Post-Expansion Tank Replacement Issues

wirsbozo

Hi, all. After using this forum to help me get through replacing my water-logged expansion tank, I've found that I'm no longer getting hot water circulating through my radiant heating zone (it was working just prior to changing the tank). The domestic hot water is back up and running fine. When I turn on the radiant heat, all the circulation pumps are running. The main boiler circulation pump seems to be chugging a bit louder, but I might just be noticing it now that I'm paying more attention to it. Also, the line out of the boiler for space heating that has the expansion tank on it is shaking slightly, perhaps because the tank is no longer heavy with water?

Thoughts on what might be going on? This is on a Triangle Tube Phase III from 2002. Could this be caused by air in the system? I ran water to a hose connected to the outlet shown in the bottom left of the first picture below on the line where the hot water goes to the zones, but perhaps that's not right? The boiler's manual notes to allow air to escape from the outer tank "by opening cap on automatic air vent, located on top of combination heater," but I do not see one. Any help welcome!

Attaching a couple pictures of the system, showing the red main circulator and the tank, as well as the setup with all the zones.

hot_rod

Sounds like the boiler has air in it. Is there an air vent up near the top, you need to purge the boiler, possibly the loops also.

leonz

Turn the thermostat way up and let the system run. Do you have an automatic air vent in that snakes nest of plumbing somewhere out of the picture??

hot_rod

In some cases I hold open the pressure relief valve at the top of the boiler to assure it is air free. Are expels quickly through a relief valve.

mattmia2

leonz said:

Turn the thermostat way up and let the system run. Do you have an automatic air vent in that snakes nest of plumbing somewhere out of the picture??

If it isn't circulating because it is air bound you could damage the circulator. Running it for a few minutes without water circulating isn't recommended but usually won't damage small pumps but running it for hours hoping the air somehow escapes can. You need to purge or bleed enough air to get it circulating and make sure the air elimination is working.

Were you able to isolate the expansion tank when you replaced it or did you have to drain much of the system? Purging will require you turn off the circulators and close off the loop between where you are adding water and where you are draining water so it gets forced through the part you are trying to purge.