The Well Effect

When installing air condensed chillers or heat pumps we must pay attention to their ventilation. How do they evacuate the heat? And what is more important: where do they get the fresh air they need from? Let’s remember, this air provides most of the energy the chiller or heat pump uses.

I am not sure whether I have heard “well effect” somewhere, I am translating from Spanish, or I just made up the term. I am referring to the installation of equipment in some kind of pit, where fresh air can only enter from the top, and other layouts that limit the unit ventilation.

In this post, for simplicity, we will focus on the chillers. It all applies the same to heat pumps. Usually, these units discharge the used hot air at the top, and take new, colder air from the sides.

Obstacles around the unit can impede proper ventilation. Having walls too close to the unit is a typical thing.The wall impedes fresh air getting to the?unit from the surroundings. Depending on how much air recirculates, it will reduce the chiller performance or, in the worst case scenario, it could raise the inlet air temperature to a point where the unit stops running.

This also happens when you have several units next to each other. The unit in the center in the image below hardly gets any fresh air. To prevent this, it is important to keep minimum distances to provide adequate ventilation. These distances must be given by the unit manufacturer. Some times, the equipment representatives are not aware of these limitations and even downplay them. Push to get the information from the manufacturer. The minimum recommended distance I have seen is 2.4 m (8 ft).

This can happen with the split unit condensers too. I have seen them installed on a roof like this.?The efficiency of the unit on the right is reduced.