Operation; Pre-Startup; Operation Checkout - SPX SGS REFRIGERATION STC Series User Manual

Twin unit cooler

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Table Of Contents

Table of Contents

operation

8.0 OPERATION

8.1 PRE-START UP

After the installation is completed, a review of the following items

should be preformed before the system is placed into operation:

Check electrical connections, fan bushing set screws, motor

mount bolts, coil flange bolts, drain pan flange bolts, and

all other fasteners for tightness. If required, be sure the

thermostatic expansion valve bulb is properly located, strapped,

and insulated.

For systems with a defrost time clock check the timer to see

that it is set for the correct time of day and the starting pins

have been installed (normally two or three sets per day).

Defrost should be scheduled when the freezer doors are not

likely to be open.

When the unit is first started the room temperature is typically

above the contact closing temperature of the fan delay

thermostat, if a fan delay thermostat is provided for Electric

Defrost units (see that particular units electrical diagram). The

fans may remain off for a lengthy period of time. To prevent

this delay it is permissible to install a temporary jumper wire

between terminals "1R" and "2B". Once the room temperature

is below 25°F the jumper wire should be removed.

The motors for STC units are greased from the motor

manufacturer.

8.2 OPERATION CHECKOUT

With the system operating, check the supply voltage. The voltage

must be within +/- 10% of the voltage marked on the unit nameplate

and the phase to phase unbalance should be 2% or less.

LISTEN CAREFULLY to the unit to make sure there are no unusual

sounds. Sounds such as a noisy motor, the fan(s) scraping on the

housing, or loose fasteners allowing parts to rattle need to be

addressed immediately before continued unit operation.

Check the room THERMOSTAT setting. Be sure it functions properly.

For RECIRCULATED refrigeration systems the hand expansion

valve should be opened slowly until either condensate or frost

forms on the return bends from the bottom to the top of the coil.

A good indicator is when the defrost relief valve reads 5 PSI above

suction pressure.

For FLOODED refrigeration systems check to make sure the float

valve is working properly and allows refrigerant into the drum to

the appropriate level when the level is sufficiently low. If a hand

expansion valve has been added, the valve should be set to allow

liquid make up 70% of the time.

For DIRECT EXPANSION systems let the system balance out

at the desired room temperature and check the operation of

the expansion valve by properly measuring the superheat at the

sensing bulb. As much as thirty minutes may be required for the

new balance to take place after an adjustment is made.

For BRINE or WATER COOLING systems keep the closest vent

to the coil open while the fluid fills the coil to allow trapped air to

escape. Close the vent valve once fluid flows out of the valve and

check for water hammer in the coil.

With HOT GAS DEFROST systems allow the coil to frost, then

manually advance the defrost timer to initiate a defrost cycle.

Observe the defrost cycle to see if all controls are functioning

properly and that the coil is clear of all frost before the system

returns to refrigeration. Adjust the time clock pins if necessary.

Reset the defrost timer to the correct time of day. A defrost cycle

is only needed when the frost build up is such that it impedes

the airflow through the coil. The defrost requirements will vary on

each installation and may change depending on the time of the

year and other conditions..

With ELECTRIC DEFROST systems allow the coil to frost then