venting mains. where to start?!

Travis_F

We are in the process of balancing our 6 story coop. There is a long list of things to do and I understand the process fairly well, I think. Our mains in the basement are quite confusing to I'm having problems where to start.



The issue is we are heating two buildings that used to each have their own boiler. Now there's one boiler. The main piping in the building with the boiler is quite predictable: four 4- inch mains to each corner of the building and a hoffman 45 at each end (only a couple actually are working)



The other building is where the tough part is... There's an 8 inch main coming from the boiler that feeds the other building. It then wraps around the back of the building. Part of the way a 6 inch shoots off and then splits to a 4 inch...



I've created the attached crude diagram. The sideways Vs indicate vents (or at least tappings for vent because half aren't working).. To get a sense of scale, the buildings are 100 feet wide with the boiler in the back in the building on the right side.



So my question is basically where and how to vent the huge 8 inch main?! If the charts are correct, we'll need banks and banks of Groton #2s. And where? I suspect we should vent in a couple places along the 8 inch main, not just at the end? Perhaps at each corner?



Thanks for any suggestions!

nicholas bonham-carter

a spiders web of pipes

your diagram shows the supplies, but are there any dry returns? if it is a counter-flow system, then the vents will have to be at the ends, and as you correctly surmised, banks of them. if there are dry returns going back to the boiler, then the vents could be mounted where they drop to the floor.

with 6 storeys, the risers could do with some venting as well, but only after the mains.

give us some information on the boiler, as in that size, it may have a staged burner, which could save fuel.--nbc

Travis_F

more info...

Thanks NBC...



I'm not sure the btu of the boiler, but it's huge! The burner is two stage if I'm understanding you correctly, it has high and low flame but only burns on high now. You can manually switch it, but the heat timer isn't wired to switch it and we have no idea how to do that... working on getting someone in who can... The burner is rated at 35 gallons per hour on high and 20 on low... we're burning oil, but have started the process to switch to gas...



In terms of the mains, yes, there are dry returns that drop down from the 8 inch main, a bunch of them, roughly matched to the risers that go up....

nicholas bonham-carter

staged burner control

usually these burners are controlled by pressure. your 6 floors only need 8 ounces max to heat everyone, so the burner would fire up high on a call to heat, and when the pressure rises to 8 ounces, the vaporstat will close off the high-fire and cause the burner to go to low fire. as the temperature may drop, then the low-fire, being unable to keep the pressure up as more steam is condensed, will switch to high-fire. save the resurrection of this until you can find the right steam person. use the find a contractor button here, and search by state, and not by zip code. when you see someone listed, then do a search for any postings from him. from this you can get an idea as to whether he is right for you. contractors here generally have good communication skills, enthusiasm for the art of steam, as well as knowing what they are doing.

one more thought about main venting: it might be possible to put all the main vents on the tops of the risers. you would need to keep adding vents until the back-pressure was down in the 1 ounce region, and then all mains, and risers would be filled before any of the slower higher resistance radiator vents began to let their air out. the end result should be steam entering all radiators simultaneously.--nbc