David Richardson/NCI
Interior Hvac Diagram
David Richardson/NCI
If you know what to look for, a visual inspection provides clues to unsafe operation. It's never good for one package unit to exhaust into the economizer of an adjacent unit.
National Comfort Institute
Before you jump on the heat pump bashing bandwagon, look at your duct installation practices first.

Head Pressure Problems? Check for Layered Coils

April 1, 2004
by Dave Galbreath Do you service some air conditioning units, either package or larger split systems, on which you cant get the head pressure down? ve

by Dave Galbreath

Do you service some air conditioning units, either package or larger split systems, on which you can’t get the head pressure down?

You’ve tried power washing the coil, cleaning the coil with chemicals, and you’ve even pulled the refrigerant charge because you suspect contamination with non-condensibles. Nothing works.

Chances are you’re dealing with a multi-layered condenser coil. Many manufacturers, including Trane, Carrier, Lennox, and York have been installing multi-layered condenser coils in various models for years.

The only way to tell if a unit has a multi-layered coil is to pull the top off and check. If the coil is flat, ( no curves) odds are it’s all one piece. If the coil is shaped like an “L” or a “U”, chances are there’s more then one layer.

The problem with multi-layered coils is that seeds dropped from trees, and other small contaminants floating in the air, get trapped in-between the two layers. Because the fins of the layers don’t line up, you can’t easily push this layer of junk out. Sure, you get enough of it out to keep the unit running, but not enough to get the head pressure down to normal.

The solution is to separate one end of the layered coils enough that you can get between them and wash out the layer of trapped dirt. You can spray it out with water, or blow it out with CO2. I prefer water. It takes longer, but I think it does a much better job of cleaning.

It’s also important to know what type of coils you’re dealing with when quoting a planned maintenance. There’s more time involved in cleaning a layered coil, and some of the larger units require two people to remove the tops.

On your next spring tune-up, take a look at the coils of that “problem unit.” You might be surprised at what you find. n

Dave Galbreath is the service manager at Seaman’s Heating/Air Conditioning/Refrigeration in Grand Rapids, MI. He can be reached at 616/458-1544.