Air Conditioner Performance Under Stress - One Machine Two Rooms

Factual Questions
1

My AC works fine according to the settings until the temp gets somewhere in the 90s for a certain time, and then I put it on 71 degrees, high power and leave it, and I cant get the place below 83 most of the day and til after midnight now.

I don’t know what happens to an AC that is overworked. Or if mine is. I have one machine for two rooms, using fans. The room with the machine is 82 at midnight.

I wonder whether the machine thinks it is doing the job, or even whether it is but there are other factors.

2

An air conditioner has a limited capacity–say 5,000 or 10,000 BTU. And

The size of your space determines how much cooling capacity you need. Budget air conditioners range from 5,000 BTU, which can handle about 150 square feet , to 12,000 BTU, enough to cover about 550 square feet. Naturally, air conditioners with higher capacities have higher price tags.

So you just don’t have a big enough machine to remove all the heat which needs to be removed.

3

Air conditioners are pretty simple. If the room temperature is above the unit’s set point (71 degrees in your case), then the AC turns on. When the temperature gets below the set point, the AC turns off, though it will still run the fan. That’s it. It’s either on or off. The air conditioner doesn’t know if it’s doing a good job or not. It’s not smart enough to figure that out. It just turns itself on or off based on whether the room temperature is above or below what you set it to.

The High and Low setting usually just controls the fan speed. I suppose some of the fancy ones might cycle the compressor on and off on the low setting but the cheaper ones don’t do that.

Since your AC doesn’t have the capacity to cool both of your rooms, it will run continuously, as long as the temperature is above your set point (71 deg). That is going to make it wear out faster.

4

Check the temperature of the air coming out of the AC vents. It should be at least 15 degrees (F) less than the room temperature. An infrared thermometer works very well for this measurement.

If the air coming out of the vents is not cold enough (15 F lower temp than the room), then you most likely have a freon leak that needs to be fixed and refilled.

5

The thing is I could swear that under conditions of 95 degrees or so the machine just puts out warmer air.

Maybe it’s an illusion produced by the room and the situation, but that’s the way it feels. Is it an illusion?

6

It’s 15,000 to cool 650 sq feet in two rooms.

7

Lower than the room? I don’t know what this means. The room is at 84 degrees. The machine is set to 71. The air seems too warm to cool the area.

8

This same guy ran everyone around in circles 2 years ago with air conditioner issues. He refused to provide the make and model, or do any testing to help resolve the issue. Thread here:

9

That linked thread makes me skeptical we’ll be able to help much here, but in my real estate business replacing ACs in units is a common thing, and I also have a lot of experience with window AC and portable AC, albeit I’m not an expert in heating/cooling. Every indication from what OP is saying simply suggests a unit that has BTU too low to meaningfully cool the volume of air in question at higher temperatures.

I have not generally seen good results with cooling multiple rooms using a window or portable AC and trying to use fans to “distribute” the cool air. Generally, if you have two rooms to cool and no central AC you should get two window ACs with the BTU necessary to cool down the rooms in question.

In this scenario 650 sq. ft. over two rooms, let’s say the two rooms are equal in size, you’d want around a 10,000 BTU unit for each room. If it was one big 650 sq. ft. room the 15000 BTU unit would probably work, but as I said in my experience window or portable ACs do not ever very effectively cool any room except the room they are in.

10

Out of interest I actually read the thread from 2019, and noted that it was brought up as a point in that thread that the same poster started a thread a year prior to that complaining about an AC working. In all three threads it frankly sounds like a person whose AC just isn’t powerful enough to cool his space in high heat waves. Most likely if you’re seeing temperatures 100+ or higher outside you probably would need a pretty serious wall AC to keep up with in a space like that, one that would require a 230v outlet etc.

