ReplyHigh heat load and humidity 85 is not a problemOriginally Posted by edwyn
Regular Guest
Hi Guys
I installed a 4 ton R22 unit (12seer), 4 ton coil, TXv, furnace. Unit came charged with nitrogen. Evac'd, charger to what I thought was a right amount of 22 then left. (installed in March) Came back today. 90 o/s temp. 80 inside. Put my gauges on 80 lbs suction 200 lbs head. no super heat, warm suction. 5 ton blower so I slowed it down to 4 ton , no change.
Dumped Freon to get suction to 65 lbs. now warm suction 8 degree split.
Added r22 to get head up to 225. Now 85 suction, cold suction line and 14 degree split. Mild super heat. ( looks like I'm going the right way, but 85 suction ?)
what do you think is going on here ? I afraid to get the suction any higher but I need the split up to 20 to cool this house.
I looked at the coil , looks like all pass's are sweating but still only got a 14 split.
Any ideas ?
Professional Member*
High heat load and humidity 85 is not a problem
AOP Committee/Professional Member*
You have to check the humidity level in the home; a high humidity will cause a low indoor split.
It could have a 14°F split with a very high latent load.
Go outside & check the split off the condenser discharge air, it should be around 110°F., that's a 20°F temp-rise, which seems okay with a high indoor humidity.
The sensible temp-split will increase up toward 20°F as the humidity level is finally pulled down.
Check to see if there is too much air infiltration into the home, as that will impede the lowering of the indoor humidity.
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udarrell
Professional Member*
Specific superheat and subcooling numbers as well as indoor wet bulb will help complete the puzzle.
Professional Member*
You will never nail a charge until you learn the value of a wet bulb reading, even when working with TXVs. 80 degrees dry bulb return air and a fourteen degree split does not sound out of line. The more readings you get, the better decisions you can make when charging a system. The phrase "get my suction up" should be stricken from your vocabulary. Learn that temperatures rule the roost.
Psychrometrics: the very foundation of HVAC. A comfort troubleshooter's best friend.
Professional Member*
Are you sure you're checking superheat? That's not how you charge a system with a txv. Did you find the leak?
Regular Guest
Thank you for your Help Darrell, no the humidity level is in the norm level. I did get heat transfer threw the condenser when I jacked up the head to 225. (hot discharge). I am concerned the head it to high right now but to get any transfer I had to get it up or I would be back at 8 split. This is a 22 unit and only a 12 seer. So 20 is not out of the capacity of this system. I just never had a floodback at such a low head and nice warm air in the return. I cant put my finger on this one. TXV stuck open ???
Professional Member
Mr. Ridley and the shop hound provide the level of assistance that is much needed. The word of the day is enthalpy. Yes spelled e n t h a l p y.
Correct data points and a psychometric chart will enlighten even the most hard headed of us!
Regular Guest
Thank you
Professional Member*
12 Seer? Your condenser (if new) is a minimum of 13 Seer. But if paired with a mismatched air handler, you'll end up with less than 10 seer.
20 degree split is out of the range of the system if you have a high entering evaporator wet bulb. Search this site for keyword: TEET (Target Evap Exit Temp). That will explain why you shouldn't always expect a 18-20 degree temp split.
Are you a tech? This is kinda sounding like a DIY.
Regular Guest
Not really a tremendous inside load. 80, humidity level norm, not wet That's why I am surprised of the high suction. Combined with only a 200 head . where is the transfer going ?.. The coil is saying I don't need liquid so it's sending it back via the by pass tube, right (high suction)? So why when I increased the head the coil (TXV) says "OK" I'll now flood the coil making the split higher ! But still the suction stays up there.
Global Moderator
This thread certainly didn't belong in AOP. Moved here but might be something that belongs in the pro section.
Regular Guest
AC biz 36 yrs. Now retired 15yrs. Out of touch with all the new tricks.
Professional Member*
You're going nowhere by focusing on pressures.
You have to take a lot more readings.
"Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler
Professional Member*
Make sure you're not drawing return air from the attic. You could have a disconnected return air duct in the attic and drawing in 95* return air. Did you take your split at the registers or at the unit?
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Regular Guest
My return air at the unit was 80, discharge at it best at the unit 66. And that ismwith a 225 head and still a 80 lb suction. Thanks for the help
Regular Guest
Thanks for all you help...
“Of all sad words of tongue or pen, the saddest are these, 'It might have been.”
Professional Member*
How do you know the humidity was "normal", did you measure it?
Without actual superheat and subcooling readings, any attempt at diagnostics is just guessing.
Professional Member
How much sub cooling? Indoor temp? How long is unit operating between adjustments? Amp draw on compressor? Did you have 20 delta t when you installed it originally?
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