Capacity Control Block 3

7/31/2019 Capacity Control Block 3

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COP = Energy Out

Energy In

COP = Btus Out

Btus In

COP = Watts Out

Watts In

Btus divide 3.413 = Watts

Watts times 3.413 = Btus

Btus divide 3413 =

Kilowatts

Btus Out = Btus in times COP


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Bristol TS TechnologyBristol TS Technology

Twin-Single 2 Stage CompressorTwin-Single 2 Stage Compressor

http://ts.bristolcompressors.com/tstour.html

http://ts.bristolcompressors.com/cts.html
http://ts.bristolcompressors.com/tstour.htmlhttp://ts.bristolcompressors.com/cts.htmlhttp://ts.bristolcompressors.com/cts.htmlhttp://ts.bristolcompressors.com/cts.htmlhttp://ts.bristolcompressors.com/tstour.html


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Oil return is a major issue in variable capacity multiple evaporator systems. Current

technologies use an oil separator and/or complicated oil return cycle to ensure oilreturn after some period of operation. The Digital Scroll is a unique compressor it

does not require an oil separator or an oil return cycle.

There are 2 factors that make the oil return easy. First, the oil leaves the compressor

only during the loaded cycle. So at low capacities, very little oil leaves the

compressor. Second, as explained before, the compressor operates at full capacityduring the loaded cycle. The gas velocity in the loaded cycle is sufficient to return oil

back to the compressor. Our testing has shown that oil is able to return back to the

compressor even in the worst operating conditions low modulation, 100 meter pipe

length and 30 meter elevation (with standard oil traps), both straight and reverse

elevation.

http://www.digitalscroll.com/sb300/portal/home/normal/17/show/0/2?

Variable Capacity Oil Return
http://www.digitalscroll.com/sb300/portal/home/normal/17/show/0/http://www.digitalscroll.com/sb300/portal/home/normal/17/show/0/


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Ultra Tech ScrollUltra Tech Scroll


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Copeland Ultra-Tech


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A piston is fixed to the top scroll to ensure that when the piston moves up, the top scroll also moves up.

There is a modulation chamber at the top of the piston that is connected to the discharge pressure

through a bleed hole of diameter 0.6 mm. An external solenoid valve connects the modulation chamber

with the suction side pressure. When the solenoid valve is in the normally closed position, the pressureon either side of the piston is discharge pressure and a spring force ensures that the two scrolls are

loaded together. When the solenoid valve is energized, the discharge gas in the modulation chamber is

relieved to the low pressure. This causes the piston to move up and consequently the top scroll also

moves up. This action separates the scrolls and results in no mass flow through the scrolls. De-

energizing the external solenoid valve again loads the compressor fully and the compression is

resumed. It should be noted that the movement of the top scroll is very small - 1.0 mm and consequently

the amount of high-pressure gas that is bled from the high side to the low side is very little.


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Copeland Semi-Hermetic Screw CompressorCopeland Semi-Hermetic Screw Compressor


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http://www.emersonclimatecontractor.com/products/air-conditioning/astp.shtm
http://www.emersonclimatecontractor.com/products/air-conditioning/astp.shtmhttp://www.emersonclimatecontractor.com/products/air-conditioning/astp.shtm


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Three PhaseThree Phase

Voltage MonitorVoltage Monitor


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To test if the compressor is pumping properly,

the compressor current draw must be compared to

published compressor performance curves using

the operating pressures and voltage of the system.

If the average measured current deviates more than

15% from published values,

a faulty compressor may be indicated.

A current imbalance exceeding 15% of the average on the

three phases may indicate a voltage imbalance

and should be investigated further.

A more comprehensive troubleshooting sequence for

compressors and systems can be found in Section H of the

Copeland Electrical Handbook.

IDENTIFYING COMPRESSOR MECHANICAL FAILURES


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Most compressors fail due to system malfunctions which must be corrected to

prevent repeat failures. After a compressor fails, field examination of the failed

compressor often will reveal symptoms of system problems.

Proper corrections will help eliminate future failures.

REFRIGERANT FLOODBACK

This is a result of liquid refrigerant returning to the compressorduring the running

cycle. The oil is diluted with refrigerant to the point it cannot properly lubricate the load

bearing surfaces. The liquid washed the oil off the pistons and cylinders during the

suction stroke causing them to wear during the compression stroke. The liquid dilutesthe oil in the crankcase and the refrigerant rich oil will be pumped to the rods and the

bearings through the crankshaft. As the refrigerant boils off, there will not be enough oil

for sufficient lubrication at the bearings farthest from the oil pump. The center and rear

bearings may seize or may wear enough to allow the rotor to drop and drag on the stator

causing it to short.

Correction: (1) Maintain proper evaporator and compressor superheat.(2) Correct abnormally low load conditions.

(3) Install accumulators to stop uncontrolled liquid return.

IDENTIFYING COMPRESSOR MECHANICAL FAILURES


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FLOODED STARTS

This is the result of refrigerant vapor migrating to the crankcase oil during

the off cycle. When the compressor starts, the diluted oil cannot properly

lubricate the crankshaft load bearing surface causing an erratic wear or

seizure pattern.

Correction: (1) Locate compressor in warm ambient or install continuous pump

down.

(2) Check crankcase heater operation.

SLUGGING

This is the result of trying to compress liquid refrigerant and/or oil, in the cylinders.

Slugging is an extreme floodback in air cooled compressors and a severe flooded

start on refrigerant cooled compressors.

Correction: (1) Maintain proper evaporator and compressor superheat.

(2) Correct abnormally low load conditions.(3) Install accumulators to stop uncontrolled liquid return.

(4) Locate compressor in warm ambient or install continuous pump down.


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R-717 SystemR-717 System

Corrosion FailureCorrosion Failure

Documents

Capacity Control Block 3