11

It should also be noted (as I think I noted in the other thread) that in this super hot weather, ACs will, and do, struggle to maintain the set temp. At my store we have upmteen different coolers and freezers. For the last few days, when it’s been super hot, they’ve been struggling. They have a hard time maintaining their temperature. They struggle to bring the temp down if it gets to warm (in the cooler/freezer, ie after a defrost cycle or people in and out). To deal with that, we do what we can to keep the coolers/freezers sealed up. We try to keep the compressors out of the blazing hot sun. Often times we end up putting a hose on the condenser (outside) coils and that usually does the trick.

12

Yeah, my life experience is living mostly in the Mid Atlantic, to the upper south and a bit in the Northeast. I haven’t normally lived places where it regularly gets over 100, it sounds like this guy across three threads is living through heatwaves that sit at over 100F for several days on end, at least annually and maybe more frequently. A typical central AC unit here is sized to handle the typical weather here, and that does mean when we rarely get a very bad heat wave, it is unlikely anyone’s central AC is keeping their house exactly at say, a frosty 70F or whatever.

I’ve never lived in Vegas or the Deep South (spent lots of time there over the years, but never a permanent residence), so I don’t know what people do in places where it sits sometimes at 110+ for days, since that means you’d be looking at 85-90F+ all the time inside, maybe they have to install much larger systems than I’m used to seeing in residential properties, not sure.

I do know that the way this guy has described his residence across three threads, I think it was improperly designed for the climate it is in. It’s designed with no central AC, which I frankly think is not appropriate for a condo/apartment in a place where 100F heatwaves are common. Then it’s designed with a wall AC in one room, which because of innate limitations to ACs like that will never be great at healing adjacent rooms. Then the adjacent rooms all have horizontal windows (for which they do make special window ACs, but they’re always harder to find than ones made for normal sash-windows), and no cut outs for additional wall units. It just doesn’t feel like it was designed with proper cooling in mind. The fact he’s in a top floor unit exacerbates the problem.

Of course maybe he’s in the Pacific NW which historically didn’t need much AC but has had bad heat waves the last few years, and that would explain it.

13

Thanks for keeping tabs on me.

14

When you run the same bullshit shtick several times, you shouldn’t be surprised that people catch on.

15

In the northeast. We are getting waves of 3 days at high 90s sometimes now. 3 or 4 times a year. Who needs las vegas.

If it’s just that if the machine puts outs warmer air under those conditions I’d like to understand why it happens.

i notice on these threads folks want to deliver a “truth” and then defend it no matter what you are actually saying.

16

Maybe I’m naive, but what’s the motive for anyone to be here besides general information that they don’t know, or haven’t been able to clarify in prior attempts?

And how do you come into it as an aggrieved party?

17

Like I said, I am not an expert on heating/cooling, I’ve just been involved in paying for and seeing to the installation of air conditioners/heatpumps etc many times. I’ve also had to make sure complaints about them “not working correctly” get handled.

What I can tell you is very simply, an AC takes warm room air, runs it through the AC, and blows back out air that has had heat removed from it. We don’t need to get more specific than that, but in both a wall unit and a central AC, the heat is dissipated to the outside.

Your living space is continuously heating up due to ambient temperature outside being hot.

A traditional central AC has a “return vent” or many return vents all through out the house, the system “sucks” air into those vents. It then has supply vents that blow out cold air. In a normally functioning system, the AC can take that air that is being “sucked in” and cool it by about 15 to 20 degrees. So that means you should be able to measure the temperature of the air (with an infrared thermometer) at a return vent, and then measure it at a supply vent, and find a 15 to 20F differential. You have an in-wall AC, I don’t personally know how to take this measurement on an in-wall AC–in my experience they are typically just replaced instead of being repaired, so I’ve never known people to do much diagnostics on them.

But what the sum of all this means: if the air going in is really really hot, the air coming out won’t be super cold. So yes, in extremely hot temperatures, your AC will “blow” warmer air, it should still (if it is functioning correctly) blow colder air than it is “sucking in.” But if you are used to be it being a more comfortable temperature, the perceived temperature of the air it is blowing will feel warm, and not particularly cooling.

