3. Alan Rushforth uses STSS
ON BULK DRAINBACK SYSTEMS
” Failsafe freeze protection. The piping and collectors are pitched so that when the pump for the collector loop shuts off for any reason (including black-outs), the water in the collectors and piping all drains back safe and snug into the insulated storage tank, so there are no worries about freezing collectors. Unlike ‘drain-down’, or ‘recirculation’ systems, ‘drainback’ systems are not dependent on electricity for freeze protection.
No heat exchange chemicals are used. Unlike glycol systems, our drainback systems run on plain water that does not turn acidic; our drain back systems do not need periodic fluid changes; and our drain back systems allow for extra long collector life.
The thermal storage tanks in bulk drainback systems have no need to be pressurized. On large systems, this turns out to be a big plus, allowing more storage for less cost.”