Image of evaporator coil with ice formed on the bottom thrid

Evaporator Freezing

Frozen evaporators are a common problem with air conditioning systems. A typical evaporator coil will run at 40°F/4°C, if the coil temperature drops to 32°F/0°C, the coil will start to freeze. This reduces the efficiency of the system and can damage the equipment.  The evaporator can freeze and then thaw, when the compressor cycles off, so there may be no indication of a problem until the day you really need it.

When the load increases on an air conditioning system on hot summer days, it is not uncommon for the compressors to run continuously. If the coil is below freezing and with no off cycle,  the ice will build up on the coil as shown here.

On split AC systems, you may not be able to see the evaporator coil but you can see the copper piping.  If ice is forming on the suction line, it means the coil is likely to freeze. If the line is insulated, then pull back a little bit of the insulation to expose the pipe and see if frost forms.

Image of a frozen suction line and compressor on a Carrier roof top unit.
Frozen suction line on a Carrier roof top unit

The most common cause of a coil freezing is low air flow. As the ice covers the coil, the air flow is restricted and accelerates the freezing process. Other common causes are refrigerant leaks, low ambient temperature, undersized liquid lines and dirty filters.




Image of a clip on anti-ice control
Clip on Anti Ice Control

Anti-ice controls are common on large air conditioning system and can be installed on any air conditioning system to shut off the compressor when ice is detected. This is a safety device to protect the equipment under extreme conditions when something has gone wrong.  There are contractors that will use the anti-ice control to mask a problem with an installation and can go undetected for years. When the coil is freezing the unit will use a lot more energy, drip water outside of the drain pan and shorten the life of the equipment. If the AC coil is freezing up, there is a problem that needs to be corrected.

Cheakamus Crossing Fall Maintenance

Many residents in the Cheakamus Crossing, ask about the maintenance required for their heat pumps. These heat pumps, do not have items that require annual service, there are no filters to change, motors to oil or belts to replace. Having the units inspected every year is not necessary but couldn’t hurt, if inspected by a qualified refrigeration technician. Anyone else, and it just may hurt, the heat pump and the wallet. A qualified technician can identify hidden issues such as overheating, control problems, circulation problems and other issues, preventing future issues.

Buffer Tank – Heat Pump – Hot Water Tank

In the past, there have been number of problems which had nothing to do with maintenance. Most of which were manufacturer issues with the equipment, installation issues that have been corrected or operator issues.

The only, “maintenance type” item that has been an issue, is the cleaning of the load heat exchangers, the frequency of which is undetermined.

These units have run since the fall of 2008 and, several of these units have been tripping on high pressure. The load heat exchangers, that transfers heat from the refrigerant, to the heating water, have built up scale on the interior surfaces which cause the unit run higher pressures. These units trip on high pressure at 610 PSI. Pressures this high can do serious damage and is not something that can be resolved by a DIYer or unqualified service tech safely. If you see a red screen that reads E2 High pressure fault, call a qualified technician for service. Resetting the control, will restart the unit for a while but it will run hotter than normal. Resting the control multiple times can lead to compressor damage.

Scale from Cheakamus Crossing heat pumps

There are no access valves on the heat exchanger which makes cleaning difficult and there is a limited number of choices for cleaning and treatment. The heat pump is used for potable water which places several restrictions on what treatment that can be used. If a potable water system, is even at risk of being contaminated, it is considered a serious issue and very expensive to resolve.

There are two other heat exchangers, one for the potable hot water and one the source water. It may be necessary to clean these heat exchangers as well in the future. Several source heat exchangers required cleaning, in the first two years of operation, due to DESS water quality issues, which has since been resolved.

The two storage tanks have aluminum anodes which will need to be replaced in a few years, even sooner if you live in the upper rise. This image was taken last year and shows some corrosion but will be several years before it needs to be replaced.

Image of anode in a hot water tank
Buffer tank anode