Monday, June 28, 2010

Programmable Thermostats and Zone Control

Programmable thermostats have taken the HVAC community by a storm with their ability to significantly reduce energy use when the air conditioning blower is not needed. The next big step in thermostat technology is zone control, where you can not only program the system to turn on and off, but you can set what areas turn on and off and what areas need what kind of ventilation. The technology basically breaks up the house into a bunch of independent interconnected units that each receive special attention from the thermostat.

Why this step has not been taken yet by most HVAC companies is a mystery to some professionals. On Denver air conditioning services company employee explained it like this:
"We already turn off our lights when we leave the room and close the vents to unused rooms, so why cant we apply simple cost saving features to AC, which costs many times more than lighting?"

With computer technology, a simple thermostat makes zoning much more advanced than just on/off. HVAC zone technology can make significant changes to areas that were previously hot or cold spots. This allows a much smaller and more efficient exterior unit to evenly heat a building that would have previously cost much more.

The zone control technology is just as easy to install as traditional Denver HVAC systems, but the number of manufacturers is still small. The two most popular brands right now for zone control are Arzel zone control and Bryant Evolution. One way these brands deliver energy saving is through longer cooling and heating cycles. Each time your unit cycles on and off there is a significant energy waste. The compressor fan has to run at an increased speed to make up for the time it was off. Zone thermostat systems try and maintain a lower compressor speed, targeted at the houses needs for a longer time. Reduced cycling is also much better at maintaining consistent interior temperature.

For a new building, installing programmable zone thermostats does not require much different other than using new ducts. For retrofitting old units, your Denver HVAC company will have to install dampers inside the existing ducts. These dampers redirect airflow to parts of the building that are not used. The actual work required to install the dampers is not much harder than a routine duct cleaning.

The effectiveness of a these new technologies can be enhanced with new geothermal heat pump products. The evolution of combined ventilation technology has reduced the overall consumption of HVAC units in the US by more than half in the last 20 years, while improving comfort and air quality.

The Failure of "Building Star"

After the success of the Energy Star system, some political pundits were pushing for the concept to be expanded to other areas of the US market. The Energy Star system awards electrical appliances that use significantly less energy with a government sponsored distinction notifying consumers of its environment and cost-saving abilities. The role of government in stimulating green businesses has been well established, so new legislation offering federal government incentives for well built buildings had a good chance of being a positive influence, although traditionally building codes were regulated on the state and local level.

Unfortunately, the HVAC industry works off lower paid employees, and the most recent legislative push to establish a "Building Star" system included regulations that made it mandatory to pay construction workers according to federal wage requirements. This legislation could not get the approval of the largest air conditioning trade group: the Air Conditioning Contractors of America because of these wage requirements. For example, many Denver air conditioning companies use immigrant or illegal labor. Without the support of these Denver HVAC companies and the ACCA as a whole, the legislation was doomed to fail.

The Building Star Energy Efficiency Act, as it was to be called would not only reward buildings that comply with the act with official designation, but also offer tax rebates as an incentive.

Some of the special features that a building would have to display to receive loans and rebates included: Mechanical Insulation, Advanced Exterior Lighting, and Envelope and Roof Insulation. These options, as well as incentives for new furnaces, variable speed compressors and heat pumps were popular with Denver air conditioner companies because they include technologies that they are already pushing on customers.

The real deal breaker turned out to be the government wage regulations. Although the Davis-Bacon requirements only require contractors to pay the "prevailing wage," contractors argued that the increase in labor costs would hamper job creation and make the certification much less appealing to most HVAC companies.

Heat Pump Repair Mysteries

HVAC technicians must go through a significant amount of training before they are certified by their state board to work on your air conditioner. However sometimes there are customers with problems with their HVAC systems that can only be figured out with step by step deductive reasoning... and sometimes a little luck. Modern AC units are less finicky than the old ones, but they also incorporate new technology that many Denver air conditioning services companies are not familiar with.

Heat pump technology in particular has advanced quite a lot recently. While the actual operation of a heat pump is simpler than an air conditioner, one in particular required a Denver HVAC technician friend of mine a long time unravel. The unit, a R-410A heat pump was installed and operating fine in the first year. Then summer began and the owner switched the unit over to cooling. It worked fine, but after a few days the owner noticed that the fan never turned off.

Now most experienced air conditioner techs would assume this was one of two things - a minor fault in the thermostat, or damaged compressor electronics. However, as the heat increased, the unit never turned off and the house did not cool down. So of course the owner calls her nearest Denver heating company.

This is the point where the tech must take all the evidence into account in order to investigate. Of course most AC techs do not view this job as a murder mystery, but the use of logical steps that need to be taken in order to figure out the problem are similar.

The first thing he notices is that it is hot. The interior is almost 90 degrees and the compressor is obviously not wicking any moisture out of the air. However at the compressor suction inlet, the temperature is 70 degrees, and 60 degrees at the outlet.

