charging small reach in subcool question

[flangehead]

If I am charging up small reach in cooler, ambient temp= 70f, add 30= 100f convert to 124 psi which is proposed high side press. for 134a. This is a cap tube sys. What should temp be at condensor outlet? (liquid line)

[Freezeking2000]

I have never checked that in 12 years of fractional H.P. service. You suction should be 11-17 psig with 10-20 degrees superheat. Put a digital thermometer in it to see the temp dropp.

[Retro]

Originally posted by flangehead
If I am charging up small reach in cooler, ambient temp= 70f, add 30= 100f convert to 124 psi which is proposed high side press. for 134a. This is a cap tube sys. What should temp be at condensor outlet? (liquid line)


If all things are equal, clean and good air flow such like new. 25 to 30 deg less than discharge line temp.

[gosteelers]

if it was me i would try my hardest to find factory charge & match it but i assume u tried. i normally do the +30 when i need to. it works for me & hopefully as it will for u. providing cond coil & evap are clean & box runs for at leat 15 minutes . but hey thats just me. if there is a better way i would like to know. one tech told me to stick digital therm probe inside evap coil & temp should match up with pressure. thats his way. good luck

[Dad]

There is another way and it works OK when the system has been so hacked up that the factory charge will be no where close

Charge the system with the evap motor off.

Continue to add 2 oz at a time until it frosts back to the compressor. Stop and start the evap motor again.

It will be very close.

[shaka]

Flangehead If you are just charging the unit you discribe
then the box temp is very hot.

At this point your head pressure is probably have a higher
condenser TD than 30. superheat and subcooling is pointless
and does not mean squat at this point.


Also since its a cap tube system then you should be more concern for the superheat not subcooling.

Cap tube system are critical charge. I suggest you weigh in the charge and if you want to check all the SH and SC then check it when the box is at the proper temp.

When you first start a Fractinal HP unit. the head pressure are a lot higher due to very high evap load. when the load decrease so does your head pressure.
Hope this helps.

[hvacmd2002]

Never in my life have I checked superheat or subcool on a critically charged system. Weigh in the charge and walk away. It doesn't have to be that complicated

[coldmilk]

I agree with lusker, you can charge the system slowly until you see the frost line coming out of the evap then pull some out to take the frost line back to evap.

[smurphy]

Originally posted by coldmilk
I agree with lusker, you can charge the system slowly until you see the frost line coming out of the evap then pull some out to take the frost line back to evap.

Thats not what lusker said,disconnect evap motor till a frost line comes back to compressor, then reconnect motor and charge SHOULD BE CLOSE.Never tried this method butwill try soon.If there is no data plate with the correct weight in charge, i normally charge till my highside reachs about 115 degrees,i watch the box temp come all the way down to temp, when the box temp reachs idea conditions i shoot for a 20 degree suction and between 105 and 120 degree head depending on the superheat.

[Dad]

Originally posted by smurphy

Originally posted by coldmilk
I agree with lusker, you can charge the system slowly until you see the frost line coming out of the evap then pull some out to take the frost line back to evap.

Thats not what lusker said,disconnect evap motor till a frost line comes back to compressor, then reconnect motor and charge SHOULD BE CLOSE.Never tried this method butwill try soon.If there is no data plate with the correct weight in charge, i normally charge till my highside reachs about 115 degrees,i watch the box temp come all the way down to temp, when the box temp reachs idea conditions i shoot for a 20 degree suction and between 105 and 120 degree head depending on the superheat.

smurphy

You put all of that together, shake it up real good, it is called experiance. :)

When you have to fly by the seat of your pants on a cap system the above is where I start and hopefully end.

[rayr]

Yep after 5 or 6 u will get the hang of er. Not rocket science.

[taylortech]

I agree with coldmilk but will try out what Lusker said.