Another Quality AC System Installation by ACME Air Conditioning

This customer called in with the complaint that her upstairs unit was not cooling and she saw ice on the outdoor unit.  We went out and found that the system was low on Freon.

Customers ask all the time how an A/C system can have ice on it when the temperatures outside are over 100 degrees.  The answer to this is:  there is a pressure/temperature relationship to the refrigerant.  If you know the pressure, you know the temperature and vise versa.  The pressure will decrease when the refrigerant levels drop.  Therefore, if the pressure decreases, the temperature decreases.  If the refrigerant level drops low enough the temperature will drop below freezing causing the evaporator coil to start to ice up.  90% of the time the system will continue to run (customers don’t know to shut it off) and the ice builds and builds.  The evaporator coil will be a solid block of ice and then the ice will follow the low side Freon line all  the way outside to the outdoor unit and to the compressor.

A technician knows two things if he sees ice on the outdoor unit:

  1. The unit has been running for a long time and
  2. The evaporator coil is a SOLID block of ice. The most common complaint of customers when the unit is not cooling and the evaporator is a solid block of ice is they tell us there is no air coming out of the vents.  And that is because the air can’t move across the coil because of the ice.

There are five things that cause an evaporator coil to ice up, low Freon levels are the most common, but not always the problem.  And it can be a combination of a couple of things.  The five things that cause a system to freeze up are:

  1. Low Freon levels.
  2. Dirty evaporator coil.
  3. Dirty air filter.
  4. Stuck contactor on outdoor unit.
  5. Blower motor not operational.

We returned to her house the following day with the equipment and all the materials and began the install.  We always start the install by laying down drop cloths all along the entire path of where we will be walking with the old equipment to keep the area tidy.

Acme AC Service - Garland, Plano, Richardson

Then we start in the attic by removing the old evaporator coil.

In this case, it’s an AllStyle brand coil, which is called a Plenum coil.  A plenum is an insulated box that attaches to the end of the evaporator that the ducts connect to.

In the case of the AllStyle Plenum coil it’s sort of an all-in-one.

It’s a plenum and a coil.

We take it loose from the furnace and detach the duct work and take it out of the attic.

The new evaporator coil we will be installing is a quality Trane boxed “A” evaporator coil.

It’s got all-aluminum coils for better heat exchange and it’s non-corrosive.

We attach the new Trane coil to the existing furnace, make sure it’s level and get it strapped up.

Next we have to prepare the new insulated Supply Air Plenum Box by cutting the holes for the duct work and installing the start collars for the duct work to attach to the plenum box.


Then we attach the supply plenum box to the evaporator coil.


We attach the duct runs to the start collars on the supply plenum and add duct mastik to the joints to ensure there is no air loss, install a new auxiliary drain pan and pipe it in and it’s done.

During this install we also addressed a duct work situation in the upstairs area where her children’s rooms weren’t getting enough air flow due to a common problem of the duct work being “tapped out” and expected to feed too many rooms on one run and with too small of a duct.

We ran two new dedicated lines to the children’s bedrooms.  The customer told us that they had lived in the house since her daughter was in 2nd grade.  She’s a senior this year and the duct work has always been an issue (too cold in the winter and too hot in the summer in her bedroom) and the daughter told her mother that now that she’s a senior and moving out this year they FINALLY get her room fixed.

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