For some quick envelope math, let’s say the air being sucked in is 100F. That’s a hot and unfortunate temperature. The air it can blow back out, at the very best, is going to be 80F. More likely around 85F. So an AC in those conditions set to 65F will run nonstop and will never cool to much below the mid-80sF.

Remember the whole residence is being heated up constantly from the outside. So even if it’s actually achieving say, 18F of cooling, unless your thermometer is right beside the blower, portions of the residence will be a lot warmer than that 18F differential. So in your bedroom it could very likely be 90-91F, in the kitchen maybe 88F, right by the unit in the living room, maybe closer to 85-86F.

18

When you ask a question, we ask for clarifying information and you come right out and refuse to clarify, it’s rude. A lot of us here spent a lot of time in that thread typing up long, detailed posts that both explained concepts and gave you some troubleshooting tips. A lot of these posts had questions that we wanted answered so we’d have some direction instead of just throwing random suggestions at you, but you come back with " I am choosing not to say more than that. What is the issue with that? Just do the best you can do" and it’s a slap in the face.
As I said in that thread, it’s like posting “my Dodge doesn’t run properly” and then refusing to tell us what model it is or what the problem even is.

I don’t know. Maybe that thread should have just been a pit thread about the warranty as opposed to a GQ thread that draws in posters looking to help.

But we can’t give you any general information without some specifics. And as for prior attempts, it seems pretty clear to me that your AC doesn’t function well during these heat waves.

What was anyone saying that you felt wasn’t true? What we’re we defending? We asked you a lot of the same questions over and over because we all had our own theories as to the problem, but you wouldn’t give us any information so we couldn’t do anything with our ideas. You gave us little to no ability to confirm or deny our theories. I can honestly say that most of us in that thread (myself for sure), would have happily walked back our ‘truths’ if you answered some of our follow up questions with information that showed we were wrong. I promise. Personally, I’m a ‘shade tree’ HVAC guy. I have no real training but I’ve been doing HVAC repairs my entire life (though I call the pros when the problem involves the refrigerant). If something you said showed I was wrong, I wouldn’t continue down that rabbit hole, instead looking for a different cause for the problem. I feel like House dealing with a stubborn patient. Raindog is an actual HVAC repair guy and would have been worth engaging with him.

19

Also, and I’m going out on a limb a little bit, if you ask how the 20F limit intersects with the reality that many people even in very hot weather can get their homes down to mid-70s or even a little lower, it is usually only very hot for a little portion of the day. With the proper home design, the right insulation, the right shading etc, a house will naturally be able to heat up slower, and give the AC more of a fighting chance to keep the internal temperature reasonable. Note that the 20F difference doesn’t mean if it’s 100F outside, it has to be 80F inside. It means that it can only cool the internal ambient temperature by 20F or so, the internal ambient temperature can and often will be a good amount cooler than the air temperature outside, although without any sort of cooling system at all the internal temperature inside can actually heat up in an oven-like process and eventually get to be just as hot as outside or even hotter in some circumstances.

It sounds like OPs residence is particularly poorly suited for passively managed heat, top floor units are always the warmest in any building, I can tell you that from owning apartment buildings. Blackout shades and other things will absolutely help keep some of the heat out, and it sounds like OP is operating with large windows that he likes to keep unobstructed, this will carry with it a heat cost.

OP also has said he lives in the Northeast, historically the Northeast didn’t get crazy hot very often, so it is likely some of these concerns were not present when this building was constructed.

20

Just a regular cheap probe thermometer. Sure, it’s not designed to measure air, but it’ll do the job just fine. We don’t need exact numbers here. If the air coming out is 60 or 65 isn’t important, it’s how much it’s being cooled. In any case, hold it in front of the coils until it stabilizes and then hold it in front of the exhaust vent (or stick the probe in there). That’ll get you your two numbers.
You can use an IR thermometer, you just have to make sure you’re measuring the air coming in and not the coils themselves. But hopefully that’ll be obvious when you’re expecting the IR gun to say 80f and it says 40f.