Balancing Steam Systems

Lurker_2

The main concern for the venting speed is how fast the system vents when the boiler starts making steam and distributing steam (as opposed to when it's cycling on the pressuretrol).

At this point, because all of the vents are open, you shouldn't be generating significant positive pressure in the system since the air is escaping. Hence, measurements in ounces, not 0.5lb to 1.5lb. If you managed to pressure up to 1.5lb before the system was fully hot, that would turn off your boiler, be "short-cycling", and all sorts of other bad stuff. Hence, what you care most about is the venting speed at the near total absence of positive pressure when the system is starting up.

-Michael

Scott Kuchta

Balancing Steam Systems

I just got the E-book, "Balancing Steam Systems - Using a Venting Capacity Chart" by Gill and Pajek. I think it's pretty good and I understand it to a point. My confusion comes in when I look at the charts or in the text when they reference, "1oz CFM, 2oz CFM, or 3oz CFM". What is this pressure refering to and how does this relate to my system running on a cut-in pressure of .5 and the cut-out pressure of 1.5? I am going to call a pro to install main vents ASAP and to balance my system but I would like to be able to understand the basics involved so I can follow what he proposes or does.

thfurnitureguy_4

As I understand it you want the mains to vent as fast as possible. 1 to 3 min on a res. sys. is what I keep hearing is good. Time from where you feel steam at your boiler main, till your main vents close. This is the real time your existing vents take to purge the air. If you have done this, and you have a long purge time. The charts give the venting rate of vents at certin pressures. The higher the pressure the longer it will take to vent through the same size hole. The air is "thicker". I would assume that during start up you could choose the lowest oz figure. You will still need to know the cu. ft. of air you are trying to vent. IE the length and ID of your main pipes. The vents were tested for Cubic Feet of air per Min. at these pressures. This is a guide to help guess the size and number of vents needed to hit that 1-3 min vent time. Another thought. If you have the luxury of being able to remove your vents, and lets say vent, through a 1" or 3/4" open fitting. Try the test again under these conditions. This could give you an actual best possible time your system can vent. You could than use enough vents to give the same result. Steamhead, or others,is this the way the chart works? What does your experiance tell you about using an open fitting test for the systems actual best possible.

Scott Kuchta

Still not sure

Thanks Mike. I only have a small knowledge of this stuff but I understand what the cut-in/cut-out pressures do. I guess I can just refine the question and simply ask, "How do I use the charts in the "Balancing Steam Systems" to properly vent my rads - which column do I use, 1, 2, or 3oz?

Steamhead (in transit)

Start

with the 2-ounce column.