Recently replaced the heating system for a NYC School. Replacement included Boilers, Boiler Feed, Duplex Vacuum/Condensate Pumps, Radiator Valves and Traps. Once the traps were replaced and we operated the temp boilers, there is this high-pitched whining noise that lasts for about 10 minutes and then disappears. This noise continues throughout the entire day and even after the boilers are turned off. Its a very strange phenomenon. i uploaded videos of this noise at the following links: https://youtu.be/qJK7jq1E2dAhttps://youtu.be/enZ0nCnG3xw
We have tried various methods in resolving this issue but haven't found a solution:
1) We operated the condensate pumps to run with no vacuum, only condensate.
2) We have lowered the steam boiler operation from 7 psi down to 4 psi.
3) The traps have been serviced and inspected by the trap manufacturer, Mepco & Dunham, they have found no fault with the installed traps.
A solution we haven't checked yet are the air vents. the noise sounds like air is travelling through the radiators at an extreme velocity and thus producing a sound, the loud high pitched whining noise.
There are no air vents installed at the ends of the main. i could not locate if you should install air vents at the ends of the main for two-pipe pumped return systems, thoughts?
Heating season is almost over, so hoping to find a solution soon to close out this project.