Bard W24G1-A Installation Instructions Manual

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Bard W24G1-A Installation Instructions Manual Manual pdf 29 page image

Manual 2100-525APage 29 of 6721. 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. You may need to change orifices to getcorrect gas input. Whether you do or not depends oninput, and your gas heat value at standard conditionsand elevation. Consult your local gas supplier for gasheat value and any special derating requirements. SeeSection 20 for more information.At higher altitudes, the density of the air is reduced.Therefore, for proper combustion, the quantity of gasburned in the furnace must also be reduced. This iscalled derating. This unit must be derated wheninstalled at altitudes greater than 6,000 feet above sealevel. A high altitude pressure switch must also beinstalled for operation above 6,000 feet. High altitudepressure switch kit number 8620-189 is designed forthis application.TABLE 7NATURAL GAS DERATE CAPACITIESFOR ALL MODELSdetaRGWtupnIaeSleveL 000,1 000,2 000,3 000,4 000,5 000,6 000,7 000,8 000,9 000,01000,14000,54005,04000,54402,93065,34809,73021,24216,63086,04046,53006,93299,43088,83281,43089,73696,33044,73840,33027,63346,23072,63670,23046,53000,16000,86057,06005,76608,85043,56268,65081,36819,45020,16064,35004,95884,25023,85372,15079,65445,05061,65275,94080,55569,84504,45411,84064,35000,57000,18000,57000,18006,27804,87002,07618,57008,76422,37000,66082,17008,46489,96003,36463,86004,26293,76002,16690,66054,06682,56004,95251,46000,09000,001000,09000,001021,78008,69042,48006,39063,18004,09002,97000,88067,77004,68069,57004,48088,47002,38044,37006,18045,27006,08082,17002,97000,311000,521005,211000,521009,801000,121003,501000,711007,101000,311000,99000,011002,79000,801059,49005,501006,39000,401008,19000,201576,09057,001001,98000,99It is the installer’s responsibility to see that the furnaceinput rate is adjusted properly. Derating must beachieved by reducing the size of the main burnerorifices. Derating the furnace by adjusting the manifoldpressure lower than the range specified in the Section19, “Manifold Pressure Adjustment” is considered to bean improper procedure.Above 6,000 feet elevation orifice changes are required,and capacity reductions are a function of altitudeimpact and orifice change. Pressure switch change isrequired above 6,000 feet elevation. For Natural Gassee the Altitude Table 7 below and the Orifice Tables 8and 8A on following pages.