Refrigeration gauge set © D Friedman at Refrigerant Charging Procedure FAQs
Q&A on How to charge refrigerant in an A/C or heat pump

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Frequently-asked questions about how to add or replace air conditioner or heat pump refrigerant:

Questions & answers about refrigerant charging procedures using a gauge and refrigerant canister and other equipment.

This article series describes the procedures for charging an air conditioner, heat pump, refrigerator, freezer, or similar equipment - how does an HVAC service tech put the proper amount of refrigerant into the system?

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Refrigerant Charging Procedures for HVAC Appliance FAQs

R-22 refrigerant and air conditioning test gauges (C) Daniel Friedman

These questions & answers on charging HVAC equpment refrigerants were posted originally at REFRIGERANT CHARGING PROCEDURE - home

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On 2017-10-31 by (mod) - Can you charge a heat pump air conditioning many split below 75゚

Generally yes, Tim. Particularly, it's safer easier to charge on the low side.


On 2017-10-30 by Tim

Can you charge a heat pump air conditioning many split below 75゚

On 2017-10-31 by (mod) - how can I tell how many pounds of freon the mechanic is charging me for


The technician should be using a weight-scale or other charge metering device to know the charge voume but often they don't. Instead the tech will add refrigerant by monitoring the temperature of the suction line at the compressor/condenser.

In that case you're paying whatever they decide is their "standard" or guesstimated charge. The tech should make clear ahead of time how they're going to bill you and for what.

On 2017-06-23 by sonny

how can I tell how many pounds of freon the mechanic is charging me for

On 2017-06-22 0 by (mod) - Ive been told to recover from high side then low side collect the rest through vapor

You only need tho charge from one side, installing the proper charge quantity.

On 2017-06-21 by Anonymous

If you want you can give answers here email from Gary email is thanks

Ive been told to recover from high side then low side collect the rest through vapor my question and might be stupid beacuase im a student in Hvac in.

my last class but Igot alot of head knowledge but verry little handd on my question when charging a unit do you want to start from low tp high side or high side first or can you do them both same time ive herd of the pull push or push

my question is whats thecorrect way to charge a systym and if you ever herd of the pull push systym please explain that I here its alot faster im not even sure im saying it right

I lnow this much I learned alot in school well alot to me and I worked with this idiot contractror just to get the hands on and he was doing everything wrong that I learned time is money but this guy never recovered the refrigerent he just hooked up the hose and dumped it in the air no recovery machine then he just pulled a vacum lol

is this common out there and even worse did not ever get super heat subcooling readings lol anyways back question what the right way to charge a system as far as do you charge from low side or high side first and whats the right and fast way of doing it

also what do you usually want your evaporator temp reading at for airconditioning when I was working with that guy the evap temp was usually between 34 f to 38f also should there be about a 20 degree delta t drop from your return to your supply

nether words if its coming in at 75 should your supply be around 55 degrees last class air distribution sorry for all the questions but j want to get it right needless to say im not training with that contractor choice thanks guys

On 2017-02-05 by Anonymous


On 2016-06-01 by (mod) -

Liquid in the receiver and gas on the low side

On 2016-05-31 by Abhishek

Where is the refrigerant position when system is still or is stopped?? Is it in liquid state or vapor state??

On 2016-05-09 by (mod) - To avoid sending liquid refrigerant into the compressor techs might charge on the low side

That's an interesting idea, Henry but I am afraid it might get confusing.

To avoid sending liquid refrigerant into the compressor techs charge on the low side (which swaps positions when you change from cooling to heating) and use a charging device that forces the measured liquid to enter the low side suction line as a gas. There are both charging device heaters and cylinders that change the measured liquid to a gas as it passes through.

On 2016-05-09 by Henry

To prevent the liquid 410a goes into the compressor, is it a good method to charge 410a in running heating mode if the split air conditioner with heating pump?

On 2015-08-12 by Drew F. - lot of good info

I'm not a professional, just an EPA cert. apartment a/c tech. And yes, there is a big difference between those who work on numerous different brands and makes on a daily basis, rather than some of us who have the same unit's throughout and get to know them well.

Question: how to evacuate a common home HVAC (refrigerant-based) system

(Aug 1, 2011) Brian said:

what is procedure to evacuate most common home hvac system


Current regulations in Northamerica require that refrigeration systems that are going to be evacuated are first emptied of whatever refrigerant remains in the system - but that refrigerant is NOT vented to the atmosphere. It must be collected into a retrieval canister. There are two ways this is done.

Traditionally a vacuum pump is connected to a service port on the HVAC system and the output of the pump is connected to a receiving canister. The pump is run until there is a vacuum on the HVAC system for some specified interval then the receiving canister is closed and the pump shut off.

Currently there are also refrigerant receiving canisters that are sold already having been pumped to a vacuum. The canister can be connected to the service port on the HVAC system.

In either case a gauge set with appropriate connecting hoses and control valves would be used to make the connections between the HVAC system service port(s) and the receiving canister.

Following removal of refrigerant from the system, depending on the HVAC system size, a vacuum pump may be left on and running for minutes to hours to attempt to clean the system as thoroughly as possible of refrigerant, moisture, and debris. The reason we need to allow some time to pass is that the initial "vacuum" is incomplete. Some moisture may remain in the refrigeration system that can convert to gaseous form as the system warms up, thus allowing still more moisture to be removed in vapor state. On a home system this may be just an hour or three; on a commercial HVAC or other refrigeration system we might leave the vacuum running for 24 hours.

Finally, when the system is to recharged, the HVAC tech will normally also install a dryer/filter to help remove any remaining moisture or debris.


(Sept 12, 2012) Anonymous said:

How to transfer coolant from refill tank to fill yank on machine

(Oct 25, 2012) Anonymous said:

reza how charging gas

Question: does the amount of gas in the system vary depending on weather conditions

(Sept 29, 2012) said:

In measuring the level of r-22 in a central Ac, Does the level and amount of gas in the system vary in cool weather vs hot weather? I had a service technician tell me my system needed 4 pounds but when I asked another technician he said it showed low because it was too cool to get a proper reading. Whose right?

(Mar 21, 2013) Anonymous said:

what is the pressure when we put refirgerant in the system?



At the article links near page bottom where you find an ARTICLE INDEX and more reading suggestions check out

REFRIGERANT PRESSURE READINGS - separate article. You'll see that while the total volume of refrigerant in the system remains constant - a refrigeration system is a closed system with a fixed charge of refrigerant

- it is indeed the case that the pressure and temperature of the refrigerant on the high and low side as well as the apportionment of refrigerant volume between liquid and vapour states changes when the system is being run and at different ambient temperatures.



If you are asking about preserving refrigerant when disconnecting and moving HVAC equipment, I am doubtful. IN a conventional split system cut, move, and reinstall, the tech will need to pull a vacuum, clean the system piping and equipment after it's reconnected in the new location, then install refrigerant.

Question: removing air from a split system that has not been bled

(Oct 15, 2012) Rob said:

Was wondering if yhere is an easy way to remove the air from a split system that has not been bled


The service tech needs to install a vacuum pump, remove refrigerant, pull a vacuum, remove all gas, air, and all possible moisture, install a new filter/drier, and then recharge the system. There's no shortcut that will remove "just the contaminating air" from a refrigeration system that was not properly charged.


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Air Conditioning & Heat Pump Refrigerant Articles

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