IBC VFC 15-150 Installation And Operating Instructions Manual

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INSTALLATION AND OPERATION INSTRUCTIONS1-26VFC 15-150, VFC 45-225 MODULATING GAS BOILERSGAS PIPINGThe boiler requires an inlet gas pressure of at least 3.0" w.c. for natural gas orpropane. For either fuel, the inlet pressure shall be no greater than 14.0" w.c.Confirm this pressure range is available with your local gas supplier.The inlet gas connection of the boiler’s gas valve is 1/2" NPT (female).Adequate gas supply piping shall be provided with no smaller than 1/2" Iron PipeSize (IPS), in accordance with the following chart:MODEL 1/2" IPS 3/4" IPS 1" IPSVFC 15-150 (Natural Gas) 10 40 130VFC 15-150 (Propane) 50 180 620VFC 45-225 (Natural Gas) 5 20 60VFC 45-225 (Propane) 25 90 290Table 7: Maximum Pipe Length (ft)Gas piping must have a sediment trap ahead of the boiler’s gas valve (see Figure30). A manual shutoff valve must be located outside the boiler, in accordance withlocal codes/standards. All threaded joints in gas piping should be made with anapproved piping compound resistant to the action of natural gas/propane. Useproper hangers to support gas supply piping as per applicable codes.The boiler must be disconnected or otherwise isolated from the gas supplyduring any pressure testing of the system at test pressures in excess of 1/2 psig.Dissipate test pressure prior to reconnecting. The boiler and its gas piping shallbe leak tested before being placed into operation.The gas valve is provided with pressure taps to measure gas pressure upstream(supply pressure) and downstream (manifold pressure) of the gas valve (seeFigure 32). Note that manifold pressure varies slightly in accordance with firingrates with the modulating series boilers, but will always be close to 0” w.c.1.7Figure 30: Typical gas pipingNOTEDue to the precision ofmodern modulating boilersit is important to pay specialattention to gas pressureregulation.It is essential to check gassupply pressure to eachboiler with a manometer orother high-quality precisionmeasuring device. Pressureshould be monitored beforefiring the boiler, when theregulator is in a “lock-up” condition and duringoperation, throughout theboiler’s full modulation range.Pay special attention toretrofit situations whereexisting regulators may havean over-sized orifice and/orworn seats, causing pressure“creep” and high lock uppressures.A high quality regulator willmaintain constant pressureabove the boiler’s minimumspecification at all firingrates, and will not exceed theboiler’s maximum pressurerating when locked-up with noload.