Faux Pas By Hvac Contractors

Improper installation and servicing of HVACs can bring down its efficiency from 100% to a zilch. There are some faux pas that HVAC makers make. Let’s take a look at them-

Back drafting not checked

CO (carbon monoxide) poisoning is a very common complaint among owners of HVAC units. Often contractors are called to check for CO leakages from the gas furnaces. When they get such a call, their usual process is to look for cracks in the heat exchanger of the furnace. If that is fine they confirm that there is no CO leakage as such. They assume that homeowners were given a false alarm by the leakage detector. Therefore they change the batteries of the alarm and wrap up their servicing.

But checking the heat exchanger is not enough. Any contractor before confirming that the house is safe from CO leakage should check if there is any back drafting in the unit. This can only be done by testing for flue gas. When the exhaust from the furnace is vented out through the flue, the heat of the flue gases creates a negative pressure, or suction, inside the chimney. This pulls the flue gas from the chimney. This suction is called draft pressure.

Ideally the draft pressure in the vent and chimney has to be more negative than the air pressure in the combustion appliance zone (CAZ). The CAZ is the area where the appliance is located. If the pressure in the CAZ is higher than what it is in the flue, then the combustion by-products will come back down the chimney, into the CAZ, and then into the building. This is called back drafting. Back drafting is one of the root causes of CO poising.

Undersized ducts

This is a very common problem that is found in houses equipped with a HVAC. This can be compared to situation where a person is made to breathe through a straw. This happens because the ducts have a smaller cross-section than required. They are made without doing enough calculation about their probable sizes. If the supply ducts that deliver air to the rooms are too small, the airflow will get less. The HVAC unit has to work harder and longer to heat or cool your house. This will lead to skyrocketing power bills. If the return duct is too small it will be unable to take in enough air from the rooms for cooling or heating it. According to Mike Mac Farland of Energy Docs, an HVAC contractor in California, a contractor before going for a system change-out, should check if there is a need for duct change-out as well.

Ignoring the loopholes in insulation

When HVAC contractors go to homes to install a new HVAC or address a problem that the unit is making, they often visit the areas of the house through which the ducts of the unit pass. They go into attics, crawl spaces, and basements. Most homes have enclosure problem. In other words the insulation level of the house is very poor. Although the problem comes to their notice, they ignore notifying the homeowner about this. It is true that it is not a HVAC contractor's job to work on insulation and air-sealing of the house but they can at least advise the homeowner about them. It is really ironical that although most HVAC companiesemphasize on ‘comfort’ factor, they do little to address all the issues that affect comfort.

Inadequate ventilation in HVAC

There are some homes whose insulation are in bad shape with leaks and holes here and there from where the conditioned air leaks out. These are generally older homes. The newer homes are tighter. Tight homes need mechanical ventilation. All homes need spot ventilation in kitchens and bathrooms. There are some measures that should be undertaken by HVAC contractors to ensure a proper level of ventilation. However this aspect is often ignored. Inadequate ventilation can lead to the build-up of contaminants which are difficult to identify and test.

Ignoring manual J calculation

Most homes apply the rule of thumb when deciding the size of HVAC unit. They assume that as they had installed a unit of a particular size for a house which was very similar to the one they working on at present, they can install a similarly sized unit. They bank on their experience. But this does not work always. Heating and cooling systems aren't the same as they were 50 years ago.Moreover, two houses may look same apparently but there could be many subtle differences. Every contractor before deciding on the size of the unit should calculate the rate of heat loss and heat gain by the house. This is done through manual J calculation.

Low bidding

Most homeowners opt for low bidding when choosing a HVAC contractor. But they do not realize that there is a catch here. A contractor who would bid low will have to economise on servicing costs. They will as a result hire poorly trained techs. They would give equipment that won't last. They will try to cut short on the installation process as they have to save on manpower and man- hours.

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