ideal temp to check A/C

ray hickethier

What is the ideal outside temp to check a straight a/c system and what is the lowest temp?

bhop2920

65-70

Ideal temp is above 65. I'm sure you can get a 'more exact' answer but I've always been told to make sure its at least 65ºf before removing or adding refrigerant and it seems to be true!

Techman

Unfair Question

-Asking for the "best temp to check/charge an AC system" is awful demanding of my time as an AC guy. How can I possibly get to all of my AC customers at that "given time frame",why not ask "how to properly charge an AC unit under different/varing conditions" ? Sure its tougher on me the AC guy but, hay, I'm supposed to know what I'm doing ,

bhop2920

65-70

Ideal temp is above 65. I'm sure you can get a 'more exact' answer but I've always been told to make sure its at least 65ºf before removing or adding refrigerant and it seems to be true!

Rich_L

Look for the chart

Look for a super heat chart inside of the condenser access cover near the schematic, on most newer units. Charge by super heat or sub cooling, depending on type of metering device. If it's cool out block the air discharge with a piece of cardboard or similar to build refrigerant pressure.

unclejohn

Man said ideal

So that would be 92*f @ 70%rh. Thank you and good night.

Techman

Ideal temp

would be 72-75* w/ 70% rh,Thank you and Good Morning!

JStar

Ideal

If my indoor wet bulb, and outdoor temperature are high enough to give me at least 5 degrees Superheat, I'll test the system. That's usually 55F wet bulb, and 70F outdoor.

unclejohn

At 72*

The grass is still wet with dew on account of it being 70% rh and my kness get wet. Not really ideal, unless it's late in the afternoon and the unit is on the southside of the house and we have a breeze.

Techman

ideal temp?

Let me send a memo to ALL of my customers that I'll be back on the first 92* day we get. Also , I thought TXV's  try to maintain the factory set superheat under varying loads?

Rich_L

Superheat

" I thought TXV's try to maintain the factory set superheat under varying loads?"



They will try, if they're working properly and you have enough refrigerant in the system. If the system has a TXV, charge by sub-cooling.

Techman

TXV's

I agree Rich L.! What do you mean by "raising the head press" with a piece of cardboard?

unclejohn

Cardboard

To block the outdoor coil inlet. Not really do-able with the top dischars units. Worked ok in the old side discharge days.

Rich_L

Cardboard

Techman, I just take either the condenser elec cover (if it has enough surface area, big and flat) or a heavy piece of cardboard and put it on top of the condenser to block the air discharge. I hold it in place with my tool pouch. This allows you to raise the refrigerant pressures to a "normal" range so you can charge by super heat or sub-cooling. Depending on ambient temps you may need to block the discharge completely (colder temps) or just partially. Works like a dream for charging a system in cool temps.

JStar

Ugh!

I haaaaaaaate the idea of blocking the condenser. All you simulate is a dirty condenser. You do not change anything useful.

Rich_L

Dirty Condenser

Think about that dirty condenser, Joe. It's going to raise your pressure which is going to help you in low ambient conditions. It's going to do that by blocking airflow. It's not perfect but is very helpful when you have to charge a system on a "cooler" than perfect day. I've been doing it in cool weather for many years with very good results.

Techman

ideal temp

RichL.I agree with you completely!!!!!!!!!! I have been doing the same thing for LOTS AND LOTS OF YEARS. I wanted some else to say that first, Thank You. I also bring my head press upto "normal" pressurers.The use of a "condensor fan cycling control" or a "motor master head press control" or a "headmaster" or even the "adjustable louvered head press device" does the same thing!!!!!!!!!!!!!!!! Let me ask this "foolish" question. What is the MINIMUM head press (converted over to CONDENSING TEMPERATURE) that ALL of these devices try to maintain???????

JStar

AC

Yes, you raise the head pressure, but you do not raise the indoor temperature or wet bulb. All you change is one side of the system. Are you checking superheat as you do this? What is your theoretical ambient temperature at that point?



Yes, it does work. I just don't think it's very accurate. We always schedule a spring startup on winter installs. It protects our work and our equipment.

Techman

ideal

There is a reason why all of those "head press controlling device" mfrgs produce those things to maintain a certain MINIMUM CONDENSING TEMP . Now on a system all I have to do is mimic those devices. Once a system is in there is nothing I can do about the SuperHeat and only a little control over the SubCooling.Most AC TXV's are nonadjustable and set for ,lets say 10*f. If that evap/TXV winds up out west where its "dry heat" or on the East Coast w/hi humidity. The TXV will maintain the same 10* SH.

 On a 50* ambient the operating head (with the proper ammount of R22 freon WEIGHED in ) will be KindaSorta be 120 -140psig and w/ a 75* indoor temp the suction press will be KindaSorta 43psig( 23*)  upto 54.9psig(30*) ,if your lucky.Bring that head press up to KindaSorta  180psig= 95* condensing temp= to a 70*-73* day and that low side press comes up to above 60psig.