Inspecting Commercial HVAC Systems Course Student Forum

This thread is exclusively for students currently enrolled in InterNACHI’s free, online Inspecting Commercial HVAC Systems Course.

Students may ask questions, write essays, and chat with other students on this online student forum.

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I’m diving into it right now. Thanks Ben.

Dan McCarthy and Dave Gaston are great instructors. Thanks InterNACHI “You guys and gals Rock the inspection industry”.

Great course. The simple explanations of equipment makes it very easy to follow along and get a basic understanding.

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Thanks for the class! Getting started now…


Finished - thank you very much for providing this. I have a question though - one slide in the A/C (last part) showed a coil in the shape of a triangle (A-coil), I thought that was an evaporator coil. It was labeled a condenser. Was this a mistake, or should I stick with condenser on commercial systems?

I was looking to see if there any commercial inspection courses and I saw this?
I will get started!

Just starting this course, it should be good.

From the article:

A building’s central air-conditioning system must be periodically inspected and maintained in order to function properly. While an annual inspection performed by a trained professional is recommended, homeowners can do a lot of the work themselves by following the tips offered in this guide.


Condensate drain lines collect condensed water and drain it away from the unit. They are located on the side of the inside fan unit. Sometimes there are two drain lines—a primary drain line that’s built into the unit, and a secondary drain line that can drain if the first line becomes blocked. Homeowners can inspect the drain line by using the following tips, which take very little time and require no specialized tools:

•Inspect the drain line for obstructions, such as algae and debris. If the line becomes blocked, water will back up into the drain pan and overflow, potentially causing a safety hazard or water damage to your home.
•Make sure the hoses are secured and fit properly.

Humidifiers are devices that humidify air so that building occupants are comfortable. Central humidifiers are hard-wired into a house’s plumbing and forced-air heating systems.



Inspection and Writing Assignment

  1. Furnace Type Observations:
    This furnace was propane gas-fired, high-efficiency, downflow forced-air unit.

  2. Furnace Location Observations:
    This furnace was located in the laundry/utility room. Furnace filter is dirty and should be replaced. It is important to follow manufacturers recommendation to have a yearly service for cleaning and any needed adjustments.

Reading and Writing Assignment

Inspecting Furnaces

Article describes how to inspect, identify and describe a furnace using fuel type, airflow distribution, effiency and ignition type. Covers every system type from gravity flow to high efficiency downflow units.

Identifying and Describing Heating Systems

Article describes how to identify and describe heating system. Describe the various heat-conveying medium, fuel systems. Nature of the heat, efficiency and capacity of the system.

This commercial boiler exhaust hood handles two boilers that are linked together. There are two zones, and thus two separate thermostats, but the boilers work in tandem. The wall through which the exhaust runs is approximately 15 inches thick (12 inches of poured concrete with a full brick veneer.

Radiant Heating Systems was a good summary of in-floor heat. It gives a brief history of similar systems, an explanation of the differences between electrical and hydronic systems, and closes with advantages and disadvantages of these systems. Inspection experience has found hydronic systems primarily on farm sites in workshops, while electrical systems have been found primarily in bathrooms or entryways.

Geothermal Heating and Cooling Systems gives the reader a good overview of these relatively rare heating systems. It reminds us of the expense involved in the installation. Personal experience has found this integrated with a radiant heating system in a 7,000+ square foot shop. Extremely inexpensive to run.

Looks like another great class. Eager to get started.

This is an image of a condenser that appears to have been damaged by a gutter downspout and / or lawn equipment. This was a residential application and the unit pad was also too low to the ground. Residential condensing units should have three inches of clearance above grade and commercial units should normally have four inches of clearance to prevent this type of damage. This defect was written up in the report and recommended to have repaired by a HVAC company.

I read the article on inspecting furnaces. Furnaces come in several different types with different types of fuel, such as gas, oil, coal. wood or wood pellets, and also electricity. Heating furnaces are rated as to their efficiency with many of the older low efficiency and gravity furnaces being upgraded to mid and high efficiency units. Forced air furnaces are central air type units, but do not need to be centrally located in the structure. Furnaces are sized according to the BTU rating of the unit. BTU is the amount of energy needed to raise the temperature of one pound of water one degree. Commercial heating units are normally larger than residential units, but work on the same principals. Commercial HVAC inspections will usually use a third party HVAC company to perform that portion of the inspection and then furnishing a report to the commercial property inspector.

Factory built fireplaces was the article I chose for one of my HVAC articles. The first types o f fireplaces were invented in the eighteenth century by Count Rumford and he based his theory on thermodynamics, basically a way to introduce the outside air with fire and create heat without smoke. Seventy five percent of all new furnaces are factory built. They are much more efficient, and are studied and put through much testing by The Underwriter Laboratories. Factory Built Fireplaces are just another example of HVAC.

Firestops is my second article choice and an interesting one at that. A Firestop is a passive, fire-protection method designed to diminish the opportunity for fire to spread through unprotected openings in a rated firewall. The three most common type of firestops are firestop mortar, intumescent firestop, and firestop pillows. This application is applied whenever wires or plumbing pipes go through a fire-proof wall. Inspectors need to watch for missing firestops where there has been a repair made.

This picture was taken of some pour duct work in a house that was one hundred years old. The problem is when you add, cut out, or replace duct work and it is not attached one hundred percent by the contractor it starts a series of problems. The first problem is with proper air flow amd moisture intrusion. This problem was evident here with the black mold that had accumulated.Duct work needs to be attached all the way around by rivets and I highly recommend taping the seams as well. It may take a while to cause problems but if your duct work is not sealed properly it will.

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This photo was taken in a small commercial office setting, where a natural gas fired, 40 US gallon (tank type) water heater was in use. The image shows a missing extension tube at the unit’s TPR valve. The following comment was included in the written report:
A Temperature Pressure Relief Valve (TPR Valve) was present on this water heater. This safety valve releases water (and thus relieves pressure) if either the temp or pressure in the tank gets too high. A TPR valve extension pipe or “tube” should also be in place. This tube ensures that any discharged scalding water exits near the floor level for safety - typically terminating approximately 6" from the surface of the floor. The extension tube was missing in this installation. This is a potential safety concern as scalding water can discharge improperly. I recommended further review, for correction as needed, by a licensed plumbing contractor.