Steam problem

hmulter

I have a steam system that has a wierd problem that I know has a simple solution, But I am to  smart to see it. For a little backround, It is a 68 unit building with two pipe radiators and steam vents. 14 risers and returns with traps in the basement on both. thermostatic traps on supply risers and F&Ts on the returns. I have one stack that works fine when you fire the boiler, everything heats. If you steam the building for a long time this stack stops heating. This issue has not been a problem for tenant's or landlord I just stumbled on it, which is a storey for another day. I know I am trapping water somewhere. I can here gurgling in the pipe, not sure if it is supply or return. I have taken apart and rebuilt both traps the first time I found this issue. Then I discovered the problem again. Here is the only thing I can think of but I am not sure it makes sense. The trap on the supply riser is located about 8" below and 6" horizontally from the riser. Could this trap be staying hot even though it is full of condensate? Thus the trap does not cool enough to open. Just to let you know the return pipe goes to boiler feed tank that is open the atmospheric pressure. There are also stacks upstream and down stream in the open return going to boiler feed tank and they all seem to work fine. The return is a dry return. The building has a zone valve on every riser, large honeywellzone  valves.  They all stay open all the timne since we installed a Heat Timer MPC to control for the building

Charlie from wmass

Is steam backing up

the return and stopping the return trap? What is the pressure set at? The trap at the supply riser is it thermostatic or a F&T trap? If it is a F&T it should drain even hot as the condensate will open the float causing it to drain.

hmulter

Steam Problem

The trap on riser is thermostatic, return has F&T. I don't believe steam is backing up return because that pie is open to atmosphere at other end. But it is possible it could be coming from return upstream. now that you mention it I did notice the return was hot after F&T trap but it should open anyway. My Heat Timer MPC sensor happens to be on the return of this stack. That is how I noticed problem. The boiler had been down and when I re started it I watched and the return sensor was at 212. I walked the building checking with various tenants making sure things were warm. I wanted to warm building before I left it running on MPC. When I returned to basement I found sensor reading 139. I was checking things out and when I came back to mpc 15 minutes later the temp had dropped to 125. The pressure on boiler is at 1 psi with differential of 1 or less. I have it cranked down. That was set that way when we took building over 11/2 years ago. I did not check it but I am sure know one would mess with it. Only my techs and maintenance man have access and Lenny the building super would never touch it. The gurgling noise i here i think is in supply riser. The return riser cooled of to quickly it seems to have been full of condensate. Did not measure temp of supply and return risers. I will if I return. it was a Sunday morning I was in there and I had the building up and running and the system was working so  I figured I would deal with it another day and think it through. When the building is running on MPC it runs very little once sensor detects temp. If you are familiar with MPC it is set for A and a 240 minute cycle.