Freeze Protection for short vacations

[Mushroom Man]

I was wondering if anyone has a plumbing solution for a sidearm mounted on the DHW heater (oil, gas, propane or electric) to be used for prevention of freezing in the entire system?

 

[Tony H]

Do you mean using the DHW to heat the boiler water and keep from freezing ? I have considered that and probably will give it a test and see how warm the water gets after I put a bypass valve to allow water to pass around the termovar in a couple of weeks. I would assume you could do it using a small water heater dedicater just for that use after all many systems in europe use them to heat the whole house
I have added glycol to my system (no storage) because the boiler is in a shed with about 75' of buried pipe. I also intend to run the circulation pump on low to move the water thru the system.
I would guess pumping thru the sidearm it would pick up some heat and in my case running it thru the HX in the furnace would also transfer some heat but I can bypass that if wanted.

 

[Mushroom Man]

That's right Tony. I have an oil fired DHW tank. Seems to me that with the right plumbing it might be possible to keep the boiler from freezing by using heat from the sidearm and the oil furnace's plenum installed heat exchanger. It doesn't have to produce huge heat, just enough to stay above freezing. Is there additional plumbing needed or will the heat transfer happen on its own.

 

[Tony H]

Seems to me if heat transfers one way it will transfer the other way instead of convection the boiler water will have to be pumped thru the sidearm to gain heat.
After I get the bypass installed in my system I will probably experiment and run the pump and see what the water temp does. I also have a need to keep it from freezing and if I can do it with the HWH and pump I won't have to run glycol in the system.
Maybe one of the experts will chime in with some more info for us.

 

[Donl]

I have done a bit of testing with this and have found it to work well, I don't know exactly how much heat is transferred but running cooled boiler water through the sidearm of an operating DHW will suck out quite a bit of heat. In my situation I am confident that it would prevent freezing of the system in most situations.

 

[magnumhntr]

I did this exact test last week when the temp dropped to 34 degrees here one morning. I was running the pump on the OWB with no fire to see if the hot water heater could keep the 112 gallons in the Woodmaster up with just the sidearm. Worked like a charm. Water was 100 degrees in the burner while it was 34 outside. Glad to see it works because I'll be in North Dakota the for a week in Nov with noone to load the stove while I am gone....

Chris

 

[Sting]

Constant circulation of 40 degree (or less) liquid for idle outhouse, will give you frost protection with far less energy cost.

 

[pybyr]

Constant circulation of 40 degree (or less) liquid for idle outhouse, will give you frost protection with far less energy cost.

If the fire is definitely out in the OWB, you'd also probably use less energy even to keep it at 40 if you cover the top of the flue so that air is not convecting up through it and taking heat with it.