Measuring A/C Temp Solved, sort of...

[Retirednoguilt]

I was told when I replaced my entire A/C system 7-8 years ago that the newer A/C evaporator coils were a much more efficient match with the newer refrigerant gases than using ann older technology evaporator coil with a new condensing unit. However, the newer coils wouldn't fit in my old (1980s) gas furnace. I replaced the entire system with a 92% efficient gas furnace and an entirely new A/C system. On average, my gas bills during the winter heating season have been about $75/mo cheaper and my electrical bills during the A/C season have been about $100/mo cheaper than before the changeover, despite higher utility rates since then. The savings paid for the new equipment in about 6 years and meanwhile, I've got a more comfortable house and am using a smaller carbon footprint.

If you're thinking of keeping your house for more than about 5 years, the cost is more an investment than an expense. Besides, you'll probably get at least some of the cost back as a higher sales price when and if you sell.

[Boris]

Retirednoguilt wrote in news:mkn3qj$b82$ [e-mail]:

big snip

That's what I was wondering. One could purchase a modern a/c unit only to find that the unit's coils won't fit in the furnace.

I replaced the entire system with a 92%

If my math is correct, the install cost about $6300. and

All good points.

Thanks.

[Boris]

Stormin Mormon wrote in news:wItbx.59014$ [e-mail]:

Well, I'm going with the easiest thing to eliminate, first. I'm going to clean the compressor before considering a new unit.

I did call another a/c company in the Sacramento area, and talked with their tech, and he advised cleaning the compressor and see if that helps. I asked him if he could get out there and do the cleaning, but he's booked for a while, and I've got some visitors coming in one week.

One problem I may have is that the back side of the unit is less than

12" from the side of the house. The tech suggested that I remove the top of the cabinet (and the other three sides), and perhaps I can get to the inside of the backside fins, and using a spray hose, force any debris/dirt from the inside, out.

I'm going up early Friday morning to clean the thing. By the time I finish cleaning, it probably won't be hot outside, so I'll have to lower the thermostat to get the unit to run. Then I'll wait.

If it wasn't for the mileage charge, I'd have you out.

[Boris]

Stormin Mormon wrote in news:wItbx.59014$ [e-mail]:

What's the name of the purple stuff? Is it the foaming type?

BTW, took my family to visits friends in SLC a few years ago, and saw the Mormon Tabernacle Choir do a 4th of July performance. Amazing building with some pretty good singers.

[Boris]

Stormin Mormon wrote in news:wItbx.59014$ [e-mail]:

snip

snip

Going to use this:

AC-920/100599017

[J Burns]

The OP didn't say he knew that. He said only that they were baffled.

What data? If the outlet tube is close to ambient, the condenser has cooled the freon about as much as possible.

It can cool faster when it's running, with all that 80 F air being blown through it. The specific heat of copper is 0.09 btu per pound per F. On a 24,000 btu unit, do you really think it would take an hour to overheat if the blown air weren't doing the job?

That's because you're not experienced. Back when I was inexperienced, in

1997, my niece borrowed my car. She reported that the AC was feeble. I tried it and it was fine.

Ten years later it happened to me. It started cooling fine, then all I got was warm air. When I tried it a few minutes later, it worked fine and didn't quit.

Both incidents happened the first time it was used in the season. The owner's manual says to run it for a 15-minute period each month, but I forget. I believe moisture can migrate out of the drier, and running it every month puts it back into the drier before there's enough to ice the orifice. The problems I had at the start of two seasons solved themselves when the ice melted and the system put the moisture back in the dryer.

[Stormin Mormon]

Maybe we can go metric, and have smaller miles?

I'd suggest to clean the condenser (fins and tubes) rather than the compressor (the big tin can in the middle). Please keep the compressor and wires dry.

I looked online, about a thousand dollars air flight, change planes in Chicago. Food, car rental, motel. I could do it for about two and a half grand. Leaves some money left over for labor charges.

- . Christopher A. Young learn more about Jesus .

. .

