Has anyone had experience with BOC's CARE products.
THE REFRIGERANT AND ITS APPLICATION
What is CARE ?
CARE is the trade name for BOC Refrigerants. CARE refrigerants are a range of natural hydrocarbon refrigerants selected and formulated as replacements for CFC, HCFC and HFC refrigerants for use in air conditioning and refrigeration systems. The hydrocarbons used include ethane, isobutane, propane propene. There are five CARE products: CARE 10, CARE 30, CARE 40, CARE 45 and CARE 50. The number represents the Normal Boiling Point of the refrigerant, e.g. CARE 10 boils at about -10°C at standard atmospheric pressure.
Can I use commercial LPG as a refrigerant ?
No. Commercial LPG contains an inconsistent mixture of propane, butane and other hydrocarbons, heavy oils and relatively large amounts of water. In addition, sulphur compounds are used as the stenching agents that may cause considerable internal damage to the system.
Is CARE more environmentally friendly than R22 or the new HFC refrigerants ?
CARE has a zero ozone depletion potential (ODP). R22 has an ODP of 0.05 (relative to R11). The new HFC refrigerants do not have a direct ODP, but ozone depleting substances are released during the manufacture of several HFCs, so they do possess and indirect ODP. The global warming potential (GWP) of CARE is equivalent to about 3 kg of CO2 as opposed to several thousand kg CO2 for both R22 and the HFC refrigerants. The atmospheric life of R22 and HFCs is more than 15 years compared an atmospheric lifetime of less than one for CARE. In addition, HFCs have been shown to contribute to acid rain. Thus, CARE refrigerants are shown to be significantly more environmentally friendly than other synthetic refrigerants.
Is CARE flammable ?
CARE is flammable, just as LPG as used in mobile heaters, barbecues, etc. It is flammable when mixed in concentrations between 2% and 10% with air. Most other refrigerants are non-flammable.
How can I tell when a system has been charged with CARE?
All systems containing CARE should be labelled appropriately, with a sticker stating the refrigerant contained in the system. In addition, the systems should be marked with a red 'warning' diamond. This should be located on the refrigeration compressor and on the structure of the unit close enough to any charging points.
Is the charge weight of CARE in a given system the same as for other refrigerants ?
Whereas the charge mass for HFCs is very similar to the mass of CFCs and HCFCs for a system of the same volume, the relatively low density of CARE means that systems require approximately 40% weight of CFC, HCFC or HFC refrigerant. The actual percentage may vary depending upon the dimensions of system components and operating temperatures. It is important not to over-charge systems with CARE.
Are there any special requirements when charging CARE systems ?
Since CARE refrigerants are flammable, charging should be done with special considerations relating to this, such as avoidance of ignition sources in the area and ensuring the area is well-ventilated.
In addition, two products, CARE 30 and CARE 50 are zeotropic mixtures meaning that the composition of the liquid phase is different to that of the vapour phase in the cylinder. Thus, it is vitally important when adding these to a system, to withdraw liquid and not vapour from the cylinder to maintain the correct mixture. If you are charging into the suction port then the liquid should be throttled by the manifold valves or a length of capillary be fitted in series with the charging line. For simplicity, all CARE cylinders use a "dip-tube" to ensure liquid off-take.
PERFORMANCE
Is there any loss in system performance with CARE ?
"Performance" has several meanings. In the context of cooling capacity, it depends on many factors including system operating conditions, components and controls settings. Assuming similar operating parameters such as evaporating and condensing temperatures, superheat and subcooling, the following applies:
CARE 10 has a capacity of about 40% to 50% of the capacity of R12 and R134a.
CARE 30 has between 0 and 15% lower capacity than R12 and R134a.
CARE 40 capacity is about 10% to 20% less than R22, R404A and R407C at high temperature and 10% lower at freezer temperatures.
