Wood Boiler Update – anti-themosiphon valve

Thats right, an update to my wood boiler. Yes,.. its been probably a couple years since I blogged on it. What changed? Well my dad was visiting so I figured I”d get him to help me – always good to have a backup when getting into projects that require the water to be shut off to the whole house for any period. The worst case scenarios for that are when you realize part way into the project you don’t have the correct fitting or something.. and you have to home depot – if it hasn’t closed yet. Thats depressing!

As yo can see below, I installed a 1 inch ball valve inline with the hot water loop that goes through the hot water coil in the wood furnace. We noticed much higher electricity bills and for the most part I figured it was the extra cost of electricity since we were using that to heat our domestic hot water instead of oil. And to some extent, it was that. The flaw in the original design of the hot water loop was that in summer, it would thermosiphon as designed but in the opposite direction.

In the winter, the fire heats up the water, the water rises to the top of the hot water tank and pushes cold water around into the wood furnace to be heated, hence the thermosiphon. However, that same principle works in the summer when the boiler itself heats the water, the hot water in the top of the loop outside of the insulated part cools, it then drops down into the coil and into the furnace and generally to the bottom sucking hot water off the top of the electric hot water tank and then of course it continues to siphon ever cooling the water I’m trying to keep hot!

Bad… and I didn’t really notice the difference until I got the valve installed. The current config for summer has that valve closed. Normally all the piping was hot to the touch where it came out of the tank and into the furnace and around at the bottom, because it was constantly pulling hot water round it, and cooling it.  With the valve, that whole look is cool to the touch, hardly any heat transfer!! Wow, now I know how much hot water was getting drawn through it, and that should save some significant kW hours off our monthly bill!

a bit hard to see, the copper pipe down the right side of the tank is the top of the hot water loop, disappearing into the green coloured wood furnace, then from the furnace out again at the bottom returning to the tank


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A teaser of an upcoming blog, a usedpei find, and related to food preserving.



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