Air returns to hot water system after purging

rloveys

Recently had a yearly service done on my furnace. At the time my mixing valve had to be replaced and the fore my system had air which was purged. A short time later air began being heard in all the lines of my system and I have purged them a few times. But the air returns. A week ago I noticed water under my furnace and called the repair guy. Who came 2 days later. The leak had stopped and the floor was dry. I preceded to purge the air again every few days and still returning but no sign of the leak until yesterday a small amount of water on floor. It appears when I aggressively purge all the circuits it is leaking somewhere and must be sucking air
What can be the issue?

hot_rod

Got a pic or two of the near boiler piping?

rloveys

hot_rod

I don't see an air purger anywhere in those pictures. A purger automatically removes air after the first manual purge.

Over time as water is heated it displaces some additional air, it can take several days for all those micro bubbles to be vented out of the system.

The air purger should be installed at the hottest point in the system, the piping coming out of the top of that boiler.

Adding a central air purger and moving the expansion tank connection would improve things. Currently, any auto air vents up in the system could actually pull air in, also.

Some creative flue venting there.

rloveys

rloveys

Haven't heard of those but will look into it. Where could the water on the floor under the furnace be coming from. Service guy assumed furnace was rusted out and need to be replaced but it stopped leaking

hot_rod

The boiler has a pressure relief valve on the top, next to the expansion tank. If that were to trip you would see water around the boiler. They reset themselves when then pressure drops back below 28psi.

That can happen if the expansion tank fails, or is mis- charged. It looks like a fairly new expansion tank?

A slow leaking fill valve will also cause a relief valve to discharge.

All these should be checked by your service guy. An accurate pressure gauge on the system can help troubleshoot. Confirm that the pressure/ temperature gauge on the boiler works and reads accurately.

rloveys

Good eyes expansion tank is new was replaced with service along with the pressure gauge there is a hose on the relief valve which empties into a bucket but no water appeared in the bucket only on the floor around the furnace