re all trying to save our nickels. We’re looking for deals, sales, and great finds anywhere we can. People designing solar thermal systems aren’t exempt from this. Here and there you'll find a good deal on a set of unmatched collectors or a really great price on a used boiler, but the result is a mismatched system that is almost always guaranteed to work sluggishly (if at all).
It seems I’m spending a good amount of time lately trying to talk homeowners and installers out of these hodge-podge designs.
Recently, for instance, an installer sent me a drawing that featured a Bosch Water Heater, as well as a Bock tank, Caleffi controllers and a HTP stainless tank with both gas and electric heating.
In other cases, I’ve taken two dozen calls since 2013 from a homeowner who was promised by a solar dealer that a new solar system would reduce her propane bills. After the outdated 1970s-era design failed, the installer continued to add boilers and other parts to try to fix it — charging the homeowner each time. The new solar system actually produced utility bills higher than those using the homeowner’s old, inefficient boiler.
The main lesson here - you can’t determine the efficiency of a mismatched system.
When I started designing solar thermal systems back in the early ‘90s, all we had available were parts from different suppliers that had to be used together. I often found hidden conflicts with heaters and tanks that would not respond correctly, or the controls were so complicated it was difficult to get one sequence to initiate after another.
You simply can’t predict if these systems, designed to be built only once, will work. There is no backlog testing and its performance history has never been measured. These are all unknowns until you actually build one, test and measure, changing what didn’t work — until it performs adequately.
Some manufacturers have begun to provide whole systems in which all components work together. At HTP, its innovative owner and I have spent years developing integrated solar heating systems designed — and proven — to work seamlessly.
But there are still plenty of manufacturers who don’t have the capability to expand around a whole system because they don’t make the whole system. I am contacted regularly, for instance, by companies wanting to sell their collectors. That’s all they make — the easy stuff.
More important than the sales price of individual components is the long-term return on investment of the whole system. You can save yourself countless hours and endless frustration by installing systems in which all components are happy to work together.
Have questions about an upcoming solar project? Contact me, I'll be happy to help.