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

[Ashton Crusher]

That doesn't sound like all that hot a temperature for teh compressor to me. But I'm just guessing. I know I've had compressors in the past that would run all day long and be so hot that you couldn't touch them without getting burned but they never stopped running. So maybe it's overheat protection is a little too touchy.

I also got the impression from my AC guy that part of having a proper amount of refrigerant in the system is so that there is a certain amount of COLD refrigerant that for whatever reason trickles into the compressor to keep it from getting too hot. I got the impression that a low charge meant there wasn't enough of the "left over cold refrigerant" to cool down the compressor and that could make the compressor run hot. Sooooo... if there is any truth to that I would hypothesize that if you were to have your AC guy shove some additional "freon" into your system, whether he thinks it needs it or not, that it might make the compressor run cooler and solve your problem.

[Boris]

Tony Hwang wrote in news:%Imbx.22350$bM1.18144 @fx01.iad:

I guess I should have said that the tech said he'd replace with a 3.5 ton a/c unit. I assumed the current one is of similar capacity. He does know the size of the house. Is there a place online where I can calculate the size needed?

[Boris]

Boris wrote in news:XnsA4AD8C93F1B45nospamnospaminvalid@213.239.209.88:

snip

Well, I just looked around, and some sites give me 4.5 tons, and this one gives me 3 tons.

calculator

[Boris]

Ashton Crusher wrote in news: [e-mail]:

Yes, the tech did say that freon also cools the compressor. He checked it, and said it was fine. But...I had to ask him to check it. This company, SierraPacific (Rancho Cordova, CA), is the company that installed solar pool heat on my dad's roof 30 years ago. It's been maintained and keeps the pool between 84 and 90 in the summer. I've got an annual maintenance contract with them. With the a/c, my dad never had a contract, and would just call any old company when service was needed. I did add to the solar contract, an HVAC maintenance contract last month, and they have been very responsive when I call them out. The last two visits were about 2 hours each doing diagnostics, with no charge. They come highly rated locally, and on Angie's List (for what it's worth),and drive around in expensive, well stocked vans. However, they are always trying to sell something.

I'm thinking I should clean the compressor fins and then see what happens. If no better, I may call another company out for a second opinion.

As you can tell, there's a pool at this house. All this reminds me of last year when I hired a pool guy (I live two hours away in the S.F. Peninsula) to take care of the pool. The first thing he told me was I needed a new sand filter. Funny, it always worked well, even though the zeo-sand was 8 year old on a ten year life span. He wanted $1000 to put in a new filter. I knew nothing about pool maintenance (I'd rather not have a pool, but this is Sacramento), but I taught myself, and cleaned up the filter for about $50. Works great now.

But I digress...

[Tony Hwang]

Hi, Yes, Google it, you'll find "manual J calculation method" to calculate. Over-sizing is common mistake causing short cycling system. If you decide to go for new system, replace both a/c and furnace for improved efficiency resulting cost saving in power consumption and more comfort. I am just a retired EE but I went thru the system replacement at my home(~20 yo). I let the installer do mechanical part and electrical part I did saving some $$. Going into 4th year and not an issue yet. I just replace air filter twice a year(16x25x5 size, MERV 11) Just finished cleaning condenser coil and checked Puron level as cooling season begins.

[Ed Pawlowski]

That site is giving vague averages. Fist step, did the old unit do the job? If yes,it is probably right or very close to it.

The "square foot" calculations just take a lot of averages, but may be way off on some houses.

Proper calculations consider: Exposed walls and direction they face. Insulation Ceiling/roof and insulation Window square footage and type

Too small, you won't be cool. Too big, you won't remove the humidity and it will be cold and clammy.

[Stormin Mormon]

The condenser is clogged with dust, and needs to be professionally cleaned. Use the purple stuff. Any good tech would have picked up on this very simple diagnosis in a few minutes.

Gee whiz, you told the entire class what was wrong, wonder if I'll be the only simple minded (but excellent quality) AC tech to pick up on the answer you handed us on silver platter.

Your guy and tech support "baffled". What a bunch of maroons.

BTW, remit $147.50 for consultation. I also make house calls, buck a mile (one way) from western NY, USA.

I have an uncle in Los Angeles who would love to have me visit.

- . Christopher A. Young learn more about Jesus .

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[Stormin Mormon]

More than once, I've worked on radiator looking things that looked clean, but benefitted greatly from professional cleaning. I'm really amazed the tech and tech support didn't figure it out.

- . Christopher A. Young learn more about Jesus .

. .

[Stormin Mormon]

Hey, tell you want. If you decide to replace the entire unit, let me know what the quote is. I'll fly out have my tools shipped via ground, and do the job for much less than the replacement cost.

