Gas and Oil Home Heating Furnaces - Hot Water Heat Maintenance

My first post here... Yearly maint for the homeowner...

1) How does one maintain a "closed' expansion tank above the boiler? I see there's a water valve on the bottom of the tank.

2) Whats should the pressure setting and tempurature be? isn't there a formula based on verticle height of the system?

Seeing how I was supposed to provide more info, I just now went down to the boiler to discover the pressure is over 30, that's in the red danger zone, and the relief valve is leaking. i think this has something to do with the fact that I have not maintained the expansion chamber in a few years. Help this loser, please!

PS;
Burning natural gas
One zone
Temp 140?
3 story brick home

Can you shut the tank off and drain it at all??? Temp can be set for 160 on and about 180 off. 140 sounds low but dont know what you have there. Psi for 3 floors in the home 20psi.???Or what ever it takes there to "just" get water out of the top bleeder. Yes the pop off should go off at 30 psi;) ED

You need to completely drain the expansion tank. Actually what you are doing is refilling it with air. Close the valve leading from the heating system to the expansion tank and open the drain valve on the tank. You may have trouble getting air back into the tank if there is no vent. After the tank is empty, close the drain valve and re-open the valve leading to the tank. Make sure water pressure in the system reaches about 15psi and all should be well. It would be best to turn the boiler off during the draining operation because if the burner starts the relief valve will dump more water. Afterward, watch the pressure to be sure the problem was corrected. If the pressure rises in a day or two back up to 30 psi, your automatic water feed may be bad.

That's helpful, thanks, but I'm still a tad confused. I have a valve and regulator controlling the supply to the whole system, but i don't think I have a valve to shut off the line to the expansion chamber. What I do have is a copper line leading to a regular hose bib right below the tank. On the side of the hose bib is a smaller (3/8"?) screw which is supposed to be used (somehow) in the process of maintaining the proper level of water in the expansion tank.

So my question is, what's the process for getting the water level right in the tank? Or should I say, which valve do I open in which order?

Thanks so much for your time, patience and undersanding.

What you described could be a special valve just for expansion tanks. Especially if there is no valve in the line going to the tank. Here's how to do it. Turn off the automatic water feed to the boiler. Close the caps on any automatic air vents near the boiler. Put as short a hose as you can on the drain valve and run it to a drain. Open the valve all the way. Then remove the small plug in the side. You may get a little water out of the hole but it is an air vent to the top of the tank. After you are sure the tank is completely empty. Put some teflon tape or good sealer on the small plug and re-install it. Now close the drain valve and open the auto water feed valve. Also open any automatic air vents that you may have closed.

The tank needs to be completely full of AIR when you start to refill it. That air becomes the cushion that accepts the expansion of water in the system. If you only partilly drain the tank as many people do, you will actually make the situation worse. Thats why I said the tank needs to be FULL of air and not empty of water. Not because I'm an optimist but because it makes it easier to understand.