Ask Vince – air conditioning problems

1. Design, installation, capacity


QUESTION: My house is 3,000 square feet. All but a guest room and bathroom are on the main floor. When we set the air conditioning at 78 degrees on a hot day, it does not cool the house and will only cool to 82 degrees downstairs and will be 90-plus degrees upstairs. We have a dual-control Lennox SEER-rated 12.45 air conditioner but only one compressor. Would a second compressor help pull the hot air out? If that is not feasible, what would you suggest to at least cool the upstairs (other than a window unit)?
C. Ogden, via email

ANSWER: Vince McDonald of McDonald Plumbing, Heating and Air Conditioning in Sacramento believes that your system failure is due to one or more of the following:
The system needs repair;
The system was not properly designed;
The system was not properly installed; and/or
The system’s capacity is too small.

“My first suggestion is to have an air-conditioning contractor check to make sure the system is operating according to the manufacturer specifications,” he says. “A good contractor will run a series of tests, including one to monitor the system’s refrigerant charge. If the charge is too high or too low, it can have a large impact on its cooling capacity and efficiency.”

“The contractor should also make sure the filter and indoor components are clean, he adds. “This has to be the No.1 problem we find that affects the overall system performance. Also, homeowners should regularly change or clean their filters. Something as simple and easy to rectify as a clogged filter can cause your problem.”

“The contractor should also inspect your air duct system to make sure the ducts are free of leaks, are properly supported and that any exposed metal is insulated.” If you are still having problems after the checkup or they discover the system is clean, airtight and operating properly, McDonald suggests having the contractor inspect the system for proper design, installation and sizing.”

“Two-story homes are always a concern when designing and installing a HVAC system simply because hot air rises,” he says. “it sounds like you may have a zone system, with on thermostat upstairs and one down, to direct cooled air where needed according to the individual thermostats. Zone systems should definitely help even out temperatures, so have the contractor make sure your system was properly designed and installed.”

“Finally, the problem may be an issue of capacity, meaning there may be nothing wrong with your current equipment. The largest single residential air conditioning system is 5 tons. If you already have a 5-ton system, and you have taken steps to make your home more energy efficient (by adding more insulation, etc.), you will need to add another air conditioning system.”

“One option would be to take the upstairs ductwork off the current system and add another system that will serve the upstairs only,” McDonald says. “You mentioned that the upstairs consists of a guest bedroom and bathroom. If you use this area only occasionally when guests come over, this option would allow you to direct the full capacity of the existing system to service the downstairs only, and save energy by not cooling the upstairs when it is not being used.” he says.

Common Air Conditioner Problems

The following are some of the common problems found with air conditioning units that could affect the cooling of your Sacramento home or office. You can read the entire article at


If your air conditioner is low on refrigerant, either it was undercharged at installation or it leaks. If it leaks, simply adding refrigerant is not a solution. A trained technician should fix any leak, test the repair, and then charge the system with the correct amount of refrigerant. Remember that the performance and efficiency of your air conditioner is greatest when the refrigerant charge exactly matches the manufacturer’s specification, and is neither undercharged nor overcharged. Refrigerant leaks can also be harmful to the environment.


If you allow filters and air conditioning coils to become dirty, the air conditioner will not work properly, and the compressor or fans are likely to fail prematurely.


The compressor and fan controls can wear out, especially when the air conditioner turns on and off frequently, as is common when a system is oversized. Because corrosion of wire and terminals is also a problem in many systems, electrical connections and contacts should be checked during a professional service call.


Room air conditioners feature a thermostat sensor, located behind the control panel, which measures the temperature of air coming into the evaporative coil. If the sensor is knocked out of position, the air conditioner could cycle constantly or behave erratically. The sensor should be near the coil but not touching it; adjust its position by carefully bending the wire that holds it in place.


When it’s humid outside, check the condensate drain to make sure it isn’t clogged and is draining properly. Room air conditioners may not drain properly if not mounted level.

How to Check Your Air Conditioner Before Calling for Service in Sacramento.

The following are some great tips from WikiHow on how to check for problems with your air conditioner before calling a Sacramento HVAC contractor.

