Air source heat pump - winter icing
 

My Mom has an ASHP at her house in NC and recently complained that she has to turn it off when it rains during heating season because of icing. Is this normal?

We once thought about an awning of some sort, both to keep the rain off in the winter and for shade in the summer (it's on the west side of the house, so gets a lot of sun in the afternoon). But then rain on the coils is good as long as it doesn't freeze, right?

Any help, please?

Ice
 

I got some frost on my Sanyo ASHP last winter. Snow gets sucked into the coil.

http://i46.photobucket.com/albums/f1...r/NCL/A017.jpg

It has a defrost mode. It flips into cooling mode, but does not turn on the indoor fan.
It just pumps a little of indoor heat out to the coil to melt any ice.

In order to keep rain from being pulled in, I sealed our little snow roof
to the side of my house. It keeps most of the dripping water from getting on the coil.

http://i46.photobucket.com/albums/f1.../anti-rain.jpg

I'm hoping the lattice will act as a snow drift barrier and keep snow from building up behind the unit.


As your Mom to check the manual (or you can check it on-line) and find
out about the defrost mode of her ASHP. Maybe she just needs to wait
a half hour for it to warm up and melt..

It might be a good idea to turn off and ASHP when it's raining on cold days,
and turn it back on when the rain stops.
When it's snowing real hard and it's blowing around, sometimes, I'll turn ours off for a while.
No sense asking for icing.. ;)

She says that her unit goes into defrost mode (she can tell by the sound), but that doesn't always help. I found a few write-ups on the Net and it seems that defrost mode won't help in the "perfect storm", and central NC seems to get more than its share of freezing rain each year.

That's what she does when there is freezing rain in the forecast.

Thanks, Xringer! I'm glad this isn't a problem only with unit.

I love your snow roof! Her unit has the fan blowing straight up, so the roof would have to be much higher, so less effective. Also, it would reduce the amount of light going into the already darkish office room, so she's not willing to go that way.

I've seen some of those old style systems with the "fan blowing straight up"
and it sure makes me wonder what they were thinking.
When it's off during a snow storm.?.
Or just leafs coming down, filling up the tub.

http://www.electrical-forensics.com/...dAcUnit-SM.jpg
http://www.electrical-forensics.com/...pressor-SM.jpg
Is there a family of squirrels living in there? :rolleyes:
http://www.electrical-forensics.com/...pressor-SM.jpg

Pics from:
Recipocating (Piston) Compressor


Anyways, some of those units have heating elements to defrost the coils.
And some of them may be optional, so maybe her systems can be upgraded?
There might even be a generic add-on defrost kit that will fit her system..

Cheers,
Rich

Those are designed primarily as AC units. Cooler air is sucked in from the sides and hotter air is blown upward, where it continues to rise. Nice and efficient. Then to (conveniently) make a heat pump out of it, they just put a reversing valve in the freon part of the system. The cold air is then sucked in at the sides and even colder air is blown out at the top, where it drops down to be recycled (but mixes with other, warmer air). Not so efficient. But in areas like the South where the main requirement is AC, they work nicely. Every system I see down here is that design.

Mine is like that. I had to take the top grill guard off of it last week to bang the ice off of the fan blades because it was amazingly out of balance. The issue is I can't really put a roof over it because it needs to vent out the top... I'm not sure if there is a good solution.

Geo-thermal Heat Pumps, Ground-source Heat Pumps

"Do not let the outdoor unit sit underneath a leaking gutter.
In the winter months, water will drip on the top of the unit and freeze solid.
This will restrict the air flow and cause the whole unit to freeze-up. "


I had rain water dripping down the east wall of my house. It would work it's way
down and splash around the air intake.
I've sealed off that water entry point and hope to see less icing now.

You can build a roof over it - use about a 30 degree slope - but the roof needs to be at least 3 feet above the outlet of the AC to allow for the air flow.

Trane has an interesting top on the some of their units that changes the airflow direction to sideways. This would help prevent fan icing.

http://www.acostahvaccharlotte.com/i...e_ac_units.jpg

It looks like their larger units have it. But, the shape of the top covers
seem like they would allow a lot of run-off rain water to get inside the unit.
(Unless they have a little water channel ruining around the inside perimeter).

test, test, test.