a/c not big enough?

[hamons]

yes -- performance is consistent with last year.

[hamons]

Ok -- Here is todays performance

Time -Outside -- Inside --------- thermostat set at 75 degrees
8am --- 87 --- 78
9am --- 94 --- 78
10am --- 95 --- 77
12:30 --- 100 ---78
1pm --- 101 --- 77
2pm --- 101 --- 77
4pm --- 100 --- 78
5pm --- 100 ---79
6pm --- 99 ---79
7pm --- 94 ---79
8pm --- 92 ---79
10:30--- 90 --- 78
11:30 --- 88 --- 79
Current -- 85 -- 79 -- A/c has not shut off since it went ont his morning

What do you guys think?

[tigerdunes]

hamons

This is not normal operation for a properly sized AC condenser and anyone who suggests that it is is either being intellectually dishonest or ignorant. Your dealer should provide in writing a load calculation both heating and cooling. You should sit down face to face with installing dealer/owner ASAP.

IMO

[leapfrog]

Originally posted by hamons
On the news last night they had a n hvac guy onthat said it is not reasonable to expect your homes a/c to lower the temp more than 20 degrees

Don't believe everything you hear on the news. Using this logic you wouldn't find the inside of a home or building in Phoenix under 90 degrees in the peak of the summer heat.

[leapfrog]

Originally posted by hamons
They did not do a manual j or d

There is at least one source of your problem. They guessed at the sizing, and they were wrong.

Take 'em up on that guarantee.

[Shophound]

Originally posted by hamons

Subcooling required 9 derees
Liquid line pressure 201 #
convert above to temp - 72 degrees
liquid line temp - 6 degrees
actual subcooling 9 degrees
suction line pressure - 101 #

Were these numbers from the installer's startup data? Are we talking R22 refrigerant? If so, that suction pressure looks high, and the head pressure low. Those numbers look off to me, but if they're the real deal, I'd be looking at the compressor. As it is there's not enough data to make an internet approximation...would need superheat, ambient air temp, indoor delta T, etc. to get closer.

[hamons]

Yes - that is the start-up data from THIS season.

My sytem uses r-410a

return air temp was 51 - supply air temp was 71 - outside air temp was 60

The superhet part of the form is crossed out -- is this because of the TXV?

[dynalowrider79]

if those are r410 pressures i would have to say somthing is wrong there on startup i would expect to see a suction of around 120-130 and a head closer to 270-280 somthing doesnt sound correct here sounds a little undercharged to me

[hamons]

Service manager came out today. had to leave jobsite (i'm a landscape contractor) early to meet him.

He said that he was going to slow down the fan because we were only getting a 15 degree drop across the coil and he wants a 20 degree drop.

When i explained they had done this last year he said that they might not have adjusted the line pressure to go along with that. Then he tried charging it up a little over and still could get a max of 17 degree drop.

Another mystery was that the house is 79 degrees -- but the return air is 73. Couldn't figure that out. Of course all of my returns are on the floor -- so I wonder if that is part of it.

He was coing to call Bryant and talk to theri represenative. He was thinking maybe the txv was not operating efficiently.

[blockey]

Have you considered any air leaks on the supply or return. Too much outside air sucked into the return or losing too much supply would reduce system efficiency.

[alexb]

I'd like to post the pressures from my system which was recently started up on July 14th. R22 system, 2.5 ton new matched system from Am. Std.
At time of startup, when they charged the system:

Outdoor temp: 90
Indoor temp: 82
drop accross coil: Not measured
System running for 20min
suction line: 75
Liquid line: 150

System label says it should be charged to 10degrees subcooling. Do these numbers look right at all? Head pressure for ~90degrees outdoor temp indicated I should have ~163psi from the chart supplied with the unit. I've measured the delta across the coil; and the best I can get is 76in, 61 output - 15degrees.

The tech was holding his container of R22 upside down when I was outside talking to him - maybe he ran out of refer??

[leapfrog]

Originally posted by leapfrog

Originally posted by hamons
They did not do a manual j or d

There is at least one source of your problem. They guessed at the sizing, and they were wrong.

When are they planning on doing the load calculation to see what size system you really need?

[pstu]

Keeping in mind I am not a pro but a homeowner... you have no more than 17 degree delta-T across the coil, at normal airflow CFM, correct? Isn't that proof the machine is not delivering cooling as designed to?

Your temperature readings at supply and return sound crazy, I have to believe there is a typo. Are you actually getting 73 degrees somewhere in the house?

This is a pretty interesting puzzle, hope you find something wrong soon so you can fix it. I would be very wary of any solution which upsizes the AC, as 1) it ignores the existing delta-T problem, and 2) there is a real likelihood your duct system will become inadequate at the higher CFM airflow.

Best of luck -- Pstu

P.S. Oops, I typed too fast and did not think fast enough. The fact you used to have 1 ton more, probably means you have no problem with airflow.

[Edited by pstu on 07-27-2006 at 10:38 AM]