Cold Climate Heat Pumps

[oil pan 4]

Correct but not sure of the word "rapidly" I was surprised to see the slow ramp up meaning if you look at my post after running for 5 minutes the intake measures 62 and out 70 and pretty much for the first close to hour air didnt seem that warm.
Exactly one hour later intake air temp was 68 and output 92 so knew we were on the right track at that point. Also the intake is 11 feet off the ground in the main living area 11 ft ceilings. So heat settles high up at first.

With that said, previous post our last home (16 year old home) 2nd floor heat pump unit had coils that would kick in if the spread was more than 2 or 3 degrees. I guess that is no more in the "green world" ? or is it simply a matter of thermostat programming which I suspect.

Anyway, my post was just to make sure someone in here with experience would confirm this as about right. The responses re-assure me as I look for every single thing and reason I can put in a warranty claim before our 1 year "bumper to bumper" no cost to fix or change anything we want on this house expires.

I do also know part of the start up time is the defrost cycle as it was 20 degrees in the morning and we are near the coast. (humidity) there was quite a bit of melted water on the condenser and still some sheets of ice on the coils. I checked my neighbors and his was the same.

So thinking it all through and the comments in here it sounds about right. No concerns, if there was even the slightest I would file a warranty service, whether a bit more freon etc.

We did have a home inspection done this week also, pretty much anything he find you hand off to the warranty dept to have them fix or correct. He said we were in better shape then most, actually seemed surprised. Worst thing he could find which he said to get corrected right away is the plumber didnt ground the propane system correctly. the wire is there I suspect he ran out of clamps *LOL* Lots of other little stuff, but no big things like broken trusses etc. He also ran the HVAC system while he was here, had temperature gauges on a couple vents.

I have to say for a production builder we have been very impressed with the smooth operation of the warranty dept. Pretty much, scan a QR code and with drop downs click on what needs service. Follow up call follows with video and that is usually it, sometimes our local warranty guy needs to check something. Not once have we been denied a claim, including tearing out and putting in a new driveway last summer. Anyway, in a few weeks they will do another walkthrough with us to see if we can find anything else wrong before warranty expires.

You can see ice on the coil. (ps that isnt rust, its mud, I went back out to check*LOL*)

View attachment 201126

A torpedo heater will cure that ice real quick.

 

[Snagglefoot]

Checking in on my neighbour’s new Daiken heat pump. The set point is 0 F. It ran well down to 0 F, keeping his house at 70 F with no problems. At 0 F it flips to his built in propane furnace.

He commented that when the relative humidity is high,it will ice up if the outdoor temps are 40 to 30 F. At lower temps the humidity is lower and it doesn’t tend to occur. It goes into a warming cycle to melt the ice if it occurs.

There were 11 days when the temp was below 0 F and the unit flipped to propane.

 

[Snagglefoot]

I have a few pictures to share. Things are melting pretty good with only shaded areas still having snow and ice. The temperature is still freezing in the morning, getting to around 50 f in the afternoon. The relative humidity is at around 65-70 % at around 32 F in the morning. The heat pump coils are getting iced but the heat coming out indoors is still warm. After several hours of iced operation the heat pump finally goes into a de-icing stage with the compressor running and the outdoor fan off. I was a bit worried it took so long to start the cycle. I was amazed the heat pump could put out good temps with ice on the coils. The temp of the ice was -8 C ( 18 C).

During the de-frost cycle the inside of the coils melt first, starting at the top and working its way down. In about 20 minutes its defrosted, except for the bottom coil. Then the heat pump goes back into its normal mode, but the rising outdoor temps stop the formation of more ice. The last three pics show the heat pump in the defrost mode, with the top coils defrosted, then most of the coils defrosted, then with only one coil with ice in it.

I'm not sure what triggers the de-frost cycle, whether its output temp or fluid temp going into the compressor.

Anyone have icing observations on their cold climate heat pump?

 

[CDX825]

Surprised that thing isn't on snow legs. American standard/ Trane uses demand defrost activated by a coil temperature sensor on the coil. Some other manufacturers use timed defrost which is not as good.

My bosch heat pump is demand defrost and on certain days the coil will be completely frost covered by the time it goes in to defrost. This is normal for all heat pumps though.

 

[Snagglefoot]

One other observation is that while the heat pump is in the defrost mode, if there is a call for heat, my backup propane boiler heat source will kick in and supply heat through its heat exchanger. When the defrost cycle is over, it will switch back to the heat pump. Very convenient.