Primary/Secondary Parallel sizing?

Steve_45

If I’m setting up a primary/secondary boiler with 4 circulators in Parallel loops and the primary is 1 1/4” can the parallel pipes be 3/4” or do they also have to be 1 1/4? The total primary loop will be approx. 20 feet total and the secondarys are 151, 130, 110, 98 feet respectively. Each with its’ own taco 007. Primary will also
have a Taco 007.


||---TT---|| || = 1 1/4

||---TT---||

||---TT---|| ---- = 3/4 ??????

||---TT---||

Thanks,
Steve

Dave_22

Flow

Someone correct me if I'm wrong, but it should be based on your heatloss calc for that zone. BTU load/500XdeltaT. 500 is for water. 10,000 BTU load with a 20 degree delta T= 1GPM. Then you would find a pipe size that would move that much water at the proper velocity. I have a table for it at home, but I'm sure someone may be able to send you a link that would help you out. As far as I know, this would be the "correct" way to do it.

Steve_45

Thanks Dave,

Larges BTU loss is 30000 other three are around
20000 each. That table sure would be helpful.

Dave_22

Pipe size

OK- according to my table, 3/4" would be fine for all secondary zones that you have listed. 3/4" would be alright up to 4 GPM. Hope this helps.

Steve_45

Thanks again Dave,
According to the formula you gave everything
looks good also.

Thanks for your help,
Steve

Joe Mattiello

Primary/secondary, Taco, circulators

Good Morning
Primary, secondary piping is an excellent versatile piping technique used for multizones/multitemperature systems. Primary circulator is sized by the design temperature differential. Assuming a 20 degree delta, 150,000btu output, formula is 150,000/500x20=15gpm. The piping is sized to accommodate the flow rate without exceeding 4'per second velocity. Taco, 007-F5 will work just fine. The use of closely spaced tees to minimize the potential for induced flow in the secondary circuits is fundamental. Secondary piping tees have to be placed no more than Four times the nominal diameter of the primary loop piping apart. The secondary pipe size is dictated by the flow rate required for each loop, which is based on the load calculated in each circuit.

Joe Mattiello
Technical Support Services
Tel. 401-942-8000 X 484
Fax. 401-942-2360
joemat@taco-hvac.com

Steve_45

Joe 007-F5? All mine just say 007-IFC