How To Rebuild A One Pipe Steam System

Rodney Summers

Good evening all.

Thanks to the recomendations on a prior thread my one pipe steam, 26 unit, brick condo building (with newly replaced windows) is installing a Tekmar 269 based boiler controller and TRVs for the radiators. I have tested installation of the TRVs on the 4th floor of the building but am getting some spitting.

So I started down the check list: the building manager that I am working with tells me the boiler is services/cleaned every year, Radiators are sloped properly (away from the vents), can't check the pipe sloping since they are in the walls/ceilings, checked the water quality in the boiler and drained out the sludge from the seperator, and then... attempted to check the pressure settings for the steam. Lo and behold there are three, yes three, seperate units on the pigtail. 2 seperate pressuretrols and a vaporstat. Obviously something is wrong. I check the vaporstat first (easiest to read) and it is connected to an old boiler conroller. looks like the system was cut out of operation but they never bothered to actually remove it from the wall/boiler. The remaining pressuretrols are connected to the blower, one labled "high" and the other labled "low". Unfortunatley the faces of the gauges are unreadable due to age and grime.

I have the HVAC company coming friday to install the controller and I have three basic questions:

1: Should I have the HAVC company either replace the Pressurtrols, or more simply hook up the existing vaporstat instead?

2: Why are there 2 pressuretrols? I may have missed it but I thought you only needed one. (or is it one for the cut in and one for the cut out)

3: What other things should I have the HVAC techs look at while they are here? The association is investing alot of money for this new system to be a flop!

Thanks in advance for any insite you have!

Derek

bob young

complete tune-up

one pressuretrol is the hi-limit manual reset safety. the mechanic installing the new controls shold check all safeties & limits when he is there. no sense doing half a job. this stuff is all seiously related and everything works in conjunction with each other.