Selecting Circulators Guide
TD10 – 2
TUBING
SIZE/TYPE
MINIMUM
FLOW
RATE
1
(gpm)
MAXIMUM
FLOW
RATE
2
(gpm)
3
⁄
8
" copper
1.0 2.0
1
⁄
2
" copper
1.6 3.2
3
⁄
4
" copper
3.2 6.5
1" copper 5.5 10.9
1.25" copper 8.2 16.3
1.5" copper 11.4 22.9
2" copper 19.8 39.6
2.5" copper 30.5 61.1
3" copper 43.6 87.1
3
⁄
8
" PEX
0.6 1.3
1
⁄
2
" PEX
1.2 2.3
5
⁄
8
" PEX
1.7 3.3
3
⁄
4
" PEX
2.3 4.6
1" PEX 3.8 7.5
1.25" PEX 5.6 11.2
1.5" PEX 7.8 15.6
2" PEX 13.4 26.8
3
⁄
8
" PEX-AL-PEX
0.6 1.2
1
⁄
2
" PEX-AL-PEX
1.2 2.5
5
⁄
8
" PEX-AL-PEX
2.0 4.0
3
⁄
4
" PEX-AL-PEX
3.2 6.4
1" PEX-AL-PEX 5.2
TABLE 1
(1) BASED ON 2 FT/SEC
(2) BASED ON 4 FT/SEC
10.4
Answer: Look at the copper tube sizes in Table 1. Find a size (or sizes)
for which the target flow rate of 10 gpm falls within the values in the
second and third column. In this case, a 1-inch copper tube meets this
condition and so does a 1.25-inch copper tube. Either tube size is thus
a possibility for the system based on the conditions stated. The 1.25-
inch tube would generate less head loss than the 1-inch tube. This
might mean that a smaller less expensive circulator could be used. On
the other hand, the 1.25-inch tubing will increase initial cost.To make
an informed decision as to which tube size is best the designer can fol-
low the remainder of this procedure assuming 1-inch tube, repeat the
procedure assuming 1.25-inch tubing, and then compare results.This is
the only way to know if the larger tubing would allow a smaller circu-
lator to be used. Based on the outcome the designer can then factor
in cost estimates and make a final selection.
STEP 3: FIND THE EQUIVALENT LENGTH OF THE
PIPING CIRCUIT
The total equivalent length of the piping circuit is the length of all
straight tube segments plus the equivalent lengths of other compo-
nents such as fittings and valves.
Table 2 lists the equivalent lengths of some common fittings and valves
based on their tube size. To get the total equivalent length of the cir-
cuit add the equivalent lengths of all fittings and valves to the total
length of straight tubing.
Example 3: A piping circuit consists of 150 feet of 1-inch type M cop-
per tubing as well as 25, 90º copper elbows, three side port tees, and
four ball valves.What is the total equivalent length of the circuit?
Answer: The equivalent length of the 1-inch fittings and valves is found
in Table 2:
• 90º elbows – equivalent length for each elbow = 2.62 feet
• Side port tees – equivalent length for each tee = 5.25 feet
• Ball valves – equivalent length for each ball valve = 1.8 feet
The total equivalent length of the circuit is therefore:
(25x2.62) + (3x5.25) + (4x1.8) + 150 = 238.45 or about 239 feet.
TABLE 2
Copper Tube Sizes / Equivalent Length of Pipe *
Fitting or Valve
1
⁄
2
"
3
⁄
4
"
1"
1
1
⁄
4
"1
1
⁄
2
"
2"
2
1
⁄
2
"
3"
90-degree elbow 1.55 2.06 2.62 3.45 4.03 5.17 6.17 7.67
45-degree elbow 0.83 1.10 1.40 1.84 2.15 2.76 3.29 4.09
Std. Tee (thru flow) 1.04 1.37 1.75 2.30 2.68 3.45 4.12 5.11
Std. Tee (branch flow) 3.11 4.12 5.25 6.90 8.05 10.3 12.3 15.3
Taco Venturi Tee N/A 28.9 19.3 25.7 N/A N/A N/A N/A
Gate Valve 0.41 0.55 0.70 0.92 1.07 1.38 1.65 2.04
Ball Valve 0.60 1.20 1.80 6.80 6.50 14.2 5.40 9.20
Swing Check 5.18 6.86 8.74 11.5 13.4 17.2 20.6 25.5
Taco Flow-Chek N/A 143.0 83.7 47.8 57.9 61.8 N/A N/A
Angle Valve 7.78 10.3 13.1 17.3 20.1 25.8 30.9 38.4
Globe Valve 17.6 23.3 29.7 39.1 45.6 58.6 70.0 86.9
Butterfly Valve N/A N/A N/A N/A N/A 7.75 9.26 11.5
Taco ESP Zone Valve 9.50 8.40 47.4 N/A N/A N/A N/A N/A
Taco 570 Series Valve 10.0 20.0 60.0 130.0 N/A N/A N/A N/A
* Calculated from data in Crane Co. Technical Paper 410 or testing.