Refrigerant Charging Procedure FAQs

Q&A on How to charge refrigerant in an A/C or heat pump

HVAC Service Tech Says Refrigerant Leak Hissing Sound Means a Part Needs Replacement: Am I Being Ripped Off?

RE-posting discussion by private email:

Anonymous said:

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: 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 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 the refrigerant charge is "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.

the High Class refrigerant recharge position:

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. remove any remaining refrigerant into a recovery device - it is illegal to discharge it into the atmosphere

2. 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.

3. attach a vacuum pump and pull a vacuum on the system

4. leave that vacuum long enough to confirm that there are no leaks elsewhere

5. 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.

6. return the system to operation, run it long enough to reach stable conditions and monitor that it's working properly.

...

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. - On 2018-12-05 by Anon -

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 Quality 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. Check for refrigerant leaks again, especially at any points of repair of of cut and modified refrigerant piping

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

How can I tell how many pounds of freon the mechanic is charging me for- On 2017-06-23 by sonny -

Reply by (mod)

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.

At what outside ambient temperatures can refrigerant be added to a system?

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 2018-01-28 by Melanie -

...

Can you charge a heat pump air conditioning many split below 75ﾟ - On 2017-10-30 by Tim

Reply 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.

Sure, Tim. Particularly safer easier to charge on the low side.

Can we charge from the refrigerant receiver when the system is running?

Can we charge from receiver when the system is running - On 2018-01-01 by nitesh

Reply by (mod) -

Yes with proper connections and equipment.

Push-Pull Method to Recover refrigerant from high side then low side collect the rest through vapor

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 what;s the correct way to charge a system and if you ever herd of the pull push system 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

In other 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 2017-06-21 by Anonymous -

Reply by (mod)

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

Refrigerant recovery systems generally will pull the liquid and then gas refrigerant out of the system using a vacuum pump.

But the "push pull" method of refrigerant recovery provides a faster way to recover refrigerant from any HVACR system.

A refrigerant recovery pump system is connected to the refrigeration system as follows:

1. The vapour side of the refrigerant recovery cylinder is connected to the suction inlet of the refrigerant recovery vacuum pump system
2. The "hot liquid out" side of the recovery pump is connected to the system vapour in side of the refrigeration equipment
3. The "liquid out" port or side of the refrigeration equipment is connected to the liquid side of the dual valve/port on the recovery refrigerant gas cylinder

 

See this article

• ACR Journal, HOW TO USE THE PUSH-PULL METHOD OF REFRIGERANT RECOVERY [Web article] (2015) - last retrieved 2025/01/12 - ACR Journal, Web: https://www.acrjournal.uk/ Editor Email: acr.editor@ warnersgroup.co.uk
  
  Excerpts: The now famous “Push-Pull” method is the fastest way but believe me you may be surprised as to how little it is used. The first reason is that it’s not accessible on some plant if a liquid connection is not available. The other reason is many people have not grasped the “Push-Pull” technique.
  
  ... the push [step is achieved] by connecting the discharge of the recovery unit back into the vapour side of the plant.
  
  ... the hot high pressure discharge from the recovery unit increases the pressure over the remaining liquid in the plant and pushes it into the recovery cylinder as well.

and

• Javec XTR XTR-PRO-DV A2L XTR-ALTIMA A2L LIQUID & VAPOUR REFRIGERANT RECOVERY INSTRUCTIONS [PDF] - retrieved 2025/01/12 Javec, UK, Tel: 01642 232880 sales@javac.co.uk offices also in the EU, - local copy filed as Javec-Ultra-Recovery-Pro-Pump-Manual.pdf
• Javec XTR- Ultra REFRIGERANT RECOVERY PUMP JAV-1063 INSTRUCTIONS - retrieved 2025/01/12 - local copy filed as Javec-Ultra-Recovery-Pump-Manual.pdf
  

When the HVACR system is stopped is the refrigeraant in a liquid or gas state?

Where is the refrigerant position when system is still or is stopped? Is it in liquid state or vapor state? On 2016-05-31 by Abhishek -

Reply by (mod) -

Refrigerant will be stored as a liquid in the receiver and it will be present as a gas on the low side of the system. ,

To avoid sending liquid refrigerant into the compressor techs might charge on the low side

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 2016-05-09 by Henry -

Reply by (mod)

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.

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

What is procedure to evacuate most common home hvac system (Aug 1, 2011) Brian said:

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.

At least 4 hours needed to evacuate a refrigeration system

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 2018-04-25 by Thaddeus -

Reply by (mod) - Agreed: 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.

Question: how to remove air from a split system that has not been bled

Was wondering if yhere is an easy way to remove the air from a split system that has not been bled (Oct 15, 2012) Rob said:

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.

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?

Reply: No

The volume of refrigerant in a system is fixed and should not change unless there is a leak or a deliberate change in the refrigerant charge quantity by a service tech. Weather conditions don't affect the refrigerant charge.

The distribution of refrigerant in an HVACR system between liquid refrigerant and refrigerant in gas form depends on the running state of the system.