Re: That reminds me...
When we arrived, the AC was iced up, literally, there was a block of ice hanging out the ventilation flap!
Common problem, and often caused by incorrect specification/selection of the cooling system - put another way, the air is too dry so it's iced up. I've had this conversation a few times, because it sounds crazy - how can the air being too dry cause ice formation ?
With a system designed for comfort cooling in a typical office environment, there will be a fair bit of water vapour in the air. As the air is cooled, the water will condense, and this takes a lot of energy extraction to do. As a result, for a given rate of heat extraction, the evaporator will run warmer than if it wasn't having to extract all that latent heat of evaporation from the water. If everything is within specs, then the evaporator will stay above freezing point (of water), and so the water will dribble out and go down the drain.
But put very dry air through that same system, and for the same (or less) energy extraction, the evaporator will now run a lot colder - and as a result, what water vapour does get condensed will freeze. As bits of ice will prevent airflow over/through localised bits of the evaporator, then those will get colder still as will the adjacent areas - thus the ice will get colder and harder. Left unchecked, this will continue until airflow is blocked completely by the ice, and the ice will be set "like concrete" in a now exceedingly cold evaporator. The best way to deal with this is by turning off the compressor but keeping the fan running - if that's possible. This will (unless things really are completely blocked) pull above-freezing air over the heat exchanger, warming it up and melting the ice. Better systems will detect such conditions and automatically defrost the heat exchanger - whether that's in the inside unit in cooling mode, or the outdoor unit in heating mode, many don't (I've seen a building with a whole wall full of "blocks of ice" !)
Biting the hand that feeds IT
