Has the AC had the problem for the last 13 years or is this a recent problem? The AC should be designed to maintain a 75 degree indoor temperature on the average hot summer day. On a record temperature day the AC may not be able maintain 75 degree, but I would expect to keep it below 80 degree and drop down to 75 as the outside temperature drops.

When was the last time the AC has a preventative maintenance check?

"ginjj: How would the house cool to 75 when the outside temperature was still 80+? Are you saying if I leave the ac on overnight it will bring the temperature down to 75 as the night air becomes cooler? I haven't left it on, figuring it wasn't working anyway I turn it off at 10pm."

It would cool the house down to (hopefully) 75°F at night when the outdoor temp is 80°+F by continuing to remove 30,000 BTUs of heat per hour (assuming the capacity isn't impaired by age deterioration or malfunction). Leaving it on allows it to catch up and get somewhat of a head-start on the next day's weather. If you're turning it off at night and not back on the next day until the outdoor temperature is high and the structure of the house is heated up to an uncomfortable level, then it will have more trouble fighting against that already-accumulated heat plus the "heat wave" of the day.

Mike I only remember this being a problem for the past year or so. We are however experiencing many more hot days every summer and they are hotter! No I don't think it has ever had a "Preventative Maintenance check." Thanks for that recommendation. I am trying to learn all I can before the owner of the company calls me back which should be tomorrow. The company does get high marks on "Consumers Checkbook."

Dadoes I will definitely keep it on overnight now that I know that it should bring the temperature down. One thing I don't do is I don't let the house get hot before turning it on, I was told that years ago.

During heat spells like this is it ok to run the ac 24 hours a day for 4-5 days?

Thanks so much for all this great information.

"ginjj: During heat spells like this is it ok to run the ac 24 hours a day for 4-5 days?"

Surely. A properly-sized system normally will cool to the target temperature and cycle off/on/off/on several times through the day. Run-time increases during weather extremes which is normal operation. I never turn my thermostat / system Off. I adjust the temperature through the seasons and it runs as needed (cooling or heating) to maintain the setpoint.

Leaving the system on is perfectly fine. The only harm that will come is to your wallet. Cooling off your home at night will take some of the load off during the day and you will be able to maintain a more comfortable temperature. Assuming of course there are no other issues.

WOW that is such a great piece of news. Tomorrow will tell and I'll let you guys know.

I suspect you are low on refrigerant. That implies there is a leak that needs to be fixed. Let’s see what the company owner says. So far I am not impressed by his tech and service. Don’t be fooled by online reviews.

After running the ac all night the inside is 77 and the outside is 74. This is the first time I"ve run the ac all night. Now it will be interesting to see if the ac can keep it at or close to 77 and not climb to over 80 which it has done every day since this heatwave started was 4 days ago. It stays at 80+ until the next morning.

0950 just edited this post, trying to explain things more clearly,

Thanks again for all your information and advice. I'll be ready to question the owner when he calls!

One heat "source" dadoes didn't mention is the stored heat in heated-up objects, including walls, floors, furniture, etc. If you let it run all night, that should reduce this stored heat. I'm wondering why, when the outside temperature is 74°, the inside temperature is 77°? How hot was the inside temperature the evening before you ran the system all night?

You need to measure the air intake temperature at the filter using indoor/outdoor probe therm.. Then take temp at register closest to air handler., this is called Delta T. Should be between 16-20 degrees difference. This will give you a good indication how your unit is performing. Also make sure your outdoor condenser coils are clean.. There are several videos on YouTube. showing how. to clean.

BTW I Iive in the southwest , and it has been 106+ over the last several days and my 26 year old 4 ton AC keeps my 2650 sf, house with 9 1/2 ft ceilings, at 78 even during hottest part of the day.

Greg

"ginjj: ... 3 sun tunnels/skylights, sliding glass doors in the living room, not
sure how good the insulation is anymore, old windows, weatherstripping
on front door and garage door isn't very good."

