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McQuay MicroTech III RAH Operation And Maintenance Manual Download Page 45

McQuay OM 920-1

45

Keypad/Display Menu Structure

OAD OpCl

 is an adjustable item which is used to turn the OA damper output on. This output 

is available only on self contained units.

Comp 1 OnOff

 is an adjustable item that turns on compressor #1.

Comp 2 OnOff

 is an adjustable item that turns on compressor #2.

Comp 3 OnOff

 is an adjustable item that turns on compressor #3.

Comp 4 OnOff 

is an adjustable item that turns on compressor #4.

Comp 5 OnOff 

is an adjustable item that turns on compressor #5.

Comp 6 OnOff

 is an adjustable item that turns on compressor #6.

Comp 7 OnOff

 is an adjustable item that turns on compressor #7.

Comp 8 OnOff

 is an adjustable item that turns on compressor #8.

CFan Outpt 1

 an adjustable item that turns on the condenser fan output #1.

CFan Outpt 2

 an adjustable item that turns on the condenser fan output #2.

CFan Outpt 3

 an adjustable item that turns on the condenser fan output #3.

Note –

Turning on any one of the compressors will automatically turn on the first condenser fan on 

the circuit. Other condenser fans must be manually turned on to control the head pressure 

of the unit. Refrigerant gauges must be connected to the unit for observation of the head 

pressure in the manual control mode of operation. Additional condenser fans must be 

turned on to maintain the head pressure.

BP/WR Valve

 is an adjustable item used to manually drive the bypass/water regulating valve 

open and closed.

CW Valve

 is an adjustable item used to manually drive the chilled water valve open and 

closed.

ECond VFD

 is an adjustable item which is used to turn on/off the evaporative cooling 

condenser fan VFD.

ECFan Spd Cmd

 is an adjustable item which is used to set the evaporative cooling condenser 

fan VFD speed position.

EC Drn Valve

 is an adjustable item which is used to open/close the evaporative cooling drain 

valve.

Sump Pump

 is an adjustable item which is used to turn on/off the evaporative cooling sump 

pump.

GasHtgOnOff 

is an adjustable item used to manually turn the main gas valve output on/off.

Htg Valve

 is an adjustable item used to manually drive the modulating heating valve open and 

closed.

F&BP Damper

 is an adjustable item used to manually drive the F&BP damper open and 

closed.

Htg Stg 1

 is an adjustable item that turns on the first stage of electric heat.

SCR Ena 1

 is an adjustable item used to turn on and off the SCR output # 1.

 

Htg Stg 2

 is an adjustable item that turns on the second stage of electric heat.

SCR Ena 2 

is an adjustable item used to turn on and off the SCR output # 2.

 

Htg Stg 3

 is an adjustable item that turns on the third stage of electric heat.

Htg Stg 4

 is an adjustable item that turns on the fourth stage of electric heat.

Htg Stg 5

 is an adjustable item that turns on the fifth stage of electric heat.

Htg Stg 6

 is an adjustable item that turns on the sixth stage of electric heat.

Reheat Valve

 is an adjustable item used to manually drive the reheat valve open and closed.

Reheat Stage

 is an adjustable item that turns on the staged reheat output.

Summary of Contents for MicroTech III RAH

Page 1: ...ional RAH RCS RDS RDT RFS RPS SWP and SWT Operation and Maintenance Manual OM 920 1 MicroTech III Unit Controller for Applied Rooftop and Self Contained Systems Group Applied Systems Part Number OM 92...

Page 2: ......

Page 3: ...Menu 49 LON BACnetIP BACnetMSTP Setup Menu 50 Alarm Delays Setup Menu 50 Analog Input Status Menu 50 Universal I O Status Menu 51 Digital Input Status Menu 52 Digital Output Status Menu 52 Adv Setup...

Page 4: ...917 MicroTech III Rooftop Unit Controller BACnet LON Communications IM 918 MicroTech III Unit Controller IM 919 RPS RDT RFS RCS 015C 105C IM 926 RPS RDT RFS RCS 050D 140D IM 893 SWP Self Contained 01...

Page 5: ...operation When servicing this equipment during rainy weather the electrical components in the main control panel must be protected from the rain CAUTION Extreme temperature hazard Can cause damage to...

Page 6: ...s a changeable value and the cursor is at that line the entire line is highlighted Each line on a page may also be defined as a jump line meaning pushing the navigation wheel will cause a jump to a ne...

Page 7: ...2 password is 6363 the Level 4 is 2526 and the Level 6 password is 5321 Continuing without entering one of these three levels allows access only to the Alarm Lists Menu and the System Summary Menu Not...

Page 8: ...edit mode pressing the wheel again causes the editable field to be highlighted Turning the wheel clockwise while the editable field is highlighted causes the value to be increased Turning the wheel co...

