One of the biggest and potentially damaging misconceptions about heat pumps that homeowners will run up against today is that a bigger heat pump must be better than a smaller one. If a 9000 BTU heat pump is good, an 18,000 BTU must be twice as good right?
Of course, by that opening, you can already tell that is not the case. But why isn’t more better? Shouldn’t double the power mean double the effectiveness? While this may be true in race cars or monster trucks when it comes to heat pumps you can think of them more like the gears on a bicycle.
Heat Pump Training Wheels
When a heat pump starts up, it has to work quite hard to get the air from outside cooled or heated to the desired indoor temperature. This draws a lot of power, like peddling the low gears on a bicycle, there is initially a lot of resistance to get the bike in motion. Once the room reaches the set temperature, the heat pump begins to draw significantly less power.
A heat pump operates very efficiently when maintaining a temperature, like rotating the higher gears of a bicycle to maintain motion. The low energy cost heat pump uses when maintaining a consistent temperature is how it allows for such amazing cost savings.
Big Problems For Big Heat Pumps
If a heat pump is oversized for its area of operation then there are two main problems that arise;
- The heat pump will bring the room to temperature very quickly, which sounds good up front but the problem is that it will almost always be operating in its high power consumption mode, its “lower gears”.
- An oversizing heat pump may run into serious issues in cold weather and possibly freeze up completely
It is easy to see why too large of a heat pump would be an issue in the first scenario. A machine that is twice as powerful as need be will get the room to temperature quickly but because the heating output of the unit is so high it becomes difficult to maintain that set temperature.
This results in the machine turning off and waiting for the room’s temperature to drop. Once it does the heat pump begins operating in the high energy cost cycle again, never being able to enter the low power maintenance setting.
The issue facing oversized heat pumps in cold weather is directly related to the first. A heat pump that is constantly shutting down and starting up, typically for only a few minutes at a time, will not be able to enter into its defrost cycle. This can require the heat pump to run for at least 10 to 15 minutes, and ensures that any ice that has accumulated on the outdoor unit is melted off.
If the heat pump never gets to run its defrost cycle and the ice is able to build up on the outdoor unit it will restrict the amount of airflow, potentially leading to a burnt out motor if the airflow is completely blocked or a broken fan blade if the ice was to encroach on the internal workings.
What size is right for my home?
This chart can be used as a starting point for sizing a heat pump for a particular area of your home.
It is important to remember that although this is a good reference for heat pump sizes, the only way to get the perfect fit for your home is with a professional in-home assessment. A qualified heat pump contractor can tell you if there are areas of your home that might be losing heat, or areas of high solar gain that will make a difference is sizing whether it be larger or smaller.
9,000 BTU – 250 sq ft – 450 sq ft
12,000 BTU – 400 sq ft – 750 sq ft
15,000 BTU – 700 sq ft – 1000 sq ft
18,000 BTU – 800 sq ft – 1200 sq ft
You won’t find much use for heat pumps larger than 18,000 BTU in a residential setting.
If you would like to find out what size heat pump perfectly fits your home’s needs, book your complimentary in-home assessment online, or give us a call today. When we inspect your home we will:
- Determine the best indoor and outdoor installation locations
- Look for possible areas of heat loss or gain
- Inspect your home electrical for suitable service and panel space
- Answer any questions you might have about heat pumps, rebates, or financing
Don’t wait to start saving with a heat pump that’s a perfect fit for your home. Book your no commitment in-home assessment today.