Chapter 14 – Inspecting HVAC Systems

We will continue our inspection with the HVAC system.

As you recall HVAC is an acronym for Heating, Ventilation and Air Conditioning.  The heating and/or air conditioning system of the home is a vital component.  One of the qualifications for listing a room as a bedroom is the presence of a permanent heat source.

As with the water heater, there are very few things a homeowner can personally do to service or repair a heating system.  These systems are often more complicated than water heaters and there are many factors to consider.

Remember these comments from an earlier discussion?

“The furnace did not appear to provide adequate air flow to the upper floor.”

and

“The furnace did not appear to provide adequate air flow to the upper floor and may be undersized for the square footage of this building.”

The factors to determine what size HVAC system is adequate for a given home are calculated from a series of formulas that can contain as many as 9 pages of instructions.  It is not our intention to provide that training nor is it necessary.

In the spirit of this project we will provide general information on what is checked by the home inspector.  The advantage to you is that you will have time to shop for the most reasonable repairs if needed.  Thus you avoid getting slammed by expensive repairs or replacements because you are faced with a rapidly approaching close.  You get to choose your destiny.

Heating systems come in different types, designs, shapes and sizes.  Like the water heater, the system may be located in a multitude of places including closets, attics, garages, crawl spaces, any room or hallway, on the roof or sitting next to the building on a platform.  There are many different heating systems.  Some homes may have multiple types of systems or multiple units.

Let’s talk about types and designs I am familiar with.  There are wood stoves, propane stoves, natural gas stoves, kerosene stoves, electric stoves, oil stoves, radiant heating systems, radiators and heat pumps. There are freestanding, built-in, wall mounted, floor mounted, ceiling mounted, central forced air systems and package units.  There are manually operated, clock operated or thermostatically operated systems.  There are single systems, single systems with zone controls and multiple systems.  There are geothermal systems that use the natural temperature of the earth or a pond for improving efficiency.  There are solar assist units.

There are probably other types and designs I have never seen.

The conditioned air is delivered from the heating and cooling system to the living space through the ducting material.  We will be discussing ducting material in the chapters covering the attic and the crawl space.  We briefly touched on ducting materials in the chapter on garages during the discussion about firewall penetrations.

Isn’t that great?  You know what a firewall is!

By the way, we call a home inspection a “visual” inspection.  Perhaps a more accurate term is an “observable inspection” where observations include utilizing all the human senses.

Let’s talk about a very common system first – the gas fired forced air heater and A/C.

Central or forced air systems have several items to look for and several components to inspect.  Many of these components cross over to other systems.  Homeowners are expected to monitor the cold air return filter.

Check your filter and clean or replace it if needed.  A dirty air filter will restrict the performance of your heater and A/C and generate an automatic note on the inspection report.  I see this over and over again.

Most heating systems have some type of thermostat.  Check your heating system to see if all the controls work properly?

Many home inspectors use an infrared thermostat gun to check for sufficient operation of the furnace and A/C.  The temperature reading taken with this tool at the cold air return is compared to the temperature at the output registers.  We look for a 17 to 20 degree spread between the intake and registers that indicates the A./C system is working.  The video shows an example of this tool in action.

Do you have any rooms that always seem to be too cold or too hot?  With just the blower fan running, are there any registers that do not produce an adequate airflow?  There may be a loose, disconnected or restricted duct pipe.

Let’s look at your system provided it is not a roof mounted package unit.

SPECIAL HAZARD

Don’t go on the roof.  It is just too dangerous.  Like I mentioned before, there are things you won’t be able to do.  Getting on the roof is one of them.

Components of the furnace include the housing, gas supply lines, vent piping, mounting hardware, duct piping and perhaps a drip pan.

You had a lesson on drip legs in the water heater chapter.  Drip legs are usually only installed on appliances that are considered “unattended” such as the water heater and furnace.  The manufacturer’s installation instructions determine if a drip leg is required.  All gas fired furnaces should have a “properly installed” drip leg on the gas supply line and a gas shut off valve that is readily visible.  A qualified tradesman should immediately investigate any smell of gas.  The local gas provider can inspect for leaks.

Is there carbon soot anywhere around the exhaust pipe or on the furnace housing?

Is there evidence of corrosion from condensation or leaks around any of the pipes or flue?

Is there dirt or debris touching the appliance?  If so clear it away.  Gas fired units in the garage should be on an elevated pad.  If the unit is in the crawl space, make sure it is out of the soil.

