A/C basic questions:

[cralx2k]

-The temperatures and PSIG are applied to all A/C that ask for R22 even with different tons capacity?


-What is the relationship between the length of the lines and temperatures and PSIG?


-If outside temp is over 95F. How the condense is cooling the liquid?


-If A/C has low *****, can a tech determine how many lbs is need by just checking the manifold gauge? How can it be done by going by the PSIG?


-How can I find out the temperature for superheat and sub cooling is right? Is it different for each coolant?
Thanks Carlos

[Gary]

Maybe this will help:

http://www.refrigeration-engineer.co...ad.php?t=19701

[nike123]

-The temperatures and PSIG are applied to all A/C that ask for R22 even with different tons capacity?

All gases has relation between temperature and pressures. Question is not logical. Rephrase.

-What is the relationship between the length of the lines and temperatures and PSIG?

Same as above! Longer the lines, pressure drop is higher, saturation temperature changes. We need some context for meaningful answer.

-If outside temp is over 95F. How the condense is cooling the liquid?

If gas entering condenser is at 120°F and air entering condenser is 95°F than, at right pressures, that gas could change state to liquid (condense) at say 100°C without problem.
Check at Google "Saturation pressure" and "latent energy".
In refrigeration, everything is connected with change of state of matter (refrigerant) from gas to liquid and vice-verse.

-If A/C has low *****, can a tech determine how many lbs is need by just checking the manifold gauge?

No!

How can it be done by going by the PSIG?

It cannot be done! More information's needed and still cannot be determined how many! It only could be determined if it is short of refrigerant or overcharged but amount in lbs stays enigma.
Check link supplied by Gary.

-How can I find out the temperature for superheat and sub cooling is right?

Check link supplied by Gary.

[cralx2k]

Thanks Gary, great info. Where I can buy your book?

[cralx2k]

Thanks for the reply nike123. I just started my HVAC education. My questions were about what I’m studying and the last A/C repair in my home.
I have the “Refrigerating & Air Conditioning Technology 5th Edition as a text book. I understand a typical air-conditioning system temp, pressure and airflow. Let me try to rephrase my question.
If I don’t have any manufacturer parameters that the unit should optimally be running and I know only:
Evap air in temp
Evap air out temp
Low side pressure
Suction line temp

Cond air in temp
Cond air out temp
High side pressure
Liquid line temp


-After calculating the Superheat and/or Sub cooling, how do I know that values are acceptable?
Low charge? Over charge? Etc

How do I know how many lbs I need to add if the system is low charge or remove if the system is over charge?

[Gary]

Thanks Gary, great info. Where I can buy your book?

My website is currently out of service as I am in the process of switching servers. I hope to have it up and running again soon... until then it seems I am out of business.

[nike123]

How do I know how many lbs I need to add if the system is low charge or remove if the system is over charge?

You need to recover refrigerant from unit, weigh recovered amount and compare that with unit nameplate where refrigerant amount is stated. If your line-set is exceeding length for which unit is pre-charged, you need to add to that additional amount specified in instalation manual of that unit.
If your weighed amount is different from that, you need to leak test unit to find leak and fix it. After that you need to pressure test unit with dry nitrogen to see if test pressure hold for 12-24 hours (note temperature before and after test, pressure could change at rate of 0,1Bar/1°C).
After you should evacuate to 500microns vacuum (at least 30 min) and than weigh in accurate amount of refrigerant.

That is only proper way to know how much lbs of refrigerant you should add or remove.

[nike123]

Thanks for the reply nike123. I just started my HVAC education. My questions were about what I’m studying and the last A/C repair in my home.
I have the “Refrigerating & Air Conditioning Technology 5th Edition as a text book. I understand a typical air-conditioning system temp, pressure and airflow. Let me try to rephrase my question.
If I don’t have any manufacturer parameters that the unit should optimally be running and I know only:
Evap air in temp
Evap air out temp
Low side pressure
Suction line temp

Cond air in temp
Cond air out temp
High side pressure
Liquid line temp


-After calculating the Superheat and/or Sub cooling, how do I know that values are acceptable?
Low charge? Over charge? Etc

Read this article and then ask more questions!

[cralx2k]

You need to recover refrigerant from unit, weigh recovered amount and compare that with unit nameplate where refrigerant amount is stated. If your line-set is exceeding length for which unit is pre-charged, you need to add to that additional amount specified in instalation manual of that unit.
If your weighed amount is different from that, you need to leak test unit to find leak and fix it. After that you need to pressure test unit with dry nitrogen to see if test pressure hold for 12-24 hours (note temperature before and after test, pressure could change at rate of 0,1Bar/1°C).
After you should evacuate to 500microns vacuum (at least 30 min) and than weigh in accurate amount of refrigerant.

That is only proper way to know how much lbs of refrigerant you should add or remove.

Thank you for your professional response. I really appreciated.

[cralx2k]

Read this article and then ask more questions!

I'll check this out and I'll let you know. Thanks again.

[Gary]

Thanks Gary, great info. Where I can buy your book?

My website is currently out of service as I am in the process of switching servers. I hope to have it up and running again soon... until then it seems I am out of business.

Good news. I am back in business:

http://prostores1.carrierzone.com/se...com/StoreFront

[cralx2k]

Check your e-mail.

[Gary]

Check your e-mail.

Got it... thanks.

[pjkflat]

98 subaru 2.5 outback ac just gets cold t hen off duct emp hits 45 f