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Originally Posted by socotech

Ahhh yes. Short charge. I get it. Thats exactlly what I did. Afraid to blow the head of the compressor through my chest I guess. Learn something new everyday.

I can understand the hesitancy to charge to correct subcooling when dealing with older coils and units in a hot climate but what will actually happen is your liquid line will cool down and you'll be providing your customer with 100 % of the capacity minus what it's lost because of it's general age.

You will probably be surprised to see your head drop a little.

Also you're Compressor amps will lower as you start cooling your wingdings more efficiently.

I've gotten into a few debates over this with some of our fellow techs.

You are not stacking refrigerant by providing a liquid seal and by providing a solid column of liquid to the TXVs, if your head DOES climb it's because you now have 100% capacity.


Charge it to correct super heat and let it ride. All three of my antique Yorks are charged to 12 to 15 degrees of sub-cooling and ran fine through the heat wave we had last month.

Ahhh yes. Short charge. I get it. Thats exactlly what I did. Afraid to blow the head of the compressor through my chest I guess. Learn something new everyday.

Originally Posted by socotech

I have never heard the term "short charged". What is that?

Purposely under charging a unit to avoid high head trip or extended high head run time. ( I'm not saying you did that I just use the term to describe an undercharged unit in general )

I don't believe in it. These Yorks I have have coils that are 2 pass and in horrible shape.

They are charged to 12 to 14 degrees of subcooling and run fine and that's in Houston.

Yep, I've got three just like it. ( two 20s and a 30 )

Old school controls with a choke coil to lower fan speed on the #1 condenser fan motor for capacity control.

One of our EX-technicians wen't out on a service call and destroyed the control wiing inside the panel on the 30 when I was on vacation.

I had to start from scratch to rebuild that panel.

Originally Posted by Six

Lol....

Liquid line is hot because units short charged and what does insuring a liquid seal in the condenser have to do with excessive head pressure. I'm not saying stack the coil with excessive refrigerant.

So it's ok to short charge a system because you're afraid your going to launch the heads off the valve plates ? Charge the thing correctly and then see what your head pressures are.

It's hackery . What does short charging do to a unit ? Lowers capacity, lowers efficiency causing the unit to run longer, can cause icing, poor cooling of the compressor windings, etc.

Ive got an old York 20 ton and a old York 30 ton split ( installed in the late 80s ) with Copelands in them and they're properly charged, running high head ( 325,330 ) and they're still in one piece after 7 years of PMs.

I have never heard the term "short charged". What is that?

Originally Posted by Six

317 on a unit that old 98 ambient is actually not that bad.

Does that unit have the mechanical timer ?

Yea its got an old camstat timer

Originally Posted by supertek65

135* SCT
130* LLT
005* SC
079*SLT
044* sst -74# SP
035* SH

HIGH EVAPORATOR TEMPERATURE
130* LIQUID ENTERING EVAPORATOR
HIGH EVAPORATOR CAPACITY
LOW CONDENSER CAPACITY
EXTREMELY LOW NET REFRIGERATION AFFECT

it is clearly low on refrigerant, i would like to see how high the head is after he gets 12 * subcooling?

Lol....

Liquid line is hot because units short charged and what does insuring a liquid seal in the condenser have to do with excessive head pressure. I'm not saying stack the coil with excessive refrigerant.

So it's ok to short charge a system because you're afraid your going to launch the heads off the valve plates ? Charge the thing correctly and then see what your head pressures are.

It's hackery . What does short charging do to a unit ? Lowers capacity, lowers efficiency causing the unit to run longer, can cause icing, poor cooling of the compressor windings, etc.

Ive got an old York 20 ton and a old York 30 ton split ( installed in the late 80s ) with Copelands in them and they're properly charged, running high head ( 325,330 ) and they're still in one piece after 7 years of PMs.

135* SCT
130* LLT
005* SC
079*SLT
044* sst -74# SP
035* SH

HIGH EVAPORATOR TEMPERATURE
130* LIQUID ENTERING EVAPORATOR
HIGH EVAPORATOR CAPACITY
LOW CONDENSER CAPACITY
EXTREMELY LOW NET REFRIGERATION AFFECT

it is clearly low on refrigerant, i would like to see how high the head is after he gets 12 * subcooling?

Originally Posted by Six

317 on a unit that old 98 ambient is actually not that bad.

Does that unit have the mechanical timer ?

317 on a unit that old 98 ambient is actually not that bad.

Does that unit have the mechanical timer ?

Went by and checked it yesterday. Its down to 280#. Its also 98* ambient in the shade.

317# head sounds high!

Single row condenser coils. They look clean, but I'll be honest....I did not wash them.

High load (80*). One txv and no solenoid. 100*+ ambient. There is possibly some condenser air recirculation too. It has a solid brick wall on three sides about 20" out.

Originally Posted by socotech

Changed the oil three times. Oil was nasty. Replaced suction core and liquid line drier. Checked suction screen. Its now running with 50 psi oil diff. Loading and unloading properly ( low voltage was wired wrong). All seems good except high superheat (35*) and low subcool (5*). 74 suction 317 liquid line. I know probably still undercharged, just wanted to let it run a while and check it after space has cooled.

Two TxVs in that AHU or just one ?

I've got an old York 15 ton that splits off into two circuits at the AHU with two solenoid valves.

Sounds undercharged a bit and maybe you're dealing with a lot of load.

I'm betting on a plugged condenser.

75# suction line
317# liquid line

35* at the compressor is not that bad!
what is 317 liquid line?
do you have 75# suction or 75* suction line????????

Changed the oil three times. Oil was nasty. Replaced suction core and liquid line drier. Checked suction screen. Its now running with 50 psi oil diff. Loading and unloading properly ( low voltage was wired wrong). All seems good except high superheat (35*) and low subcool (5*). 74 suction 317 liquid line. I know probably still undercharged, just wanted to let it run a while and check it after space has cooled.

Thanks for the help. I'll let you know what I come up with.

I think Carlyse has the jump on Copeland for better load and unloading of semi hermetic compressors.