Old Steam System

Mike_Sheppard

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?

nicholas bonham-carter

Are they really interested in improving the system, and not just waiting for you to come back in a month, and maybe doing something?
In a downfeed system, the steam would go up to the top floor of a high rise building, and then feed downwards so as to give the first steam arrival to the top floor, and then to each lower floor in succession.
With each one of those segments, with multiple drops, a larger main vent than a Hoffman 40 is needed.
Maybe the main should be changed so that it arrives back at the boiler room as a dry return, with all the main venting necessary in that location-multiple Big Mouth vents.—NBC

Jamie Hall

See if you can persuade @Steamhead to come down and take a look -- he's in Baltimore.

Mike_Sheppard

I think @Steamhead is the busiest guy I know! Lol

nicholas bonham-carter

He is the busiest, because he is the best!—NBC

Mike_Sheppard

I have no idea if they will go for the upgrades or not. But I know what their concerns were and I know the cause. I was there today on emergency service to fix the boiler. They didn’t want to look over the system on double time and I don’t blame them. We have a new service contract with them and we will be doing monthly visits.

I’m just pondering what kind of piping they may have. Will know for sure soon enough.

mikeg2015

Probably best to add TRV's for zoning. However, the boiler would probably end up being oversized then.

Really have to know the overall layout of the piping to determine anything else.

Mike_Sheppard

@mikeg2015 you’re right. I will update this post after I go back later this month to scope out the system.

Thank you

Steamhead

Thanks, guys.