York ZT078-102 Installation Manual

Also see for ZT SERIES: Technical guide

6021980-UIM-A-112036 Johnson Controls Ducted SystemsFigure 23: Bottom entry gas pipingNote: Maximum capacity of pipe in cubic feet of gas per hourbased upon a pressure drop of 0.3 inch W.C. and 0.6specific gravity gas.Note: There may be a local gas utility requirement specifying aminimum diameter for gas piping. All units require a 3/4inch pipe connection at the entrance fitting. Line shouldnot be sized smaller than the entrance fitting size.Gas connectionRoute the gas supply line within the space and roof curb with theexit through the unit’s basepan. See Figures 22 and 23 for thegas piping inlet location. Typical supply piping arrangements areshown in Figures 22 and 23. All pipe nipples, fittings, and the gascock are field supplied or may be purchased in the DuctedSystems accessory kit #1GP0405.Apply the following gas piping recommendations.• You must install a drip leg and a ground joint union in thegas piping.• When required by local codes, install a manual shut-offvalve outside of the unit.• Use wrought iron or steel pipe for all gas lines. Apply pipedope sparingly to male threads only.• Clean all piping of dirt and scale. Hammer on the outsideof the pipe and blow out loose particles. Before initialstart-up, make sure that all gas lines external to the unitare purged of air.• The gas supply must be a separate line and installed inaccordance with all safety codes as prescribed underLimitations.OPTIONALCOILGUARDSHOWNTable 15: Gas pipe sizing - capacity of pipeLength ofpipe (ft.)Nominal iron pipe size3/4 in. 1 in. 1-1/4 in.10 278 520 105020 190 350 73030 152 285 59040 130 245 50050 115 215 44060 105 195 40070 96 180 37080 90 170 35090 84 160 320100 79 150 305Table 16: Gas heat minimum supply airSize (tons) Model Heat sizeSupply air (CFM)HeatingMinimum Maximum078(6.5) ZT N12 1950 3250N18 1950 3250090(7.5) ZT N12 2250 3750N18 2250 3750102(8.5) ZT N12 2550 4250N18 2550 4250120(10.0) ZT N18 3000 5000N24 3000 5000150(12.5) ZT N18 3750 6250N24 3750 6250Natural gas may contain some propane. Propane is anexcellent solvent and will quickly dissolve white lead andmost standard commercial compounds. A special pipedope must be used when assembling wrought iron orsteel pipe. Shellac based compounds such as Gaskolacor Stalastic, and compounds such as Rectorseal #5,Clydes’s or John Crane may be used.