"Dehumidify" and "night" modes for central air?

[Percival P. Cassidy]

When we lived in Taiwan almost twenty years ago we had Hitachi computer-controlled window/hole-in-the-wall air conditioners with a "dehumidfy" mode. In this mode they would run for a while then stop, then repeat the cycle, irrespective of the temperature. I don't recall what the on/off ratio was, and I don't think it was adjustable. Would it not be possible to cycle a typical central air system in the same way to reduce the humidity without necessarily reducing the temperature by much?

These also had a "night-time" mode, in which after 4 hours they would raise the temperature by half a degree (Celsius) every half hour. The idea was that one would not keep waking up because of being too cold. Have North American A/C systems ever had such a mode?

Perce

[Beachcomber]

If the condensing coils are outside, then heat will be removed whenever the compressor is "ON", the rate-of-removal depending upon the size of the system in tons or BTU's and, to a lesser extent, upon the outside temperature.

Most residential A/C's are strictly fixed sized units that operate either in the ON or OFF mode from the sensing thermostat, hence the requirement for proper sizing to the load. An oversize unit may bring down the temperature too fast in relation to its dehumidifying functions. Some of the newer units with variable speed compressors can counteract this.

Recall that a dehumidifier is just an A/C with its condenser and evaporator coils exposed to the ambient air. The net heating/cooling effect is zero, except for the heat added to the environment by the electrical and mechanical resistance of the electric motors in the system.

Beachcomber

[Joseph Meehan]

I don't recall any with a "dehumidify" mode, but you can use a programmable thermostat to do much the same thing on raising the temperature. We don't generally have the the same humidity problem you may have had. I would guess most people would just use a dehumidifier if needed.

[DT]

My newly installed ductless mini-split system uses this method, labeled "Dry" on the controller. It is on for 8 minutes, then off for 3 minutes and 45 seconds.

-- Dennis

[Michael B]

When we moved into our house, the A/C unit hadn't been used for years. I repaired it temporarily, but wasn't ready to replace it till I finished upgrading the ductwork. But that A/C unit was horribly inefficient, the house had no insulation, and it was running virtually nonstop.

One night I was in the laundry room when the unit came on and started delivering into the sump crock. The condensate was steady for the first half hour, and then started slowing down.

Glancing at the thermostat showed that the temperature hadn't changed, but it was already more comfortable.

So rather than trying to bring down the temperature, I worked on simply using the A/C as a whole-house dehumidifier. After all, a reasonably dry 83 degrees is more comfortable than a muggy 73.

If any> Percival P. Cassidy wrote:

[No]

I would love a dehumidify only setting on my thermostat or even better, the ability to set temp and humidity levels independently. Add to that set-back and such and it would save some energy and make things more comfortable.

someone post that magic link to a supplier who has what we are looking for.

[Altrus]

use a climatouch CT03TS32H (also called Climatouch C3), it does that and more most thermidistat's (as opposed to thermostat's) will overcool by one and up to three degrees to maintain RH%

[No]

Thanks! I'm reading up on the c3 now.

How about one more feature... A "remote" sensing unit. in other words, have a temp/Rh sensor in a different part, or parts, of the house. You set max temp or Rh for all sensors.