Dual Fuel

I have been installing heat pumps in New England for 7 years. However, I still have customers that don't believe that a heat pump can take heat energy out of the Ambient outdoor air in the middle of the winter. But they would still like to get away from their fossil fuel furnace and convert to electric based heat and air conditioning source so that they can take advantage of solar panels.  What if we added a heat pump to your current gas or oil furnace and ran your heat pump most of the year off of your solar electric system while you continued to have the security of the fossil fuel furnace as a backup. I've done just that and it works great. Here are more details on how it works.

In the above picture you will see the entire dual fuel heat pump hybrid system.  What is it really? It  is a furnace with a heat pump coil (indoor) and a coil in the compressor unit (outdoor).  The Indoor equipment is a basic gas or oil furnace with a blower motor.  But instead of an A/C coil, you would have a heat pump coil. It provides both heating and cooling capability, where an A/C coil will just give you cooling.  The outdoor unit looks just like an A/C Condenser but it is not.  It has the capability to run cooling or heating.  

So what does that give us?  For above the same amount of money to replace an old furnace and A/C coil combination with a new furnace and heat pump coil combination, you will get a heat pump running your cooling and heating through 80 to 99% of the year depending on your latitude.  The heat mode heat pump is more efficient that the gas/oil burning heat and the cool mode is also more efficient than the old R22 or R410A Air Conditioner. Especially if you have or plan to put in Solar panels.  If designed correctly, you could have virtually net zero energy expense. 

Q: How low can the heat pump heat your home?

A: I personnaly have set the customers gas furnace to take over when the ambient outdoor air gets down below 0°F. There are other claims of -15°F.  

Q: How does a dual fuel configuration know when the fuel should switch from heat pump to gas/oil fuel.

A:  Typically a thermostat will control this.  Sometimes there is a temperature  sensor that is wired to the outdoors to determine the threashold temperature for switch over (let's say 0°F).  Sometimes the more updated thermostats such as ECOBEE, will connect to tghe home wifi system and can get outdoor temperature information from the web..

Q: So what do I need to do when it gets down to 0°F?

A: Nothing, if configured correctly, and the temperature dips to the switch over threshold point (let's say 0°F) the heat pump will shut off and the flame from the gas or oil burner will come on.