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CONTINUED | 5 <br />creeping up to the regulator line side pressure during <br />long periods of zero gas flow when the generator is <br />not running. If excessive gas pressure is allowed to <br />build up on the low-pressure side of the regulator, the <br />generator solenoid valves may be unable to open <br />against the excessive pressure and the engine will <br />not start. <br />2.7. Internal vs. external pressure registration: <br />Internally registered regulators are recommended <br />because they generally have fewer operational <br />problems in the field. <br />The diaphragm case of a regulator must have a <br />connection to the low-pressure side in order to <br />function. Internally registered regulators have a <br />passage built into the body casting which provides a <br />path for low-pressure gas to act against the <br />diaphragm and spring force. Externally registered <br />regulators lack this internal connection path but <br />instead have an additional pipe fitting on the regulator <br />case where a smaller diameter pipe is field-fabricated <br />to a downstream location on the low-pressure side of <br />the main gas piping system. Because all the pipe <br />fabrication is done in the field, variation in the main <br />gas piping system and the remote pressure <br />registration line can cause unpredictable performance <br />that is difficult to troubleshoot. <br />Externally registered regulators can be used, but the <br />engineer and installation contractor must be aware of <br />the dynamic effects introduced by variables such as; <br />flow turbulence, length and diameter of the sensing <br />line, location of the sensing point in the low pressure <br />piping system, increases and decreases in pipe <br />diameter. <br />If an externally registered regulator is used, locate the <br />remote sensing point 8 to 10 pipe diameters <br />downstream of the regulator in the largest diameter <br />pipe section. The start of 8 to 10 pipe diameters is <br />after the transition to the largest diameter pipe or any <br />other throttling devices, component and/or fittings <br />that will disrupt flow and create turbulence. The <br />sensing line should be taken off the top of the main <br />line to keep it free of debris and condensate. If <br />possible, it should horizontally slope back to the main <br />so that any condensate will drain back into the main <br />rather than accumulate in the regulator’s diaphragm <br />case. Minimize the fittings used in running the sensing <br />line. An externally registered regulator will respond to <br />the pressure changes sensed at the remote tap rather <br />than within the regulator body. It is advisable to install <br />a pressure gauge at the sensing line tap on the main <br />as this will be the control point of the regulator. <br />2.8. Recommended gas regulators: <br />The list of regulators below is not an exhaustive list of <br />all suitable regulators that are available in the market, <br />nor is it a list of “Generac Approved” regulators. The <br />list is intended to help design engineers and <br />mechanical contractors identify a range of products <br />that have demonstrated their suitability for engine- <br />generator service in past projects. Consult your <br />Generac Distributor or gas regulator supplier for <br />additional information. <br /> - Sensus5 <br /> - Emerson Fisher <br /> - Itron <br />Figure 3: Major components of a direct-acting lever- <br /> type regulator, internally registered. <br /> (Courtesy Emerson Fisher). <br />Natural Gas Supply System Design Guide for Generac Industrial Spark Ignited Generators <br />Relief Valve Seat <br />Adjusting Screw Vent Stabilizer <br />Valve Disk <br />Orifice <br />Diaphragm Assembly <br />Control Spring <br />Relief Spring <br />Valve Stem Lever <br />Docusign Envelope ID: 2F58BEE5-DDBE-42EB-8DFA-5E2508488B04