Baseboard bleeding

After a closer look, you have the Watts auto fill valve with the fast fill lever on the top.


The concept here is to build up about 25 PSI on the gauge then open a valve to force the air from the loop. in order to do this you must close off several valves in order to make the loop you want to purge the only path for the water pressure to go. This water pressure will force the water thru the 3/4" pipefast enough to push the air out ahead of the water, even if the air needs to go down a vertical pipe. If the water is moving too slow it will not push the air out. It will just bubble up to the top, so you need to build up the pressure before each purge.

I am going to look at your pictures and draw a diagram for you. This will take about 30 minutes. Please be patient

SORRY FOR DELAY. Your piping diagram took longer than I thought, and there are several background pipes that are hidden by pipes that are in the foreground. There is one problem that I can not solve with the information in your photos But we will get to that at the end.
First lets label all your valves and parts that are involved with purging.


The valves are numbered all the other parts are labeled with letters.
Now here is the diagram with all the labeled

Now we can look at the piping as a complete system. There are 3 zones that I see (that means 3 thermostats). One of the zones is operated by the Black Circulator pump thru supply pipe that tees off to the flo-check valve B. From there the heat flows to the Black circulator thru the yellow pipe E. The black circulator pumps the return water back into the boiler to be reheated. I am not concerned with what type of radiators are on that zone.

Next illustration is how to force the water to purge air from Zone 2. That Is done by placing a garden hose on valve BD2, Closing valves 1, 3, 4, and 5. Then manually open zone valve C. Now look at the diagram to see the only path for the water is to enter the boiler thru valve 9, and follow the path on the AQUA color arrows and exit thru the boiler drain valve BD2.

Now comes the fun. With BD 2 closed and valve 9 open you will lift the fast fill on the feed valve A and watch the pressure gauge on the boiler rise to 25 PSI. When you get there, open BD2 to flush out the water and air from that loop. If needed to be sure, you may need to close BD2 and watch the pressure rise to 25 PSI again, then open BD2 to purge the remaining small bits of air in that loop. Once the water is flowing steady with no more air bubbles leaving the hose, you close valve 9 first, then close valve BD2. You have just purges Zone Loop 2.

Now comes the part I can not resolve. On zone 1 you will do the same thing with valves 2, 3, 4, and 5 closed and the zone valve C manually open. But there is a problem that I can not solve. Look at this illustration: There are 2 paths for the water to flow once the water goes thru the Zone Valve C. The water will take the path of least resistance and purge that loop (in this illustration that would be the short pipe RED radiators F) then return to the BD2 purge valve.

Now if Zone 3 is also baseboard loop, you can purge it the same way. The closed valves are 1, 2, 3, 5, and 6. Valve 4 is open and the garden hose is placed on BD3.

Now comes the fun again. With BD3 closed and valve 9 open you will lift the fast fill on the feed valve A and watch the pressure gauge on the boiler rise to 25 PSI. When you get there, open BD3 to flush out the water and air from that loop. If needed to be sure, you may need to close BD3 and watch the pressure rise to 25 PSI again, then open BD3 to purge the remaining small bits of air in that loop. Once the water is flowing steady with no more air bubbles leaving the hose, you close valve 9 first, then close valve BD3. You have just purges Zone Loop 3. This will only work on baseboard that is made with copper tubing. The type of baseboard the has the copper tube with the aluminum fins. If there are convectors or radiators other than copper tube radiators, the purge will not work and you will ned the use the air vents on the radiators to vent the air.


After all the loops are vented or purged the best you can, you need to put everything back to operation mode. The zone valve manual levers are returned to the up or automatic position. BD2 and BD3 are closed and capped. Valves 1 thru 8 are opened. The auto feed valve manual lever is returned to th down positio for automatic operation. Valve 9 is returned to the operating position you found it in. In most cases that is open, but can be closed. Open a boiler drain valve to lower the pressure to about 12 PSI. If you let out too much water and the pressure is below 12 PSI, then open valve 9 and let the water feed do the job of putting the pressure back to 12 PSI for you.

Once the cold water pressure is at 12 (12PSI to 15 PSI is acceptable) you can start the boiler and turn on one zone at a time to see if the circulator pump moves the heated water thru the house.

After you have done all that and you are unsuccessful, then you will probably want to call a plumber. LOL

After a closer look, that pipe looks darker than the heating system pipes. That pipe may just be a cold water pipe on the potable water system. If it is on the heating system piping then it may be a valve for separating the 2 different loops of zone 1. If it is on the potable cold water pipe then not so much.

It appears that the basement heat was added to the zone with the green circulator by adding 2 zone valves. The basement goes in 2 directions after the zone 1 zone valve and splits. Those I have labeled F head off to one side of the basement and return from that same side. The pipes labeled G, go in the opposite direction and drop to the floor near the doorway that is at the bottom of the basement steps.

Are there any valves inside those radiator covers in the room(s) that is(are) heated?

And have you tried to purge the air from any of the other loops? Were you successful?