With the blower fan running, do you hear any air noises or whistling around the furnace housing or ducting?  Sometimes you can see spider webs or fiberglass batting blowing in the breeze from a leaking furnace housing or loose duct pipe.

Are there any water stains around the unit indicating a possible leaking condensate line?

Is there any scorching on the wood components surrounding the unit or the flue pipe?  Installation instructions always provide minimum clearances around the furnace units and the vent pipes even when they are lying horizontally.

Did the installer use vinyl duct tape that is now coming loose?  Metal foil tape is the preferred adhesive product.

Does the vent pipe slope upwards at least ¼ inch per foot to the exterior of the building?  It should not come into close contact with any wood components and NOT terminate under a roof eave.

On newer construction in areas where the gas supply is propane, the appliances may be delivered and pre-set to run on natural gas.  The molecules of these two gasses are different and require different size orifice jets.  When a propane appliance is equipped with a natural gas jet you will see a wandering orange flame instead of a crisp blue flame.  The installer forgot to change the jets.  You might remember the photo of the orange flame at a cooktop burner in the photo gallery for the kitchen appliances.

For some furnaces an orange flame is normal.  I know.  It’s complicated.  Don’t worry about it.  Just do the best you can.

A home inspector will observe the operation of the burners during the inspection by removing the service panel when possible.  There are other items we look for inside the cabinet like loose wires, loose condensate lines, rust or corrosion and so forth.  I advise you not to remove the service panel, particularly while the unit is running.

You may be able to see the burners in operation through the louvered vents in the cabinet but any further investigation should be done by a qualified tradesperson.

I recommend having the furnace inspected by a qualified tradesperson if your heating system is over 12 years old, even if it is operating normally.

Repeated cycling through the hot and cold transitions puts a strain on the internal heat exchanger and can cause cracking at seams, spot welds and joints.  Only rely on a qualified tradesperson with the proper tools and training to inspect older units.  Your life could depend on it.

Except for the fact that they do not have ducting, floor and wall gas heaters are inspected in the same way as a gas fired forced air furnace.

Older wall and floor furnaces often have a single wall vent pipe.  This single wall system is not very efficient and has a tendency to collect hazardous flue gasses until heated up.  Carefully inspect the flue pipe for any holes or loose seams.

Hydronic radiant heating systems consist of pipes imbedded in the floor, in the ceiling or at baseboard heaters in each room.  Hot water flows through the pipes and the heat “radiates” into the room.

Electric radiant heating uses wires or electric pads in the floor or ceiling to produce the same effect.  Radiant systems are considered more efficient at distributing an even room temperature without the noise and dust of a forced air system.  However, the time it takes to bring a cold room to a desired temperature is considerably longer.

The boilers used for hydronic heating are essentially water heaters without a tank.  In fact, the radiant heat boiler usually works to heat the water supply for the home.  This is a rare installation in the West where I am from, as are coal and heating oil furnaces.  Inspect the hydronic boiler with the same method you inspected your water heater.

If your potential buyer is unfamiliar with the benefits of a radiant heating system, you get to be a hero and teach them all the wonderful reasons why you loved the radiant heat concept.

I have also come across kerosene and diesel heaters.  They are very efficient and work well.  Ventilation is the main concern for these devices.  The ones I observed were the direct vent type.

The air conditioning unit you see outside the building is one half of the A/C system.  That exterior unit is called the condenser.  The evaporator or “A” coil is concealed at the furnace housing.

When in operation the exterior condenser should be level and not make any unusual noises.

Leaves and debris inside and around the unit will reduce its efficiency and should be removed.

The electrical connection should be secure and in good condition.  The electrical disconnect for the A/C condenser should be within sight of the unit.  This is so a repair technician can warn away anyone who might turn it on while he is servicing the unit.

The home inspector will take temperature readings at the cold air intake and at each of the room registers.  He is looking for a difference of 17 degrees or more between the air intake and the output registers during the A/C cycle.

Electric forced air furnaces are relatively straightforward.  Either they do or do not produce adequate heat.  The condition of the ducting is important and secured electrical wiring is essential.

An electric heat pump works differently than an electric furnace or gas  fired furnace.  It is basically two air conditioning units that switch directions depending on what air temperature is desired.

If you have ever stood near an A/C condenser when it was running you probably noticed that the air blown out by the fan is very hot.  That is basically lost energy.  A heat pump utilizes that heated air to warm the interior of the building by reversing the operation of the units.  There is a great explanation of this appliance at: http://home.howstuffworks.com/question49.htm

Geothermal heating and cooling technology uses the concept of a heat pump but, instead of a condenser unit at the exterior of the building with a fan, this system uses the consistent temperatures of the earth to extract the captured heat for cooling and the warmer than air earth temperatures for heating.  The consistent temperatures of the earth provide a more even thermal variation, which requires less energy to achieve the desired temperature.

