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20
O. Applications*
*NOTE: Systems shown are primary/secondary piping systems. These recommended systems have a primary (boiler) loop, and
secondary circuits for heating. The primary loop and secondary circuits have separate circulators. The use of other near boiler
piping configurations could result in improper flow rates, leading to inadvertent boiler high limit shutdowns and poor system
performance.
NOTE: In piping applications utilizing a single zone, it is recommended that the installer use flow / check valves with weighted
seats at or near the appliance to prevent gravity circulation.
Single Boiler Space Heating
with Indirect Priority
Figure 7 - Boiler with Indirect Priority
NOTES:
1. This drawing is meant to show system piping concept only.
2. A mixing valve is recommended if the DHW temperature is set above 119
3. Install a minimum of 12 diameters of straight pipe upstream of all circulators.
4. Piping shown is Primary/Secondary.
5. System flow (secondary loop) should be greater than the boiler primary loop flow. In all cases, the boiler primary loop flow rate must be
maintained above the minimum flow rates published in this manual.
6. Installations must comply with all local codes.
7. In Massachusetts, a vacuum relief valve must be installed in the cold water line per 248 CMR.
The piping will not support the weight of the circulators. Refer to the circulator manufacturer's instructions to properly support
the circulator. Failure to comply with these instructions could result in property damage, severe personal injury, or death.
WHL-052 Rev. 4.28.16
Secondary
Circuit
o
F.
Primary Loop
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