I have a 2 year old Nordyne (Westinghouse) Dual Fuel furnace. Heatpump / Natural gas.
FG7TC 100D-VC 2 stage variable speed blower furnace - - - 4 ton coil - -
FT4BF-048ka 2 stage 16 seer heatpump with Copeland scroll compressor
Honeywell visionpro iaq thermostat. (Controls mounted in attic by furnace)
Problem:For two winters (going on three) the defrost cycle sends ice cold air drafts through the house. The furnace does not cut on when the heatpump is in defrost. Because of this cold draft, I have configured the thermostat to lock the heatpump out at 40 degrees F to avoid defrosts. Sadly, at an outdoor temp of 17F, the heat pump still does a fair job of heating.
My installer states that it is running as designed during defrost mode. However, I have read many other posts where the defrost cycle and heat pump run at the same time.
Question: For my particular unit, Should the furnace cut on during the defrost cycle? If so, is there a document I can refer my installer to?