removing zone air with no return line boiler drain installed

bfinch9

Hello,
I’m a H.O. with a technical background. When we built our house 23 years ago I had a local company install hydronic heating with 2 zones in gypcrete upstairs and downstairs, and a 3rd zone in the garage in concrete. My video of all the work being done was overwritten by kids, so I lost all of that…..

Over the last few days I’ve tried to understand the system, since I have a couple of worrisome things happening. I’ve identified and mapped out all the components. First, my backflow valve (ASSE 1013) connecting the water supply seems to be in-op. In fact, the supply side of the backflow is closed. I don’t remember when or how this occurred, but the drain is covered green, so I’m guessing at some point the backflow valve was spitting water and getting things wet and someone closed it off. I can re-build the valve then have it tested, no problem.

Over time we have developed air gaps in the upstairs loop. The system seems to be a homerun manifold design. Our boiler and piping had to in the garage, away from the house, so the common piping single supply and return lines are insulated and run in the garage concrete. The garage zone tees off those lines at the boiler, prior to going under the concrete. I’m sure the 2 house zones are tee’d off the common piping somewhere in the house or crawlspace. Each zone has a Honeywell motorized valve at the zone manifold.

I’ve seen examples of evacuating the air, but they all assume a boiler drain on the zone side of the return line(s) shut off valve. My system doesn’t have this drain.

Each zone has a Honeywell Goldtop automatic air vent installed at the highest point of the zone, with a shutoff on the return side of the vent. My question is whether I can close the return valve, and engage the end switch, and use the Goldtop air vent to evacuate air from the zone? Then once I do this to each zone, I’ll make sure the common piping has adequate water.

Second question is whether I should cut in a boiler valve to the PEX on the zone side of the return shut off valve? If I do this, could I just drain each zone from this point?

Which would be better?

Thanks,
Bob

hot_rod

Got some pics? There should be a good air purger back at the boiler. If all zones circulate that air purger should remove the last annoying air bubbles. You should only need a manual purge on first start up

What pressure is the gauge reading, assuming you have an accurate working gauge. Too low of a pressure make air removal tougher.

With improperly piped boilers, and low system pressure, high point air vents can actually allow small amounts of air into the system. Allow them to vent and close the cap, see what happens. Chronic air problems are usually piping/ pressure related. Often solvable.

ALL BFDs should have the vent piped to the floor. If they discharge occasionally they are probably doing what they were designed to do

bfinch9

Thanks. I loaded a few pictures. Hopefully they work. Also, when I turned the supply water on the BFD was shooting water, from the bottom and some from the top. I'm pretty sure the pressure gauge isn't working. The temp on the pipe and boiler both seem in sync. The pressure gauge on the boiler looks good. And yes, there is a spirovent air eliminator seen in one of the pictures. Overview-2 shows the hot supply to the zones (unwrapped PEX) and the return line (next to it). Let me know if you have any questions, or what you think.

Thanks.

bfinch9

Also meant to mention that the picture of the garage zone manifold is identical to the others. The Motorized valve is installed on the return side of the loop.

bfinch9

a new development - I turned up the thermostat to open the upstairs zone, and turned on all the supply water valves on the common loop (the BFD and the valve on the other side of the reducer). I could hear water moving and thought it was adding water to the common loop. Now when the pump closest to the mixing valve comes on it makes a vibrating noise for about 5 to 10 seconds. Not sure that it's cavitation, but sounds even worse that the previous gurgling water. Any ideas?