"ginjj: I only remember this being a problem for the past year or so. We are
however experiencing many more hot days every summer and they are
hotter!"

The system reasonably should be able to reach and maintain an indoor temperature lower than 77°F when the ambient dips down to 74°F. The factors quoted above come into play when the outdoor temp is hot but less-so when it's 74°F at night. The unit apparently is in need of maintenance or repair. Air filter changed? Evaporator and/or condensor coil cleaned? Low refrigerant (due to a leak?) as mentioned above? It may also have always been of just barely adequate capacity and the increased "heat wave" weather is revealing that.

MTVHIK -the temperature inside the house was 83 at 10 pm, it had been 83 all day.

dadoes - The filter at the furnace (which is what I assume you are talking about) is the type to hose off, which I did two weeks ago. The condenser hasn't been cleaned but the tech looked at it when he came out a month ago. There is no cover on it and it has free air on all sides.

I think the skylight in the kitchen especially, lets the hot noon sun beat in. I will call to see about a cover for it.

Weather forecast of San Jose is a high of 98 degrees around 3pm PDT, with a low tomorrow morning before sunrise of 72 degrees. The summer outdoor design temperature is 89 degrees. You are above the design temperature, but not high enough that the house can't be cooler than 83 degrees. Let's see how the AC does while you keep it on all day. You enjoy low humidity in your area. I would think 77 degrees would be comfortable for most people with a humidity around 40%.

The ac does run all day and now I'm running it at night having learned from everyone here that in my case if the unit is ok it will cool the house down by morning which it did. I'm also going to close my drapes and be careful of how the house heats up - again thanks to everyone here!!

Something to remember for our area:

Except with the extreme weather we've had and will have for a few more days, our area normally cools down overnight on even warm summer days. I've been told that it's not a good idea to run AC equipment when it's cooler than 60 degrees outside. And, it's really not necessary when open windows can bring in cool outside air. Especially when helped with fans pointing in or out.

For cost reasons you probably want to turn off the AC when outside air gets down into the 60s and the house has cooled down. Check your daily forecasts. If overnight temps are expected to be in the 50s, turn it off before you go to bed.

Some times the out side condenser coil looks clean, it is the best practice to back wash the coils, inside to out at least every year. What was the temp split between air intake and outlet?

I don't open my windows at night, would you still suggest turning the ac off if night temps are expected to be in the 50's?

Can you clarify why if the house has been at 77 all day and evening and I turn off the ac at 10, with the windows closed, how does the house get hotter before 6am when I'm up?

Greg I just looked up Delta T and it seems like something the company needs to do or can I do it?

Wasing the coils has never been done but I'll do it.

Greg I just looked up Delta T and it seems like something the company needs to do or can I do this.

You can do it. Take temps at air intake (filter) and outlet register nearest air handler. Subtract intake temp from register temp. The greater the better, 16-20 degrees. If not within this range, could be dirty condenser fins, low refrigerant, duct leak in attic, pulling hot air into system.

Also you can check suction line return temp at condenser., the largest with foam insulation., should be cold and sweaty.. You will need to peel back insulation to be able to put your fingers on it.

A good tech should have done this measurement at the time of the call.

"ginjj: ... why if the house has been at 77 all day and evening and I turn off the ac at 10, with the windows closed, how does the house get hotter before 6am when I'm up?"

Your house can get warmer under the conditions due to heat produced by
activities and devices/machinery inside and retained in / radiating from the structure of the building.

A/C units can handle running at low outdoor temperatures to maintain a reasonable indoor temp. A little different situation but it's not unusual that cooling runs for an auditorium at the theater where I've worked for 36 years when the outdoor temp is 60°F or lower if there's for example 150 to 200 people in attendance (before COVID-19, LOL), or for the lobby due to both people and concession equipment producing heat. Heat pumps run in freezing outdoor temps.

"Can you clarify why if the house has been at 77 all day and evening and I
turn off the ac at 10, with the windows closed, how does the house get
hotter before 6am when I'm up?"

