Air Conditioning, Solar Hot Water, Tankless Hot Water: EMMCo

Air Conditioning Tucson | Tankless water heater

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Managing Tucson Arizona's Energy for 30+ years!


Air Conditioning Installation
Air Conditioning Repair
Tankless Water Heat
Humidifiers & Central Air Purifier
Hydronics Space Heat
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Residential and Commercial.
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ROC# 319137

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Frequently Asked Questions for
HVAC and Water Heaters

We understand your desire to resolve a problem without the need for a service call. You may call us to ask a question. We will make every effort to resolve the problem over the phone or to at least get you through to a normal work day when overtime rates will not apply. Note below a list of the most common problems with information and resolutions. Please take a few minutes and check through these before calling.

Thermostat issues:

Programmable thermostats are a very common cause of HVAC faults. It is very important that the batteries are fresh. The time of day and the day of week need to be correct and the “events” must be in chronological order. Most residential thermostats have four events per day; typically morn, day, eve & night. For example, you can not have a day event that occurs at a time that is ahead of the morn event.

Pay very close attention to the AM/PM of any given event. If resolving thermostat problems becomes overwhelming, look for a HOLD button and press it. If the word HOLD is in the display this should suspend the program of the thermostat and render it a non programmable thermostat. Once the word HOLD is displayed, use the up/down buttons to adjust the temperature. In some thermostats this may require holding down the up/down arrow button long enough for the display to flash. Only then will you be in the change mode. Subsequent “punching” the arrow button will increment set point changes.

Double check to make sure the mode switch is in the proper position (heat-off-cool).

Filter changing issues:

It is very common for filters to be located at the bottom of the furnace. Consequently, it is necessary to remove the bottom furnace door to access and change the filter. When replacing the furnace door it is extremely important to position it properly. There is a “door switch” which will not allow furnace operation if the door is not positioned properly.

A dirty filter in the cooling mode may cause the cooling coil to go below freezing. Ice will form over the coil ultimately leading to no air flow and cooling breakdown. If you suspect this has happened because you have discovered a dirty filter, take the following action:

  • Turn off the AC system
  • Complete the filter change
  • Leave the mode switch in the off position
  • Put the fan switch in the “on” position and leave it there for two hours. Note that during this period water may appear around or near the furnace while the ice is melting. Note also that on some older Carrier family furnaces this water may make its way to the “logic board” and cause damage to this component.

Once ice has formed, simply changing the filter will not resolve the problem. You must go through the procedure above to regain AC function. After two hours the coil should be free of ice and air flow should be normal. You may now return to the “auto” fan mode and “cool” mode.

Poor filter maintenance, poor filter fit, poor filter quality and old age are all factors that contribute to chronic coil icing. This would be due to the fact that your cooling coil has functioned as a filter and is now so dirty as to restrict the air flow. Resolution of this problem usually requires coil removal and cleaning by professionals.

A dirty filter in the heating mode it will cause a furnace to overheat and cycle off on a high temperature limit, possible severe damage to the furnace heat exchanger may occur. A heat pump operating in the heat mode with a dirty filter causes high stress on the compressor. Not all systems have a high pressure safety so this is a condition to be avoided. Compressor failure is an expensive repair.

Power outage issues:

Momentary power outage or “brown out” conditions can and do cause air conditioner failures.

When an AC unit compressor is operating it is under “load” maintaining substantial pressure differences between the inlet and the outlet. If there is a momentary power outage or brown out condition, the compressor will stop. When power is restored (sometimes in less than one second) the compressor is trying to restart under that “load” unsuccessfully. Most residential air conditioners must stay off for at least three minutes before attempting to restart. This much time is usually sufficient for the pressures to “equalize”.

  • Check for a tripped circuit breaker – manual reset required (be sure to PUSH the switch to the FULL OFF position before turning ON).
  • Blown fuse in the unit disconnect – Remove the pull out disconnect and check/replace the fuse as required.
  • Thermal protector has locked out the compressor until the motor cools off – this can sometimes take several hours.

In the meantime your package unit may be “dead” and your split system outdoor unit may be off or your compressor may not run while everything else does.

Tankless - Insufficient hot water

Most tankless water heaters have a minimum flow rate. If the cold water is quite warm the ratio of hot to cold for showering can result in hot water flow that is below the minimum. If this occurs the tankless unit will stop heating.

The resolution to this problem is usually to increase the shower flow by changing or modifying the showerhead. Generally, it is very rare. Another cause of insufficient hot water can be caused by a “cold water sandwich”. There is a series of events that must take place each time the tankless provides hot water:

  • Detect flow
  • Ignite a pilot flame
  • Recognize the pilot flame
  • Turn on the main burner(s)
  • Modulate to the setpoint temperature

This series of events takes from 5 to 7 seconds. If for example, a man is shaving and uses short bursts (less than 5 seconds) of hot water to rinse his razor, hot water will not be consistent.

Preventive Maintenance:

Other than filter maintenance, virtually all newer residential air conditioning systems are now manufactured with little or no maintenance required. The days of belt drive blowers and bearings with oil cups are gone. We prefer to categorize our maintenance stops as “peace of mind” service.

We respectfully suggest that having your unit checked for proper function on a regular basis will provide the most trouble free and efficient operation.

Our routine is to put you in our system on a calendar basis and call to schedule timely service that you are comfortable with. Whatever schedule you find desirable, we would like to suggest that attention to the operating character and sounds of your system is important. If you SUSPECT that something is not right, have it checked out.