Q: My outside heat pump froze up so solid the outdoor fan was hitting the ice. What could have happened?
A: With the season in mind, let me start out with a little song that may help explain the
situation (it helps to sing it like you mean it)!
Frosty the Heat Pump was a very lonely soul,
As he sits outside in the ice and snow
Working at 20 below.
Frosty the Heat Pump takes heat out of the air,
Then puts it inside where its warm and dry
Keeping you cozy without compare.
There must have been some magic in the heat transfer that day,
He worked so hard that he turned to ice
And began to rattle around.
Frosty the Heat Pump had a defrost system that’s lame,
Once the air stops moving, the process stopped grooving
Snowball is his new name.
When Frosty’s covered the savings get smothered as heat transfer just stops,
All we do is wear him out until his compressor just goes “pop”.
Frosty the heat pump needs a regular clean and check,
With a little love and a good refrigerant charge
You can keep him from being a wreck.
Alright already, that was the worst rhyming since… the beginning of rhyming! The point is
your heat pump needs regular maintenance which is made more important by the harsh
weather we encounter. All air-source heat pumps go through defrost (much like your
refrigerators) to rid the evaporator coil of air restrictive ice. Air movement is heat transfer and
slowing or stopping that is both inefficient and harmful to your system.
Once the ice ball is noticed, it is usually a big deal to clear it off. We go on many calls where
the outdoor coil has been in the process of making glacier ice for days without stopping. We
will spend hours with hot water clearing both inside and outside the unit. It must be completely
clear before any accurate diagnostics can be made. You can clean this ice off yourself but the
power should be off and only water used (hot or warm is fine). Please do not take ANY sharp
object to the unit (ice picks come to mind) due to the construction if copper and aluminum.
One puncture will cost hundreds of dollars and sometimes is not repairable. Leaving the unit off
in above freezing weather works but usually is a long process.
Once Frosty is thawed checking refrigerant charge is the key. This may need to be done by
“weighing out” which is removing the refrigerant and actually checking its weight as it
compares to the outdoor unit nametag. If that is just dandy the defrost control board and its
sensors can be verified. This rather simple board samples outside air, coil surface temperatures,
and includes a run time calculation. Defrost initiation is not efficient because the unit is actually
running in the A/C mode in the middle of the winter. So running as long as possible without a
defrost is more efficient, but oftentimes can result in ice issues. This is adjustable but needs to
be done with consideration to efficiency and reliability. Happy holidays from Frosty and the rest
For questions on your heat pump system give us a call at AirWorks (406) 257-1341.