Some may be in a situation similar to mine where I need freeze protection for 1000 gal storage + boiler during a winter period (vacation in Aruba, hopefully!). My boiler is the sole heat source for my shop. The solution I am now installing is a 12000w tankless water heater to be triggered by low water temp which may occur when the system is idle during the winter. As I was thinking about this, it occurred to me that the Termovar will not admit system/storage return to the boiler unless the boiler supply side is about 160F, as the Termovar only recirculates boiler water at temps below 160F. Also, I don't want to heat the boiler to 160F+ with a tankless heater just to achieve system circulation.
What I did was plumb a 3/4" line between system return and boiler return, by-passing the Termovar, along with a ball valve to open/close the by-pass. I tested the plumbing and can get 2-8 gpm, depending on my circ settings with the bypass. Hope to finish the wiring for the tankless heater soon to give it a final test and see what delta-T the tankless heater delivers at various gpm's.
I considered electric heat in the shop to cover this situation, but thought keeping the whole shop at a freeze-protected temp would use a lot more electricity than just heating the insulated storage and boiler.
What I did was plumb a 3/4" line between system return and boiler return, by-passing the Termovar, along with a ball valve to open/close the by-pass. I tested the plumbing and can get 2-8 gpm, depending on my circ settings with the bypass. Hope to finish the wiring for the tankless heater soon to give it a final test and see what delta-T the tankless heater delivers at various gpm's.
I considered electric heat in the shop to cover this situation, but thought keeping the whole shop at a freeze-protected temp would use a lot more electricity than just heating the insulated storage and boiler.
