Danfoss Praktiske tips Service guide

Fitters notes	Practical tips

This chapter is devided into two sections:			Page
Installation requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . .	.	. 127
The installation process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. . .	.	. 133

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Fitters notes	Practical tips - installation requirements
Contents		Page
	Installation requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	129
	Tubing must be kept clean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
	Particularly damaging impurities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
	Problems caused by moisture in the system . . . . . . . . . . . . . . . . . . . . . . . . .	129
	Problems caused by atmospheric air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
	Problems caused by oil and refrigerant breakdown . . . . . . . . . . . . . . . . . . . . .	. 130
	Problems caused by other impurities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
	Component and material requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	130
	Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
	Impurities and moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
	Copper tubing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	131
	Refrigerant requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	131
	Compressor oil requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	132

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Notes

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Fitters notes	Practical tips - installation requirements

Installation requirements More and more commercial refrigeration systems and air conditioning plants of a similar size are built up around hermetic and semihermetic compressors. These compressors, as compared to the open type, are normally more vulnerable to impurities in the refrigerant system and to incorrect operating conditions.

Therefore, in modern refrigeration systems, there are special demands on the quality of installation work and commissioning.

Tubing must be kept clean	A well-dimensioned, correctly installed and
	correctly commissioned refrigerant system is
	fundamental to a reliable refrigeration system
	with a long operating life.
	An absolute requirement on the refrigerant
	system is that it shall remain completely free of
	foreign bodies (impurities).
	Installation work must therefore be performed
	with a high degree of cleanliness. This applies
	especially to systems containing the new
	refrigerants.

Ac0_0003

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Particularly damaging impurities

Moisture

Atmospheric air

Soldering flux

Rust, copper oxide, scale

Metal swarf

Unstable oils

Certain fluorinated solutions (e.g. R11 or carbon tetrachloride)

Dirt or dust of any description.

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Problems caused by moisture in the system

Water separation and ice formation (blockage) in the expansion valve

Acid formation

Ageing and breakdown of the oil

Corrosion

Copper precipitation (dissolved copper from tubing deposited on bright steel parts in the compressor)

Damage to the insulating lacquer on motor windings.

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Fitters notes	Practical tips - installation requirements
Problems caused by		Aeration
atmospheric air		Chemical reaction between refrigerant
		and oil
		Increased condensing pressure.

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Problems caused by oil and refrigerant breakdown

Formation of organic and inorganic acids

Corrosion

Poor lubrication

Abnormal wear

Oil discolouration (darkening)

Sludge formation

Leaking discharge valves because of oil carbon deposits

Increased discharge gas temperature

Compressor damage

Motor burnout

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Problems caused by other impurities

The other impurities mentioned can cause:

Accelerated chemical processes (breakdown)

Mechanical or electrical faults

High temperature accelerates the breakdown processes, therefore abnormally high condensing temperatures and, especially, abnormally high discharge pipe temperatures must be avoided.

For the reasons just mentioned, a number of requirements must be met. Some of these are described in the next chapter.

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Component and	Compressors for refrigeration and heat pump
material requirements	systems are put through a comprehensive clea-
Components	ning process by the manufacturer so that, prac-
	tically speaking, all traces of moisture and other
	impurities are removed.
	All other components in the system should be of
	the same standard.
	All components must fulfil cleanliness require-
	ments. In cases of doubt, components should be
	checked.

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© Danfoss A/S (AC-DSL/MWA), 10 - 2006