What is the advantage of a closed loop heat transfer system versus drain-back?
EnerWorks uses and strongly recommends the “closed loop heat transfer” type systems even in hot climates not requiring freezing protection. In drain-back systems, if mains water is being used as heat transfer fluid in an un-pressurized system then a) collector tubing will scale and require frequent maintenance or will malfunction; and b) pure water used in a closed, un-pressurized loop will eventually breed bacteria and cause bio-fouling or present a hazard to potable water. Some drain-back installers are trying to counter these effects by using a closed loop propylene glycol drain-back system – propylene glycol is an effective bactericide. If the glycol is not pressurized and it is exposed to oxygen, it will actually degrade even faster. If glycol and a nitrogen blanket are used to avoid oxygen exposure, the system becomes very complex, expensive and leak-proofing becomes very difficult (but crucial). In drain-back, all pipes have to be properly sloped otherwise the drain- back won’t
