How to know how much Freon HVAC need?

Freon is sold by weight. When HVAC tech add gas to system they charge by weight.
I assume they have to weight their supply tank before and after to determine how much they have added?

Can you determine just by pressure, how much they have added?

 

There is no chart that equates pressures to weights for refrigerants. In the hands of an experienced HVAC technician, pressures can indicate cooling output.

 

Yes...... that is correct.

 

MY HVAC was running hot. I called AC tech and he did add some Freon. I could see pressure was low. Afterwords AC now runs cold.

He charged me for 4 lbs but he did not weigh his tank. I did not even see any kind of scale he may have with him. I did not think at that time how he determined, how much gas he added to my system.

Have I been conned?

 

I weight mine during charging.
Pressures mean very little in the large scope of things. Many other readings to be taken to determine system performance.
If the unit needed to be charged there’s a leak. The system doesn’t consume refrigerant to run.
So now all the refrigerant you payed for will leak back out.

 

I agree with roughneck - the con was if there was no effort put into figuring out why refrigerant was needed.

 

I have to agree with you guys in terms of leak. I am aware of low freon means there is a leak.

I have old HVAC unit. I did ask him several time but he kept saying there is network of thin tubes in air handler unit inside house. With time they become weak and tend to leak. If you you fix one than another will pop open.

My air handler unit is 25 years old.

Again this was his explanation and he did not look for leak. He seems to be more interested in selling his left over r22 as not many units these day run on r22 and next year i am will be out of luck.

 

Still plenty of R-22, as well as retrofit options.
Why will you be out of luck next year?

 

probably reading about the manufacture and import ban starting in 2020 but suspect there will still be r22 for several more years as they use up current stock but price will likely just get higher not sure I would spend much on a system that old and would look into replacement

 

Per the EPA the tech must record how much refrigerant he used on each job.

 

For a homeowner four ponds of refrigerant may seem like a lot but the bigger picture is that there are systems that hold ten times and more than what a home system holds.

Service companies have different policies when charging for refrigerant and a small quantity of refrigerant like four pounds will not be sold with the same care for specific weight as maybe a 4 pound roast.
They could charge you by the ounce but there are losses every time you hook up guages and there needs to be a $$$ amount to cover inevitable warranty which is more common to provide than with the purchase of some meat.

They could be more up front and tell you all this but the cost of a service call is more dependant on their ability and honesty.
Really, I would not be as concerned about the weight as much as if they were competant and honest in their repair and diagnosis.

The other option is that they could charge you for one lb of refrigerant but not find and fix the leak or sell you a new system when the refigerant leaks out again.

 

It would be very easy to cause floodback or oil washout doing such a thing.