And visit my uncle in LA while I'm out.

I can provide at least one reference, fellow I did work for about a year ago. He bought a trailer and heat pump. I drove to South Carolina and serviced his system. Runs fine now, and even shocked the #### out of the seller (who made my friend sign an statement that the heat pump was totally beyond repair).

- . Christopher A. Young learn more about Jesus .

. .

[Stormin Mormon]

The heat pump my friend Kevin had, was used by smokers. My professional cleaning did so good, you couldn't even smell the stink when I got done.

And, golly did it ever stink.

- . Christopher A. Young learn more about Jesus .

. .

[Stormin Mormon]

Some have TXV and some have orifice (which for some reason is called a piston). If there is a restriction, the house won't cool well, but also there will be much less heat coming into the compressor. I doubt that's the problem.

- . Christopher A. Young learn more about Jesus .

. .

[Stormin Mormon]

Well, certain to happen before too long. Just add a couple pounds of that freon stuff, and it will be just fine. Someone had to say it.

I stand by my original diagnosis, and also my offer to come out and fix it.

- . Christopher A. Young learn more about Jesus .

. .

[J Burns]

This page says a blockage will overheat the compressor.

[J Burns]

Maybe he was baffled because he knew the condenser was cooling properly. Don't you think he checked the temperature of the outlet, with a thermometer or by touch?

If the condenser were dirty enough to overheat the compressor, how would he get a 16F drop when it was restarted? Why would it work fine for an hour or so?

If there's moisture in the freon, most would probably pass through the expansion orifice. It might take an hour for enough ice to build up, to block it enough to overheat the compressor. As soon as the compressor stops, the indoor blower heats the evaporator to 74. No more ice. The tech starts it can can't find anything wrong.

BTW, remit $247.50 for insultation by insinuation.

[Stormin Mormon]

CA is total expensive, also. I'm astounded that the tech (and telephone tech support) could not diagnose some thing so obvious. Me, I'm a fat, balding old guy who is running out of teeth. I'm no one special, just a common sense retread (polyester belted with suspenders) who thinks in simple terms.

- . Christopher A. Young learn more about Jesus .

. .

[Stormin Mormon]

With water in the system, it is very possible to block the flow of refrigerant. In that case, the refrigerant stops absorbing heat, and the compressor has much less work to do. So, no, doesn't over heat.

- . Christopher A. Young learn more about Jesus .

. .

[Stormin Mormon]

I noted inother messaged that you'd found an online heat load calculator. I think there is a misconception that if the AC isn't working, to replace it with a larger one. I had a customer say to me one time "well, if three and a half tons isn't cooling, maybe I need five?". The probelem was that he was not getting three and a half tons of cooling, he was getting zero cooling.

BTW, in that case, I checked the refrigerant, amp draw, temps, etc. A professional cleaning, and he was back to supply air vent temps about 53F, if memory serves. He was pleased for my simple minded, and totally correct diagnosis and treatment. He was ready to invest three grand in a system.

Freon (R) is a brand name, like Cheerios, or Sunoco. Refrigerant is the descriptive term, like breakfast cereal, or gasoline. I do have some Freon (R), and also some Forane (R) and maybe some Isotron (R) and some Genetron (R).

- . Christopher A. Young learn more about Jesus .

. .

[Stormin Mormon]

Says it's one of several possible causes. The article said that low suction pressure can cause a higher than normal pressure ratio. What I've found, is that restrictions cause lower discharge pressure and temperature.

If you read down two paragraphs, or maybe three, you'll find my diagnosis listed.

- . Christopher A. Young learn more about Jesus .

. .

[Stormin Mormon]

CY: And how would the OP know that?

CY: Possibly, but he needs more data to tell if the condenser is cooling properly.

CY: Because the compressor discharge can be up to 250F (not often, but now and again I see temps this high). The outdoor air is 80F or so, and the condenser has time to cool from 250F (at the discharge) to 80F or so. After an hour of pumping heat into the condenser, the condenser temp goes up again.

CY: I read the OP message, and got a totally different diagnosis from what he wrote.

CY: I can get insulted for free, I'm not paying. But, the OP can't even pay for a correct diagnosis, which makes me very valuable. I even also offered to go fix it for him.

[Boris]

Ed Pawlowski wrote in news:lOednfrCQ47U [e-mail]:

Yeah, the current unit does the job just right. But, I haven't been able to determine it's capacity. I guess I can call American Standard. My dad was meticulous and detailed about keeping records/manuals for every bit of infrastructure in his house, except for the a/c. Go figure.