Our technician had to review the key facts: The unit worked fine in the summer. The blower fan did not shut off once switched to cooling. In many heat pumps there is a emergency back-up electric heating system. It is possible the heat pump never worked, because of moisture in the cooling lines or for whatever reason. During the winter, the unit may have used back up heating the whole time without the owner's knowledge. At this stage it is all speculation, because the problem could only be that the filter is clogged or that the compressor is dirty.

However it turns out that with 410A coolant systems, using older lines or synthetic oil cooling will clog the system. The technician used a systematic approach using the heat pump manual and his training. In the end our furnace repair hero had to drain the coolant and install new piping in the compressor.

Friday, June 11, 2010

Energy Star Air Conditioning

The Energy Star label is a federal recognition of products that are more efficient in energy use than the average product in that category. Energy star is credited with being a driving force behind significant reductions in home energy use since its inception. HVAC Energy Star equipment has been especially effective because of new technologies and the fact that about half of domestic energy use in the US is used for heating and cooling.

On average, these goverment labled air conditioning products use about 1/5 less energy than other models. Depending on the size of the home, this can result in energy savings into the thousands. These units also contribute to America's goal of reduced emissions. Less energy used reduces pollution and energy demand, and therefore energy prices. Of course you will not see the benefits of an efficient air conditioning system without proper installation with sealed ducts.

Energy star has come under some criticism recently over certifying some products that were blatant energy wasters, however some standards still exist. Portable units are not eligible for Energy Star rating. Portable units are considered temporary cooling and are not yet covered under any federal standard. Denver HVAC companies often push for more efficient units because they cool better and the cheaper bills make for happier customers.

Something that is covered by the Energy Star act because it is much more efficient are integrated air source heat pumps. These heat pumps have two sets of coils, interior and exterior; heat pump works by taking advantage of the difference in temperature between the coils. For example,
air conditioning in Denver is less efficient than a heat pump. Despite popular belief, heat pumps can provide the ventilation aspect of HVAC as well, with dehumidifying and air quality control functions.

In order to take full advantage of energy saving HVAC equipment, you will need to know a few mind-bending acronyms. The first is the HSPF or heating seasonal performance factor. This measures one year's estimated worth of energy output for a unit. This is measured in Btu or British thermal units per amount of energy consumed in watt hours. These tests must meet the Air Conditioning Heating and Refrigeration Institute or AHRI test guidelines. EER, energy efficiency ratio is similar to SEER but on a shorter term. It measures instantaneous cooling ability divided by the energy use in watts.

Tuesday, June 8, 2010

Starting Up Your AC in the Summer

After the long winter, being too zealous about starting up the AC can actually lead to AC problems. Let me let you in on a secret, as a 5-year Denver HVAC mechanic: Refrigerant is not needed unless there is already serious damage to the central heating system. I get called to recharge refrigerators and air conditioning units every spring, but in reality, the refrigerant is in a closed loop and cannot leak unless there is damage to system components. Modern air conditioning appliances should not require maintenance. Regular checking and filling of refrigerant increases the likelihood of refrigerant contamination and therefore further damage down the line.
So one thing the average consumer can do before calling an expensive Denver HVAC service company is to start up the central air unit themselves, checking for any problems. This will outline air conditioner startup and common warning signs that you have a faulty AC part.

First turn off the breakers to both the furnace and central air unit. They should be on separate breakers. For safety, before disassembling or servicing any type of machine that is plugged in, turn the power off.

Remove the cover of the furnace or compressor and vacuum the whole area, making especially sure that there are not foreign parts in the fan blades. Then replace a filter with the same one your Denver HVAC technician. Spin the fan with your hand and listen for any cracks or rumbling which may indicate a failed bearing. If you can correctly identify the problem, it can make it much cheaper for a furnace repair company to fix it. Oil the motor and compressor bearings if they have an oil port.
Bearing problems are cheap and easier to fix than replacing an entire compressor.

With the power still off, clean dust and debris from the outdoor unit's electric wiring. Then spray household cleaner on the coil and rinse it off with a hose. Coils are fragile, but will not work properly if clogged with foreign material.
The compressor in the outside unit is very similar to the furnace blower. Check the outside unit fan the same way, checking for cracks or gaps in the fan and fan housing. Then oil the motor and then you are finished with the outside unit.

Then turn back on the power on a warm day to test the system's pressure. Listen for strange sounds then let the system run for a while.
Then check all the air vents in your home. Air vents should be open to let the system to run ventilation at rated pressure.

Many closed vents may increase pressure in the open ones, but this is bad for the air conditioner. Sometimes cooling problems are a result of the return vent and not the ac vents.
Next is a visual check of the outside unit. The unit should blow warm air and have two lines coming out of it. The small line should be warm or room temperature and the large one should be cool. If you have a outside thermometer you can check the temperature differential between the intake air and the air blown out of the furnace. The temperature difference on a well maintained Denver air conditioning unit should be around 15 degrees Fahrenheit.