Air Conditioning, Furnace vs. A/C
 

Q: I'm having trouble with my air-conditioning system. We installed a patio and had the air conditioner moved. It was off for about two weeks. After it was hooked up again, I bought and installed a new 90-plus furnace. The installer put the old air conditioner on the new furnace. Ever since, we have had problems with ice on the units. The furnace people say it's the air conditioner's problem and the air-conditioning guy said it's the furnace's fault. Help!--G.H.

A: Your problem could be as simple as a dirty coil or a blocked filter, but a qualified technician would have caught that right away. It would appear, therefore, that you have some poorly managed or underskilled mechanics working on your equipment.

When the outside unit (the condenser) was moved, moisture may have entered the refrigerant lines. These are the two lines that transport the coolant between the outside coil and the inside evaporator coil. The refrigerant inside the lines has to be free of moisture, which may have seeped in when the unit was moved or when the furnace installer moved the inside coil.

If so, adding dryer to the lines and replacing the refrigerant should help. Also, have the furnace's fan speed checked. If there is not enough air movement across the inside coil, the refrigerant may not evaporate properly, and ice can form on the inside coil and refrigerant lines.

Then ask the installer if the inside coil is sized for the outside system. For example, an air conditioner rated at 2 tons of cooling should have a 2-ton interior coil on the furnace. The technician should check the head pressure at the compressor and the amount of coolant in the system.

What you really need is to have a third, independent HVAC contractor check the system and tell you which installer messed up. It could be a combination of errors, but they should put your safety and comfort first and stop pointing the finger of fault.