What is the correct way to "top up" gas in a system

[teejay711]

Hi,
I am new to the refrigeration game so please don't laugh at my question.

I have a system that is low on gas, 6 years old with R22.
The customer wants me to keep the system running for a few months then replace but it is low on gas.

If i was to top up the gas what is the correct way to do it. I am assuming I should weigh out the existing gas then weigh back in again the correct amount or can i take a short cut.
Also is this legal as there is a leak somewhere in the system....

Tony

[shieldcracker]

Tony,

The first question you need to address is the size of the leak. Is it big or small? If the leak is big it would not make any sense to top off without repairing the leak first. The legality of recharging this system would depend on how small is the leak (I am not familiar with British codes).
You can charge the system as you suggest but you need to know the total amount of charge, this is available on the equipment nameplate (only packaged/self contained equipment). For split systems you would need to check maintenance logs if they exist as the system charge is not printed in the nameplate.
Assuming you don't have the system charge information you can use the sub-cooling method for systems that have TXV and superheat method for systems that employ fixed orifice throttling devices.

[teejay711]

Hi Shieldcracker,

Cheers, i knew the total amount is on the plate and now know that the best practice is find and repair the leak.
I think I could work out the sub-cooling method if needed.
Thank you for your reply..

[Neddy]

Are you F Gas qualified? I take it you are not as you have asked the above question. It is illegal to top up a known leaking system under F Gas regulations. You need to recover the R22. Pressure test with OFN. Find and repair the leak. Vac and recharge the system. System must be older than 6 years if its charged with R22?

[teejay711]

Hi Neddy,

I am actually F Gas qualified and a member of Refcom. I passed the course 2 years ago and haven't done any A/C work since. As my full time job isn't A/C but electrical.
I wanted to get my house in order before doing any work. The answer given by yourself is ideal and confirms my thoughts. Yep the system was installed in 2006.
Tony

[1mikeefc1]

As you will probably be aware, charging any refrigeration equipment with a known leak is not allowed, unfortunately we get asked all the time off customers to just "top it up" but they are unaware of the consequences it has on the engineer and the company if you do this. Explain to him why you can't but chances are he will be more bothered about the cost of reclaim, pressure test, repair, evacuation and recharge.

[still learning]

shame they wont replace now . then they only have to pay for reclaim and disposal.
and get a up to date system .
if they go down the road of keeping the pipework with a new install, the pipework will need a preasure test to see its not a bad braze or chaffed pipe .