To obtain long term system life, it is important to keep contaminants to a minimum. This is particularly true of a heavy duty application such as a heat pump. Therefore, all heat pumps should have at least one filter-drier. Two standard driers are preferred, but where this creates a piping problem, then a single reversing filter-drier provides adequate protection. In this blog we cover the benefits of applying filter-driers on heat pump systems and tips for any problems that may occur.
OEMs may prefer using two standard driers rather than a single reversible drier. This has several advantages – more desiccant in the system, less complicated drier parts, and lower cost. Field service people should follow the recommendations of the OEM. The use of two standard driers gives protection equal to, or greater than, the use of a single reversible filter-drier, see Figure 1.
Standard driers are often installed directly ahead of the expansion device – one in the outdoor section and one in the indoor section. Another common design is to locate both driers in the outdoor section, where they are easier to service. In this design one drier is ahead of the expansion device, and the other drier is ahead of the check valve. When installed in these locations, the flow through each drier is always in the same direction, see Figure 2. Standard filter-driers will not tolerate flow in the reverse direction. Reverse flow washes out the dirt previously collected, and also tends to result in high pressure drop.
When servicing units in the field, it is advisable to replace the original filter-drier with the next larger size, or the size recommended by the unit manufacturer. Where other information is lacking, the Parker Sporlan C-080 Series Catch-Alls are recommended for use on heat pumps up through 2 tons R-410A; the C-160 Series Catch-Alls are recommended for 2 through 5 tons R-410A; and the C-300 Series Catch-Alls are recommended for systems of 5 to 10 tons R-410A. When replacing the original driers on a unit, standard filter-driers are preferred. If the original unit does not have a drier, a reversible HPC-160-HH style drier is recommended.
The simplest way to install a drier on a heat pump system is to use a Parker Sporlan Reversible Filter-Drier. For most A/C systems select an HPC-160-HH Series Catch-All with the appropriate fitting size. This reversible filter-drier series is suitable for heat pump systems up through 5 tons R-410A capacity. These driers are installed in the reversing liquid line that runs between the indoor and outdoor section. Reversible driers should never be installed in the reversing gas line that runs between the indoor coil and the 4-Way valve, or the reversing gas line that runs between the outdoor coil and the 4-Way valve. Installation in this location will not give protection to the close tolerance parts of the system, and may result in excessive pressure drop. If the reversible drier is used on a highly contaminated system, such as after a hermetic motor burnout, it is essential that the old filter-driers be removed, see Figures 3 and 4.
In the past, Parker Sporlan offered several other types of reversible driers. These included the HCG-030 Series, HPCG-030 Series, and the HPC-080 Series. The HPC-160-HH Series are the proper replacements for any of these obsolete types.
Some heat pumps have only one expansion device – a bi-directional thermostatic expansion valve, or special short-tube flow restrictor. These systems are properly protected using a reversible filter-drier in the line between the expansion device and the outdoor coil. In this location the drier receives solid liquid on the cooling cycle, and a mixture of liquid and vapor on the heating cycle. Under these conditions, the Parker Sporlan HPC-160-HH Series Catch-Alls are suitable for use up through 5 tons capacity.
Typical recommendations for clean-up after a hermetic motor burnout are as follows:
A filter-drier should be installed in the suction line to clean up a heat pump after severe hermetic motor burnout. First, make sure the burnout is “severe” by testing the acidity of the oil from the burned out compressor using the Parker Sporlan TA-1 Acid Test Kit. If the burnout is severe, install a standard “HH” Catch-All in the common suction line. This drier can be installed either before or after the accumulator, but always between the 4-Way valve and the compressor. If some contaminants have remained in the accumulator, then the preferred location is between the accumulator and the compressor. This is usually a crowded location on the unit, and installing the drier may be difficult. In some cases, it may be necessary to re-pipe the suction line so the drier is located outside the cabinet.
Follow the unit manufacturer’s size recommendations if possible. Where this information is not available, use C-140-S-TT-HH Series Catch-Alls in systems up to 5 tons. Select a C-4300-S-T-HH Series Catch-All for units in the range of 5 to 10 tons. The exact model should be selected according to capacities and line size, consult Parker Sporlan Bulletin 40-10.
Most heat pumps are compact, unitary systems, with cramped piping, making it difficult to replace or install filter-driers. Here are some suggestions to solve these practical problems.
Reversible Heat Pump Catch-Alls are designed for installation in the reversing liquid line. The smaller HPC-100 Series, using the standard Catch-All core, is designed specifically for new installations and for use on OEM equipment. The HPC-160-HH Series uses a larger core which includes activated charcoal for maximum performance in removing all types of contaminants generated from a hermetic motor burnout. Both filter-driers consist of one core in a shell with a check valve at either end. The check valves control the flow so the filtration occurs on the outside of the core, regardless of the flow direction.
The reliability of the check valves used in these filter-driers have passed the most rigid OEM testing – no synthetic materials are used. The check valves have been thoroughly proven in actual field performance over a period of many years. They function well, even in the presence of solid contaminants.
Article contributed by Glen Steinkoenig, product manager, Contaminant Controls, Sporlan Division of Parker Hannifin.
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