  1. Assess the problem. Is the unit simply not working at all, is it not cooling the air much, or is it simply blowing around warm air?
  2. It’s not working at all: the condenser (for an outdoor unit) or air handler/furnace (indoor unit) are not running.
  3. Make sure it’s plugged in. This may seem obvious, but there are occasions when this is exactly the problem. Whether kids, dogs, or an accidental tap with the vacuum cleaner, the plug could be partially or completely dislodged.
  4. Check the circuit breakers and fuses. Make sure they are in place, turned on, and functioning properly. Circuits, especially with older homes, are easily overloaded if the air conditioner shares a circuit with appliances such as irons, refrigerators, or microwaves.
  5. Check your thermostat (cooling control) and make sure it is set to cool at the current temperature, and working properly. As with plugs, sometimes settings can change by accident.
  6. Check your fan blower belt for excessive slack, damage, or breakage. This can cause low air flow which allows ice to form, and thus causes low cooling performance.
  7. Repair or replace the blower belt. Allow the ice to melt before restarting the AC unit.
  8. Check the coils and filter. If they are caked with dust and debris, clean them thoroughly. Make sure you let any ice melt before restarting your unit.
  9. Call for service. If you’ve verified that everything is connected, powered, set up properly, and clean, it may be time to call the service department.

Troubleshooting Central Air Conditioners in Sacramento

If you are having trouble with your air conditioning unit in your Sacramento home, you might want to check the following troubleshooting chart. See all the details at



Possible cause


doesn’t run
1. No power. 1. Check for blown fuses or tripped
circuit breakers at main entrance
panel or at separate entrance
panel; restore circuit.
2. Thermostat set
too high.
2. Lower thermostat setting 5°.
3. Motor faulty. 3. Call a professional.
4. Compressor
4. Call a professional.
Uneven cooling 1. Distribution
system out of
1. Balance system.
1. Thermostat set
too high.
1. Lower thermostat setting 5°.
2. Evaporator dirty. 2. Clean evaporator
3. Unit too small. 3. Replace with larger unit;
call a professional.
Unit doesn’t 1. Thermostat set 1. Lower thermostat setting 5°.
cool too high.
2. Condenser dirty. 2. Clean condenser coil and fins;
if necessary, straighten fins.
3. Condenser unit 3. Remove debris blocking condenser;
blocked. cut down weeds, grass, and vines.
4. Evaporator dirty. 4. Clean evaporator.
5. Compressor faulty. 5. Call a professional.
6. Not enough
refrigerant in system.
6. Call a professional.
Condenser unit
turns on and
off repeatedly
1. Condenser dirty.
2. Condenser unit
1. Clean condenser coil and fins.
2. Remove debris blocking condenser;
cut down weeds, grass, and vines.
3. Evaporator dirty. 3. Clean evaporator.


Contact McDonald Plumbing, Heating and Air Conditioning in Sacramento to Fix Your Air Conditioning and Home Cooling Problems.

Since 1957 McDonald Plumbing, Heating Air Conditioning has been providing noisy, gurgling pipe repairs to Sacramento residents and businesses. We also serve Sacramento and the surrounding communities with a full line of plumbing, heating and air conditioning repairs such as tankless and regular water heater installation and repair, air conditioning installation and repair, home energy audits, home comfort systems, sewer and drain cleaning, sewer and water line repair and repair of slab leaks.

Sacramento, CA

Sacramento is the capital city of the U.S. state of California and the seat of government of Sacramento County. It is at the confluence of the Sacramento River and the American River in the northern portion of California’s expansive Central Valley. With an estimated 2011 population of 477,892, it is the sixth-largest city in California and the 35th largest city in the United States. Sacramento is the core cultural and economic center of the Sacramento metropolitan area which includes seven counties with an estimated 2009 population of 2,527,123. Its metropolitan area is the fourth largest in California after the Greater Los Angeles Area, San Francisco Bay Area, and the San Diego metropolitan area, as well as the 27th largest in the United States. In 2002, the Civil Rights Project at Harvard University conducted for TIME magazine named Sacramento “America’s Most Diverse City.



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