System Voltage - That nominal voltage value assigned to a circuit or system for the purpose of designating its voltage class.
Nameplate Voltage - That voltage assigned to a piece of equipment for the purpose of designating its voltage class and for the purpose of defining the minimum and maximum voltage at which the equipment will operate.
Utilization Voltage - The voltage of the line terminals of the equipment at which the equipment must give fully satisfac- tory performance. Once it is established that supply voltage will be maintained within the utilization range under all sys- tem conditions, check and calculate if an unbalanced condi- tion exists between phases. Calculate percent voltage un- balance as follows.
Three Phase Models Only
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| 2) MAXIMUM VOLTAGE DEVIATIONS | ||
3) PERCENT VOLTAGE | = 100 X |
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UNBALANCE |
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| 1) AVERAGE VOLTAGE | |
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HOW TO USE THE FORMULA:
EXAMPLE: With voltage of 220, 216, and 213
1)Average Voltage = 220+216+213=649 / 3 = 216
2)Maximum Voltage Deviations from Average Voltage = 220 - 216 = 4
3) Percent Voltage Unbalance = 100 x | 4 | = | 400 | = 1.8% | |
216 | 216 | ||||
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Percent voltage unbalance MUST NOT exceed 2%.
FIELD DUCT CONNECTIONS
Verify that all duct connections are tight and that there is no air bypass between supply and return.
CONTROL VOLTAGE CHECK
With disconnect switch in the open “OFF” position, discon- nect blue wire from low voltage transformer TRANS1. Close the disconnect switch to energize TRANS1 control trans- former. Check primary and secondary (24V) of control trans- former TRANS1.
THERMOSTAT PRELIMINARY CHECK
With disconnect switch open and blue wire disconnected from TRANS1 transformer, attach one lead of ohmmeter to termi- nal R on TB1 terminal block. Touch, in order, the other ohm- meter lead to terminals Y1, Y2 and G at TB1 terminal block. There must be continuity from terminal R to terminals Y and G. R to Y indicates cool. R to G indicates fan (auto). Replace blue wire on TRANS1 transformer.
FILTER SECTION CHECK
Remove filter section access panels and check that filters are properly installed. Note airflow arrows on filter frames.
BELT DRIVE MODELS ONLY
BEARING CHECK
Prior to energizing any fans, check and make sure that all setscrews are tight so that bearings are properly secured to shafts.
SET EVAPORATOR FAN RPM
Actual RPM’s must be set and verified with a tachometer or strobe light. Refer to Appendices A and B for basic unit fan RPM. Refer also to “Airflow” section of this manual. With disconnect switch open, disconnect thermostat wires from terminals Y and W. This will prevent heating and mechanical cooling from coming on. Place a jumper wire across termi- nals R and G at TB1 terminal block. Close disconnect switch; evaporator fan motor will operate so RPM can be checked.
For gas heat units, the airflow must be adjusted so that the air temperature rise falls within the ranges given stated on Data Plate (see Appendix A - Blower Performance).
TENSION AND ALIGNMENT ADJUSTMENT
Correct belt tension is very important to the life of your belt. Too loose a belt will shorten its life; too tight, premature mo- tor and bearing failure will occur. Check you belt drive for adequate
Belt Tension Adjustment
t = Span length, inches
C = Center distance, inches
D = Larger sheave diameter, inches d = Smaller sheave diameter, inches
h = Deflection height, inches
TYPE | SMALL | DEFLECTION |
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SHEAVE |
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FORCE (lbs) |
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BELT | DRIVE | (in) | USED | NEW |
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AX | Standard | 3.0 to 4.0 | 4.2 ± 0.5 | 5.5 ± 0 | .5 | 0.313 |
Recommended Pounds of Force Per Belt
New
15