b. The circulator should be sized based on gross
output of the boiler. Table 4.3 shows the Boiler
Output as reported to the Hydronics Institute
Section of AHRI. c. The required flow is calculated based on the design
temperature difference from the return to the supply
of the boiler. For a PF-110 with a design temperature
difference of 20°F the calculation is as follows.
Output 101,000
Required Flow =
________
=
_________
= 10.1 GPM
D
T x 500 20 x 500
d. The boiler pressure drop for various flow rates can
be determined using Figure 4.4, the P
UREFIRE
®
Boiler Circulator Sizing Graph.
19
WATER PIPING AND CONTROLS
PUREFIRE
®
Model
Boiler Input
Btu/hr (kW)
Gross Output
Btu/hr (kW)
PF-50 50,000 (14.7) 46,000 (13.5)
PF-80 80,000 (23.4) 74,000 (21.7)
PF-110 110,000 (34.2) 102,000 (29.9)
PF-140 140,000 (41.0) 131,000 (38.4)
PF-210 210,000 (61.5) 193,000 (56.6)
PF-399 399,000 (116.9) 373,000 (109.3)
Table 4.3: Boiler Inputs and Outputs
Figure 4.4: PUREFIRE
®
Circulator Sizing Graph (General Pump – Primary/Secondary)
Figure 4.2: Relief Valve Installation – PF-50, PF-80,
PF-110 & PF-140
Figure 4.3: Relief Valve Installation – PF-210 & PF-399
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