2-1/2 mains, single pipe converted gravity system.
I'd like to know because straight tees mean, I think, that the radiators are supplied purely from gravity flow off the main; and also that radiators depend on some stratification of "hot" and "not so hot" water in the main. Which means that flow rate in the main s/b kept quite slow. Some prior threads pointed this out and it looks like it applies to my system.
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Image may be NSFW.
Clik here to view.
Image may be NSFW.
Clik here to view.
If the radiators do run on gravity, does anybody have ideas about how fast the flow in the main can be? I think it would be better to keep a more even temperature across the system, supply to return, and that would mean boosting the gpm in the main. (Insulating, too. All in good time,) I have a huge delta between system input and return - greater than 40*F. ; this is at 135*F. system supply. I'd like to figure out if a "quicker" pump could help help that. That would lower the delta across the boiler and, I think, keep temperature swings at the emitters a smaller. The present 35*F diff at the boiler (to allow a burn of 5 minutes or more) injects a "hump" of hot water into the system every 15 minutes or so. Seems like 35*F. change would be noticeable to the occupants. Or maybe because of the way the gravity flow (I think) works in the radiators it would average out and nobody would notice and I don't have to do a thing... Be nice.
Right now I'm looking for tables showing the flow speed in different pipe sizes for any particular gpm. I thought I had a handle on the present pumping rate - about 9gpm through the boiler - based on specs about temperature rise but further thought looking at the pump curve I'm not at all sure. The BG Series 100 curves say about 28gpm at 3.5' head (which several old threads here say is what old gravity systems present a pump). That would be in the 1" pipe at the pump which would translate to something less in the main; and maybe something more in the boiler which uses a 3/4" coil. But I haven't seen any spec for the head presented by the Burkay boiler and I've been through a lot of documents. The prior pump was a big old PR series which the curve says actually pumps a little less - say 26gpm. But if I understand the curve right, the PR doesn't care much about head, it just pumps somewhere in the 22-27 gpm range regardless.
Thanks for any comment.
Rufus
I'd like to know because straight tees mean, I think, that the radiators are supplied purely from gravity flow off the main; and also that radiators depend on some stratification of "hot" and "not so hot" water in the main. Which means that flow rate in the main s/b kept quite slow. Some prior threads pointed this out and it looks like it applies to my system.
Image may be NSFW.
Clik here to view.
Image may be NSFW.
Clik here to view.
Image may be NSFW.
Clik here to view.
If the radiators do run on gravity, does anybody have ideas about how fast the flow in the main can be? I think it would be better to keep a more even temperature across the system, supply to return, and that would mean boosting the gpm in the main. (Insulating, too. All in good time,) I have a huge delta between system input and return - greater than 40*F. ; this is at 135*F. system supply. I'd like to figure out if a "quicker" pump could help help that. That would lower the delta across the boiler and, I think, keep temperature swings at the emitters a smaller. The present 35*F diff at the boiler (to allow a burn of 5 minutes or more) injects a "hump" of hot water into the system every 15 minutes or so. Seems like 35*F. change would be noticeable to the occupants. Or maybe because of the way the gravity flow (I think) works in the radiators it would average out and nobody would notice and I don't have to do a thing... Be nice.
Right now I'm looking for tables showing the flow speed in different pipe sizes for any particular gpm. I thought I had a handle on the present pumping rate - about 9gpm through the boiler - based on specs about temperature rise but further thought looking at the pump curve I'm not at all sure. The BG Series 100 curves say about 28gpm at 3.5' head (which several old threads here say is what old gravity systems present a pump). That would be in the 1" pipe at the pump which would translate to something less in the main; and maybe something more in the boiler which uses a 3/4" coil. But I haven't seen any spec for the head presented by the Burkay boiler and I've been through a lot of documents. The prior pump was a big old PR series which the curve says actually pumps a little less - say 26gpm. But if I understand the curve right, the PR doesn't care much about head, it just pumps somewhere in the 22-27 gpm range regardless.
Thanks for any comment.
Rufus
