Low pressure

[Tony H]

The boiler has been running a bit lower pressure than normal and I can't find the reason. The pressure tonight reads 7psi the psi lately has been around 12 and last year it seems it was closer to 15psi.
I find no big leaks just one joint that's a little damp no dripping water off it at all . The system has a fill valve and backflow prevention valve. The only thought I had was maybe a air bubble in the system and the air scoop is clogged up or just not working and needs to be taken apart and cleaned or repaired.
What or where else should I be looking for ?

 

[stee6043]

Is it running 7psi hot or cold? Seems like you need to add some water and see if it holds pressure. I run 12-14psi cold and 22-25psi at full temp. You shouldn't be loosing pressure once you have it set. I'd be looking for leaks anywhere and everywhere if pressure didn't stay put....

 

[Tony H]

The 7psi was at about 140 degrees and it went up to 10 or 12 at 170 degrees. The highest it has ever been is 18-20 at 175 180. Wondering now if the fill valve is clogged and not working we do have hard water and I have not cleaned the filter for a while. I did have a small drip back in october could have lost some water and not made it up. Time to go check it out and then put the snow blade on the 4wheeler we are supposed to get 6" tomorrow !
I went over the entire system and only found a coupling with a damp joint but not enough to drip. The only part I can not see and there are no connections there is the buried pipe and I sure hope that's not a problem.

Well I got so excited I forgot to submit this post and went to check the boiler:

Turned off the valves before and after auto fill valve and took out the filter screen and it looks like some of it's eaten away so I set it aside and put the cap back on and open the valves .... nothing . Decide to see what happens if I flip the lever on to fast fill and water starts a flowing after a minute or so it slows down so I flip it back. I go out to the shed and see the pressure relief valve has puked a little water and lo and behold the pressure is up at 25lbs at 160 that is higher than it has ever run. I can hear the air scoop purging a little air and I check for and find no leaks. back in the basement I look for leaks and find none.
Looks like the fill valve is shot and I recall HVAC guy telling me they fail often and cannot be relied upon.

Thanks to Stee6043 for getting me going in the right direction. Now will have to keep an eye on the pressure and kick the valve on to refill next time I have a leak or make a change.
I like the idea of the auto fill in case a leak starts unnoticed the boiler will refill to keep it from burning up.
After looking at the instruction sheet the "reducing Valve" is designed to fill boilers and I bold type says " not intended to control boiler water at a safe operating level" and follows with some model numbers of devices that are.
Guess I know what to look for now.
Seems like my wood consumption was up a little and I bet this low water was causing it so that will be back to normal also.

Well I better get ready to put that plow together.