Air conditioning charging

Paul Mitchell_2

Yes...I know this is basically steam or hydronics....But I had a great little charging chart for 15 years...lost it...It crossed outdoor ambient with suction pressure and gave you anapproximate suction line temp you should be at. Great for piston/orifice systems. Also lost a chart I had for sub cooling....Any of you guys know where I can find replacements???

Randy Tibbits

Go to HVAC-TALK in the special interest section there is an article by Jim Wheeler on charging. I think there is a chart there.

Alan_6

slide chart

Contact your local bryant or carrier dealer. They have a good slide chart that makes charging easy.

Ken D.

AC

York used to have charging and superheat charts available.

Bud_14

Did it look like this, This I find is very accurate and fast to use. Ambient temp. down the left side, Suction Presure along the top (taken from the suction line near the condensing unit. The Suction line temperatures that you should be at in the mid section of the chart.

For instance if your ambient temperature (outside air near the condensing unit) is at 80 degrees. And your Suction presure is 64 psig, the suction line temperature should be at 59 degrees. I attach a digital lead to the suction side just before the service valve for the suction line temperature.

If the actual suction temp. is not within two degrees of the figure shown in the table for the conditions, the system is incorrectly charged..If the actual suction line temperature is higher then the value given, the system is under charged, If the actual suction line temperature is lower then the value given, the system is over charged.

I have had no problems with this simple chart for systems with pistons. Importantly, make sure the correct piston is being used or you'll be very frustrated trying to get the charge correct...

Hope this helps, and if this is what you're looking for I'll gat a fresh copy in PDF for whoever would like to download it...

Bud

Bud_14

Is this what you're looking for?

I've been using it for years..(looks like it)

Bud

www.TheSheetMetalShop.Com

clammy

sub cooling and superheat

As for charging most manfactors condensing units come with a super heat and sub cooling temperture out lines .Besides laying out your duct work properly and having enough return charging a/c systems isn,t just about dumping refregerant into the unit also after having your super heat with in 2 to 4 degrees and your refregerant sub cooling should be on the money also alot depends wheather your coil is equipted with a metering device or a txv and you should always check these with a good strap on digital surface thermooter and checking your compressor amp draw and indoor fan amperage is also a good thought.I believe alot of the bigger a/c companies don't do any of this they just feel a beer cold suction line or a filled sight glass and there gone ps and digital dry bulb /wet bulb thermontor is a real plus peace

Bud_14

Temperature Drop

Exactly, there are many variables and also, one should always check the temperature drop across the coil. From what I have learned and been following is a 20-degree drop from supply temperature and return airside temp. The temperature drop many times can be corrected by the airflow across the coil. This is where you need to understand duct size, is it correctly sized for the airflow needed across the coil? If the duct work is not able to handle the proper airflow by being to small (undersized) or perhaps to many restrictions in the duct it is often mistaken for undercharged unit and those without the experience will dump more refrigerant into the system and then the system becomes overcharged. Or they sit and scratch their head because they can't bring up the suction side pressure up. This happens a lot! When charging a system, you have to look at the whole system.

Holding the line or watching the suction line until it just breaks a sweat is wrong. The suction line will sweat at different rate in relation to the Rh?


Bud

www.thesheetmetalshop.com

How many of you use those point and shoot lasers to check suction temperature?

jim lockard

Clammy and Bud

-Thank you for explaining that "Beer Can" Cold is not properly charged. I find that not all Techs understand an A/C system can be too cold. As for charts they are only as good as the person using them. J.Lockard

mike w._2

charging chart

This is the one from carrier

mike w._2

charging chart

This is the one from carrier

Mark J Strawcutter

indoor wet-bulb

All the superheat explanations/instructions I've seen use indoor wet-bulb temperature as one of the determining factors.

The carrier calculator Mike W posted seem consistent with this. The chart Bud posted does not appear to take indoor wet-bulb temp into consideration.

Subcooling seems to be a single value specified for the condensor, althought I have run across some instructions that make adjustments for lineset length and/or height of evap above condensor.

And then there's the Lennox "approach temperature" method. Anyone care to explain what the theory is behind that?

Mark

Mark J Strawcutter

evap delta T

For high velocity systems (at least for Spacepak) you want delta T across the evap in the upper 20s

Mark

flange

go to your refrigeration wholesaler and get a pressure temperature chart. this will encompass usually many refrigerants and fit into your pocket. in general most manu's like to see a certain number of degrees superheat pretty close to the compressor. this is to get the charge correct, but also to give you the correct amount of motor cooling which will keep the compressor fat, dumb and happy. the amount of superheat is different for dsifferent types of expansion device. some also like to see a certain amount of subcooling of the liquid, but this can vary due to cleanliness.

fishface

charging chart/slide rule

Try www.123supply.com They have Carrier charging charts for sale that are not too expensive. Hope this helps.