Bard WG Series Installation Instructions Manual

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Bard WG Series Installation Instructions Manual Manual pdf 29 page image

Manual 2100-587JPage 29 of 5921. STANDARD ORIFICE SIZING ANDHIGH ALTITUDE DERATEThis furnace is shipped with fixed gas orifices for usewith natural gas and sized for 1000 BTU/cubic footgas. Make sure actual gas input does not exceed ratingplate input. The orifices may need to changed to getthe correct gas input. Whether they need changedor not depends on input and the gas heat value atstandard conditions and elevation. Consult the localgas supplier for gas heat value and any special deratingrequirements. See Section 20 for more information.At higher altitudes, the density of the air is reduced.Therefore, for proper combustion, the quantity of gasTable 7Natural Gas Derate Capacities for All Modelsburned in the furnace must also be reduced. Thisis called derating. This unit must be derated wheninstalled at altitudes greater than 6,000' above sealevel. A high altitude pressure switch must also beinstalled for operation above 6,000'. High altitudepressure switch kit number 8620-189 is designed forthis application.It is the installer’s responsibility to see that thefurnace input rate is adjusted properly. Deratingmust be achieved by reducing the size of the mainburner orifices. Derating the furnace by adjusting themanifold pressure lower than the range specified inthe Section 19, “Manifold Pressure Adjustment” isconsidered to be an improper procedure.WG Rated Input Sea Level 1000 2000 3000 4000 5000 600045,000 45,000 43,560 42,120 40,680 39,600 38,880 37,98050,000 50,000 48,400 46,800 45,200 44,000 43,200 42,20067,500 67,500 65,340 63,180 61,020 59,400 58,320 56,97075,000 75,000 72,600 70,200 67,800 66,000 64,800 63,30090,000 90,000 87,120 84,240 81,360 79,200 77,760 75,960100,000 100,000 96,800 93,600 90,400 88,000 86,400 84,400112,500 112,500 108,900 105,300 101,700 99,000 97,200 94,950125,000 125,000 121,000 117,000 113,000 110,000 108,000 105,500