Sure, the same thing happens in my house and everyone else's. There's a lot of heat buildup in the attic. Your attic will remain much hotter than the interior and will radiate that heat through the ceiling though the night. That was why I recommended taking a look at your attic insulation and perhaps beefing that up. It makes a big difference.

Also, how well ventilated is your attic? Any chance to put in something like a gable fan thermostatically controlled or having a switch? That will make a difference too.

I don't think the preceding comment regarding an industrial HVAC installation in a commercial building is relevant to home equipment. Home AC condensers can be made to operate at lower temperature with the addition of a piece of equipment that the commercial equipment may have, it's something like a crankcase heater but I forget the name. It has to do with the thickening of the coolant and reduced flow at lower temperatures. Ask about that when you check with your HVAC contractor and follow their advice.

Elmer, my understanding is that all central a/c compressors typically have a crankcase heater. Window units don't.

The average residential condensing unit is not designed to run in cooler temperatures. Doing so can cause damage to the unit. As a general rule I will not operate my unit when I know the temperature is going to be below 68. In reality you are probably good to about 64 maybe even a bit lower, but I am not willing to risk it. Not to mention at those temperatures opening a window can be very pleasant. The refrigerant needs some heat in order to do its job properly. There are commercial units that are designed to work at lower temperatures, but they are very expensive, and most likely would see little use in a residential setting, think server rooms that need cooling all year round.

I always like to learn new stuff and maybe what I was told before was wrong. It happens I have an appointment next week for periodic maintenance and I'll get all of this clarified by asking the HVAC technician. I'll try to remember to report back what I learn.

I recall advice years ago aimed at people who turn off their condensor breakers during the winter season to turn the breakers on at least 24 hrs before running the system in the spring to allow the crankcase heater time to warm up. Maybe the heaters have largely been eliminated nowadays.

A window unit we had that featured both reverse cycle (heat pump) and electric resistance heating had a temp sensor that shut off the compressor below 45°F and switched to the resistance heat. Seems reasonable that central systems would have a similar safety to avoid (cooling) damage, but maybe not.

No HVAC servicer or installer has yet directly told me to not run cooling when the ambient is below such-and-such temperature, although maybe they just assume that I wouldn't have a reason to do so.

Well house is now 80 with outside temp 92. It started climbing 4 hours ago when the temperature was 93. I am learning a lot and now know what to ask of the owner, hopefully he'll call tomorrow or I'll call him again. I imagine he's servicing potential new clients rather than me, makes sense but not good for me. I had been quite happy with them before this happened, visits were all free.

I did find this great video some you might enjoy.AC Maintenance

Crankcase heaters for compressors: Some units have them, some do not. ( the cheaper units don't, the exception to this rule is heat pumps).

Running an AC unit in cold weather: It's typically fine for anything above 55F outside. (This can vary slightly from one manufacturer to another) I say min temp 60F OAT and 120F OAT max you should be fine.

I say the max temp here because some desert areas are in the realm of 130F recently. What happens at those higher temps? Nothing good.

That being said, if you have a digital thermostat in most cases this is pretty much dummy proof. Most digital stats limit AC to 65F indoors.... Well unless you have nest T-stat now that I think about it.

It's possible to run AC in lower temps, but would require additional controls to pull it off.

On extreme days, close up! Close up everything! That means closing drapes on glass doors and any windows to stop radiant heat entering. On any summer's day glass will give off heat. When you close the drapes, after a while put your hand between the drape and the glass, you'll feel the heat that is being generated. If needed, invest in drapes that have blockout (a covering on the material to assist with insulation). If you don't have good weather seals, you will be drawing in hot air. If it is possible to have exterior blinds to stop sun from hitting glass, you will assist in reducing summer heat. Then you might find your unit feels more effective. If it is a cool night, open up once the sun is down. Let nature cool your home. If you can just run the fan to help air move, night cooled air is just as effective as ac! Then close up again before the heat hits. You might just find a difference in your summer electric bill if you use these simple but effective tools.

Should I buy a new air conditioner or just the motor for a 13 year old system?

