1
$\begingroup$

Air conditioner's coil Blower of an air conditioner Blower of air conditioner

I observed the fan on external units of air conditioners does not force air towards the hot coil containing hot liquid to make it cooler. Instead it draws air from from the direction of the coil it and blows it away. In my opinion, it would be more effective if the air from the fan was blown toward the coil rather than the fan is drawing air from the coil and blowing it away.

Then my question, why?

$\endgroup$
1
  • $\begingroup$ Surely it is temperature difference that will make the heat move? $\endgroup$ – Solar Mike Dec 5 '19 at 7:41
1
$\begingroup$

You are correct. In terms of fan efficiency, it is more efficient to force cool air onto or through a hot zone, than to draw hot air from a hot zone and expel it to the atmosphere.

With the external unit of split system air conditioners (heat pumps) you have to consider other things.

The current arrangement may be easier and/or cheaper to manufacture.

Also, under the current arrangement, the external units of split system air conditioners is compact and thus requires occupies less space where they will be located. Also, the fan is located at the front of the unit, away from the wall. When it expels the hot air from around the coil it does so freely, without any obstacles impeding the air flow.

For the fan to blow cooler air onto the coil two situations are possible. Firstly the fan could be at the front of the unit drawing unimpeded air from the atmosphere. It then blows that air onto the coil forcing the hot air around the coil to move. That forced hot air will have to negotiate any internal obstacles within the unit and could hit the wall of the building, which may restrict the movement of the air away from the air conditioning unit.

The other possibility is to locate the fan at the rear of the unit drawing in air from the narrow gap between the wall of the building and the unit, which is restriction to airflow, and forcing it onto the coil. Again, that forced hot air will have to negotiate any internal obstacles within the unit - a further restriction to airflow - before exhausting to the atmosphere, at the front of the unit.

$\endgroup$
1
  • $\begingroup$ Not forgetting if the fan is pulling air there's the risk of pulling some small birds (not a good idea) and that any close particle in suspension would be pulled too (if by chance pulls something similar to a rope things will get ugly). $\endgroup$ – Leafk Dec 5 '19 at 15:51
0
$\begingroup$

Putting the fan behind the coil makes it harder to stick a finger into the fan arc. Positioning the fan as close as possible to the coil and shrouding it on the sides minimizes the efficiency difference mentioned in the comments above.

$\endgroup$
3
  • $\begingroup$ Two closely identical answers... $\endgroup$ – Solar Mike Dec 5 '19 at 18:03
  • $\begingroup$ should I delete? $\endgroup$ – niels nielsen Dec 6 '19 at 4:13
  • $\begingroup$ Add a few words and make a third... what do you think? How about just keep the best one... $\endgroup$ – Solar Mike Dec 6 '19 at 5:25
0
$\begingroup$

Putting the fan behind the coil makes it harder to stick a finger into the fan arc. It also directs the air blast directly over the fan motor, improving its cooling. Positioning the fan as close as possible to the coil and shrouding it on the sides minimizes the efficiency difference mentioned in the comments above.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.