Defrost Cycle of a Heat Pump. Please proof this new inspection article.

[Nick Gromicko]

http://www.nachi.org/defrost-cycle-heat-pump.htm

[Joe Farsetta]

To learn how to properly inspect a heat pump system using the best non-invasive, visual-only inspection techniques as required by the Standards of Practice, an inspector should be professionally trained.

While this may be true, officially stating this from an association standpoint has opened the inspector up to a possible lawsuit. The question comes down to what is "professionally trained"

To inspect and identify a particular heating system, describe its heating method, and identify any material defects observed, an inspector should be able to explain and discuss with their client:

• its type or identification
• how to maintain it

In the above quote, please explain what "identification" means?

Also, in the above quote, I disagree with the 2nd identified statement. We, are generalists, not experts. This is beyond our responsibility and we may ultimately provide incorrect information on maintenance.

The inspector must be able to thoroughly examine a heating system, understand how a particular heating system operates, and analyze and draw conclusions as to its apparent condition. An inspector should also be able to justify his/her observations, opinions and recommendations that were written in the inspection report.

I would agree, to a point. The word "thoroughly" is too ambiguous, and runs contrary to the realities of performing a visual, non-invasive inspection. In fact, it helps to incorrectly set the Client's expectations. We consider it to be "thorough", but our perception, the Clients, and the HVAC expert may all have differing views. Also, the notion of justifying one's obeservations must be couched, specifically, within the true and intended scope of the SOP; that is to identify the readily apparent conditions observed of readily accessible components and systems at the time of the inspection using non-invasive and non-destructive inspection techniques. Let's not lose sight of any of this.

[David A. Andersen]

There are three cycles of a heat pump: heating, cooling and defrost cycles.

Emergency or auxiliary heat is also an individual cycle.

There are many reasons why an inspector might find frost and ice stuck on an outdoor coil of a heat pump that is not properly defrosting.

Frost on the outdoor coil is not a defect by itself. Depending on outdoor conditions, Frost is a common occurrence.

If the defrost cycle is not functioning properly, the outdoor coil will appear like a big block of ice,

Ice usually extends beyond the protective grills or outdoor cabinet, not just a frosted/iced coil. This condition should go away within an hour if the system is functioning properly.

If the outdoor coil temperature drops to around 32° F, the thermostat closes the circuit and makes the system respond.

It doesn't matter what the temperature drops down to for the device to activate. Many devices operate at different temperatures and thermostat settings. Most defrost thermostat operating well below the 32° point. In order to absorb heat, the outdoor coil must be substantially colder than the outdoor air (as much as 30°). This means that when its 60° outside, the coil is below freezing (32°F). If 32° were used, the unit would defrost every cycle on a winter day.

The components that make up the defrost cycle system includes a thermostat, timer and a relay.

Some defrost systems also include pressure switches that correlate temperature through pressure.

Also, air pressure switches are frequently used to detect the amount of air blockage from Frost on the coil.

[Joe Farsetta]

I just received an e-mail from Ben G, where he has announced the sale of a new video on this subject. The funny part is that the "introductory" content includes the article as written above, less any changes or advice.

[Nick Gromicko]

Good points, but we won't be adjusting the article based on those points.

[David A. Andersen]

That's fine...

We can refer to the post when half educated HI's' ask at a later date.

Defrost is a very complex operation. I made $thousands/mo in the winter taking care of this single issue...

As a matter of fact, my $400 inspection two days ago had a condenser fan invoice for $480 on the table.

It makes me think about going back into service!
I spent 6 hours, they spent 1...

However, there are few and far between willing to pay that much for an $80 fan motor!