Termovar By-pass Freeze Protection

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jebatty

Minister of Fire
Hearth Supporter
Jan 1, 2008
5,796
Northern MN
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.
 
Jim, your body must go into thermal shock when you land in Aruba from Northern MN in the winter-time!
 
you could just pull the Termovar element and cage so that it does not restrict flow at the low temp freeze protection mode. I assume you will have the circulator turn on at low temp? Or will it be constant circulation?
 
...you could just pull the Termovar element...

The gaskets on the Termovar are a bit fragile, and based on past experience, I don't want to mess with the Termovar unless absolutely necessary. Installing a valve and a little bit of plumbing was pretty easy, and from now on I just have to flip a valve.
 
jebatty said:
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.

This is exactly what I did to get freeze protection. My circulator is controlled by a differential controller with built-in freeze protection. So when I go away I just flip open the bypass valve and the controller will activate the circulator as needed to keep the boiler from freezing. I have found there is easily enough heat stored in my ~600 gal of storage to last a couple of weeks in the winter in this mode.
 
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