Frozen Coil

[Garet]

When I unlocked today's vacant property, the thermostat had set to 52 deg in the air conditioning mode. No telling how long it had been running that way.

Normal installations in my area don't allow direct access to the evaporator coil, so I don't usually see the coil when I suspect icing. This roof-top unit has a handy access panel (what a concept!). The coil was encrusted in a solid 1" of ice. It had ice on the outside of the casing and coolant lines near the compressor as well. I couldn't see the compressor itself.

I'll be calling for a full evaluation by a contractor, but it gets me to wondering: Is the icing itself likely to cause problems, or just reflective of a mis-adjusted system?

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[John Dirks Jr]

When I unlocked today's vacant property, the thermostat had set to 52 deg in the air conditioning mode. No telling how long it had been running that way.

Normal installations in my area don't allow direct access to the evaporator coil, so I don't usually see the coil when I suspect icing. This roof-top unit has a handy access panel (what a concept!). The coil was encrusted in a solid 1" of ice. It had ice on the outside of the casing and coolant lines near the compressor as well. I couldn't see the compressor itself.

I'll be calling for a full evaluation by a contractor, but it gets me to wondering: Is the icing itself likely to cause problems, or just reflective of a mis-adjusted system?

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Download Attachment: IMGP9847 (Small).JPG

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Low airflow or low refrigerant usually causes it but I too would like to hear what damage can be caused by icing.

[Scottpat]

Looks like a new package unit. I have seen new units ice when the installer does not properly charge the unit when it is installed.

[Marc]

I'll be calling for a full evaluation by a contractor, but it gets me to wondering: Is the icing itself likely to cause problems, or just reflective of a mis-adjusted system?

Icing may allow liquid refrigerant to reach the compressor suction. That would quickly ruin the valves on a piston unit but a scroll unit is more tolerant. It can do only harm. When it melts, a slab of ice that big drips outside the bounds of the pan and may wet insulation as well as damage some interior ceiling finishes. It should never ice up. Like John said, it could be a low refrigerant charge which implies a leak unless it wasn't charge properly, like Scott opined. Low air flow would do it and that could result from an undersized air return duct - most common cause in my area, dirty coil, dirty air filter, problem with blower or the circuitry controlling it or any problem causing incorrect blower function such as thermostat, wiring, etc. Lotsa possibilities.

This is how I'd write it up: 'The cooling coil on the air conditioner is iced up. Because it's an air conditioner and not an ice maker it shouldn't ever do that. You should have it serviced immediately before damage results to the compressor and the unit fails. Once it fails the ice starts melting and that could damage insulation within the appliance as well as the interior finishes.'

You can leave out the part about the icemaker.[]

Marc

[Erby]

Nah, you gotta leave the icemaker part in there. Helps understanding!

[Garet]

Liquid slugging into the compressor is what I was looking for.

Thanks.

[Charlie R]

My interior coil iced up this past summer, it turned out the furnace fan motor was going bad and turning too slow so I had reduced air flow over the coil. New fan motor made the problem go away.