Central Boiler: How to find your return or supply line

So you have an outdoor wood furnace or outdoor wood boiler and you aren’t sure what line is which going to the house or structure. Well, like many, we bought a house with an outdoor wood boiler (OWB) that we knew nothing about. Our boiler was a Central Boiler Classic 5036 and it’s a very nice setup. However, the previous owner did the installation completely on his own. That ultimately left us with more questions and quite honestly issues we weren’t expecting.

We started having problems with the operation of the unit. It was constantly boiling over and we had no idea how to diagnose the problem. I looked at the manual for the unit, but quickly found out that the previous owners modifications did not match the manual at all!

To start from scratch, I knew I needed to figure out what lines were which coming in to the house. On your boiler system, there will be two lines.

Supply Line: The line going to the house that supplies the hot water from the boiler to your furnace or hot water heater.

Return Line: The line going from the house to the boiler returning the water back to the boiler for re-heating.

It will also save you some time in the future if you mark the lines to indicate which is which once you have it established.

For me, my boiler was installed using the thermopex from Central Boiler. Strangely, they use the same color pex for both lines, which by design adds difficulty to figuring out which is which once it’s installed. However, if you are careful and peel back the foam insulation on the Central Boiler thermopex, you will see one line has a black stripe. This will tell you which is which. Of course, how you install it may be different. Check out the video below!

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