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

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?

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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 - be sure to check out the diagnostic and repair suggestions and procedures given there.

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On 2018-12-05 by Anon - worried that AC repair technician is taking advantage - $1200. Freon Charge


I am worried a repairman is trying to take advantage. Mt heat pump is under warranty and alll work should be covered but when we were outside i heard a hissing sound (for the first time) then the repairman said where is that cap , then found it, screwed it back on and the hissing stopped.

He then went on to tell me that the there was a defective part that broke off and caused the feon to leak out and although the broken part is covered it is going to be $1200 for the freon.

I think he let it out in order to make money on this job. Any help would be appreciated.

Moderator Reply: signs of accurate & honest HVAC repair servcie

I think that your AC tech is being honest and correct.

I am GUESSING since I can't see your compressor/condenser unit nor what the repair person did, that the "cap" is a cover cap that is fitted atop one of the refrigerant gauge test ports on the compressor condenser unit.

YOu can see what these look like in photos in this article: GAUGE, REFRIGERATION PRESSURE TEST

The gauge test port contains a small valve - much like the Schrader valve inside of an automobile or bicycle tire air valve - that is normally closed (keeping refrigerant in) but is opened by pressing on a center pin by the attachment end of the pressure gauge.

If that valve leaks indeed you lose refrigerant. The valve may leak by being defective OR the refrigerant test port gauge might leak if dirt was forced into the valve - by leaving the cap off or by attaching a dirty test instrument.

Typical compressor/condenser warranties will cover parts but not labor for repairs.

The cost of to replace lost refrigerant seems steep at $1200 since the cost of the refrigerant itself in the quantity needed to fill a home air conditioner system is around $20. (You can buy a whole canister of R410A for about $100 - for example).

However there's more to it than that. There are two approaches to replacing refrigerant in your system.

In my OPINION

The Quick-and-Easy HVACR Refrigerant Re-charge Method

that is nearly universal in the industry, is to avoid a lot of time and trouble by simply connecting up the refrigerant canister through a gauge set and a charging device that sends refrigerant gas into the low pressure side of the system slowly while the tech monitors the temperature on the suction line or return line to the compressor.

When the line gets cold enough (according to refrigerant type, ambient temperatures &c.) the refrigerant charge is deemed "sufficient" for the system to work and the tech stops.

And may bill you whatever. I'd have charged the hourly rate + materials, including 2 trips to the home if 2 were needed.

But some service techs might accomplish this in minutes and some might bill more than $1000. for "the refrigerant", even specifying a refrigerant quantity in pounds even though in fact there was no measurement of quantity made.

8-Step High Qualith HVACR Refrigerant Recharge Procedure

This approach is technically most-correct and most-reliable and involves more time and trouble, possibly considerably more time and trouble, and for this work $1200. would be a bargain. In this approach the technician would

  1. Find and fix the refrigerant leak
  2. Remove any remaining refrigerant into a recovery device - it is illegal to discharge it into the atmosphere
  3. Possibly cut the refrigerant line and add a filter drier if none is installed. This is definitely necessary if a compressor was replaced, for example, or if there is reason to think the system refrigerant piping is contaminated.
  4. Attach a vacuum pump and pull a vacuum on the system
  5. Leave that vacuum long enough to confirm that there are no leaks elsewhere - this can require a 24 hour test and thus two site visits.
  6. Put a *measured* quantity of refrigerant into the system so that the liquid charge matches the manufacturer's specifications. This will be a bit more refrigerant (probably) than in the el cheapo method but the added refrigerant quantity cost is insignificant. The measured charge quantity may need to be adjusted or increased to account for extra lengths of refrigerant piping in the whole system.
  7. Return the system to operation, run it long enough to reach stable conditions and monitor that it's working properly.
  8. heck for refrigerant leaks again, especially at any points of repair of of cut and modified refrigerant piping

On 2018-09-09 by (mod) -

Sorry I don't understand the question.

On 2018-09-09 by khagendra

A/C gass why charging time coming coling gass selander?

how do i get condense slip ?

On 2018-04-25 by (mod) - Vac pump on one end of system- takes hours to fully evacuate the entire system.

Thaddeus

I'm not sure what you found that makes you think we differ - I agree with you completely. We used to leave our vacuum pump on the system for four hours or sometimes much longer when it was necessary to fully evacuate the system. Your advice is spot-on.

On 2018-04-25 by Thaddeus

Beg to differ on the vac time. Vac pump on one end of system- takes hours to fully evacuate the entire system. Getting a reading at the gauge will not be accurate unless you let it sit for an hour so the molecules can get over to the gauge and exert pressure

. Four hours is minimum with a really good pump. Otherwise, you'll leave moisture in the system leading to corrosion and failure.

On 2018-02-22 by (mod) - what is used to add refrigerant?

Allan

A refrigerant gauge set and a charging cylinder or an electronic metering device to place the correct measure charge into the system. I would caution you that this is not something that can be done by a person who doesn't have the proper training and equipment.

On 2018-02-21 by Allan

What will be use to enter the refrigerant after i finish to vacuum it? In low side or high side?

On 2018-02-01 by (mod) - Refrigerant can be added at any temperature above its boiling point

Refrigerant can be added at any temperature above its boiling point - which for R12 is at about -40F. However a tech who needs to actually run the equipment as part of her service procedure may not be able to do so at very low temperatures - lower than the minimum operating temperature for the equipment.

On 2018-01-28 by Melanie

I need freon on my heat pump which is an outdoor unit. A local bsns. Says it's too cold to add it now .is this true

On 2018-01-01 by (mod) - Can we charge from receiver when the system is running

Yes with proper connections and equipment.

On 2018-01-01 by nitesh

Can we charge from receiver when the system is running

On 2017-12-22 by Nawazish

How to recharge gas using manifold gauge?

On 2017-10-31 by (mod) -

Sure, Tim. Particularly 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) - 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.

Also see REFRIGERANT DIAGNOSTIC FAQS

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

Sonny,

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 to.my email from Gary email is pyrdeckg@gmail.com 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 I.now 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 to.my 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 thats.my 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 any.more.my choice thanks guys

On 2017-02-05 by Anonymous

WHAT IS THE CORRECT POSITION THAT THE FREON TANK SHOULD BE TAKEN TO DOWNLOAD THE GAS?

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

Reply:

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.

Question:

(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) Edrotman@aol.com 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?

Reply:

Anon

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.

Reply:

Gaudy

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

Reply:

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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