The HVAC System

Photographs of the HVAC system found during home inspections.

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This
unit is called the compressor, condenser, or outside air conditioning
unit by various people. This is an older unit that still functions
well enough, but there are some issues. First, it needs to sit higher
off of the ground to prevent water damage. If you see the tubes to
the right, you will notice that the insulation is coming off of it.
This is the refrigerant line, and it needs to be covered. Another
problem with this unit is that it has not electrical shut-off. If the
electrical panel was on the same side of the house, the unit would
not need one. It is needed as a safety issue for working on the unit.

space for a return
This is the space left under a closet air conditioning unit (heater and evaporator coils can be placed in a closet, while compressors/condensers are outside). This is meant to serve as the return air duct, so do not store anything in this space.

HVAC in closet
Here is a unit in a closet. It was a tight hallway, and I was trying to find the best angle for the shot.

HVAC burner compartment
Heat from a gas fired unit comes from these burners. The gas is ignited to heat the air down these tubes. Air from the home passes over these tubes to warm up.

plenum
There are two plenums on an air conditioning system. The retrun plenum is just a box on one end. This is the plenum which distributes the conditioned air to the different rooms through the ducts.

safety pan
Underneath your evaporator coil is a pan to catch any water which does not go out of the primary. It is always a concern to see rust, because that means that water was in the pan. You also do not want to see debris in the pan, because this can clog the line. What is that I see? Burn marks on the evaporator coil around the cable entrance. Everything seemed fine now, but the homeowner knew nothing about this. She believed that it had been repaired by a previous owner.

This is where the compressor and condenser are located in the exterior part of the cooling system. You can see the fins which have copper tubes running through them for the refrigerant. This unit has a housing to protect those fins. Rusting is occurring, and leaf debris in the housing helps with damage from moisture.

Here the air conditioning duct is on top of the insulation. This can compress the insulation some (depending upon what the duct is made of factors how much weight will depress down), which can hinder insulation performance. However, the duct can develop kinks with people moving it about, which prohibits air flow. It is also easier to damage a duct when it is not supported.

Damaged fins on an air conditioning compressor can cause the unit to be inefficient.

The safety pan sits under the evaporator coil, which is where the refrigerant cools the air of your home. This process causes condensation. This water should go out the primary drain line. If there is a problem, the condensate water will drop out of the evaporator coil, so the safety pan is there to catch it. When you see rust or stains in the pan, the cooling system has had a problem. As you can see, this pan has rust. The safety pan should have a drain to allow water to flow out. This drain is often placed over a window or pipe to allow you to see the dripping water, hence you know that your cooling system has a problem. This pan does not have that drain pipe. You see a white box on the pan. This is a switch. When the water level is too high in the pan, this switch turns off your cooling system. This kind of switch is often found in town homes or condominiums, where having a secondary drain is not always practical.

There is not always a great deal of room in attics. This makes organizing the ducts harder. One consistent problem in these cramped spaces is crimping the duct, which restricts air flow. You may better understand this scenario by thinking of your garden hose. Bend the hose while water is flowing through the hose, and you begin to limit the water that comes through. The same happens with air ducts. In the photograph, we see a return air duct being crimped on a framing member supporting the roof. This will make the air conditioning system work harder as the equipment has to pull the air through the system.

Do your rooms have two vents for the air conditioning? Sometimes people see these vents, and they do not understand what is happening. One vent is called the register, which is the vent supplying air to your room. The other vent is connected to the other rooms, but not to any equipment conditioning the air. This is called a jump drive. As we make our homes tighter, we also have the tendency to isolate the air in the different rooms when the door is closed. To equalize the air pressure between rooms, we connect them through ducts. Sometimes these ducts are connected to a central vent, which may be placed near the return air vent for the air conditioning system. The photographs show two vents in a room; two large return vents in a hallway; and two boxes, plenums, in the attic. Often the jump drive system will be simpler with a duct attaching two rooms only. Do these vents need a filter? You will find builders placing filters in these ducts more for appearance. The filter in the return air line cleans the air; filters in a jump drive hardly ever need to be replaced. You do not need filters here, but there is an exception: if the vent was designed to hold a filter, it should have a filter- the idea being that the system design intended a filter. Why do you need this system? The main benefit homeowners will notice concerns opening doors. If the pressure is lower in one room, and the door opens into the higher pressure space, you will have to really tug on that door, which can be hard for small children.

I understand that people wish to hide their air conditioning compressors, but this can lead to issues. In the photograph, we do have a fence that hides; and the fence allows air flow, which is good. The problem here is service. To examine the units, I had to hop over the fence, trying to find a place to stand. How is a technician to work on the units when he has no space. Making the area enclosed by the fence larger, giving three feet of space between fence and unit, would allow for access; however, this is a porch with limited space. Having a fence that can be easily disassembled would be the best option here. The fence does not effect function, but the repair costs would be higher.

Floor vents are not the standard in Houston (we have few homes with basements). You do find them in the Medical center area, or any section of town with older homes, but this was in a relative new construction. I do not have a problem with them in general, but I question the placement of this register. This is located in the kitchen area, where you want a conditioned space while prepping the meal, but you also have various pieces of equipment present. The builder placed the vent here as a way to condition the air of both the kitchen and neighboring breakfast area, with other options not being easy due to layout. This vent may need cleaning more often if you use the kitchen frequently.

This photograph was taken while I was standing on the ground, so you are looking at an air conditioning compressor on a platform about six and a half feet above the ground. The location is not an issue, but workspace is a problem. Simple repairs can take longer since a technician will have to be on a ladder. Longer repair time means higher repair cost. The other problem here is the items being stored up against the unit and vine growth impede the free flow of air around the unit while also causing damage.