CARE 45 gives slightly higher capacity than R22, R404A and R407C at high temperature, and about 10% to 20% higher capacities at freezer temperatures.
CARE 50 provides the same capacity as R22, R404A and R407C at high temperature but is about 10% greater at freezer temperatures.
Coefficient of Performance (COP) of CARE products is generally found to be 5% to 15% higher than most CFC, HCFC and HFC refrigerants although this is also subject to system design and operating conditions. Thus, power consumption of CARE refrigerants is generally less.
How do head pressures and temperatures compare ?
For the same operating temperatures, head pressures for CARE 10 are about half of the absolute pressure of R12 and R134a. CARE 30 head pressures are about 15% to 20% lower than R12 and R134a.
Again, for fixed condensing temperatures, CARE 40 has 10% to 20% lower pressure than R22, R404A and R407C. Head pressure CARE 45 is about 10% higher. CARE 50 has about the same head pressure as R22 and R407C, but is 20% lower than the absolute pressure of R404A.
CARE 10 and CARE 30 give discharge temperatures about 10K - 15K lower than R12 and R134a. CARE 40, CARE 45 and CARE 50 discharge temperature are about the same as R404A and R407C but about 10K to 20K lower than R22.
How will suction pressures and temperatures compare ?
For the same evaporating temperatures, CARE 10 has a suction pressure of about half the absolute suction pressure of R12 and R134a, whereas CARE 30 is about 10% to 20% less. CARE 40, CARE 45 and CARE 50 suction pressures are similar to those of R22, R404A and R407C within +/- 20% of the absolute pressures.
What effect does the temperature glide have ?
CARE 30 has a temperature glide of about 7K and CARE 50 about 4K. For direct expansion (DX) applications the temperature glide has no significant effect on the system's operation. In flooded systems refrigerants with temperature glide should not be used as this result in significant composition shift leading to loss of efficiency and changing saturation pressures. The temperature glide of CARE is similar to that of other blends such as R407C. It is important however, to consider the temperature glide when setting evaporator superheat and when rating and selecting components.
How do you select the evaporating and condensing temperature ?
There is no true "equivalent evaporating temperature" for zeotropic refrigerants. As a guide, some manufacturers suggest a "mid-point" temperature, which is half way between the bubble and dew point temperature at a specific pressure. However, In order to maintain consistent design reference temperature, the dew-point should be used.
Will recharging a system after a leak, result in a different refrigerant composition within the system ?
"Preferential leakage", i.e. where more of the higher pressure refrigerant component leaks out than the lower pressure component, occurs only from the evaporator or condenser. Studies have shown that the variation of overall composition over a number of leak-recharge cycles is minimal and therefore the effect on the system performance is negligible. The change in performance is generally a slight reduction of cooling capacity, and either a positive or negative effect on COP depending upon the operating conditions.
SYSTEM ACCESSORIES
Can I use my non-hydrocarbon gauges, manifold and hoses?
There is no problem with materials compatibility, although the user should purge the equipment with CARE to avoid cross-contamination. Either a hydrocarbon gauge scale or a CARE comparitor can be used to provide corresponding saturation temperatures from gauge pressures.
Can I use my non-hydrocarbon reclaim unit with CARE ?
As with the manifolds and hoses, there is no problem with compatibility of materials. However, it is important that the reclaim unit is safe in terms of ignition sources, i.e. that there is no way by which refrigerant could leak from the reclaim unit and accumulate around any electrical components that have the potential to spark. To ensure that the equipment is safe for use with CARE then changes should be made to the appropriate electrical components. Also, remember to flush the unit first to avoid contamination. Alternatively, a specially designed reclaim unit has been developed by Calor in conjunction with RDA, known as the "CARE Saver".
Is system evacuation any different for equipment containing CARE ?
The evacuation process remains the same as for non-hydrocarbon systems. An area check for sources of ignition is necessary, as well as ensuring a degree of ventilation in the event of a release of refrigerant.
