Distance between heat pump and wall: What is the rule?

If you decide to install your air-to-water heat pump outdoor unit in front of your house, you may wonder if there is a distance to the wall of your own house.

The distance between the wall and the heat pump outdoor unit should be between 30cm and 50cm, depending on the manufacturer.

In fact, heat pump manufacturers usually recommend a distance of 300mm between the rear of the outdoor unit and the wall, and 500mm between the front of the outdoor unit and any wall in front of it. This is to facilitate air circulation, at both suction and discharge levels, and thus ensure the machine's power output.

But we'll see that not all suppliers agree on the same figures, and that it depends on the configuration of the location in which you want to install the heat pump outdoor unit.

How far is the wall from the heat pump?

If you look at the various installers' manuals, you can agree on a distance of 300 mm between the rear part (outside air intake) of the heat pump's outdoor unit and the house wall. This applies to the standard case: simply position the outdoor unit along the house wall. (not for other special cases, see below). The various manufacturers of heat pumps propose or advise, depending on their models, several distances to be respected so that everything goes well.

Name of the heat pump manufacturer	Distance wall - back PAC	Distance to PAC at air discharge level	Download the recommendations manufacturers
Daikin	300mm or more	500mm or more	Distance from Daikin heat pump wall
Toshiba	150mm or more	500mm or more	Distance from Toshiba PAC wall
Atlantic	100mm or more	600mm or more	Distance from Atlantic PAC wall
Hitachi	100mm or more	700mm or more	Distance from Hitachi PAC wall
NIBE	350mm or more	1000mm or more	Distance from the wall PAC NIBE
Panasonic	100mm or more	1000mm or more	Distance heat pump wall Panasonic
Stiebel Eltron	200mm or more	2000mm or more	Wall distance heat pump Stiebel Eltron
Viessmann	100-200mm or more*	1000mm or more	Distance from the wall of a Viessmann heat pump
De Dietrich	100mm or more	500mm or more	Distance from the wall of a De Dietrich heat pump
LG	300mm or more	700mm or more	Distance from the wall of the LG heat pump

*depending on power

Some examples in pictures:

What happens if the heat pump is too close to the wall?

If you stick the heat pump a little too close to the wall at the air intake (on the evaporator at the rear), the risk is a loss of power due to poor air intake and therefore poor capture of calories from the outside air. COP falls, power consumption rises.

If the fan grille on the front of the heat pump is too close to a wall opposite the outdoor unit, there's a risk of a "short circuit". The rejected air, whose calories have been captured (and therefore colder), could hit the opposite wall and return to the heat pump, which will then suck it back in. Your heat pump then sucks in some of this lower-energy air, which means a lower coefficient of performance, and therefore higher power consumption for the heat pump.

In short, without necessarily doing a master's degree in precision, you should respect the distance recommendations of the heat pump manufacturerif possible. And you'd better plan where to install the outdoor unit, so as not to be surprised.

Special cases of heat pump outdoor unit installation and PAC wall distance

Obstacle on top

If the heat pump's outdoor unit is installed outdoors, but in a kind of room or space with a ceiling, then a little more attention needs to be paid to the distances from the various walls to avoid any air recirculation. This air recirculation would impair the heat pump's operation and cause it to deviate significantly from its theoretical consumption or COP data.

First of all, we generally recommend a distance of 1000mm between the top of the heat pump and the ceiling.
Then, if the configuration of the premises lends itself to air recirculation (short-circuit), and the external discharge grille of the heat pump faces the solid wall, you'll need to leave at least one metre between this grille and the wall so that the air can escape before being sucked back onto the back of the heat pump. See image below from Daikin documentation

Heat pump in a wall recess

If you have a recess in your facade that would ideally conceal your external heat pump unit, you may consider it, but you'll need to respect the distance between the heat pump and the wall at the rear, as well as not sticking the heat pump too tightly to the sides. In general, it's advisable to leave around 300 to 500mm on one side, so as not to impede air intake, but also to always have maintenance access for a technician who needs to work on the unit.

How far is the heat pump from the neighbor's wall?

If you don't want to disturb your neighbors - and, moreover, comply with noise regulations - you may want to ask yourself how far away from your neighbor's wall and first living area you should install your outdoor unit. The idea is that the sound generated by your outdoor unit (fan, compressor, defrosting noise) should not become a noise nuisance and lead to conflict with your neighbors.

In the vast majority of cases, if you place the outdoor unit 20m or more from the first living-room window of the house adjacent to yours, there will be no nuisance.

However, this is not always possible.

To find out the theoretical distance to be respected, you can first refer to the acoustic data on the heat pump data sheets and make a small calculation. The Swiss heat pump association, gsp or fws, has set up a page where you can make this calculation based on several heat pump models. You enter your heat pump models, and you can play with the distance to the neighbor: you can determine by trial and error the distance at which you should place the outdoor unit. I put the link here https://www.fws.ch/fr/cercle-bruit/

However, this is only theoretical, and in reality you may need to opt for a heat pump sound insulation box to limit noise.

Read also:

Our article on heat pump installation diagrams