Necessary preparations before retrofit of R404A/R507A to R448A/R449A

The conversion changes the operating pressures, and depending on the operating conditions and system design probably also the refrigerating capacity.
Before a refrigeration system can be retrofitted from a current to a new refrigerant, the present status is to be determined. During this, the opportunity to eliminate leaks and malfunctions should be used. Following this, the components and the layout are checked for compatibility with the new refrigerant. Amongst others, the following is to be noted:

Checklist 1: Note conditions before retrofit
Design operating conditions or application range, like medium temperature or low temperature refrigeration, ...
Year of establishment.
Refrigerating capacity at design operating conditions.
Current refrigerating capacity demand at design operating conditions: Refrigerant comparison to R404A/R507A.
Current refrigerant.
Compressor: Model, manufacturer, year of manufacture.
Expansion devices: Design (thermostatic expansion valve, electronic EV, ...). Model, manufacturer, orifice size/capacity step.
Solenoid valves: Model, manufacturer, ...
Pressure controls: Evaporator pressure, crankcase pressure, condenser pressure regulators aso. Model, manufacturer, ...
Filter drier: Model, manufacturer, ...
Heat exchangers (evaporators, condensers, desuperheaters, internal heat exchangers, ...): Design, operation in counter flow, parallel flow or other. Model, manufacturer, ...
Oil: Type, manufacturer. Oil analysis for humidity, acid, colour aso. recommended.
Visible damages, dirt aso.

Before retrofitting, it should be checked whether the refrigerant change touches safety or approval rules, where the documentation maybe lists specific refrigerants.
Data for components and materials are to be provided to show whether they can be used further on.
If this is not possible to get, new components and materials are to be purchased, that are suitable for the new refrigerant.

Checkliste 2: Further preparations before retrofit
New refrigerant (Refrigerant comparison to R404A/R507A).
New refrigerant stickers.
Oil: Oil change is recommended. Use only original oils, that are compatible and proven with HFO refrigerants (blend components in R448A, R449A).
Compressor: Manufacturers statement on compatibility. If necessary, new gaskets.
Expansion devices: Manufacturers statements on applicability, capacity adjustment, adjustment of superheat, ... (Refrigerant comparison to R404A/R507A − operating conditions and system design). New vapour pressure data for electronic expansion valves.
Solenoid valves: Manfacturers statement on compatibility. If necessary, new gaskets.
Filter drier: New filter drier is recommended.
Pressure controls: Manfacturers statement on compatibility. If necessary, new gaskets.
For screw compressors the necessity to install or enlarge the oil cooler is checked. Calculations are done with the BITZER SOFTWARE.
Bottles for disposal or recycling of refrigerant.
Container/bottles for disposal of oil.
Availability of appropriate tools and test equipment.