air conditioner running mode

[Lc_shi]

which one is more energy efficient for residential AC:
#continuous run all the day;
#only run when you need


welcome your comment

regards
LC

[Abby Normal]

Usually the answer is "you are only saving energy when you shut it off".

I think the best answer is "It depends"

[Abe]

Are there any similarities with a vehicle?
Engine running all day, or rapid start/stops?

Depends on type of system, inverter which modulates to demands, or fixed speed which runs constant

I would say an inverter type which never shuts down is the more economical

[Abby Normal]

That is a good analogy for oversized equipment vs properly sized equipment.

'City' gas mileage vs 'Highway' gas mileage

Sticking with cars, I think the analogy would be similar to "Do you shut the engine off while waiting at a train crossing, or do you let the engine idle while you wait?"

[mr_naxs]

when u start the unit, the peak of starting amp is more than 10x from running amp.
So..you can imagine when you start/stop the unit 4x per day.

[Abby Normal]

The posts keep going in the direction of a system sized to maintain vs something oversized that cycles.

My interpretation is as follows.

Do we save energy by shutting off an air conditioner, until we need the space cool? Is it less expensive to let it run all the time maintaining temperature?

A system that was shut off, would run for a while to recover, it would not be starting and stopping. Something that recovered quickly would be grossly oversized when compared to something sized to maintain. Not as critical with a furnace but a little critical with cooling/dehumidification.

The answer to this question is "It depends", but for 9 times out of 10, I would suspect shutting it off when not needed saves energy.

How frequently the space is used, the thermal mass of the structure, the insulation and air tightness of the structure, the orientation to the sun, etc all have an impact.

Also consider the consequences of elevated humidity in the setback periods.

Personal observations: If you leave the system off in a home with un-insulated concrete walls, leaky windows(with a lot of western exposure) and poor attic insulation in a hot humid environment, and go to work, it will be about 35C when you return from work and the system will run steady for seven hours to pull it down to under 27C.

A better built place would not pick up so much heat, be about 28C at dinner time, and would recover faster, to a lower temperature of say 24 or 25C.

[Abby Normal]

IMHO, when you look at this situation from a heating standpoint, as part of a daily setback routine with "AWAY" and "RETURN" settings, consider having the system recovering while the sun is still shining.

[chistine]

IMHO, when you look at this situation from a heating standpoint, as part of a daily setback routine with "AWAY" and "RETURN" settings, consider having the system recovering while the sun is still shining.

Absolutly right , cool!