When I was outside a few weeks ago I noticed the ac was making a new sound in addition to the normal sound, it sounded like the whishing of a heartbeat. When the tech came out he said I needed a new motor but could continue to use the ac until he got it.

Since the ac is 13 years maybe I should buy a new air conditioner. What do you think?

Before making that decision you need a capable tech to assess the problem and give you a quote as to how much it will cost to fix it. Don't be talked into buying a new system without knowing all the information.

This is outside fan condenser motor?...What’s the cost of new motor?...

TD

ginjj, the outdoor part of the system (where the compressor is housed) has two motors ... a fan motor and the compressor. Presumably the fan motor is the issue. It's normally a reasonable repair ... sort of equivalent to replacing the battery on your car (you wouldn't buy a new car because of bad battery, or a broken belt or worn tires). However, a noisy fan motor (bad bearings?) doesn't impair the performance ... until the motor seizes and won't run at all. You may have other problems related to the system not performing well that could be factors in whether to repair or replace.

The technician from the company "said" the motor cost $200 plus labor. I didn't ask the labor charge. I also need the "annual maintenance" done which has never been done!

I have been happy with the company I bought this from 13 years ago. When I had concerns the same tech came out and fixed whatever the problem was and there was no charge. It's a company owned by one person, who I met when I signed up but haven't seen since, his tech must do all his repairs.

I assume it's the "outside fan condenser motor," It's outside and that's what we were talking about when he was here. Is there another motor?

The other "motor" is the compressor. That is an expensive repair. I highly doubt that is what he quoted for $200 plus labor. I am not sure if I believe the fan motor is not available from Trane right now. It is a common part that should be available in a day or two. I think you are getting the run around. This is not a good way to treat a customer of 13 years.

fan motor should be readily available, usually on a service truck...if nothing else for repair, I would have new motor installed...should not be more than $300 total...you still have a cooling issue...

TD

..you still have a cooling issue...

What he said

Yes I do. I need to re-read this wonderful discussion and make a list of all the possible problem areas before the tech comes out.

"Running an AC unit in cold weather: It's typically fine for anything
above 55F outside. (This can vary slightly from one manufacturer to
another) I say min temp 60F OAT and 120F OAT max you should be fine."

Thanks Austin Air. This confirms what I was told though individual owners can check with their technician next time one is on site, to see if their unit has equipment installed to safely operate at lower outdoor temperatures than 60 deg.

But I'll stick with once outdoor air is below 65deg and the house is cool, I'd much rather open windows unless there's a noise or safety issue.

Let us know how it woks out. Information could be useful fo others.

I will! He's coming today and I've got my list of questions and things for him to do, thanks to all of you!

The unit needed coolant. Because of everything I learned from all of you I had a list of all the things I wanted him to check and he checked them all. Thank you again to all of you for helping me to learn about my air conditioner!! You are the best.

Ginny

The thing about needing coolant (refrigerant) is that's not necessary unless there's a leak in the system. Refrigerant doesn't wear out or get used up such that it must be changed or refilled. A tiny leak that doesn't cause an adverse effect until enough leaks out over a couple/few years is somewhat less of a concern, but it's still a leak that shouldn't be there.

I talked to the owner today and he said the small amount of coolant that was added was nothing to worry about. He did say If I wanted every possible location for a leak checked they could do that but for lots of money.

Thanks again for everyone's input!

Ginny

Now that refrigerant was added, is the AC performing any better? Are you able to maintain a 77 degree temperature?

Yes, however temperatures have not been over 90.

My AC has been working fine in this summer's heat wave, it just needed coolant. Good luck fixing yours.

Glad to hear the problem was resolved. Was the leak found and fixed?

Had same issue here. Ended up finding holes in ductwork on the underside where you can’t see. Duct cleaning people found them.

"HU-880937981" is a spammer. Please flag.

Why do you say that. His post may not be particularly informative but I don't think that makes him a spammer(?)

susphipup2 considers him/herself a Moderator in Training.