Do I need special leak testing equipment for CARE ?
Methods of leak detection such as refrigerant discolouration/UV additives or soapy water can be used without any problem. Electronic leak detectors should be calibrated for hydrocarbons and should be intrinsically safe, although. Most HCFC/HFC detectors do work with hydrocarbons but the manufacturer should be consulted to check that they do not present safety risks. Many universal refrigerant leak detectors are available. Halide lamp detectors should not be used. Apart from the obvious fire risks, there is no chlorine in CARE to cause the flame to change colour.
SYSTEM COMPONENTS
What compressors can I use ?
It is recommended that specific hydrocarbon compressors be used in CARE refrigerating systems. These include reciprocating hermetic, reciprocating semi-hermetic, scroll, rotary, screw compressor and centrifugal compressors. In theory, any compressor can be used with CARE, but generally manufacturers warranties may not be honoured if a refrigerant is used that is not stated on the compressor nameplate. Regardless of this, any compressor for use with a flammable refrigerant should not have any sources of ignition associated with it. Examples are common sources of ignition are thermal overloads and compressor relays. Another important aspect to consider is the oils selection - high solubility of most oils will result in a thinning of the oil that is normally compensated for with the use of high viscosity grades.
Will I need to use different evaporator or condenser heat exchangers ?
For the same evaporating or condensing capacity, refrigerant heat transfer coefficients tend to be higher and pressure drops lower. This manifests as slightly reduced temperature differences. If any change were necessary, it would be a slightly reduced surface area. Improvements in system performance can be achieved under certain conditions with a zeotropic refrigerant if the heat exchangers are designed specifically, i.e. designed for counter-flow to take advantage of temperature glide.
Are the expansion device sizes different ?
Hydrocarbon thermostatic expansion valves (TEVs) are available for most CARE refrigerants. However, in their absence, non-hydrocarbon TEVs may be used. TEVs operate by modulating refrigerant flow through an orifice in response to the change in superheat at the evaporator outlet. A non-hydrocarbon TEV may provide 50% less capacity at full opening, so rated capacities should be checked. Most importantly, it is important to check that the vapour pressure/temperature curve of the intended CARE refrigerant matches that of the rated refrigerants so that the mimicking fluid within the phial provides the correct amount of opening in response to changes in superheat. Also, when a zeotrope is being used, the superheat setting should be made with consideration of the evaporator temperature glide.
Capillary tube length is generally unique for a refrigerant, the system and the conditions its operating under. Thus, the selection of a TEV is normally done through trial and error. As a guide, when replacing a non-hydrocarbon refrigerant with a CARE product of similar vapour pressure, an increase of capillary tube length of about one third is commonly found.
Does CARE have any effect on the size of pipe I should use ?
For an identical capacity, pressure losses tend to be less than with non-hydrocarbons since viscosity of CARE refrigerants tends to be lower. As a result, refrigerant line sizes will generally be the same or one size smaller with CARE than usual.
Can I use the same types of pipework joint with CARE as with other refrigerants ?
Provided that the joint is made correctly there should be no problem. However, as it is particularly important to prevent leakage because of the flammable nature of the refrigerant, we suggest brazed joints or lock-ring joints be used as they are less susceptible to leaks than say, flare connections.
How much oil should I add for long pipe runs?
Use the same quantity as for non-hydrocarbon systems, approximately and additional 70g of oil per kg of CARE.
Do I need to use special oils with CARE ?
Most common refrigeration oils are compatible with CARE, such as mineral oils, polyolester (POE), polyalkylglycol (PAG), polyalphaolefin (POE) and alkyl benzene (AB) oils. It is generally recommended to use oil with a viscosity grade one higher than would be typically used for the given application to account for increased solubility with CARE. Lubricants that are not recommended are natural or silicon oils and hydrotreated mineral oils. As with all refrigeration lubricants, care must be taken so as not to introduce moisture to them.