Page 9: ...away from the unit and let it run at the manual settings When Manual Control is set to Yes the Control Mode is set to Off so that the unit will not restart automatically When Manual Control is set to...

Page 10: ...n all be displayed with the keypad display Menu items displayed will change based on the selected unit configuration Keypad display menus are divided into 1 System Summary menu password required 2 Sta...

Page 11: ...McQuay OM 920 1 11 Keypad Display Menu Structure...

Page 12: ...Temp is a status only item which displays the current value of the Control Temperature The Control Temperature is defined as the temperature input selected by the Control Temperature Source parameter...

Page 13: ...y item which displays the current duct static pressure reading DuctSP Spt is a status only item which indicates the duct static pressure set point used for controlling the VFD for the supply air fan T...

Page 14: ...git level 6 password 5321 using the keypad buttons located on the controller interface Table 3 Standard Menus Menu Display Name Item Display Name Default Setting Range Password Level Standard Menu Sys...

Page 15: ...te Off 6 Start Recirc FanOnly MinDAT Htg Econo Clg Unit Status Enable 6 OffMan OffMnCtl OffNet OffAlm OffFnRty Dehum Status Inactive 6 Active Ctrl Mode Off Off 6 HeatOnly CoolOnly FanOnly HeatCool Aut...

Page 16: ...indicates the percentage of the unit maximum cooling capacity currently operating Htg Capacity is a status only item which indicates the percentage of the unit maximum heating capacity currently oper...

Page 17: ...ndicates the input source or function that is responsible for setting the Occupancy parameter to Occ UnoccSrc is a status only item which indicates the input source or function that is responsible for...

Page 18: ...emperature sensor This sensor is standard on all units EFT LCT RTU is a status only item which displays the current entering fan leaving coil temperature reading from the unit mounted temperature sens...

Page 19: ...g requirements for using this output refer to Field Wiring in the MicroTech III Installation Manual IM 919 The Pump Start Output is turned on whenever the economizer bypass valve is open the unit is i...

Page 20: ...status only item that indicates the current return exhaust fan VFD commanded speed Min Speed is a status only item that indicates the minimum return exhaust fan VFD speed Bldg Press is a status only i...

Page 21: ...item which sets the minimum cooling discharge set point for use with a cooling discharge air temperature set point reset schedule Min Clg Spt is an adjustable item which sets the value of the sensor i...

Page 22: ...enu The Head Pressure menu contains parameters that are used to maintain head pressure control WRV Pos is a status only item that indicates the current water regulating valve position Head P Circ 1 is...

Page 23: ...item used to set a minimum sump temperature The sump is emptied to prevent freezing if the sump temperature drops below this set point Sump Pump Status is a status only item that displays the current...

Page 24: ...not go above a value called the Ventilation Limit and does not go below a value called the Demand Control Ventilation Limit Table 13 Economizer Menu Menu Display Name Item Display Name Default Settin...

Page 25: ...easuring reset function on and off This is one of several available methods of automatically resetting the Min OA Pos parameter OA MinV mA is is an adjustable item used when Min OA Reset is set to Ext...

Page 26: ...it goes into the heating mode of operation by analyzing the control temperature The control temperature can be return temperature space temperature or outside air temperature The unit goes into the he...

Page 27: ...les the daytime heating mode of operation If the Occ Heating parameter is set to No the unit will only go into heating during the initial morning warm up cycle If the Occ Heating parameter is set to Y...

Page 28: ...r Return Air value depending on the setting of the Humidity Sensor Location This parameter can either be set to Space or Return Dehum Method is an adjustable item used to set the dehumidification meth...

Page 29: ...9 6 Wed 00 00 00 00 00 00 23 59 6 Thu 00 00 00 00 00 00 23 59 6 Fri 00 00 00 00 00 00 23 59 6 Sat 00 00 00 00 00 00 23 59 6 Sun 00 00 00 00 00 00 23 59 6 Hol 00 00 00 00 00 00 23 59 6 Table 19 One Eve...

Page 30: ...n is a status item which gives the number of hours the return exhaust fans have operated Mech Cool is a status item which gives the number of hours that mechanical cooling has operated Comp 1 is a sta...

Page 31: ...r sensor input will be used 100 OA SCU is an adjustable item used to select whether or not a self contained unit will be configured for 100 outside air operation OAT Sensor is an adjustable item used...

Page 32: ...ter of the password Low DAT is an adjustable item that sets the duration of a time period upon unit start up during which the Low Discharge Temperature fault is ignored This may be particularly import...

Page 33: ...be changed whenever the Ramp Time of the VFD is changed The Ramp up Time must equal the Ramp down Time to provide stable operation Min Period is an adjustable item that sets the duration of the sampl...

