Supply or return main circ pump

jeff_51

boiler, then air eliminator then pump. Read the article called pumping away. Go to Heating Q&A on this sight, upper left for more info. Primary, secondary pumping may be a nice set up, but it depends on the system and what you want to do with controls. The larger sized pipes may move water at a lower velocity, but have a much larger volume, so you still move alot of btu's so that is not a problem. We do this all the time when we work on old systems that of course were all gravity. Unless you have a rally big system, you won't need anything special as far as pumps go. What you need is BTU and head to size the pipe correctly. The btu should be on the boiler and head is found by measuring the longest heat run in feet, adding 50% and multiply by .04

CJRS

Supply or return main circ pump

I have an existing gravity hot water system. The system is original to the house built in 1925. I want to install a circ pump to aid water flow through the old pipes. System is a CLOSED system. I know that I have to reduce my main supply and return pipe sizes.... what I need to know is the difference installing a circulation pump to the main supply line versus to install it on the return main. Which method would be better? Boiler is in basement and house has two floors with cast iron radiators. System is currently balanced very good for each supply main.

Empire_2

My thoughts

Although I am not the expert you seek, I would definatly Install the pump on the supply side. Not only that, but I would utalize a primary Secondary loop set up due to the fact that your existing pipe mains are probably 2 to 3". While using a pump will induce flo, the volocity in your larger pipe will slow to a crawl unless you use a larger pump. An HV pump will be ok, but alot of planning and engineering need to be done so you dont have overkill.....Not an easy fix but it can be done.

Empire_2

Hi Jeff

CHeck my math but even though the larger pipe can carry a larger btu content, it's a good Idea to maintain a larger gpm on that large pipe to aid in elimination of entrained air. Ideal volocity range should be between .9 and 4.5 friction loss per 100 ft. for a given gpm. Moving the water to slow will not be the greatest idea especially when you gey called back for constant air problems. Any higher than 4.5, noise is possible and any lower the air will just sit there and not move along... Just a thought and would like your opinion.
Mike T.

jeff_51

maybe I am misssing something

but I don't know why the air would sit there. It is going to move to the highest point in the system or to the point of lowest pressure. I always set up for force bleeding and use a Spirovent even in a rad setup and use bladder expansion tanks. Certainly with rads you still ahve to bleed them, but notheing out of the ordinary. Once a year when the system starts. Just have never had any problems regarding air or flow. Have always pumped away. Maybe we have just been lucky, but have been doing it this way for twenty years when I first started to read Dan in P&M

Rich P.

primary/secondary

The way I do it is primary secondary and it works great!
You need two circ's and probably 007's will work
connect the supply's from the rads. and install a circ pumping towards them then have two closely spaced tee's
then connect all the rads returns to the run of those close tee's. Take the supply from the boiler circ (pumping away from the expansion tank) connect it to one of the closely spaced tee's.. The other should go to the return of the boiler..
I run the system circ all the time it helps blend the temps of all the rads
On a call for heat I turn on the boiler pump and slowly move heat into the loop for the rads nice even heating.
Its late hope I got that right
Good luck

Rich P.