Perform all weekly and monthly maintenance procedures.
The R-410A scroll compressor uses POE oil as required by the manufacturer of the compressor. Refer to compressor manufacturer for exact type and amount of oil in the specific model in question.
While the compressor is running, the oil level may be below the sight glass but still visible through the sight glass. The oil level should NEVER be above the sight glass!
If the oil is dark and smells burnt, it was overheated because of compressor operation at extremely high condensing temperatures, a compressor mechanical failure, or occurrence of a motor burnout. If the oil is black and contains metal flakes, a mechanical failure has occurred. This symptom is often accompanied by a high amperage draw at the compressor motor.
Scroll Compressor Functional Test
Since the scroll compressor does not use discharge or suction valves, it is not necessary to perform a pumpdown capability test, i.e. a test where the liquid line valve is closed and the compressor is pumped in a vacuum to see if it will pump-down and hold. In fact, this kind of test may actually damage the scroll compressor.
Do not pump the scroll compressor into a vacuum. Scroll compressors can pull internal low vacuums when the suction side is closed or restricted. This, in turn, can lead to compressor failure due to internal arcing and instability in the scroll wraps.
The proper procedure for checking scroll compressor operation is outlined below:
Discharge pressure: Take at Schrader fitting provided on the discharge line. Normal discharge pressures are:
Suction pressure: Take at Schrader fitting provided on the suction line. Normal suction pressures are:
Compressor Operational Noises
At low ambient startup: When the compressor starts up under low ambient conditions, the initial flow rate of the compressor is low. Under these conditions, it is not unusual to hear the compressor rattle until the suction pressure climbs and the flow rate increases. These sounds are normal and do NOT affect the operation or reliability of the compressor.
Excessive Amp Draw
Excessive Amp Draw occurs either because the compressor is operating at an abnormally high condensing temperature OR because of low voltage at the compressor motor.
Motor amp draw may also be excessive if the compressor has internal mechanical damage. In this situation, vibration and discolored oil can also be observed.
Continuous low suction pressures are most likely caused by low evaporator load coupled with a system anomaly such as low chilled water flow.
Note: Operation of the chiller with saturated suction temperatures below freezing will cause damage to the evaporator. If this occurs immediately stop the machine, diagnose and correct the problem.
Heat Exchanger Maintenance
When to Clean a Brazed Plate Heat Exchanger (BPHE)
A temperature difference, less than specified, indicates a sign of scaling because fouling of the channel plate surface decreases the heat transfer. Hence the inlet and outlet temperatures of the BPHE should be measured continuously. Pressure drops larger than specified indicate scaling since it restricts the channel passage and thus increases velocity.
Make sure that readings follow water flow rate corresponding to the specification, since changes in flow rate effect temperatures and pressure drops. By removing the scale build-ups, the operating efficiencies of the equipment and heat transfer surfaces are restored. Other benefits from removing the scale are that it lowers the pressure drops, reduces the power consumption and extends the lifetime of the equipment.
How to Clean a Brazed Plate Heat Exchanger (BPHE)
CICD chiller BPHEs are cleaned quickly and easily with Cleaning in Place (CIP), a method used for the interior surfaces of closed systems, such as pipes, vessels, process equipment, and filters. A chemical fluid is circulated through the BPHE, without the need for disassembly.
The chemicals dissolve or loosen deposits from process equipment and piping, giving uniform removal and lower overall operating costs. Following is a general description of the system setup, the CIP procedure, and the various cleaning fluids.
Cleaning in Place (CIP) Procedure
Bio Gen Active – Scale 132 Copper
Commercially available Scale 132 Copper removes lime scale and other carbonates as well as rust and other metal oxides without the risk of corrosion.
Organic acids are less hazardous than mineral acids, which makes them a good choice for BPHE cleaning. Organic acids include formic, acetic, and citric acids, among others, and are commonly applied at concentrations between 1 and 5 volume percent.
Formic acid alone is unable to remove iron oxide why it's used as a mixture with citric acid or HCl. Formic acid can be used on stainless steels, it's relatively inexpensive and can be disposed by incineration.
Dissolves lime scale, but doesn't remove iron oxide deposits. Since it's weaker than formic acid, it is preferred where long contact times are necessary.
Mild iron contamination can be removed by using a mixture of 1% each of citric acid and HNO3. For more persistent contaminations, stronger solutions must be used.
Bases have the ability of removing oil, grease and biological deposits from the heat exchanger surface and may be applied as a complement during cleaning. They may also be added at the end of the cleaning procedure, before the last rinse with water, to neutralize any acid content left in the system. A solution of 1-2% sodium hydroxide (NaOH) or sodium bicarbonate (NaHCO3) before the last rinse ensures that all acid is neutralized.
COMMERCIALLY AVAILABLE CIP FLUIDS
Bio Gen Active – Scale 132 Copper
Description: Scale 132 effectively removes lime scale and metal oxides (e.g. rust) without etching the material. It's used for reconditioning of waterborne systems. The product is mild to user, material and the environment.
Source: Trane (www.trane.com)