[Stormin Mormon]

I've used 4-x, Alki Foam, or Nubrite. They all work.

Yes, some of those singers are good.

- . Christopher A. Young learn more about Jesus .

. .

[Stormin Mormon]

I'm promoting you to field tester, second grade, with pay increase and rank and authority.

I've never used this stuff. Please give it a go, and write here so we know if it's any good.

This message will self destruct in five seconds.

- . Christopher A. Young learn more about Jesus .

. .

[Stormin Mormon]

CY: I'm getting lost in the layers of quotes.

CY: Be nice to know the inlet tube temp.

CY: I'd expect the unit to over heat in much less than an hour.

CY: Oh, I'm not experienced. Well, that explains a lot. Hey, you want to tell me how long I've had my EPA card, and how long I've been working on central AC systems?

CY: I forget stuff, also.

I believe moisture can migrate out of the drier, and running it

CY: As an inexperienced hack, I've also learned that it takes a while to get an idle system going again, but it's got nothing to do with internal water, or putting moisture back into dryer.

CY: Gently put, my understanding is considerably different than what you're writing.

- . Christopher A. Young learn more about Jesus .

. .

[J Burns]

A condenser can cool only down to the ambient air temperature. I believe the OP said it was 80F. If the outlet tube is close to 80, the evaporator has cooled it about as much as possible. What does the inlet temperature have to do with it?

If it read 90F, I would see if I could gain efficiency by cleaning the fins, but I would not expect that outlet temperature to overheat the compressor. It would be equivalent to running the system when it was

90F outside with a condenser that cooled perfectly.

[hrhofmann]

The Compressor uses the electricity to pump the freon through the condensor (the thing outside with the fins) which cools the freon so that when it ex pands inside the thing with fins inside on the furnace(the evaporator) it c ools the air flowing/blowing through the evaporator.

[J Burns]

So he wasn't getting great cooling for an hour at a time with a dirty condenser.

[Tony Hwang]

I moved from 80% furnace and 12 SEER a/c unit to 96% efficiency and 18 SEER unit. I could get 98% furnace furnace but it is often trouble some being so fine tuned. I realized big energy saving when a/c is running.

[Stormin Mormon]

the freon through the condensor (the thing out side with the fins) which cools the freon so that when it expands inside the thing with fins inside on the furnace(the evaporator) it cools the air flowing/blowing through the evaporator.

Freon is a brand of refrigerant. Compressors can also move Isotron, Genetron, Forane, or other brands of refrigerant.

- . Christopher A. Young learn more about Jesus .

. .

[Stormin Mormon]

True, he was not getting great cooling, at all.

[Stormin Mormon]

It's nice to know the temperature drop across the coil. That's a good indicator how well the coil is working. Also, nice to check the surface temp of the coil near inlet, and different places on the coil. See if most of the cooling happens in the first third or half, for example. Plenty more data to be had.

. Christopher A. Young learn more about Jesus .

. .

[trader_4]

I would think 90F coming out of the condenser when it's 80F is probably normal. On AC units that I've seen, the pressure line even all the way back at the air handler, is still just slightly warm to the touch. Whether it's 80F or 90F it still going to drop a lot when it expands.

[trader_4]

I agree with Mr. Burns. If the pressure line near where it enters the evaporator is close to ambient temp, then cleaning the condenser isn't the issue, because it's obviously cooling. And if that's the case, if it were me, I wouldn't be paying to clean a defective unit. In my experience, it's normal for it to still be just slightly warm.

[trader_4]

That may be a problem in some cases, but I wouldn't think it would be a problem in most cases. The coil box just sits on top of the furnace and I think most of the furnace dimensions have remained the same, simply because it makes interchange, alignment with existing ducts, possible. I would think plenty of AC installers though would come up with simple excuses to get you to replace the whole thing. And I said previously, with an 18 year old furnace, there are good valid reasons for replacing the whole thing even if you can just replace the AC part. The fuel savings cited here can be one of them, depending on the efficiency of the old furnace, cost of fuel, climate, etc.