I have a 10,000 square foot building that has four new 5 ton Ruud units outside. All four units are icing up around the compressor. All units have been cleaned, freon checked, blower motor checked, grills checked, air filters replaced, thermostats replaced and copper lines coming out of compressor replaced with bigger lines. Nothing has worked. Three different repairmen have looked at these units and agree that its an air flow problem. These units freeze up during the day and night, but mostly at night. What could possibly be causing this? Any suggestions will be greatly appreciated. Thanks.

Addition to question -When units are first turned on and not frozen it seems that air is not coming out of vents into building fast enough. Inside units were checked as well. Servicemen say that duct work looks okay.
One did mention something like a tornado effect may be happening.

Have the A-Coils been checked?

XenoSapien

Have the A-Coils been checked?

XenoSapien

I will check on that. Thanks for the reply. It is very humid where I live. Would that have anything to do with it?

Melissa

New 5 ton Ruud units outside

New units should be under warranty by the installer. Have them do the work or your warranty might go out the window.

Air recirculation. Sucking supply air right back into the return air. This will make them freeze up pronto.

Improper location of thermostat.

Dirty air filters.

Someone played with the refrigerant charge and now the units freeze up.

Many open large buildings we did over the years were helped quite a bit by using industrial ceiling fans to force more air circulation.

You mention mostly at night, this could mean you may be operating the thermostats too low, they should never be set below 70 degrees unless they were designed for this as in a computer room. If your service person checks the temperature across the evaporator coil he will be able to determine if it has proper air flow (should be about 20 degrees differential) If it is higher , say around 24 that shows not enough air flow, duct sizing is one thing that needs to be checked to provide proper air flow. Are the fan coils on a timer to shut them off at night? Not shutting off condensing units? Also, you might want to check your programing on the thermostat to insure it is not dropping the cool setting at night instead of raising it. (assuming you have a programable)

DEpending upon the outdoor temperature you might have to install low ambiant kits for the condenser fan motors.

Try fan handler LOOK under products list on left.

FanHandler.com (http://www.fanhandler.com/Main%20Frame%20Pages/Testimonials/index.htm?Testimonials.htm~main)

The owner will only sell to a listed HVAC company. No do it yourselfers allowed. They work great been using them for years.