A few venting questions...

mcvetyty

Happy winter steamers! As I am doing my annual boiler/radiator optimizing attempt this year, I decided to buy the Balancing Steam Systems Using a Venting Capacity Chart PDF and have come across a few questions that I'd love your thoughts on:

1) I am not understanding the difference between the three columns of venting capacity (1oz, 2oz, 3oz), could someone please explain the factors with why someone would use one over the other?
2) Under the "How much air is in the pipe?" section, is the Pipe Size column referring to the inner or outer diameter?
3) Finally, after doing the exercise with my system, I have found that the third column appears to 'line up' the best with my figures for (Total Air to Vent)/3, but I have a few radiators in the .4 range and am not finding a good option for vents in that column for .4. Does anyone have any suggestions on how to handle this?

Thanks!

KC_Jones

The first column is pressure. So that is the amount of air at that pressure the vent will flow. I always try and shoot for the lowest number possible, but it depends on your system. Pipe is sized nominally, there technically isn't a dimension on pie that matches the nominal size. Here is a chart you can use for reference.
http://www.harvel.com/piping-systems/harvel-pvc-pipe/schedule-40-80/dimensions
As to your last question as stated in the book it's somewhat a matter of personal preference. It sound like you want to vent slowly since you are using the 3 oz scale so for the .4 you either step up to a slightly bigger vent or step down to a slightly slower vent this is when the geography can come into play. I have a fairly large radiator in my living room, but I vent it on the slow side because it's the first rad to see steam in the whole house and it's in the same room as the thermostat. Here is another link showing how Gerry tests the flow, interesting stuff. Don't forget you may need to tweak it later even after doing all the calculations. If you find you have an oversized radiator in one room you may need to vent is slower to keep from overheating. I have one like that and I also have the opposite I am lacking radiation in one part of the house so I have a huge vent on a little tiny 10 EDR rad so it heats fully almost all the time.
https://www.youtube.com/watch?v=aNUY0t1piZc

mcvetyty

Thanks KC. I'm still having some difficulty dialing in on two radiators. When I put a Gorton C on them, they heat no problem, but it throws off the balance of all of the other radiators in the house, however, when I drop down one vent to a Hoffman #6, they don't heat at all while the others seem completely balanced. That is why I am thinking I need a vent in between the two, and am not really seeing a good option on the PDF chart.

Quick question... Do you think I should try a couple of Varivalve Heat Timers on these two radiators to try and dial in a range between those two vents?

KC_Jones

You could try anything in all honesty. It is sometimes a matter of tinkering with it. You do have all your main venting squared away right? Unless that is done you can't really balance the radiators effectively.

Fred

This may be a case where the weather just hasn't been cold enough for the boiler to run long enough for all the radiators to heat. While we all try to get steam to every radiator at about the same time, that is perfection and sometimes a radiator or two, especially if it is on a long run, may take a couple or three minutes longer to vent all the air out and start to heat. I think if you leave the C on there, the other rads will heat on a normal heat cycle or if you but the #6 back on , those two rads will take a little longer but still heat, on a normal heat cycle, just take a little longer. We are in that "shoulder season" right now so it's difficult to know during milder outside temps.