Another AC Question

Prior threads have suggested that in 95 degree heat, the AC will run continuously for highest efficiency.

Someone said their AC is recycling every 10-15 minutes.

In his case, would the AC perform at highest efficiency if you leave the furnace fan in the ON position instead of on AUTO?

I thought this may help, but leave the answer to the experts.

Thanks,

Tim

Tim - The difference in energy efficiency between continuous running and constant cyling is miniscule. It's not likely to be noticed in your electric bill.

Constant cycling (especially short-cycling) IS harder on the compressor however - startup is what puts the most stress the compressor, contactor, etc.

Running the furnace blower continuously very slightly reduces efficiency. There is energy required to run the fan plus the latent heat added to the air as the small amount of condensation left on cooling coil evaporates at the end of each cooling cycle. However I've found the house feels more comfortable (and wife/kids less likely to fiddle with the cooling setting....) if I let the blower run continuously.

FWIW my home A/C cycles every 15 - 20 minutes at 90 deg and high humidity.

The most efficient system is one that runs continuously at the worst heat load. Reason is that all the heat pockets have been eliminated. Air is circulating, freon is flowing, effect of duct heat absorption from the attic is minimized, condenser is receiving cooling air, and maximum moisture is being removed which in itself improves comfort....cool dry air is much more comfortable than hot humid air....ala the Gulf Coast, Texas, Florida....BTDT and I went to school on the subject. Every time your AC cycles, it has to start the averaging process all over and those delays cost you money in addition to the start up current surge.

That's one of the neat things about room AC's the cooling loop is right there in the unit and there is no attic heat load to consider. Additionally, the room AC routes the condensed moisture (water) from the room to the rear of the AC where the condenser coil is located and a slinger ring on the condenser fan blade, slings this water onto the condenser coil and you enjoy the added efficiency of the "heat (removal) of vaporization" which your central unit doesn't have and costs you that much more money.

I built my house with my family by hand 30 years ago on that concept and my light bill last month was about $70 and this month was about $95 and I live in N. Texas....had a lot of 90 thru 100+ degree days in this months cycle.....hot water and cooking are gas. I have a 2400+ sq. ft. house.

So if some AC replacement guy wants to sell you a 5 ton AC for a 1000 sq. ft insulated home in the USA, run him off....unless you have 6 kids and they are in and out all day and leave the doors open and all that stuff.

Mark

If you have a two story house, there is no other way to balance cooling than to leave the blower running 100 percent of the time, and adjust downstairs vents to force more air upstairs.

A little of topic but I have a hundred yr old 1800 square foot house two story with two 10000 btu window units one up and one down cools whole house to 75 average with a couple fans running to move the air around and they don't short cycle they run for awhile then are off for awhile

Old windows probably no insulation in walls