Main Vent Help

JohnCT

I'm trying to address radiator hissing at start up. Utica boiler with 90', 2" single main serving 8 radiators. Pressuretrol set at .5 cut in with diff of 1. I replaced all the radiator vents with Gorton 4, 5 or 6, based on distance from boiler. Also replaced end of main frozen Caldwell #10 main vent with two Gorton #2 on a 1/2 inch pipe. There was another frozen Caldwell #10 where the copper meets one of the return pipes above the radiator. Replaced that with two Gorton #1. Hissing is significantly reduced, radiators are well balanced, and hammer is gone, but I think I'm still under vented.

1. Am I correct in assuming there is no benefit to placing more than two Gorton 2's on a half inch pipe?
2. I could squeeze in another Gorton #1 on the near boiler vent. Any benefit there?
3. Other suggestions?

KC_Jones

1/2" pipe will support just a little more than 2 Gorton #2's, but not enough to justify doing anything IMHO.

You have 2 different main vent locations? One at end of main and one at the boiler right at the wet return?

What size pipe is available at each location? Pictures of the set ups would help.

I would suggest you need more main venting to address the radiator vent hissing, but would also need to know how the boiler size relates to the system. If the boiler is significantly over sized the venting may not fix the issue alone.

nicholas bonham-carter

Put all your main vents at the end of the dry return(s), and measure your backpressure during the venting phase as the boiler begins to make steam. Add main venting until all the air escapes at a pressure less than 2 ounces for maximum economy, and comfort.--NBC