pipe sizing

STEVEN MARKS

I am looking to replace an HB Smith boiler with a Crown model #TWZ120. The original boiler was probably a gravity system from looking at the pipe size. It is 1 zone system with 2 2" hot water loops for the mains. When the HB Smith was installed the installers built 1" headers on the supply and return on the boiler and teed into the 2" mains. I would like to keep this setup as it would make installation much easier. Is the 1" large enough? I am also installing valves on my new headers to seperate the 1st and 2nd floors in the future. I also plan on using the 007 pump supplied with boiler. The house is about 2300 sg ft.

Mike T., Swampeast MO

If it was a gravity system (sounds quite possible) the general rule of thumb for sizing the near boiler piping is to first reduce the largest main size by half, then drop one size.

For instance, with 2" pipes, near boiler becomes ¾"; with 2½" pipes, near boiler becomes 1".

Again, if gravity, that sizing sounds reasonable. Considering the high-flow circulators typically installed on these systems, I'd be a bit reluctant to size down to ¾" myself.

Bruce M.

Present Circulator

Is there a circulator on the system now? If so, what type and model? Is it base mounted (on the floor) or flange mounted?

STEVEN MARKS

pipe sizing

It is a flange mount taco oo7

Ron Schroeder_2

I din't think that I would go below 1" either to prevent velocity noise. I would probably also use a Grundfos UPS15-58FRC in the supply after the expansion tank to replace the Taco 007. That way you could use eithe medium or low speed if needed for proper flow.

Ron