Older style Compression tank question

HVACRTEK83

So I realize each year its a good idea to drain down and reset the air charge in these compression tanks,I have a system with 2 20 inch tanks overhead with site glasses,and each year at the start of season I drain them down because the water levels in both are almost full but not quite. The tanks are piped in parallel,each with their own shutoff valves upstream of the b&G ATF-20 tank fittings where the system is connected to them. On the opposite end there is those airtrol boiler drain type valves with a stem that rises up into tank. I just want to make sure im doing this rite because I find the tanks become quite full even before water is even heated. From my understanding you should drain each tank until you start to suck air up through that airtrol drain fitting correct? Which in my case would start at about 1/2 tank or a bit more. Before that point it just spits out solid streams of water because the water is over the tube. So I stop draining when it gets to that level, I changed site glass nuts/washers/gaskets,so when I open up system valves,pressure in system dropped down to 6 to 8 psi and I started bypassing the prv to bring system up to 12,but the level in my tanks were rising as well while doing this. I also opened the drain on the atf-20 fittings while filling system back up,as the instructions say to have that vent/drain open while filling to push air out,and close it once a solid stream of water occurs. So I did that as well. But I guess my problem is the level in the tanks ended up around 3/4 up the glass roughly. And system was around 86f at the time. So im worried what the level will be once water is 200f. I tightened all fittings around gage glasses,packing nuts,ect. Because my thoughts were I may be losing air somewhere causing it to keep filling. But didnt seem like It was. Where do you guys like to see the tank levels,I know not all have gauge glass but am I doing something wrong maybe? Thanks

Jamie Hall

Almost. The tank should be drained until it is empty. Completely empty. Then when you open it back to the system, water will compress the air and give you your cushion. The Airtrol will, if all is going well, attempt to maintain that more or less half full condition when the system is under pressure.

leonz

If your system is intact and has no leaks you should not have to refill it OR drain it every year BECAUSE this allows excess oxygen to enter the system and you do not want that ever if your system has no leaks.

Why are you running your high limit to 200 Degrees Fahrenheit when 170-180 degrees Fahrenheit will do if you have baseboard heat???????

How much water do you have in your system?

Is your fill valve shut off completely? If not, it should be.

Have you reached a point where you have had a screaming vacuum leak when you started a circulator and traced it back to the sight glass packing gland nuts???

You have to remember that you are compressing the air in the tank when the water in the system expands when the boiler is heating the water so that is not a problem.