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Now that the main is finally vented well, I've done a little skimming and flushing of the boiler, things are lining out. Sight glass is much more steady and I finally have my system almost perfectly balanced. Boiler actually never even gets to 1oz now when running since the steam is heating more area, more evenly. The radiators are just sucking up all the steam and my previous theory that the 3" header is a little small, is apparently wrong. Couple observations along the way:
1) I have one or two Maid O Mists that I think are Duds out of the box. When I switch them with a Gorton the same size, it works perfectly. Maybe you get what you pay for sometimes. Others however, work great.
2) Good old Hoffman 40 fill the gap nicely between the #5 and #4. So does a Ventrite 1.
3) I ditched 2 varivalves at the end of the system on radiators that were still heating up slowly. replaced them with a Gorton D and a Gorton 6 and balanced it out almost perfectly.
4) Big Mouth "burps" just a little steam right before it closes.
5) Hoffman 1A, #5, #6 and a couple #4 are working everywhere based mainly on radiator size... except a single radiator with a long run out. I'm suspecting that run out has a partial blockage. I wonder if it was left partially or mostly closed over the years or someone was trying the "throttle" the radiator using the valve.... or just lack of condensate flow from imbalance. Not sure how I could flush it out. I'm hoping with use, over time it's starts to clear itself a little. It's heating up descent now. Its valve stem may need repacked.
Here's one theory, I've seen that valve stem leak a little steam when pressure climbs, It's unnoticeable at 0.5-1oz. But, maybe it's leaks more under vacuum as it's heating so rather than drawing more steam in under vacuum, the leak balances the run out to atmosphere and slows the steam.
Anyone of the veterans seen that?