We were called out to a house in Katy Texas, because a gas furnace was not operating right. We check out the furnace and it was kicking out on the high limit safety. We quickly diagnosed it as an air flow issue. We checked the air filters to make sure they were clean. Then we checked the static pressure and it was (1.10). The flex duct came from the return into the back end of the furnace. We recommended to the customer to add a plenum on the back end of the furnace giving us the space we needed to add a new return and tie in the existing return. We messured the static pressure and it was (.10). We checked the operation of the gas furnace and now it was not kicking out on high limit safety. More information on air flow can be found on my Air Flow Blog article.

Here is why: Most home inspection services only look at the HVAC system. They will write down the model numbers and serial numbers and run the system. They will check the return temperature while it's running and the supply air temperature and tell you what the difference is in the temperature. They will only notice obvious signs. An a/c contractor should take a static pressure reading, this will tell them about the duct work ie: too small of a return air and supply air duct issues.

In the Katy, Cinco Ranch, and Cypress areas of Texas we are finding gas furnaces installed vertically in attics. This type of installation should be avoided and here is why: Gas furnaces nowadays are more compact than ever. The airflow goes in the furnace through the side when installed vertically and in the bottom when installed horizontally. This is the best way to install it, and here is why: When you install a furnace vertically because of its size you are limited to the opening. The manufacturer's installation instrutions show that they want you to use a square opening not less than the recommended size. If you use sheet metal duct work with a liner you will loose a total of three inches on the four sides of the inside of the duct. Sheet metal wrapped with insulation on the outside does not reduce the inside dimensions.

When making repairs on A/C equipment here is why you should use OEM (Original Equipment Manufacturing) parts. Evaporator motors now days are using X13 and ECM (Electronically Commutated Motors). These motors are engineered and are factory preset for specific air volume. The manufactures have designed them for use in their equipment (gas furnaces and air handlers). This is why you need to replace that motor with the part that the manufacturer has designed for that equipment. Two stage gas furnaces use a variable speed draft blower motor which operates low and high, which draw combustion gases through the heat exchanger to maximize heating efficiency.

There are two types of heat pumps, air to air and geothermal. Air to air is the most used; its source of cooling and heating is the outside air. It uses a reversing valve and two expansion devices. The reversing valve changes the refrigerant flow. The therory on this principal is that heat transfer will move from higher temperatures to lower temperatures allowing the heat transfer coil to be kept at a lower temperature. The surrounding air will pick up heat making the evaporator coil and the condenser coil the heat transfer devices. The problem with air to air heat pumps is deminished capacity. When the temperature outside drops so does the output. These heat pumps are best suited for southern climates. The problem that we have found is the sizing of the auxillary heat (heat strips). The heat strips should be sized for the heat load for heating. For example: if the loss is 60,000btu, and 1kw is equal to 3,413btus,then the heat strip should be 20kw, equal to 68,260btus of heating. A 15kw heater is equal to 51,195btus of heating, some customers would be happy with that. So the ideal heater would be 68,260btus of heating. When using air to air heat pumps the heat strip sizing is everything.

In the 1990's ASHRAE wrote an article called The Peridox of High Efficiency. This article talked about laden sensible heat. As the seer rating increases the BTU output drops dramatically. (One ton of air conditioning is equal to 12,000 BTUs). Equipment manufacturers in their quest to keep up with government mandates started manufacturing condensers with decreased compressor BTU output.

The EPA(Environmental Protection Agency)can force up to 20% of coal fired power plants to shut down. The regulation will cost utility companies $129 Billion Dollars. With the closures of these plants there are only two possible outcomes when supply exceeds demand; energy bills will be rising, rolling blackouts will happen. This will bring on incentives for higher air conditioning equipment efficiencies. This has already happened with the three region zoning I talked about in my recent blog (All A/C and Gas Furnaces are not equal).

Nowadays when you are looking for a building or office to lease it is so important to have your air conditioning company
to look at the a/c unit. So much of what I have seen is questionable:
ie: needs to be replaced or has not been properly maintained, leaving you to repair or
replace it at your own expense. and as for the leasing agent's a/c company, you know who they are working for. If you have any questions feel
free to call me. Hope this helps!