High pressure on EFM AP520-1

I have an EFM ap 520-1 coal stoker and was having problems with the pressure rising to 30 on a regular basis and it was dumping water out the relief valve. It has an old cast iron or steel expansion tank hanging from the ceiling of the basement. The tank has no valve to check pressure. It only has a valve that you can hook a garden hose to for draining water. I was doing some reading on EFM products, although I couldn't find anything on my exact model. I ended up being able to stabilize the pressure between 12 - 15 now. It has stayed good now for a couple months. There are 2 main water supply lines that hook to the back of the stoker. One runs through a regular shutoff valve and the other runs through a shutoff valve and then through a pressure reducer. What I did was close the shutoff valve on the line that goes to the pressure reducer and this seems to have stabilized the pressure. Does this make any sense? Is this supply line only supposed to be used if you need to top off the water level? If so, how do I know if and when I need to add water and how much? Any input would be greatly appreciated. There's still alot
I don't know about my own system. Thanks!

Welcome to the forum!
The system in your house is probably equipped with the type of expansion tank that was used before captive air tanks were invented. There's nothing wrong with continuing to use it. Over time the air in the tank is gradually absorbed by the water. You should drain the tank at least once a year, usually at the start of the heating season. There should be a valve on the pipe to the tank. Close that valve. Then connect a hose to the drain spigot and open it. Most installations have an air bleed on the shutoff valve to the tank, if there is one open it as well. When the tank stops draining close the drain and the air bleed, open the valve to the tank. That's it!

John covered the topic very well! Drain it, check for leaks, and don't be afraid to do that a few times each season, especially if you burn 24/7-365. If that does not resolve the problem, it could be a tankless coil with a pinhole, but that usually allows water pressures that would not be controllable.

I looked at some diagrams online, it seems some tanks are equipped with an air bleed near the top of the tank, might want to make note of that as well.

Thank you everybody. I really appreciate your responses. About the shutoff valve that goes to the pressure reducer, should I open that back up and keep it open? Right now I have it closed. Thanks again.

You're welcome. That valve should be left open, the system will need water after you drain the tank. The tank will refill partially with water after you drain it.

Thank you very much. I will go do that now.

Ok, I closed the valve on the pipe going to the expansion tank and opened the air bleed on that valve. I then drained the exp tank and my pressure is now at 5. How can I get the pressure back to 12? Thanks again.

Edit: I just went down and looked at it again and it's up to 8 right now. I'll keep an eye on it.

The incoming water valve (by the pressure regulator) is open?

Yea, it's open. I just looked and it's up to 8 right now, so it looks like it's slowly rising back up.

It's up to 12 now. Right where it should be. I'll just keep an eye on it and make sure it don't go higher. Right now it's perfect though and I now understand it better. Thank you very much. I really appreciate your help.

No problem!
The fill is slow through the pressure regulator, if it has a fast fill lever it will speed things up but will probably over-pressurize the system. Hope this solves your problem.

The pressure seems to be hanging out around 15 or 16 now. I guess that's good. It's sure better than going up to 30. No water in my bucket from relief valve, so I should be good to go. Thanks again. God Bless!

Glad we could help.