In the Scranton Pa area we have many newer homes equipped with heat pumps for both heat and air conditioning. When we lived in the south these hard working units were the HVAC of choice. While they are not as prevelant in northern PA we nevertheless see many of them in newer homes.
If you own a home which has a heat pump you should have an understanding of how they work. An ice or frost build up can be very damaging to your system.
Jay Markanich has authored a wonderful article explaining how these units work, and what you should watch out for in the winter season which I'm pleased to share with you.
It's been cold here lately and when it gets real cold are you seeing this from your heat pump?
Does it look like an ice cube?
A heat pump is essentially an air conditioner that can work backwards!
In winter months many heat pumps will have to put themselves through what is called a "defrost cycle."
During the heating season, a heat pump will compress heat from outside and transfer it indoors.
When the air outside is very cold, it will freeze on the heat exchanger when the fan is blowing air over it. The purpose of the defrost cycle is that when the unit recognizes that the ice is forming the unit will work to eliminate it.
When ice builds up on the outdoor unit, air cannot flow through it. This can reduce efficiency dramatically and can even damage the unit. The defrost cycle should eliminate icing before it has a chance to build up.
How often the unit goes through the defrost cycle depends on many things - outdoor temperature and humidity, the condition of the system and the amount of indoor heat it is expected to provide.
UNITS HAVE TO BE SIZED PROPERLY FOR THE VOLUME OF AIR THEY ARE TO TREAT. IT SHOULD BE JUST RIGHT - NOT TOO LARGE AND NOT TOO SMALL. SOME HOUSES NEED MORE THAN ONE SYSTEM.
There are sensors on the outdoor compressor unit that tell it when it's temperature has risen enough to turn off the defrost cycle. This can take a while, even 30 minutes or so. Also, if the cycle is not stopped by these sensors defrosting will continue for about 10 minutes.
If your heat pump is not providing adequate heat it can be because:
- it was not installed correctly,
- or is undersized for the load it is expected to carry,
- or maybe the filter needs to be changed
- or the unit is surrounded by bushes or plants and not getting adequate air flow.
If ice build up is sudden you may be in need of a service call, or other maintenance.
During periods of frequent use, do you know how often once a month you should replace your furnace filter?
Yes! About once a month!
My recommendation: regular maintenance may reduce the frequency and longevity of the defrost cycle. Reducing the load the unit is expected to handle, like not raising indoor thermostat temps really high, or adding extra insulation into the attic space, will go a long way toward saving money and increasing the life span of the system. Good windows and doors, and good window shades and curtains, will also help reduce the heating requirement the system is expected to handle. Bottom line: maintain your system and use it properly.
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560