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CONTINUED | 3 <br />2.2. Pressure differential: The maximum flow rate <br />of a service regulator is constrained by the gas <br />pressure differential across the inlet and outlet port. <br />When selecting a regulator for a specific gas flow <br />requirement, it must correspond to the expected <br />nominal upstream and downstream gas pressures. <br />Consult manufacturers’ published flow rate tables at <br />various inlet and outlet pressure values to select an <br />appropriate regulator (See the example in Table 1). <br />2.3. Flow and droop: Select a direct acting <br />regulator that will deliver approximately 1.5 times <br />the maximum gas flow required by the generator with <br />1" – 2" water column (w.c.) pressure droop at the <br />expected nominal upstream and downstream gas <br />pressures. Direct acting regulators provide the quick <br />response required for controlling fast changing gas <br />flow demands encountered in engine-generator <br />applications. <br />For example, a Generac SG500 generator, configured <br />for 7" – 11 " w.c. nominal gas pressure, requires 6,000 <br />CFH of gas at full load. The selected regulator must <br />be rated to flow approximately 9,000 CFH (1.5 X 6000 <br />CFH = 9000 CFH). Given an upstream gas pressure <br />of 2 psi, a 1½" Model 122–12 regulator with a blue <br />spring would be the first choice. However, assume <br />there is a substantial risk of seasonal pressure <br />variation where the upstream gas pressure may fall <br />closer to 1 psi, a larger 2" Model 122–12 regulator <br />with a blue spring will still provide the required flow at <br />the lower upstream pressure. <br />INLET <br />PRESSURE <br />Set Point <br />5" w.c. <br />Set Point <br />7" w.c. <br />Set Point <br />11" w.c. <br />Set Point <br />18" w.c. <br />Set Point <br />28" w.c. <br />Set Point <br />2 w.c.REGULATOR <br />SIZE <br />AND MODELRed Spring <br />1" w.c. DROOP <br />Blue Spring <br />1" w.c. DROOP <br />Green Spring <br />2" w.c. DROOP <br />Orange Spring <br />2" w.c. DROOP <br />Orange Spring <br />3" w.c. DROOP <br />Black Spring <br />1/4" PSI DROOP <br />8" w.c.4000 3000 ---- <br />1 1/2" <br />Model 122-12 <br />14" w.c.4900 4500 3700 --- <br />1 psi 6600 6500 6000 5750 -- <br />2 psi 10500 10000 9800 9000 9500 - <br />3 psi 12000 12000 11100 10000 10500 8900 <br />5 psi 14500 14500 13900 12000 12700 10000 <br />10 psi 16000 16000 15000 13500 14000 12700 <br />15 psi 18000 18000 19000 19000 20000 18000 <br />8" w.c.5000 4000 ---- <br />2 1/2" <br />Model 122-12 <br />14" w.c.8800 8000 6600 --- <br />1 psi 12200 12000 11500 10700 -- <br />2 psi 18200 18000 17300 16500 16900 - <br />3 psi 25000 25000 24000 22300 23000 18000 <br />5 psi 32000 32000 30000 28100 29000 27400 <br />10 psi 38000 38000 35000 32200 33000 30000 <br />15 psi 38000 38000 40000 39000 40000 36000 <br />Natural Gas Supply System Design Guide for Generac Industrial Spark Ignited Generators <br />Table 1: Typical regulator flow capacity table. Note how the same model regulator will flow larger volumes of gas with a <br />higher inlet pressure while maintaining a set downstream pressure. Courtesy of Sensus. <br />Docusign Envelope ID: 2F58BEE5-DDBE-42EB-8DFA-5E2508488B04