Should heat pump be positioned to get direct winter sun or be out of the way

fclauson

Quick question all

Would the COP of an Air to water heat pump be improved by any measureable amount by placing it such that it gets a little winter sun ?


My thinking comes from expeirence with my car - when parked at the rear/norh side of the house it gets frost on it which is a little hard to clear but when parked at the the south side the ice has normally melted by its time to go to school.

Its a choice of being a bit of an eye-sore for a better COP or being out of site at the rear of the property.

JD6910

Great question - can't wait to hear thoughts on this issue!

Do-more

I'd like to hear a definitive answer on this also, but FWIW I will share my thinking on this which is open to criticism.

I think that the efficiency of the HP is going to be dictated by the air temperature of the large volume of air being drawn across the outdoor unit. In winter I don't think that there is going to be a huge difference in outdoor air temperatures from one side of the house to the other, is there?

On my HP the outdoor unit can be located up to 30m away from the indoor unit but it is best to keep the pipe run as short as possible so for that reason it is my intention to place the outdoor unit directly on the other side of the wall from the indoor unit so they are less than a metre apart. This means it will be on the north east corner of the house.

Also in winter the sunlight hours are short so for two-thirds of the day the unit will be in darkness anyway.

Here in Sweden it is not unusual to see outdoor units located under car ports or with a small roof built over the unit to protect it from the worst of the weather. Just as long as it gets adequate airflow then it's fine.

JD6910

Do-more wrote: »

I'd like to hear a definitive answer on this also, but FWIW I will share my thinking on this which is open to criticism.

I think that the efficiency of the HP is going to be dictated by the air temperature of the large volume of air being drawn across the outdoor unit. In winter I don't think that there is going to be a huge difference in outdoor air temperatures from one side of the house to the other, is there?

On my HP the outdoor unit can be located up to 30m away from the indoor unit but it is best to keep the pipe run as short as possible so for that reason it is my intention to place the outdoor unit directly on the other side of the wall from the indoor unit so they are less than a metre apart. This means it will be on the north east corner of the house.

Also in winter the sunlight hours are short so for two-thirds of the day the unit will be in darkness anyway.

Here in Sweden it is not unusual to see outdoor units located under car ports or with a small roof built over the unit to protect it from the worst of the weather. Just as long as it gets adequate airflow then it's fine.

ya i think i am going to build a little wall on two sides with the back of the unit up against the house. going to put a small little lean to roof to keep the rain off!!! the outside face of the unit will be completely free to suck in air. i would imagine the unit should be on any elevation except the NORTH face as this will be the coldest. i would imagine south would be ideal and typically the warmest?????

threeball

JD6910 wrote: »

ya i think i am going to build a little wall on two sides with the back of the unit up against the house. going to put a small little lean to roof to keep the rain off!!! the outside face of the unit will be completely free to suck in air. i would imagine the unit should be on any elevation except the NORTH face as this will be the coldest. i would imagine south would be ideal and typically the warmest?????

DO NOT DO THIS ^^^. The air will be too confined and will short cycle causing already cooled air to recirculate through the unit.

The most important issue with siting a unit is to keep it out of prevailing winds so the heat doesn't get stripped away when the unit is defrosting. Everything after that has minimal effect.

JD6910

threeball wrote: »

DO NOT DO THIS ^^^. The air will be too confined and will short cycle causing already cooled air to recirculate through the unit.

The most important issue with siting a unit is to keep it out of prevailing winds so the heat doesn't get stripped away when the unit is defrosting. Everything after that has minimal effect.

can you expand more on this issue.

is it advisable to locate the unit circa 8 meters from the tank?

threeball

JD6910 wrote: »

can you expand more on this issue.

is it advisable to locate the unit circa 8 meters from the tank?

In a confined space air that is pulled through the unit (evaporator) will get stuck in a rotation and never really escape the influence of the fans. It will get pulled through, discharged and pulled through again each time getting colder and colder and dropping the efficiency of the unit each time.

I'm not sure what you mean by positioning the unit 8m from the tank? Which tank are you refering to?

JD6910

the tank i referr to is the tank that comes with teh air to water unit.

i understand that it is best to keep the air intake unit close to the tank/brains of the operation!!!!!!

sydthebeat

i often though of the idea locating a heat pump in a 'winter garden' type area external to the house... the theory being 2 fold...

1. the intake air is pre heated through solar gains in the glass house

2. the air intake is richly oxygenated by the plants.

what kind of volume you you need in this area pro rata to the dwelling??

Do-more

sydthebeat wrote: »

i often though of the idea locating a heat pump in a 'winter garden' type area external to the house... the theory being 2 fold...

1. the intake air is pre heated through solar gains in the glass house

2. the air intake is richly oxygenated by the plants.

what kind of volume you you need in this area pro rata to the dwelling??

No good you need far more air flow than you could provide in an enclosed space like that.

As I said they are often located in a car port, but that would be a lean to structure with two or three open sides.

Otherwise they sometimes have a simple roof structure overhead the outside unit to prevent snow building up around the unit (possibly from falling off the roof of the house) but always it is important not to restrict the flow of air to the outside unit.

Condenser

sydthebeat wrote: »

i often though of the idea locating a heat pump in a 'winter garden' type area external to the house... the theory being 2 fold...

1. the intake air is pre heated through solar gains in the glass house

2. the air intake is richly oxygenated by the plants.

what kind of volume you you need in this area pro rata to the dwelling??

Your average unit will move about 5,000m3 of air per hour. If you placed it in a winter garden everything would be dead from the cold within a week. It would resemble something out of the day after tomorrow.

Oxygen or the lack of it has no effect on the efficiency of the units. Less oxygen would actually be an advantage as they wouldn't corrode as quickly.