Best direction of flow for old overhead gravity system

Steamhead (in transit)

whoever replaced the boiler got it backwards.

For determining circ size- how much radiation is on the system?

"Steamhead"

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Al Roethlisberger

First, let me say that I finally received Dan's excellent books today, "How Come?" and "Pumping Away"(along with a few others) and I read them cover to cover this afternoon. This answered several questions, but also raised a few new ones as I plan for my tune-up of my old overhead gravity system following its conversion to a sealed circulator system around 1991.

Al Roethlisberger

Best direction of flow for old overhead gravity system?


First, let me say that I finally received Dan's excellent books today, "How Come?" and "Pumping Away"(along with a few others) and I read them cover to cover this afternoon. This answered several questions, but also raised a few new ones as I plan for my tune-up of my old overhead gravity system following its conversion to a sealed circulator system around 1991.

I had asked the following question a week or so ago as part of an overall set of questions regarding identifying what type of system I had. But I'd like to see if I can get some more specific answers to this one issue, as it will affect how I design the "tune up" of my converted system.

So, as I have mentioned before, I have a ca1929 overhead gravity hot water system, that in ca1991 was converted to a sealed circulator system.

When the did this conversion, they oriented the pump output to supply hot water now into what HAD BEEN the RETURN line from the system as it was originally designed/plumbed. So now, the return cooler water returns via what had been the original express hot water riser to the attic.

My question is basically: Is this correct?

Should a conversion to a circulator based system for an overhead system with a huge 4 inch riser be run in "reverse", or do you think this was a mistake during the conversion.


I have read quite a bit about the type of circulator one needs for one of these conversions, and it is not the same as a high-pressure circulator that often comes packaged with new boilers. Instead one would want a high-flow low head pressure pump on one of these.

Currently I have a Grundfos UP15-42F, which I have yet to determine whether is "high flow" or "high pressure" relatively speaking. If it is "high pressure" it may have made sense to reverse the flow perhaps since it otherwise would have been pumping into that huge 4" pipe. But that is just one theory I have.

But if I had another type of pump geared toward high flow, maybe the original circulation direction would be fine.

But I really don't want the circulator type to define which direction I circulate the water. I can get a different circulator if one direction is more ideal than another.

It seems to me that the original designed direction of circulation would be best, but that is just this layman's opinion. If so, I'll get the correct circulator type to support that.

So if anyone can confirm the best direction a converted overhead gravity system should circulate, regardless of circulator type, that would help me quite a bit on design decisions.

Thanks!
Al

Al Roethlisberger

System EDR of 1278


Thanks so much for the concise answer on the circulation!


I am currently missing one radiator that has an EDR of 70 per the blueprints, but I do plan to put it back in the next year. So with that radiator included, I have about 1278 of EDR based on my calculations from the blueprints.

I have checked "reality" of what radiators I have against a handful of those listed on the blueprint specified EDR values, and so far they are correct. So right now my system EDR is based upon adding up the blueprint specs.

At some point in the near future, I'll go measure all 20 radiators and add it up manually to double check for sure.

For now, I think the 1278 figure is fairly accurate though.

Currently I have a Grundfos "Brute" UP15-42F circulator, and am thinking about a B&G Series 100 instead once I repipe, etc.

Thanks
Al

Steamhead (in transit)

That B&G would be fine

but I'd use the Taco 0010, which uses less electricity and does not need to be oiled.

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John Ketterman

Water flows at the same rate going out and coming back in ("what goes out must come back"). So what kind of pump you use does not have anything to do with flow direction. The head (which is the net 'resistance' in the complete circuit) is the same in either direction. What kind of pipe the water encounters first vs last is irrelevant for flow purposes.

The only thing that matters in choosing flow direction is the preference for Pumping Away...that means you should pump away from the expansion tank, not necessarily from the boiler.