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I have a customer with an old steam system. It is a small 5 story apartment building in Washington DC. They are very motivated to get their system working as well as possible. They had their boiler replaced, and it is piped correctly, I can’t believe it! This is very rare in DC. And it’s running on 10 ounces instead of the 10 pounds that I come across more often...
It used to be a coal boiler, the steam main runs around the basement in a loop. In the middle of that loop there is a single Gorton #2 which was tapped and screwed directly into the top of the main. There are several returns that drop down along the perimeter and each of them have Hoffman #40s tapped into them. These are 1-1/4 inch returns. The reason they have air vents there is because the return line drops underground and then back up into their feedwater unit, creating a water seal.
Obviously these vents are inadequate and they need larger vents on the returns.
Does this sound like a downfeed system with express risers? They are one pipe radiators. Although they said it was the top floor that wasn’t heating as much as the lower floors. If it was a downfeed system wouldn’t the top floors get steam first?
They also mentioned that if floor #4 shuts off their radiators, then floor #5 barely heats. I’m assuming this is because with floor 4 radiators shut off that’s one less air vent to help steam get to the top. Which would mean it is an upfeed system. Perhaps the returns I’m seeing are coming off the bottoms of the risers?
I am going back later this month to walk the entire system to give them advice on how to improve it, and figure out exactly how it’s piped. I asked them what their complaints were and they responded with what I expected - all the radiator vents hiss, the top floors don’t get hot enough, and the lower floors have to open their windows.
There is an obvious lack of venting now that it’s a system that cycles. I believe there should be multiple vents installed around the steam main circling the basement. With a single vent in the middle steam from one side might reach it first and stop the other half from venting.
Can a 1/2 inch pipe be tapped directly into the top of the steam main? Or would a thread-o-let be better?
If it is an upfeed system, shouldn’t there be vents at the top, not at the bottoms?
Any advice on this?
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