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Old 08-19-2012, 08:14 PM   #1
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A/C Charge - "Beer Can" Method vs. Gauges


Is checking the the AC lines by temperature "feel" ever wrong?

I've never found a case in either my home or car ACs where the system was cooling properly and one line wasn't "beer can cold" and the other warm to the touch.

Reason I'm concerned is that I just had 2 new 410a SEER 13 systems installed and neither passes the beer can test, although one is markedly better.

I popped the hood on the more anemic of the 2, which isn't putting out much condensate either, and found only the lower half of the A-coil to be cold and sweaty.

I suspect undercharge - what do you experts think?

Thanks

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Old 08-19-2012, 08:23 PM   #2
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A/C Charge - "Beer Can" Method vs. Gauges


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Originally Posted by thatbobguy View Post
Is checking the the AC lines by temperature "feel" ever wrong?

I've never found a case in either my home or car ACs where the system was cooling properly and one line wasn't "beer can cold" and the other warm to the touch.

Reason I'm concerned is that I just had 2 new 410a SEER 13 systems installed and neither passes the beer can test, although one is markedly better.

I popped the hood on the more anemic of the 2, which isn't putting out much condensate either, and found only the lower half of the A-coil to be cold and sweaty.

I suspect undercharge - what do you experts think?

Thanks
need to put gauges on system to be sure as to what is going on....I never guess...even though beer is always cold.

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Old 08-19-2012, 08:55 PM   #3
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A/C Charge - "Beer Can" Method vs. Gauges


Its vey possible that they aren't fully charged.

I have had many units that the vapor line wasn't anywhere near beer can cold and it was charged properly. All depends on the conditions at the time your checking it.
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Old 08-20-2012, 02:43 PM   #4
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A/C Charge - "Beer Can" Method vs. Gauges


Is that American ice cold beer or BTU's? ( British Temperature, Ugh!) Use the gauges and a thermometer, read the tech chart, that's what they're there for. What feels cold to you may just be tepid to someone else. Pumping in gas till it feels right is a good way to blow a hole in a joint or wreck a compressor.
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Old 08-20-2012, 08:15 PM   #5
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A/C Charge - "Beer Can" Method vs. Gauges


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Is checking the the AC lines by temperature "feel" ever wrong?
Years ago when I was just the building maintenance guy I had to let the HVAC guys up on the roof and bring them to the equipment requiring work. Those were the days when the tech grabbed the suction line and let that be his guide as to what to do. Seems like it always worked for them. But that was just their initial check...the guages always came out for the final result. But the "ice cold beer" test is a good start.
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Last edited by Missouri Bound; 08-20-2012 at 10:55 PM.
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Old 08-20-2012, 10:52 PM   #6
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A/C Charge - "Beer Can" Method vs. Gauges


Good topic. My low side is not that cold. Doesnt sweat. Still have 58* coming out the ducts. Even when its 100* F outside. Is it low on 403 or does it have too much ? Cant be right if the line is not "beer can cold".
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Old 08-21-2012, 07:00 AM   #7
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A/C Charge - "Beer Can" Method vs. Gauges


if its warm out you should be at least seeing the suction line sweat
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Old 08-21-2012, 07:23 AM   #8
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A/C Charge - "Beer Can" Method vs. Gauges


Bad TXV's, failing compressor valves, plugged condenser coils, and return air leaks can cause a warm suction line.
Gauges, meters and thermometers will show these alternate causes.
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Old 08-21-2012, 07:46 AM   #9
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A/C Charge - "Beer Can" Method vs. Gauges


Quote:
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if its warm out you should be at least seeing the suction line sweat
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Bad TXV's, failing compressor valves, plugged condenser coils, and return air leaks can cause a warm suction line.
Gauges, meters and thermometers will show these alternate causes.
Its only a year old. No return air leaks. May sweat at the outside unit but I'm not seeing it at the A coil. Kept the house warm last winter when it was 12* F outside.
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Old 08-21-2012, 07:57 AM   #10
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A/C Charge - "Beer Can" Method vs. Gauges


If it has leaked enough refrigerant in a year to stop condensating you should call your installing contractor to repair this under warranty.
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Old 08-21-2012, 10:23 AM   #11
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A/C Charge - "Beer Can" Method vs. Gauges


New high efficiency A/C units may have a "variable speed" compressor. If just a little cooling is needed, it would run slower. If a lot of cooling is needed, it would run faster.

With that said, I should think if not much cooling was needed and the compressor was running slowly, the pipes would not be very cold/hot.

(Older units are just on/off.)

The question is if they are keeping the house cool?
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Old 08-21-2012, 11:42 AM   #12
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A/C Charge - "Beer Can" Method vs. Gauges


[quote=Billy_Bob;993363]New high efficiency A/C units may have a "variable speed" compressor. If just a little cooling is needed, it would run slower. If a lot of cooling is needed, it would run faster.
/quote]

Since I do not know...is that accurate or an assumption? Will the system perform properly with "a little cooling"?
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Old 08-21-2012, 02:05 PM   #13
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A/C Charge - "Beer Can" Method vs. Gauges


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New high efficiency A/C units may have a "variable speed" compressor. If just a little cooling is needed, it would run slower. If a lot of cooling is needed, it would run faster.

With that said, I should think if not much cooling was needed and the compressor was running slowly, the pipes would not be very cold/hot.

(Older units are just on/off.)

The question is if they are keeping the house cool?
Keeps the house cool, just fine. I will get some gauges on it if I ever get my storm damage project done.
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Old 08-21-2012, 04:17 PM   #14
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A/C Charge - "Beer Can" Method vs. Gauges


[quote=Missouri Bound;993411]
Quote:
Originally Posted by Billy_Bob View Post
New high efficiency A/C units may have a "variable speed" compressor. If just a little cooling is needed, it would run slower. If a lot of cooling is needed, it would run faster.
/quote]

Since I do not know...is that accurate or an assumption? Will the system perform properly with "a little cooling"?
Only 2 actual manufacturers(ok 3 if you count daikin) have variable speed compressors in ducted conventional split systems.


Both of them will have sweat on the suction line if the indoor VS blower is set up for comfort(low CFMs).
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Old 08-22-2012, 08:53 PM   #15
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Originally Posted by beenthere View Post

Only 2 actual manufacturers(ok 3 if you count daikin) have variable speed compressors in ducted conventional split systems.


Both of them will have sweat on the suction line if the indoor VS blower is set up for comfort(low CFMs).
That's interesting - I always thought the blower just ran on 2 speeds, high for A/C and low for heat.

So if the blower speed selected (assuming VS) was too high - no sweat and little condensate?

Would that affect humidity too? My AC doesn't feel as "dry" as I'm used to.

Thanks


Last edited by thatbobguy; 08-23-2012 at 09:51 PM. Reason: quote
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