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REFCO LAC Extreme User Manual

Cooling operation

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HVAC/R

Service Products

REFCO Manufacturing Ltd.

Telefon +41 41 919 72 82

Industriestrasse 11

Telefax +41 41 919 72 83

CH-6285 Hitzkirch (Switzerland)

[email protected] www.refco.ch

INSTALLATION OPERATION
AND MAINTENANCE GUIDE

LAC EXTREME

Cooling only, Heat pump and Low Temperature Cut-Off Models

The HPC controllers modulate the condenser fan speed to maintain a cons-

tant condensing pressure in heat pumps, air conditioners and refrigeration

plant. This results in higher efficiency, shorter compressor running times,

and more-stable conditions on the evaporator. Over-condensing is elimina-

ted, and freeze-up of air conditioner indoor units is prevented.

COOLING OPERATION

Controlling air movement over the condenser by varying the fan speed

maintains a constant condensing temperature, therefore a constant head

pressure. The condenser temperature is measured midway through the cir-

cuit, where the hot gas is condensing. As the condenser temperature rises

and falls, the fan speed automatically increases and slows down to maintain

the head pressure at the set point level. When first powered in the fan runs

at full speed for 10 seconds before controlling to temperature. Note: low

temperature cut-off models need to measure within range before start up.

As temperatures drop the fan speed will fall to its minimum speed. Low

temperatures cut-off models switch off the fan if the temperature continues

to drop: a temperature rise will initiate a 2 second full speed re-start to get

the fan moving. Dual circuit systems are accommodated by the 2-sensor

model where controller responds to the higher of the two temperatures.

Fig. 1 Application Example