Carrier 61WG 020 Installation, Operation And Maintenance Instructions

Contents

32The piping between the 30WGA and the condenser must becorrectly supported in line with its size and the operatingweight. Piping support is required to ensure that vibrationlevels at the piping are lower than the values at the compressor.If resonance occurs, reduce the width between the collar untilthe vibration levels are acceptable.8 - PIPE SIZING WITH REFRIGERANT FOR 30WGA UNITS8.1 - General considerations and pipe size limitsPipe size limits30WGA MaximumLinear length (discharge - liquid line) 30 mHeight difference 12 mThe pipes must be as short as possible and have the leastpossible changes (bends etc.) to minimise pressure drops. Ifthere is a risk of poor piping use, adequate measures must betaken (design, positioning, protection) to prevent incorrectuse.The following constraints must be taken into account whethe refrigerant pipes are sized:• Oil return to the compressor is ensured by entrainment.A minimum refrigerant velocity is required to ensureentrainment. This velocity depends on the pipe diameter,the refrigerant and oil temperature (these are treatedas being the same in most cases). A reduction of thepipe diameter permits an increase of the refrigerantvelocity. The problem of a minimum entrainmentvelocity does not exist for the pipes that carry liquidrefrigerant as the oil is fully miscible here.• The pressure drop at the compressor discharge (pipeslinking the compressor outlet to the condenser inlet)must be limited to avoid system performance losses(increased compressor power input and decreasedcooling capacity). Increasing the pipe diameter permitslimiting the pressure drops.• The pressure drop in the liquid line (linking the condenseroutlet to the expansion device) must not result in achange of phase. The estimate of these pressure dropsmust include those generated by possible accessoriessuch as solenoid valves and filter driers.• In applications with low outside temperature and withlong pipes use of a check valve at the condenser outletis recommended to overcome the poor supply of theexpansion device during the start-up phase. Select avalve that is not pressure-tight to avoid significantpressure rises of the liquid refrigerant that may be trappedbetween the solenoid valve (tight) and the check valve.8.2 - Pipe sizingThe following procedure can be used for pipe sizing:1. Measure the length (in metres) of the piping underconsideration.2. Add 50% to take account of special characteristics.3. Read the pipe size from tables 1 and 2 below.4. Calculate the equivalent lengths for parts included inthe piping under consideration (such as valves, filters,connections). The equivalent lengths are normallyavailable from the component supplier.Add these lengthsto the length calculated above.5. Repeat steps 3 and 4 if necessary.6. See tables “Discharge line piping” and “Liquid linepiping” below.8.3 - Discharge pipe sizingThe discharge piping must be sized to achieve reasonablepressure drops: a variation of 1.5 K of the saturated tempe-rature is normally accepted (approx. 90 kPa variation for acondensing temperature of 45 °C).Table 1 - Discharge line piping*30WGA 020 025 030 035 040 045 050 060 070 080 090Equivalent length0-10 m in 3/4 3/4 7/8 7/8 7/8 7/8 1-1/8 1-1/8 1-1/8 1-1/8 1-1/810-20 m in 7/8 7/8 7/8 1-1/8 1-1/8 1-1/8 1-1/8 1-1/8 1-3/8 1-3/8 1-3/820-30 m in 7/8 1-1/8 1-1/8 1-1/8 1-1/8 1-1/8 1-3/8 1-3/8 1-3/8 1-3/8 1-3/830-40 m in 1-1/8 1-1/8 1-1/8 1-1/8 1-1/8 1-1/8 1-3/8 1-3/8 1-3/8 1-3/8 1-5/840- 50 m in 1-1/8 1-1/8 1-1/8 1-1/8 1-3/8 1-3/8 1-3/8 1-3/8 1-3/8 1-3/8 1-5/850-60 m in 1-1/8 1-1/8 1-1/8 1-1/8 1-3/8 1-3/8 1-3/8 1-3/8 1-3/8 1-3/8 1-5/860-70 m in 1-1/8 1-1/8 1-1/8 1-3/8 1-3/8 1-3/8 1-3/8 1-3/8 1-3/8 1-3/8 1-5/870 m or more in 1-1/8 1-1/8 1-1/8 1-3/8 1-3/8 1-3/8 1-3/8 1-3/8 1-3/8 1-3/8 1-5/8* Recommended diameters to ensure oil return in the application range.Table 2 - Liquid line piping*30WGA 020 025 030 035 040 045 050 060 070 080 090Equivalent length0-10 m in 1/2 1/2 1/2 1/2 1/2 1/2 1/2 5/8 5/8 5/8 5/810-20 m in 1/2 1/2 1/2 1/2 5/8 5/8 5/8 5/8 5/8 3/4 3/420-30 m in 1/2 1/2 1/2 5/8 5/8 5/8 5/8 5/8 3/4 3/4 3/430-40 m in 1/2 5/8 5/8 5/8 5/8 5/8 3/4 3/4 3/4 3/4 3/440- 50 m in 5/8 5/8 5/8 5/8 5/8 5/8 3/4 3/4 3/4 3/4 7/850-60 m in 5/8 5/8 5/8 5/8 5/8 3/4 3/4 3/4 3/4 7/8 7/860 m or more in 5/8 5/8 5/8 5/8 3/4 3/4 3/4 3/4 7/8 7/8 7/8* Recommended diameters to limit the impact of the 1.5 K pressure loss.