My outside unit is on the north side of my house and under an area that water drains to. I have put up gutters and placed a small roof above the unit, but still the coils freeze up during winter. I'm looking for more ideas to help with this freezing problem, and ways to defrost it quicker, like rock salt, defrosters, etc. Would these methods damage the coil?
How to prevent the outside heat pump coils from icing over
freezingheat-pumpoutdoor
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The problem here of course is that snow/freezing rain gets into the lock and freezes. With a house, this isn't normally a problem for a few reasons. First, you use it often enough that it doesn't get that bad, and second the inside of the house is warm, which prevents water from freezing inside the lock (unless it gets really, really cold I suppose).
You might want to look for a lock that has a metal shield over the area where you insert the key to prevent water from getting inside. Similar to what you have on a car door lock (and for the same reason). Personally, I've never seen any home locks like that, but that's not to say they don't exist.
A simpler option, and the one I would suggest, would be to put a plastic baggie over the doorknob and secure it with a rubberband. Then just take the baggie off when you need to unlock it and put it back on after you are done. It's a bit inconvenient, but if you hardly ever use the shed in the winter anyways, it should keep the water out and is probably the most practical option.
first, if you have an air conditioner in your attic, then there should be TWO drip pans, and TWO drain lines.
- one of the drip pans should be built in to the air handler/coil unit
- the second drip pan should be at least as big as the entire air handler and coil unit, and positioned under the air handler to provide coverage for the entire unit
- both pans should have INDEPENDENT drain lines
- ideally, the second drip pan should have a float sensor unit it to shut off the system BEFORE it overflows.
either drain should be able to completely empty whatever amount of water you have in the pan within seconds. if it can't, then you have a clog somewhere.
also, the large drip pan below the air handler should typically be completely dry. it's there as a backup in case the drain line for the air handler clogs up. if you have any amount of water in there, then you have a problem somewhere else.
so, than being said, do the following:
- verify that both the air handler and the external drip pan have independent drains
- get a wet/dry shop vac and suck out both drain lines
- pour bleach down both drain lines
- if you don't have a way to pour bleach down the drain connected to the air handler, make one. a simple way is to cut the existing line at a vertical run, splice in a T, then make an L shaped piece out of some tubing and an elbow. leave the top part unglued so you can remove it. see drawing.
- test your newly cleaned drain lines. remember, both drain lines should be able to quickly remove any water you pour in them. if they drain slower than your bathroom sink, you have a clog somewhere.
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Best Answer
Heat pump?
Keep salt away from the unit. Salt will attack and totally decompose the fins and will create electrolytic corrosion in the joints between aluminum and copper leading to destruction of the system.
Icing during operation in a damp climate is normal, it's supposed to have a defrost cycle it runs through to remove the ice.
Heat Pump Operation: Heat pumps work on the standard phase change refrigeration cycle. In summer time for AC mode, the inside unit acts as the refrigerant evaporator and the external unit as the condenser. This is reversed in the cool season for heating, the external unit basically cools the outdoors in order to extract heat from the air and gives it up by condensing the refrigerant in the inside unit.
Heat Pump Defrost cycle: Since you're cooling already cool air that contains some water vapor, it's natural for frost to build up. In extremely damp climates, the fins can actually clog. To take care of this ice buildup, the heat pump system uses its shuttle valve to momentarily go into AC mode, shuts off the air circulation fan and extracts some heat from the house to be given up when the refrigerant condenses in the external units coils.
Operational failures that cause extreme icing: Older systems run this defrost cycle off a timer, newer ones have temperature sensors to determine frosting and the heating necessary to clear the coils. Failures in these can stop the defrost cycle from being run.
You can also have the shuttle valve relay fail or the shuttle valve freeze into the heat position which prevents the cycle reversal needed to do the defrost.
For Heat Pump systems that run as flooded evaporator type systems, low freon levels will cause extreme icing of the evaporator. This can cause the internal unit to become a solid block of ice during the AC season and for the external unit to do the same during heating season.
DIY Remedies: You've taken care of one major problem, keeping water from entering due to roof drain-off.
The unit must also be in a location that allows for water to drain away. Ponding allows for excessive water vapor in the atmosphere and is to be avoided. A drainage system that removes this would be a good idea.
So if you've taken care of drainage, it's probably time to have your local HVAC tech come out and give it a through inspection to figure out what's failed.