AC Setting Question
 

We have a vacation home and only get up there about every third weekend. It's in Georgia and the climiate is mid-90's with humidity this time of year. I've been leaving the AC on full-time, but set high....around 86. Objective was to keep the humidity down inside the house without running up a mega-bill in the process.

Any reason to leave it running at all in the summer? I was there yesterday for about an hour and the AC was on almost the whole time (set at 86). Wasn't uncomfortable in the house for my brief visit, but that e-meter is spinning a lot these days. What would you do?

If you can manage some sort of decent ventilation of the house while you are gone you should be OK. People lived in Georgia for many years without A/C and the houses survived.

The big discomfort will be coming into a HOT house when you first arrive.

I would look into the remote controlled thermostats that allow you to log into the system from home and turn it on several hours before you get there.

Get a programable thermostat ($50). Most have at least two cycles a day, some have more.
Set it to cycle from 86 for a couple of hours to 99 (or as high as it will go) for 10 hours or so, that way you'll have 4 hours running a day and 20 hours off. That should be enough to keep the humidity in check.

Yeah, you gotta have it on some... otherwise (1) you'll have mold and (2) it'll start to smell like a wet dog in there because of moisture in the rugs and upholstery "activating" smells that are kept at bay in drier air.

Can't you run a dehumidifier on a timer?

Isn't a dehumidifier just an A/C unit? Or vice versa?

This won't help your cause, but it's a good idea to run your compressor from time to time no matter what time of year. Heat pumps run backwards, so they get a consistent work out. You always hear about those that have to recharge their a/c system at the beginning of the a/c season, the reason is due to seals drying out and leaking. Moving a little oil and freon around the system now and again is good. Same goes for cars.

If humidity control is your primary concern, buy a whole house dehumidifier. Run it where you're gone. When you're back, turn on the A/C. A dehumidifier is a far more cost effective means of controlling humidity. An air conditioning unit is split roughly 70/30, with 70% of output removing heat from the house, and 30% of output, removing humidity (moisture via condensation at the evaporator coil). If you run the air conditioner enough to control the humidity, you will be throwing away a lot of energy cooling a house with no occupants.
jurgen

In a home AC there are no seals to dry out as in the compressor is sealed in a big can. All the copper tubing should be brazed with no fittings.

Then I guess valve cores need some pressure now and again. I know those seals dry, same deal on cars. It's the #1 leaker.

A car has a shaft seal on the compressor which needs to be polished and lubed by rotating it.

I was referring to a/c systems in general, valve cores leak. It's no different than when you were a kid and your bike tire was flat after the winter.

I'm well aware of what a compressor on a car does. I sell them, I rebuild them, but rarely do I install them anymore.

The programable thermostate is a good choice.
Change the filters on the cold air returns, and have an A/C guy come out and top off the freon charge. (makes them mor efficient). Have him inspect the cleanliness of the coiling coil.

I would think that any properly sized system would not run constantly when set to 86. But 90 during the day and 86 at night should keep it dry and not cost you an arm and a leg.

Most home ACs don't have valve cores.

EDIT: Bottom Line - You can run your central air in the middle of winter for whatever reason you want but it isn't to lubricate the seals to keep them from leaking because there aren't any. It is a sealed system.

Thanks for the advice. I've closed off the unheated/cooled sunroom (which should help a lot) and will leave it on 88 during our absence. The York heat-pump system is new and operating optimally, so no issues there. Definitely don't want a mold problem and probably won't mess with a Dehumidifier, at least for now.

Thanks again!

I hope you didn't and don't mind the hijack, if so I apologize, Chocaholic.

Please explain to me how any freon is added even if the outside unit came fully charged? How does anyone know how much freon is needed when it varies from house to house? Surely, it depends on how much copper line is needed, not to mention the evaporator. The capacity varies, and pressures vary depending on ambient temps.

Cracking the valves to inject is nice, but when the valve leaks, there's the stand bye, an old dried out bicycle valve, to catch, what escapes past the first valve. Slow leaks are inevitable.

I didn't support the ban on R22, or any other refrigerant for that matter, but there's a hold on 134, which if you ask, is left unexplained. It doesn't take a rocket scientist to figure it out. We both know. Home a/c's are sealed on one side of the argument, but are not a sealed system on the other side.

If it doesn't leak, it's not designed to leak, it will never leak. Then why tap into another refrigerant market? HCFC, HFC, going to wipe out everyone, bla, bla, bla.

I'll give you warn out parts, it happens. But please explain to the rest of us why an a/c system that still holds pressure, would leak out freon over the winter.

Maybe I'm wrong, but I'm fairly certain there are valve cores.

The service ports on your compressor/condensor are a three position valve. If I remember right.

1. All the way out the compressor is shut off, freon is in the condenser.
2. All the way in the connection to the outside is shut off but the condenser is connected to the evaporator/capillary tubes
3. midway all three connections are open

(may be vice versa)

You put the compressor/condenser outside, braze all the connections. pull a vacuum on the line set and evaporator and then add freon based on the length of the line set. Then you open the condenser unit, start it up and see if the pressures are OK.

If all OK close the valves to the service ports, pull off the guages and screw on the brass caps over the ports.

My uneducated guess is that Milt is on the right track (I know a little about A/C and a lot about mold), a dehumidifier is way cheaper to run as it isn't "pushing" air through vents. A centrally located dehumidifier to keep humidity down is what you want in a place like Georgia. You need a way to drain the condensate out of the collection basin, otherwise you'll get mold from the standing water, which could overflow into the house if not drained away.

You are on the right track just to turn up the temperature when you are not there and let the AC look after the humidity. As mentioned before, using a programmable t stat to get some run time once or twice a day wouldn't be a bad thing either.

I am not familiar with a whole home humidifier but it seems that they are basically an AC system with a thick coil to dry out the air. The condenser looks to reject its heat outside.

Self contained dehumidifiers cool down the air by using a self contained condensing unit and evaporator coil. Leaving one of these operate in a closed home in a hot climate will actually raise the temperature of the house. The energy required to cool the evaporator coil is just discharged in the house. Because of the heat of compression and the inefficiencies of the machine, that means more heat is rejected than is taken in when cooling the air past dew point to dehumidify it. Quite often you will see these located in a cool basement to keep the musty smells away. Some of these will drain by themselves, others you have to dump the water from them.

Service valves positions are for access port closed "on the back seat". (all the way counter clockwise). All the way in clockwise is "on the front seat". This will isolate a compressor on its service valves or isolate the condenser from the liquid line allowing the system to pump down, keeping most of the refrigerant in the condenser. Opening the service valve access to allow placing gauges on the system is just a matter of cranking them in a 1/2 or 1 turn.