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# A few venting questions...

Member Posts: 50
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!

• Member Posts: 5,081
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.
2014 Weil Mclain EG-40