Returned to configure outdoor heat pump defrost setpoints. Switched from a 50 degree (default) to 70 degrees. Outdoor heat pump will run at 35 degrees or higher. Gas furnace (auxiliary heat) will run without the heat pump at temperatures below 35 degrees. Verified proper settings on furnace control board and EIM. Lennox FSR will follow up in regards to the E421 code. It will not prevent the unit from operating. No return visit is needed until the next scheduled maintenance service. N/C, part of install. Lennox furnace M#EL296UH090XV48C-07, S#5922C18134 Lennox heat pump M#XP21-036-230-08, S#5822K05117. Thermostat Lennox E-30. Filter size-16x25x1.