In this blog post, you will learn:
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3 ways to retrofit an existing furnace plus air conditioner
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The implied construction involved to make it happen
If you’re like me, you have a natural gas furnace and a paired air conditioner.
My home was built in 2008. I suspect the code minimum air conditioning unit was 13 SEER back then, because that’s what I got. My wife and I built our home with a development, and I don’t even think the discussion came up regarding what brand, how efficient, etc.
Looking at my 12-1/2 year old system, maybe it’s time to change ‘er out.
Starting Point: Which Unit?
Well, no matter what, the Carrier outdoor unit is going out. If possible, I’ll switch to the 3 ton because of the size, the cost, and the efficiency. (3-ton is 18 SEER, 4-ton is 17 SEER). Let’s assume we’re sticking with 4 tons for now. By the way, pictures are not to scale.
Now to the First Option.
Option 1: All-Electric Replacement
If you have solar panels on your house, drive a Tesla, carry grocery bags to the store, and enjoy composting, then this might be the way for you.
This indoor unit is shaped like your furnace and can be installed right in its place. Out goes the furnace, in goes your indoor unit. There’s probably a little ducting that needs to be done. The coil and blower are right in there, your filter rack stays in place.
Based on the low ambient output of the unit, a small trim heater could be included. At 4 tons and -10F design, the 8KW trim heater accessory would be a good idea. This needs to be powered by the electrician, but he’ll already be involved with the outdoor unit changeout. Of course, the best idea is to determine the actual heating load of the home and design accordingly.
Here’s the process:
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Pull out the refrigerant, furnace, air conditioner, air conditioning coil, and all the refrigerant lines
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Set the indoor unit and make the necessary duct modifications to accommodate the filter
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Set the outdoor unit
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Electrician goes to work powering up outdoor unit, indoor unit and trim heater
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Run new refrigerant lines and charge
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Run new heat pump stat and program
Option 2: Leave the Furnace, Replace the Condensing Unit with a Heat Pump
This is the most cost conscious method, in that there will be benefits of running in heat pump mode all year until the trim heat would be engaged. In this case, for those few hours, burn gas instead of electricity.
My furnace has a separate cased coil mounted on top of the furnace for air conditioning. Yours probably does too. To convert this unit to a heat pump and operate in cooling and heating, the coil needs a different thermal expansion valve (TXV) to operate in both heating and cooling modes.
Here’s the process:
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Pull the refrigerant out of the system
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Replace the outdoor unit
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Disconnect the refrigerant piping from the cased coil
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Replace the coil with a heat pump coil
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Run new refrigerant lines
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Run your new heat pump thermostat
Option 3: Leave the Furnace, Replace the Condensing Unit with a Heat Pump as AC Only
In this option, the condensing unit is replaced and nothing else.
In a perfect world, the coil should be changed out because the pressure from a heat pump is higher than a standard AC. But it’s not absolutely necessary.
There will not be the benefits of running in heat pump mode, but the 17-20 SEER unit is going to save a lot of energy and operating cost in the cooling season.
Here’s the process:
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Pull the refrigerant out of the system
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Replace the outdoor unit
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Recharge and run
In this mode, the existing thermostat will run the unit just fine.
Fun Fact:
It is actually better for the environment to use the backup heat from gas than from electric. Because the electric has no COP (coefficient of performance) it actually requires the burning of more fossil fuels to power the heater.
What Did We Learn?
There are several ways to incorporate heat pump retrofits for your home and customer’s homes that will be affordable, straight forward, and energy efficient with Kinghome heat pumps.
Until Next Time,
Tom
Tom Gelin
Air Flow Inc.
8355 West Bradley Road
Milwaukee, WI 53223
414-351-1999
