25t hp aaon splits installed by resi co

[svc]

I have recently taken over a few 5 year old 25t aaon hp splits that run about 75 psi higher hot gas than liquid line. They are doomed from the beginning due to low airflow. To be corrected soon. but why the big pressure diff. is this typical for aaon. I vagually remember someone telling me that aaon uses the same condensor coil on diff. tonnage units! Not sure if thats true! On a 95 degree day I will have 300 hot gas and 225 LL. 10 sub and if I remember right high superheat with a 45 -50 psi suction! Could this all be from low airflow causing txv to produce low volume of refrigerant flow?
Thanks in advance, svc

[Krzyd]

I have recently taken over a few 5 year old 25t aaon hp splits that run about 75 psi higher hot gas than liquid line. They are doomed from the beginning due to low airflow. To be corrected soon. but why the big pressure diff. is this typical for aaon. I vagually remember someone telling me that aaon uses the same condensor coil on diff. tonnage units! Not sure if thats true! On a 95 degree day I will have 300 hot gas and 225 LL. 10 sub and if I remember right high superheat with a 45 -50 psi suction! Could this all be from low airflow causing txv to produce low volume of refrigerant flow?
Thanks in advance, svc

We've not had any positive situations with AAON splits, does your system have hot gas bypass, and or a reheat coil?

[big johnson]

Is this an R-22 system? Are you sure you have 10 degrees sub cooling and over 40 degrees superheat? That's very strange. Are these scroll compressors or recips?

[slimwoodie]

lotsa trouble here w/ AAON
one of my customer's just told them to come 'n get one of thier new unit's Off the Roof
bring bck one that'll work for more than a week straight

[cyro]

That's why I love them. Easy to work on, neat wiring, blowers slide out nice, compressors at chest level.

Oh the most important thing they break down allot and I make money.

I really like it when the first stage heat breaks no other stage will work because of there wiring job, or on there larger units that have two parts of everything when one part breaks on one half of the unit no heat stages will work on the good half either because of there wiring job.

Oh I forgot the lovely angle of there condenser coil does not allow rain to wash the coil so you must keep up on this or you will be replacing condenser fan motors like water. There new condenser motors don't drop down all the way into the motor cradle either so you have to hold them up with one hand while tightening the belly band with the other hand.. There shorter

[sabre11134]

a lot of problems are from lack of correct start up & commissing. we start up a lot of aaon units. on a regular schedule we see a lot of aaon units not programmed or started correct.

[svc]

Hey guys, there is no hgb or reheat coil/dehumid. They are scrolls and r-22. I have to agree they are easy to work on and they do break down alot. I am trying to keep positive in thinking that when we get the airflow corrected It will make a huge diff. Customer states no compressors are original. wow. This unit is old school there is no wattmaster involved.

[ACCMan]

How close are the condensing units to each other?
What is the entering air temp. on the condenser?
What is the leaving air temp. on the condenser?
What is the actual superheat and pressures?
Delta T across the evap.?
etc....etc...

As stated above... checking for set-up and installation problems will eliminate a lot of re-ocurring problems.

[svc]

Took some readings today after repairing a leak where the hot gas line enters condensor area. You would think they could have made the holes a little larger for the refrigerant piping. Readings are on 1 unit with 1st stage running. 2nd stage is grounded. as for my other unit 1st stage grounded and rev. valve stuck in heat mode. So there is only 12.5t out of 50t capable of running. The pressure differential I stated in my beggining post didnt show up on this one! but its not 95 degrees yet either.

@ compressor: 48 suction, 255 head, 117 hot gas line

@ lineset: 58 suction, 240 LL pressure, 9 sub, 23 super

condensor entering=78 condensor leaving=103

evap delta= 10 (interwoven stages)

ambient=78

[Airmechanical]

a lot of problems are from lack of correct start up, we start up a lot of aaon units. on a regular schedule we see a lot of aaon units not programmed or started correct.

Bingo, also aaon makes real nice pkg units i like their 7-1/2 and 10 ton pkgs.

never had an issue with the heaters!



.

[airman72mod]

We've not had any positive situations with AAON splits, does your system have hot gas bypass, and or a reheat coil?

i have installed hundreds of aaoons on quik trips in kc and ok they are tempormental but easy to work on. Have you checked to see if condensor is clean inbetween split coils...common problem , also have correct condensor fans?