Carrier 90MU Manual De Usuario

 

Evaporator Coil - Observe fan compartment Caution note 
at the beginning of the Service section. 
 

Remove dirt and debris from evaporator coil as 

required by condition. Clean coil with a stiff brush, vacuum 
cleaner or compressed air. Use a fin comb of the correct 
tooth spacing (Refer to Tables 1A/B/C/2A/B/C  for coil 
fins/inch) when straightening mashed or bent coil fins. 
 
Water Regulating Valve 
 
PREPARATION FOR OPERATION. 
1.  Open the water regulating valve inlet and outlet 

isolation valves. 

2.  Close the water regulating valve bypass valve. 
 
ADJUSTMENT 
 

NOTE: Adjustments to the water regulating 
valve must be made slowly, allowing ample 
time for response and stabilization. 

 

1.  The compressor discharge pressure is controlled by 

the water regulating valve and may be monitored by 
observing liquid line pressure. 

2.  Install a calibrated gauge at the liquid line service port. 

FOR 90MA: Operating liquid line range for R-407C 
units is 200 to 215 psig, operating range for R-404A 
units is 240 to 260 psig, operating range for R-134a 
units is 122 to 130 psig.  

 

FOR 90MU : Operating liquid line range for R-407C 
units is 265 to 285 psig, operating range for R-404A 
units is 290 to 315 psig, If pressure reading is below 
operating range, rotate the square head adjusting 
screw counterclockwise; this will increase spring 
tension, decrease water flow and increase pressure. 

 

If pressure reading is above operating range, rotate the 
square head adjusting screw clockwise; this will 
decrease spring tension, increase water flow and 
decrease pressure. 

3.  Only the water regulating valve opening point is 

adjustable. The closing point is 3 to 7 psig below the 
opening point and is non-adjustable. 

 
Condenser - Condensers may require cleaning of water-
deposited scale. 
 

  

 

Follow all Safety codes. Wear safety glasses 
and rubber gloves when using inhibited 
hydrochloric acid solution. 

 
 

Clean condensers with an inhibited hydrochloric acid 

solution. The acid can stain hands and clothing, attack 
concrete and, without inhibitor, can attack steel. Cover 
surroundings to guard against splashing. Vapors from vent 
pipe are not harmful, but take care to prevent liquid from 
being carried over by the gases. 
 

Warm solution acts faster, but cold solution is just as 

effective if applied for a longer period. 

 FIGURE 9 - GRAVITY FLOW METHOD 

 
GRAVITY FLOW METHOD (Figure. 9) - 
1.  Disconnect condenser piping at unit, including isolation 

valves and water regulating valve.  

2.  Fill condenser as shown in figure 9. Follow acid 

manufacturer's instructions. When condenser is full, 
allow solution to remain overnight 

3.  Drain condenser and flush with clean water. 
 
FORCED CIRCULATION METHOD (Figure. 10) - 
1.  Disconnect condenser piping at unit, including isolation 

valves and water regulating valve.  

2.  Fill system as shown in figure 10. Follow acid 

manufacturer's instructions. Fully open vent pipe when 
filling system. The vent may be closed when system is 
full and pump is operating. 

3.  Regulate flow to condenser with a supply line valve. If 

pump is a non-overloading type, the valve may be fully 
closed while pump is running. For average scale 
deposit, allow solution to remain in condenser 
overnight. For heavy scale deposit, allow 24 hours. 

4.  Drain condenser and flush with clean water. 

 FIGURE 10 - FORCED CIRCULATION METHOD 

 

 
Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations

 

Printed in U.S.A. 

90MA-3SI     SUPERCEDES FORM 62-02971-00   09-2009 

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