01 August 2016

Retrofitting R404A

A-Gas Managing Director John Ormerod with ten top tips on how to maintain best practice when replacing R404A with a lower GWP refrigerant


1 Why is it important to make the switch from R404A to a lower GWP refrigerant?

This is the time to focus on replacements for R404A, one of the most widely used refrigerants in the industry. The F-Gas quota system is making an impact as the push towards reducing the amount of high GWP refrigerant in use gathers pace. R404A, with a GWP of just under 4000, will be one of the hardest hit by the changes and everyone agrees that if business continues as usual, by 2018 there won’t be enough of this refrigerant to go around to meet the needs of the industry.

2 How do you decide on which refrigerant to choose for the retrofit?

It must have similar operating characteristics to  R404A in terms of being a medium or low temperature replacement. To achieve this you must match the refrigeration capacity as closely as possible with the lowest GWP refrigerant that is available. The industry should banish the word drop-in because there really is no such thing. With the introduction of any replacement refrigerant an adjustment will have to be made to the system to get the best out of it; it is not a case of simply ‘dropping it in’. 

3 Which retrofit refrigerants spring to mind?

Your refrigerant supplier will be able to help you in the selection of the most appropriate refrigerant for the system. You should consult with the equipment manufacturer too before making a final decision.

There are several suitable retrofit refrigerants on the market – R407F is a medium GWP option but Opteon XP40 (R449A) and Solstice N40 (R448A) offer a lower GWP alternative. They are currently the lowest GWP replacements on the market (around 1400) and are closely matched to R404A in terms of refrigeration capacity.

4 What is the easy way to record the amount of refrigerant recovered?

It is a key aspect of the retrofit to discover what the system has been running on beforehand. It is also important to record the quantity of refrigerant put in or taken out of the system to satisfy the obligations of the F-Gas Regulations.  Online reporting tools like Gas-Trak Online™ (GTO) from A-Gas make this easy. They allow engineers to cut down on paper use by producing electronic F-Gas log books and reports.

5 How should you dispose of the old oil from the compressor?

An oil change is a vital part of a refrigerant retrofit. Getting rid of waste oil, especially small quantities, has traditionally been a problem for engineers. Remember that this old oil can contain refrigerant and safe storage and responsible disposal is key. A-Gas offers an oil disposal service through its wholesale partners to take care of recovered oil. Each container has a venting cap to ensure any refrigerant  absorbed in the oil does not cause the waste container to expand. This is a safe and environmentally friendly way of dealing with what has been in the past a tricky problem.

6 How does the choice of refrigerant affect the charge size?

To avoid any problems with a retrofit, first measure the operating conditions. This includes discharge, suction pressures, suction line temperature, compressor amps and super heat before using the liquid sight glass as a guide. Follow the refrigerant manufacturer’s recommendation regarding initial charge size before making adjustments to the system. Use dew point pressure as a reference in determining the appropriate temperature for a superheat setting. To determine the saturated temperature for a sub-cooling calculation use bubble point pressure.

7 Why is leak testing so important?

Leak detection is a key part of ensuring that the F-Gas Regulations do achieve what is expected of them; if a system doesn’t leak, it won’t require topping up, and this in turn helps the industry meet the phase-down under F-Gas.. A retrofit, with the gas out of the system, is a great opportunity to raise the bar on this. Making sure a system doesn’t leak has never been more essential and this will clearly save the customer money in the long run. The route to success is to follow best practice, so relying on pressure or vacuum decay – or using bubble spray – won’t be enough. Technologies like Trace-A-Gas® from A-Gas can provide a high tech and economical solution. Using a suitable detector, this method is 100 times more sensitive than bubble spray. Leaks can be detected in the smallest quantities and very quickly.

8 How should you monitor the system performance?

This is a crucial part of a retrofit and you should start monitoring while the system is still running on R404A by recording the typical running conditions. All the standard system operating parameters should be checked to establish the benchmark temperatures and pressures.

9 Why is labelling so important?

The F-Gas Regulations have changed the labelling requirements. Not only must you now record the amount of refrigerant in the system but you should now record what the GWP is and its CO2 equivalent value. GTO has a handy calculator which can make this a quick and easy task. As the regulations march on it is likely that we are going to have many different types of refrigerants used, so labelling has never been more relevant. It is also important for engineers to know exactly what’s in a system. Generic F-Gas refrigerant tape is now available to allow systems to be labelled accordingly with all of the required information.

10 How important is it to dispose of the old refrigerant correctly?

This is a legal obligation because it is classed as hazardous waste. Under the F-Gas phase down it is crucial that as much old refrigerant as possible is recovered, reprocessed and made available to the market. The phase-down is a steep curve and leading industry organisations are pointing to the fact that reclaimed refrigerant is going to play a major part in keeping the supply chain moving beyond 2018.