Polar Bear Air Conditioning & Heating Inc. Blog: Archive for April, 2012

Common Air Conditioner Problems in Washington DC

Monday, April 23rd, 2012

Air conditioners are an important part of our lives. They keep us comfortable despite overbearing heat and humidity outside all summer, but because they run constantly for months and because they are such complicated pieces of machinery, they can experience some problems. Here are some of the most common problems you’re likely to run into with your Washington DC air conditioner and how to solve them:

 Leaks

A common problem that many people ignore or are unaware of is refrigerant leakage. It is possible that when the system was installed, it wasn’t properly charged, but most of the time if your system is low on refrigerant, it is because of a leak. You can’t just pour more refrigerant in and call it good, though.

The leak needs to be fixed, both for health and environmental reasons. If you notice that your system is low on refrigerant or you smell something off – often like acetone, call a professional immediately for inspection and repair.

 Sensors

An air conditioner doesn’t do you any good if the sensors don’t work properly. Improperly working sensors will fail to properly read the temperature in the home or from your thermostat. So, it might be 80+ degrees in your home but if the thermostat reads it as 72, the system won’t turn on. The air conditioner itself probably still works fine, but unless it can successfully read the temperature, you won’t get the cooling you need to stay comfortable.

Check first to see if the sensor was moved or knocked toward the evaporator coil (which will keep the temperature reading low).

 Drainage Problems

Your air conditioner acts as a dehumidifier as well, producing a liquid known as condensate. This liquid usually drains from the air conditioner into a designated area away from your home. However, if the condensate drain gets clogged or if the system wasn’t properly installed, that condensate can start to build up in your home. If you notice leakage around the coils, you may need a pump to remove the condensate properly.

Properly maintaining your air conditioner can usually be done with regular maintenance each year, but if one of these problems pops up, call a Washington DC air conditioning professional and get them fixed right away.

For any AC maintenance or repair, give Polar Bear a call today!

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Washington DC Air Conditioning Guide: How to Calculate Duct Size for an AC System

Monday, April 9th, 2012

Duct sizing is a complex process using one of three methodologies. The goal of duct sizing is to provide the perfect space through which heated and cooled air can travel around your home. Ducts should provide ample air flow to keep you comfortable without overworking your Washington HVAC system or costing you an arm and a leg on your energy bill.

Methods Used for Sizing

There are three methods used for most modern duct sizing. The first is the Velocity Method. The velocity method takes into account the speed at which air flows through the ducts based on their general size. A series of equations is used to determine this, including duct cross sectional area, air flow rate and air speed. A much more detailed breakdown is available on the EngineeringToolbox.com for those interested in the math behind the process.

In general though, the velocity method allows contractors to determine the appropriate size and layout of ducts based on their application (residential, commercial, industrial or high speed) and their position (main or branch ducts).

Contractors may also use the Constant Pressure Loss and Static Pressure Recovery methods to design ductwork for your HVAC system. The constant pressure loss method tends to result in more components but provides a more accurate reading of the actual pressure loss in the system based on the materials used and the layout of your ductwork.

Static pressure recovery focuses on ensuring the same pressure level is achieved at all vents and inlets for the system. It is probably the most complicated sizing method, however, so it is rarely used for residential installations.

Simplifying the Process

Were we to break down the process into its core components, this is what a Washington DC air conditioning contractor would do when sizing your duct work:

  • Determine CFM for Each Room – using the Manual J for load calculations, they would determine the CFM. This is based on the (Room Load/House Load) x Equipment CFM. The entire house must be measured and load calculations completed before this can be done.
  • Friction Loss Rate – Friction loss rate is the (Available Static Pressure x100 / Effective Length).
  • Duct Sizing – Finally, the contractor will use a chart or software to select ductwork based on the friction loss and CFM calculated in the first two steps.

The goal of all of this math is to ensure that the system installed is exactly as large as is necessary to distribute heated or cooled air to the entire house. Incorrect measurements result in improper delivery of that air and a system that doesn’t quite get the job done.

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