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Residential Product News M-260-2006 September 25, 2006 To: All Branch Managers, Branch Sales and Service Managers, Distributor Principals, Distributor Sales and Service Managers, Regional Sales Managers and Regional Sales Vice Presidents. Subject: PM9 and PC9 Modulating Furnace Installations at High Altitude This product news letter is to provide you with information regarding York Affinity PM9 and PC9 Modulating furnaces at high altitude locations. We have received reports from several sites that the modulating furnaces may not function correctly when installed above 8,000 feet (2438 m) in elevation. We have investigated this situation and have determined that there are issues that need to be clarified for proper application and use of these models under high altitude conditions. Corrective Action: The current modulating furnaces will operate correctly in applications up to 8,000 feet (2438 m) in elevation above sea level. The control will properly set the input rate including all de-rate as needed up to this point. Depending upon the physical constraints of the installation (vent lengths and vent termination location, condensate drainage, actual elevation, etc.), the furnace may experience intermittent operation or fail to operate due to lack of combustion air or vent pressure. The High Altitude Kit referenced in the propane kit instructions has not yet been released, so at this time, there is not a field modification available for installations above that altitude. Therefore, until the High Altitude Kit is released and available in the field, these modulating furnaces should not be specified, sold, or installed for any application locations above 8,000 feet (2438 m) above sea level. While the furnace may operate in some cases, the potential for intermittent operation and customer dissatisfaction does exists. Background Information: The installation instructions for these modulating furnaces state the following: “HIGH ALTITUDE OPERATION This furnace is constructed at the factory for natural gas fired operation at 0 to 4,000 feet (0 to 1220 m) above sea level. At elevations above 4,000 feet, the furnace will automatically reduce its input rate if necessary to maintain good combustion. If the natural gas being supplied has also been de-rated by the gas supplier, it may be necessary to increase the orifice size in order to achieve the rated input.” [Page 6].
“High altitude and propane (LP) conversions are required in order for the appliance to satisfactory meet the application.” [Page 7] The installation instructions included with the propane accessory kit, S1-1NP0680, says: “GENERAL This kit is intended for the conversion of new equipment only, from natural gas to propane gas operation, up to 8,000 feet. Over 8,000 feet, refer to the High Altitude Kit Instructions.” [Page 1] The information provided in these instructions is correct, but does not specify completely what is required for high altitude applications. The major concern is that information is not consistent between the two documents, and does not put an upper limit on the application installations. If there is insufficient combustion air or there are restrictions in the vent system, then the furnace will reduce the heating input rate and capacity as required maintaining operation (see fault code for 5 amber flashes). If the inducer is operating at maximum and the input rate is reduced to the minimum rate, and there is still a problem with vent pressures, the system will not operate and the fault code of three red flashes will appear on the board. Current field situation: We have received a report this week of at least one unit that has been installed at a 10,000 foot elevation, and that it is not closing the pressure switch circuit. This furnace had to be removed after field testing indicated it could not be adjusted as required for correct operation. It has been requested that we provide a special field modification for units installed at that altitude. While this may be possible, it is not as simple as just finding a lower pressure switch setting. The modulating control checks the switch closure point on each cycle and if it does not close at the programmed setting, the furnace will not light. So there is significant engineering testing required in defining a new pressure switch setting, performance impacts, and control changes required to develop new software for the board and a new set of ID plugs that would give the right combustion air/gas flow ratio for each input for altitudes above 8,000 feet (2438 m). We apologize for this situation, and are in the process of determining the timeframe and the best solution for this issue. More information will be provided on this subject when it is available.
Bryan Rocky Product Manager, Heating