Freestanding wood burning stoves, freestanding gas stoves and gas log fireplaces.

One of the primary issues with freestanding wood burning stoves is the clearance to flammable materials.  Wood stoves and fireplaces can be very dangerous and if not installed properly, can cause fire and possible death from carbon monoxide poisoning.  When installed properly, they can provide an efficient and relatively inexpensive source for heat.

Each stove manufacturer has specific installation requirements and specifications that establish the proper clearances for stoves.  Installation requirements are different for stoves that have been “listed” versus “unlisted.”  A listed stove is one that has been examined by a recognized independent laboratory.  If your stove is older than 20 years, it is a safe bet that it is either not listed or the listing has expired.

The installation requirements can vary from one manufacturer to the next.  The basic consensus is that there are sufficient barriers or distances between building materials and the stove.  The heat generated by the stove will dry out such materials and lower the temperature at which they could ignite.  As you may recall, this is known as the flash point. The barriers might be part of the stove design or construction requirements for the area around the unit.

One measurement to check is the distance from the door opening of the stove to flammable materials (measured horizontally). This distance should be at least 18”.  The reason for this distance is so embers that fall off the door land on a non-flammable material.  A fire retardant pad or floor covering material should be installed to cover any location that could ignite and start a fire.  Hot embers that land on nylon carpeting will melt the carpet and release toxic vapors.

Single wall flue pipes should also be at least 18” away from combustible material.  This distance changes when a double or triple wall flue pipe is present.  Again, it depends on the manufacturers specifications.

All stoves should have floor protection directly underneath.  This is called the “hearth.”  The distance the stove sits above the floor and the types of materials allowed for the flooring are varied depending on the manufacturer.  Some stoves are only allowed to be installed over concrete.

If you notice a dark residue or soot on the ceiling above the stove, there is likely a leak in the stove or flue pipe.  This is a HAZARD.

The flue pipe should be secure and properly installed.  Flue pipes are assembled from sections of metal tubing that slip into the end of the preceding pipe in continuous sections until the ceiling is reached.

Many times I notice that the single wall flue pipes are installed upside down.  This happens when the lower section of pipe is slipped inside of the pipe above.  Some people think this is correct so that the smoke doesn’t leak out into the room.  Actually, the lower pipe should be sleeved OVER the pipe above to contain any condensation or moisture generated inside the pipe.  The graphics to the right illustrate the point. A natural condition called “drafting” will keep smoke out of the room if the wood stove is properly installed.  Let me explain.

A fireplace chimney or fluepipe works when hot air rises creating a negative pressure in the flue.  Moving air has a lower pressure than air that is not moving. The heated air moving quickly inside the flue pipe has lower pressure than the standing air in the room.  That is why air flows from the room into the fireplace and out the chimney.

Propane gas stoves and gas log fireplaces are available in many sizes and configurations.  There are way too many to cover here.  Suffice it to say you will be time and energy ahead if you simply hire a qualified tradesman to inspect and clean this equipment.

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HVAC SYSTEMS: REMEDIES AND SOLUTIONS

As with the water heater, the action you can personally take regarding your HVAC system will probably be based around general maintenance.

Energy conservation has become a big deal for our society.  The new California Title 24 Energy Efficiency Standards and Regulations for new construction indicate how serious the government is regarding energy efficiency and conservation.  That is tough on the builders but good for you.  It is driving technology and service providers to also get serious.

You might look into the possibility that your local gas and electric utility company provides a free or low cost energy audit.  They will come out and look at your heating and air conditioning system, weather-stripping, doors, windows and insulation and make recommendations on how to improve the energy efficiency of your home.  Ask them to also do a carbon monoxide test.

If your utility company will not do it for free, ask them how much it will cost to inspect your furnace.  The cost of having a qualified HVAC technician look at your furnace is inexpensive.  Call around and get some bids.  One of them should do the job for $85 – $100.

There are different levels of chimney and fireplace inspections from a simple peak up the flue to a full-blown inspection with a robotic spider equipped with a digital camera.  I ALWAYS recommended a chimney inspector when I come across a wood stove, fireplace or a gas log furnace.

PHOTO GALLERY

An additional 42 images with descriptive captions are available in the 27 Dollar Home Inspections eBook.

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Chapter 15 – Inspecting Service Utility Equipment & Exterior Electrical