Tag Archives: wood furnace

Hydronic Heating Coil Replacement

Today was Hydronic Heating Coil Replacement day at the Ivany homestead. What is a hydronic heating coil you ask? It’s basically just a water to air heat exchanger which is really just a radiator like you find in a car. Here is a picture of the old one that I replaced today:

Our old water to air heat exchanger coil that was leaking

Our old water to air heat exchanger coil that was leaking

The house actually has an electric forced air system. At some point before we bought the house, the previous owner did a retrofit to add this hydronic heating coil system. I’m guessing it happened around the same time that heating with electricity got expensive and/or natural gas was brought to Kemptville. We heat water with a Polaris high efficiency natural gas hot water tank. That unit has two sets of outlets, one for the domestic hot water and the other for a heating system loop. I believe it’s more intended for use with radiant in floor heating but our system is basically just a radiant system with one loop.

This replacement isn’t something I plan on doing on a regular basis as these coils should be able to last for a fairly long time. For some reason, the coil I had started to spring these little pin-hole leaks. That meant I had water collecting in the plenum and that’s really not good. If you notice in the picture above, the unit on the right hand side is my blower and all of the electrical connections are on the bottom side. Further right are all of the relays and the actual electric heating elements. Yeah, that’s the side where the water was pooling. I had to break out the drill to put a few well placed drain holes in the bottom of the plenum to ensure I didn’t run into any electrical problems while I found someone to fix my system.

Now, I had a hell of a time trying to find a hydronic coil (aka duct coil, aka heat exchanger, aka water to air exchanger, aka wood furnace coil) because I couldn’t find anyone local who seemed to have a clue as to what the thing was. I contacted a couple of the local heating companies, even had one come in and just recommend we replace the whole system with a new furnace. One other local company managed to track down a coil, a different size than what I needed, but the cost to get it and have it installed would have been over $1000.

Instead I hit up Google to see what I could find. Now, the time line of this is a little out of whack. I actually started searching Google just before having one of the local heating companies come in. That was almost 3 months ago. The second company got back to me just before Christmas. In the meantime, Google had helped me find a whole lot of places where I could buy a replacement coil, once I knew what to search for.

Ironically, I ended up getting the coil through my neighbour two houses away. We were chatting one day and he started asking some detailed questions about the sizing of the coil. Only then did I find out he actually works with outdoor wood furnaces and they use hydronic coils for all of their heat transfer. Within a matter of a few days I had my replacement coil and I started collecting all the stuff I needed to change around the copper connections.

Oh, yeah, time for some plumbing! This isn’t something I had ever done before so I consulted my books, chatted with the guys at work and borrowed some tools. Now I’m sitting here, tired as a dog (holy crap I found muscles I’ve never used before) and happy as a pig in shit because I actually managed to solder a whole crap-load of connections with no leaks! Well, no leaks yet. ;)

The new copper for the water to air heat exchanger coil

The new copper for the water to air heat exchanger coil

The new copper was required due to the fact the original coil was a 1/2″ inlet/outlet coil and the new one is a 1″ inlet/outlet coil. My feed from the Polaris hot water tank is 3/4″ so I had to replace the 1/2″ copper with 3/4″. I also had to re-route the connections as this coil has it’s inlet and outlet on opposite ends. The old coil had both connections at the top. In the picture, the little blue cylindrical device is my Taco 006 circulator pump. It pulls water from the hot water tank (well, helps pull as it’s all under pressure) to be passed through the hydronic coil while my blower is on.

After reading so many websites and so much information on how these hydronic systems work, I don’t think I’ll be replacing mine anytime soon. Basically, I can heat water using any number of sources. Wood, gas, electricity and even solar could be used to heat my house.

I’ve become very interested in radiant in-floor heating systems now as well. Interestingly enough, I could run the forced air unit as one heating zone on a radiant system. That could be handy for a slow transition to a radiant system in the house. Since we will probably replace much of the flooring in the next few years, radiant is a viable solution for this house.