Water level issue

ToddB

I have been noticing a strange issue with the water level on my one pipe system. At some times the water returns to the cold level on the sight glass after running and at other times it can be up to 1/2" low when the boiler cycles on again. The boiler runs at about 0.05 psi for eighteen minutes. Run frequency is outdoor temperature dependent, but with recent 40 to 50 degree temperatures the frequency is 1h20m to 1h30m.



No changes have been mad to the system since last season when I did not notice this phenomenon. I have checked the piping and vents and found no obvious leaks.



Last evening the water returned to the cold level before the boiler fired again. This morning the level was about 1/2" down after the boiler had been off for 1h30m. I took the two main vent antlers and found little to no water in the antlers.



This is the strange thing. After reinstalling the antlers I proceeded to add a bit of water to the boiler with the fill valve barely opened. Suddenly the water level jumped to the cold line with no change in the fill valve setting. Essentially I added no new water to the boiler and the water level on the glass rose.



Any ideas what the problem could be? The system seems to run well otherwise with only some expansion noises that I have experienced before. Thanks.

BobC

Blockage

Could there be some crud in the gauge glass fittings that is intermittently preventing it from reading the true water level?

ToddB

Possibly

Thanks for your reply. I was thinking that the bottom fitting could be the problem. I had the top fitting off last year and it was clear. My pigtail is also connected to the top fitting and my low pressure gauge reads the same as last year.



If it were a problem with too much vacuum in the boiler at the end of the cycle would the water level react as I explained?

BobC

vents should open

The vents on the system should open when they cool and that should get rid of any vacuum in the system. What kind of main and radiator main vents are you using?



Bob

ToddB

Vents

Radiator vents are Hoffman 1A and 1B that are 1 to 2 years old and working. Main vents are four Gorton 1 on an antler, one antler setup on each main. Main vents are less than 1 year old. I know the main vents are closing, but I will confirm that they are opening.



How do you suggest that I clean the gauge glass fittings? I was thinking of removing the glass and cleaning them with a stiff wire or brush. Is this doable or should I remove the fittings? I had been looking into repiping the pressuretrol due to the pigtail being screwed into the top fitting tee. This makes pigtail inspection difficult. Maybe now is the time to take it apart. See photos.

BobC

copper wire

Make sure both gauge gauge valves are fully open. You might be able to snake a bare  #14 copper wire through the gauge glass cock into the boiler and move it around; if the gauge and pressuretrol appear to be working the problem would be in the lower glass gauge cock.



To remove the gauge glass assembly you will have to lower the boiler water below the lower fitting, unwire the pressuretrol (power OFF), remove the glass, and unsrew the fittings. After cleaning out the fittings and the boiler ports just reassemble with some teflon tape and you should be ok.



The glass can be cleaned with any detergent but if it has limescale you will need CLR or something like that to cut the scale. You may have to replace the rubber gauge glass washers on the glass, they tend to harden up; you might even want to replace the glass and keep the old one as a backup after it's cleaned up.



Bob

ToddB

Will do

My fiance is home today and confirmed that the main vents are opening.



I'll have to see how gunked up the fittings look after removing the glass. I replaced the glass, washers, and nuts during the last heating season, so I am familiar with the removal and installation procedure. I haven't yet had the nerve to remove the gauge cocks, so I will see how things look before I tackle that.



Thank you for your help and I will let you know what I find.

nicholas bonham-carter

cleaning the gauge cocks

before going too far, shut the gauge cocks, take out the glass tube, and then open the lower one to see if water flows out. if it is plugged, then procede as follows:

after you have dropped the level in the boiler to a poit below the lower of the two, you could unscrew the packing nut, and then unscrew the valve stem. that should give you a straight shot with the copper wire to disloge any gunk.

definitely use this oportunity to get a second glass tube cut to the same length as the original, with some extra washers.--nbc

ToddB

Thank you

Thanks. I will try unplugging the bottom gauge cock first. By removing the packing nut and valve stem do you mean that I could avoid removing the entire fitting? I do have an extra glass and washers. I had a problem last season with a small crack in the glass inside the top nut and bought two extra glasses, washers, nuts, and a glass cutter.



For what it's worth the water level has been fine after every run since yesterday morning. The water fluctuates in the gauge glass as normal.



I'll tackle the cleaning this weekend when I have the time and temperatures are forecast to be higher.