Help for the Heat Pump: What Type of Auxiliary Heating Should You Use?
Posted on November 27, 2014
A heat pump provides efficient cooling all summer long and winter warmth almost all the time. Heat pumps heat your house using a different principle than a gas-fired furnace. Instead of making heat, it moves heat. Even on a cold winter night, down to a certain temperature there’s enough latent heat energy in outdoor air to heat your home. The system extracts this heat with an outdoor coil, concentrates it in a refrigerant cycle, and moves it indoors to be dispersed into your ductwork by a coil inside the air handler.
As outdoor temperatures drop below freezing, latent heat in outdoor air eventually declines below the system’s ability to extract sufficient amounts. The exact temperature where this occurs varies according to the unit’s rated capacity. Currently, the lower limit in the average unit is between 27 and 32 degrees. New, high-efficiency models are pushing that envelope further, however, with some models harvesting sufficient heat at temperatures as low as 20 degrees.
What happens when the heat pump runs out of heat? Auxiliary heating to take up the slack during cold snaps comes in two varieties:
- Electric backup heat. The system’s default auxiliary option are electric resistance coils inside the air handler. Functioning just like the heating elements in a common electric furnace, the coils provide sufficient heat to warm the house when the outside air doesn’t.
- Dual-fuel system. Because electric resistance heating is costly, dual-fuel auxiliary heat offers a more efficient option. When outdoor temps drop below the critical “balance point,” a secondary gas-fired furnace automatically actuates to take over household heating function. Because gas is less expensive than electricity, the operating costs of resorting to auxiliary heat are more affordable. An HVAC contractor can calculate the precise temperature balance point where gas heating is more cost-efficient so the system always utilizes the most affordable available option. In many cases, a dual-fuel system simply incorporates the existing gas furnace left in place when the homeowner upgrades to a heat pump.
For more information on auxiliary heating options for a heat pump, in Wichita contact Comfort Systems.
Our goal is to help educate our customers in Wichita, Kansas about energy and home comfort issues (specific to HVAC systems). For more information about heat pumps and other HVAC topics, download our free Home Comfort Resource guide.