With the panels installed and the pex run, the next step is to prepare the radiant heat distribution in the mechanical room. Initially, I was under the impression that the system we had was all ready to accept the new zones, but it turns out that Lester didn’t really set this up for everything to just easily connect. Even though our plan for the radiant heating hasn’t changed, and our house still has the same number of floors and hence distribution zones, our existing system is only set up for three zones, and the controller is equipped for only one zone.
Unfortunately, this means that the heart of the system needs to be replaced with a larger unit. This is properly called a “hydraulic separator/manifold” but I refer to it as ‘the core’ because it’s easier and it sounds cool. Without getting too far into the weeds, the way our system works is the boiler has a supply and a return line that both connect to the core. The core in turn, has supplies and returns for each zone, or floor, of our house. It’s like an octopus reaching out to the rest of the house. On each floor there’s a supply and return manifold to distribute to individual loops on that floor.
A manifold just splits the flow of hot water from an inlet to several outlets with individual valves or, in the case of a return manifold, combines several inlets to one outlet. This way each floor has a water circuit to and from the boiler. Each zone has its own pump, and all but the hottest loop (the radiators in the attic) have mixing valves to adjust the temperature down from the boiler temp to something more suitable for that floor, since radiators generally run hotter than in-floor heat. Each zone will also have its own thermostat, so that they can call for heat individually.
I bought the same brand core as the old one, a Caleffi Hydrolink, just with more ports. I did this partly because the basement mixing valve is also made by Caleffi, and it’s sized to screw directly onto the supply and return ports. The only major change was that the new core has more ports, and one of the pairs of ports is on the bottom, which can go directly to the basement loop, and the other three sets on top can go to the first floor, second floor, and attic. I also bought fancy pre-built mixing valve and pump combo units to run the first and second floor units. I already had the parts for the attic from when we ran the radiators on the second floor.
The biggest concern is that it’s winter, and the system is running to keep the basement where we live warm. We need to shut off the heat, drain the water, completely take it apart and reconfigure it, hook the basement back up and hope nothing goes wrong, nothing leaks, and that we have heat when it’s all done. For a project like this, I called in Dean.
We got to work, and at first things mostly seemed to go smoothly. We got the system drained and the old core removed, but once we had the new core in place, we started running into some problems. First, there’s a port on the bottom that fills the system from the water supply that wasn’t in the same spot, so the plumbing didn’t line up. I hadn’t accounted for this, so I didn’t have the parts to adjust it. Before I ran to the store, though, we decided to see if everything else worked, and that’s when we discovered the bigger problem.
Caleffi apparently changed the spacing on their supply and return ports at some point in the last several years from 90mm to 120mm. This meant the Caleffi mixing valve for the basement loop that I already had didn’t fit on the new core. The new stuff fit, since it’s from the same model year or whatever. So I went to the store and picked up some brass fittings and we got it together as best we could.
Unfortunately, things didn’t line up very well, but it was getting late, so we made do and turned it on. For the next week the system had some slow leaks and the heat couldn’t quite get up to the thermostat even though it wasn’t all that cold outside. I came up with a new design, got some new pipe fittings, and started reconfiguring it yesterday. I discovered my new design still wouldn’t work, so I decided just to remove the mixing valve for now, and hooked up the system without it.
Since we’re not using the radiators right now anyway, the whole point of the mixing valves isn’t that important right now and we can decide if and when to change it later. The next steps will be connecting the pex lines that go to the other zones, running electrical to the new pumps, and replacing the controller.