[dtudryn]

Hi everyone! I have an oil-fired boiler which serves two air handlers and the water tank. The system, which my installer called a hydro-air system, has workd well for 8 years. Recently once in a while (seems like every night after I lay down!), the upstairs (attic) air handler gets the signal from the t-stat to start blowing air. Instead of relaying to the boiler that the boiler should start warming up the water in the hot water loop, the AHU just blows cold air. Then I need to go downstairs and turn up the first floor T-Stat. The AHU serving the first floor then calls for hot water and eventually the loop going upstairs also heats up and the air gets warm. What do you think the problem could be? First I thought it was an air pocket or a pressure problem in the loop, but pressure on the upstairs loop looks okay, 20-25 psi. Please help!

 

[beenthere]

Do you have a zone panel. or does each air handler have its own end switch.

 

[dtudryn]

I believe I have a zone panel; assuming that's the Taco box next to the boiler where the t-stat wire go into. It has a cicuit panel inside and indiator lights for each zone.

 

[beenthere]

Check if the end switch is closing when the upstairs zone calls for heat. The circuit for that zone may not be closing the end switch.

 

[dtudryn]

Not sure what the end switch is. Is this the electric valve that's wired to the the control panel? The one with the small lever on the top which says "auto" on one side and "manual open" on the other?

 

[beenthere]

The end switch is inside the zone panel, and is what tells the boiler to run.