AC charge?

[cretan]

Will be installing a AC unit next week.The evaporator/air handler is already installed.Unit is capillary system.How do I properly charge the system?Is there a universal chart to go by?I ask this because some of the AC units have confusing charts to go by.Thanks!

[The Viking]

If you haven't got any other data, then measuring the subcooling is the most accurate way to charge.

[nike123]

If you haven't got any other data, then measuring the subcooling is the most accurate way to charge.

It is capillary system and it must be charged by superheat table. One "universal" is Jim wheeler table:


http://tinyurl.com/56jrzl

[philfridge]

Is it just a split unit on running on r22

[cretan]

Thanks for the replies.

Is it just a split unit on running on r22

Yes it is a split on R22.

[botrous]

Hmmmm . . .
try this . . .
Put the indoor fan speed on high mode ,(first make sure that the dust filters are clean).
start charging , and measur the tempreture difference between the entering air and the leaving air , once it's about 8 centigrade stop charging.
for an outdoor tempreture of 26 centigrade the gauge pressure must be about 65 PSIG.

Not an accurate methode but will work just fine.

Respects and regards

[philfridge]

[quote=nike123;107439]

It is capillary system and it must be charged by superheat table

. [/quote


This is not the case simply charge system to between 55 to 65 psi ,ie when the suction line sweats back to the compressor , depending on the ambient tempersture but you want to be nearer 65 psi if its a hot day 28c .

[The Viking]

OK Phil, I'll take the bait...

With your method, what will happen if:
-The indoor fan doesn't run at it's rated max capacity?
-The indoor humidity is below spec.?
-There are restrictions in the pipework?
-The indoor ambient temperature is extremely high or low?

Just some thoughts....


CRETAN,

If you give us the manufacturer / model No, then I'm sure we will be able to give you better answers...

[nike123]

This is not the case simply charge system to between 55 to 65 psi ,ie when the suction line sweats back to the compressor , depending on the ambient tempersture but you want to be nearer 65 psi if its a hot day 28c .

This is quote from text which link I posted below:

Capillary/Orifice Metered Systems

In literally hundreds of visits to problem jobs, I’ve found most air conditioners/heat pumps to be overcharged with refrigerant. Why? Because incorrect charging techniques are too commonly used in the field.
I remember my first training on charging a residential air conditioner. The technician I worked with said: “Just add refrigerant until the high side is about 250-psig and the low side is about 60.” And that’s how I did it for the first six months of my career as a hvacr service technician.
Unfortunately, this is the same training many others in our industry received during the building rush of the early ‘70s.
It’s comforting to know that few still use that method today, but some are even worse! The “Gifted Finger” technique: Adding refrigerant until the suction line turns cold – is one. Another is called the Amprobe Method: you add refrigerant until the compressor reaches rated amps.
And let’s not forget the Add 35*F approach: this is a little more scientific. You add refrigerant until the saturated condensing temperature is 35*F above the outdoor ambient.

I know that by now some of you are sitting back and laughing, while others are wondering what’s so funny. I really don’t want to hurt your feelings if you use one of these methods- you certainly aren’t alone or in the minority- but each of these techniques result in an overcharge, and often a GROSS overcharge.
Back when I used to work as a training manager for a Carrier distributor, I found it strange to find contractors filing claims for 10-lbs. Of refrigerant on systems that only held 6-lbs. However, after several field calls I found many actually WERE putting 10-lbs. Of refrigerant into a6-lbs. systems!
It’s a common misconception among some technicians [and a few managers] that if you increase refrigerant beyond the specified charge, you increase system capacity. Actually, the opposite is true. Refrigerant added beyond the proper charge reduces capacity. This is because, on capillary or orifice metered equipment, as you add refrigerant you also raise the evaporator temperature.
The problem with some of these common charging methods, and the reason they shouldn’t be used, is because they fail to address such factors as:
· Temperature relationships
· Proper superheat
· System operating conditions
· Condenser efficiency

An overcharge is far more likely to damage the compressor than an undercharge. With capillary and orifice metering devices, excess refrigerant is returned to the crankcase as a constant floodback, reducing capacity, efficiency, and compressor life.
I only know two ways to properly charge non-TXV [Thermostatic Expansion Valves] systems. Both are simple to use and generally universal in application. They include: the Weight Method and the Superheat Method.
Weight Method: Weighing charge is simple, quick, and certain. The weight of the factory supplied charge is found on the model/serial number nameplate. If the system has 25-ft. of line [on split systems], the lines aren’t over or undersized, and there’s no field installed liquid line filter dryer, simply weigh the amount shown.

[cretan]

i used the link posted and the chart listed and system works great.thank you everybody for your input!!!!

[nike123]

i used the link posted and the chart listed and system works great.thank you everybody for your input!!!!

Good to hear that!

[philfridge]

OK Phil, I'll take the bait...

With your method, what will happen if:
-The indoor fan doesn't run at it's rated max capacity?
-The indoor humidity is below spec.?
-There are restrictions in the pipework?
-The indoor ambient temperature is extremely high or low?

I have the gifted finger

[archibaldtuttle]

i used the link posted and the chart listed and system works great.thank you everybody for your input!!!!

I've been through jim Wheeler's charging discussion numerous times as refresher course, but what "chart" is "listed" or do you just mean the appropriate pressure temp chart for the refrigerant involved?

I was going to post the one's I've been using but I don't seem to have 15 posts in, seems like I must have hundreds, but maybe just because it has been a problem week that lead me to seek out this board.

Soon as I am able I will post the links.

Brian

[cretan]

the unit I was working on was originally a water cooled unit.i replaced it with an air cooled condensor.i did not have a charging chart to go by.the chart on the link seemed to work fine.if you have other charts I would be interested.