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c. The boiler pressure drop for various flow rates can
be determined using Figure 4.2, the PureFire
Boiler Pump Sizing Graph.
d. Table 4.4 provides the flow rate and pressure drop
information that corresponds to 20°F temperature
rise (ΔT). The pressure drop shown is for the
boiler only. If there is significant system pressure
drop in the circulation system between the boiler
and the tank, this should be included when
specifying pumps.
Table 4.4: Flow Rate and Pressure Drop for Various
System Temperature Rise Values
Flow Rate vs Pressure Drop at 20°F
PFW-200
GPM (LPM)
Feet (m)
17.3 (5.3)
18.3 (69.3)
e. Table 4.5 provides a list of recommended pumps
for PureFire hot water supply boilers.
Table 4.5: Pump Selection Chart (20°F ΔT)
Pump
PFW-200
Manufacturer
Bell & Gossett
UPS32-80F
Grundfos
Medium Speed
Taco
* Pumps must be bronze fitted for potable water application
7. Flow Switch: The flow switch supplied with the boiler
is to be mounted as shown in figure 4.1 using the
fittings supplied with a minimum straight length of 5
pipe diameters before and after the switch.
PFW-399
GPM (LPM)
Feet (m)
37.3 (141.2)
18.1 (5.5)
PFW-399
PL-36
PL-55
UPS32-160F
Medium Speed
1400-20
1400-50
WATER PIPING AND CONTROLS
D. SYSTEM PIPING
1. Figure 4.3 shows piping for a single boiler with a
single storage tank. When using the factory specified
pump, the maximum total pipe length is 30 feet (10
meters) with 6 90° elbows all at the full pipe diameter
of the pump connections.
2. In Figure 4.4, a single boiler is used with multiple
water storage tanks. The pumps are piped in parallel
with reverse return piping.
3. Figure 4.5 shows two boilers piped into a single
storage tank.
4. Figure 4.6 shows piping for two boilers and two water
storage tanks.
5. In Figure 4.7, we show a single boiler with a single
tank using a patented anti-scale principle. In this
configuration, the boiler control switches the 3-way
valve to bypass when the call for heat ends. The
pump is then operated to draw cool water from the
anti-scale buffer tank until the supply and return
temperatures equalize.
6. In Figure 4.8, a plate heat exchanger is used to isolate
the boiler from the domestic hot water supply system.
This strategy can be used if the domestic water does
not meet the water quality guidelines presented earlier
in this section. Note that a hydronic thermal
expansion tank is required in this closed-loop system.
17
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