System loses pressure slowly?

JohnnyCB

Hi all,



My hydronic system has demonstrated a problem I don't understand a couple times now.



When cold, it has always been filled to a pressure of 15-16, when hot this climbs to 17-18.



Once or twice now, I have observed poor heating performance and the pressure will have dropped to 9-10 hot, but I can't find a leak anywhere and there's no air to bleed out of the system.  If I re-pressurize it to 17-18 (it'll be hot) it begins working fins again for several weeks.  On one of these occasions, an area on the floor below the boiler blow-off will have a small amount of water spilled, maybe a cup or two.  This doesn't always happen though.



Ideas?



Thanks!

RJ_4

leak

Your relief valve may be dribbling, if you have a diaphram type expansion tank check the air press (use a tire guage ) should be at least 12 psig, for most small systems, the fitting is underneath the big plastic nut, if you get any water the diaphram has ruptured. If the tank is ok could be the relief valve, also look around system for leaking pump flanges, fittings or press. guages

JohnnyCB

Thanks! I'll check that

Thanks!  I'll take a look at that when I get home and get back to you.



-Johnny

JohnnyCB

Yup - Air Vent Inside Boiler Leaking

Yup - it had a slow leak - There's an air vent inside the boiler cover (Veissmann Vitodens 100, the part marked "R" in the manual)