20 Degree split

[Anthony49]

I am A new tech and after charging a system the way I was taught in school. I went and checked the tempature at the supply and at the return and I was looking for a 20 degree differential. However, it was only 12. Supply 71 and Return 83. After researching this forum I found that if it is above 20 it is an indication there is poor or low air flow. Dose anyone have experience as to what would cause the the differential to be below the 15-20,
that I should be getting. Thanks in advance.


Anthony49

[iraqveteran]

20 split across the coil.....


with that being said. Get 14 more posts and get your pro status...


There is a wealth of knowledge in the Pro forums. These tech details we cannot discuss here in the open forums. Too many DIYers with wandering eyes.


Get Pro. And we can help you out more than you know. Good luck and get postin. See ya on the flip side.

[beenthere]

A. Was that at the supply and return of the air handler, or at registers.
B. How did school teach you to charge.
C. Is it a fix metering device, or TXV system.
D. What was the indoor wet bulb, what was the out door dry bulb.
E. Did you verify air flow.
F.What was it in CFM.
G. What size is the system.
H. Why do some guys ask so many questions, when they were only asked one.

[BaldLoonie]

If a sauna, 12 over the coil may be OK. If dry and cool, NOT!

And yes, we normally don't talk technical here so work on getting your pro status.

[snewman24]

These tech details we cannot discuss here in the open forums. Too many DIYers with wandering eyes.

I've always found it interesting how some people interpret the forum rules:

2. Do-It-Yourselfers - not here.

This site is for industry professionals and folks seeking HVAC/R advice and knowledge. Please do not ask for step by step instructions on purchasing, installing or repairing your own HVAC equipment, that is our job and our livelihood. We are generous, but not to a fault.

Questions of this type will not be answered and may be deleted.

[cnpro18]

How did they teach you to charge a system in school?
Was the unit flat?
New system?
Metering Device?
What type refrigerant?
12 degrees....not good....something's wrong.

[Dallas Duster]

I am A new tech and after charging a system the way I was taught in school. I went and checked the tempature at the supply and at the return and I was looking for a 20 degree differential. However, it was only 12. Supply 71 and Return 83. After researching this forum I found that if it is above 20 it is an indication there is poor or low air flow. Dose anyone have experience as to what would cause the the differential to be below the 15-20,
that I should be getting. Thanks in advance.


Anthony49

Keep answering and asking questions don`t let these guys scare you . Do a search I am sure there is alot of info in the regular area`s. Besides you have to get that post count up somehow. The pro section only has so much info questions like yours gets asked in there too.

[sir fix alot]

i smell home owner looking for advice, or tech. that need's to go back to the school he went to and get a re-fund. or i could be wrong

[thandar56]

Keep answering and asking questions don`t let these guys scare you . Do a search I am sure there is alot of info in the regular area`s. Besides you have to get that post count up somehow. The pro section only has so much info questions like yours gets asked in there too.

check the air flow and pressures it might be low on refrigerant or a leak

[Anthony49]

We all go to school to learn some instructors are better than others if you were only taught one way, chances are that all you know until you learn differently. I am only here to learn more than I already know, My current book Refrigeration & Air Condition Technology 5th Edition, Nor my instructor felt the need to cover this in any more detail than the fact that the Air Condition were designed to produce a tempature difference of 18 to 20 degree difference across the evaporator when the system is operating. Return air is 20 degrees warmer than the supply air. The Supply air is about 10 degrees warmer than the evaporator metal and the evaroporator metal fins are about 10 degrees warmer than the refrigerant. the refrigent is always the coldest.

Instead of me asking for a refund why not help me be a better tech, I have read the book and have searched this forum for answer. My only question was why and what would cause it to go below 18 Degrees.

As for charging a I was taught to charge it to 68.5 psi on the low side this was a 3 ton unit, R-22, fixed device. the tempature was at the return register and the supply resigeter. Only dry bulb tempature was taken.

[Tiger93rsl]

How did they teach you to charge a system in school?
Was the unit flat?
New system?
Metering Device?
What type refrigerant?
12 degrees....not good....something's wrong.

suction like beer can cold man

[cmajerus]

As for charging a I was taught to charge it to 68.5 psi on the low side this was a 3 ton unit, R-22, fixed device. the tempature was at the return register and the supply resigeter. Only dry bulb tempature was taken.

don't go by what you learned at school then, all kinds of factors go into what you get for a suction side reading, the way to charge a system properly is with pressures and line temps. You may have the charge wrong, or airflow, its hard to tell without all your readings. 12 degree differential may or may not be ok where you took the readings, the 20 degree split should be at the equipment not on total duct system. Like others have said get your post count up and apply for pro status to get some more technical advice. DO you work for someone that can help you learn the proper techniques of diagnosing systems or are you trying to work on your own right out of school?(not recommended)

[captain73703]

i 16-22 is a good split and over 23-? air flow problems that in you book. u are most like low on charge. i have the 5th ed too. there is more than enough info there. are you sweating back at you suc valve? is your liquid line warm? not hot warm.