Page 34: ...F SF Max is an adjustable item that sets the speed of the return exhaust fan when the supply fan is at the Sup Fan Max value Sup Fan Min is an adjustable item used with the RF SF Min parameter describ...

Page 35: ...s Max Clg Change is an adjustable item that sets the maximum value for an increase or decrease of the DAT Clg Spt in zone control applications Zone Htg DB is an adjustable item which sets a dead band...

Page 36: ...r the OAT drops below the Condenser Stage 2 Set Point by more than the Condenser Fan Differential Default 65 F CfanOut3 Spt is an adjustable item used to set the OAT temperature that the third control...

Page 37: ...he edited temperature where WRV at 100 is OK WRV Act Time is an adjustable item which is used to set the time required for the WRV to be driven from 0 to 100 Min WRV Time is an adjustable item which s...

Page 38: ...t point would be from 56 0 F to 54 0 F Econo Period is an adjustable item which sets the sampling time used in the PI control function of the economizer actuator Econo Gain is an adjustable item which...

Page 39: ...ntrol function that modulates the Min OA Pos parameter to maintain the OA Flow parameter at the MinOA Flow set point when a unit is equipped with the optional DesignFlow outdoor airflow measuring feat...

Page 40: ...THtg Lock parameter Heating operation is re enabled when the outdoor air temperature sensor input falls below the OATHtg Lock value by more than this differential F BP Method is an adjustable item use...

Page 41: ...an adjustable item is an adjustable item which sets a stage time period between the minimum and maximum cooling stages during dehumidification operation Stg Rht DB is an adjustable item used for rehe...

Page 42: ...ld supplied humidity sensor current or voltage signal Min Dehum Spd is an adjustable item used to set the minimum VFD speed on VAV units when dehumidification is active Max Dehum Spd is an adjustable...

Page 43: ...e high return air temperature alarm Manual Control Menu The manual control of operation is a function that is used for operating the unit during a service call only The unit must not be operated in th...

Page 44: ...et the speed of the return exhaust fan OAD Econo is an adjustable item which is used to set the economizer damper position Manual Control BP WR Valve 0 0 100 4 CW Valve 0 0 100 4 ECond VFD Off Off 4 O...

Page 45: ...pen and closed CW Valve is an adjustable item used to manually drive the chilled water valve open and closed ECond VFD is an adjustable item which is used to turn on off the evaporative cooling conden...

Page 46: ...alarms as well as the date and time that they were detected are displayed on the Active Alarm menu These alarms are displayed in order of group priority Faults first Problems second and Warnings last...

Page 47: ...ftware Configuration Code consists of a 28 character string of numbers and letters The code can be found on the Unit Software Identification Label located on the back side of the control panel door Ta...

Page 48: ...osition 100 3 Economizer Airside 4 Economizer Waterside 9 Design Flow 0 No Design Flow 1 018 030 800 2 036 040 802 3 045 075 047 4 080 135 077 10 Heating Type 0 None 1 F BP Control 2 Staged 3 Modulate...

Page 49: ...o 1 Yes 20 Energy Recovery 0 None 1 ConstSpdWhl 2 VarSpdWhl Grhm 3 VarSpdWhl McQ21 21 Cooling Circuit Type 0 Individual 1 Dual Circ Water Condenser 2 Dual Circ Air Condenser 22 Head Pressure Control 0...

Page 50: ...tance shown in 1 10th of an ohm scale Example MCB AI1 DAT sensor shows a value of 181380 the actual resistance would be 18 138 ohms This would translate to a temperature of 53 5 F IM 916 MicroTech III...

Page 51: ...Table 47 Universal I O Status Menu Menu Display Name Item Display Name Default Setting Range Password Level Universal I O Status MCB X1 0 9999999 2 MCB X2 0 9999999 2 MCB X3 0 9999999 2 MCB X4 0 99999...

Page 52: ...gital Input Status Menu Menu Display Name Item Display Name Default Setting Range Password Level Digital Input Status MCB DI1 Off Off 2 On MCB DI2 Off Off 2 On MCB DI3 Off Off 2 On MCB DI4 Off Off 2 O...

Page 53: ...DO3 Off Off 2 On EMB DO4 Off Off 2 On EMB DO5 Off Off 2 On EMB DO6 Off Off 2 On EMC DO1 Off Off 2 On EMC DO2 Off Off 2 On EMC DO3 Off Off 2 On EMC DO4 Off Off 2 On EMC DO5 Off Off 2 On EMC DO6 Off Of...

Page 54: ...occ Diff 3 F 0 10 F 2 Service Time 20s 0 300s 2 DLS Strt Mon Mar N A 2 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec DLS Strt Wk 2ndWeek 1stWeek 2 2ndWeek 3rdWeek 4thWeek 5thWeek DLS End Mon Nov N A...

Page 55: ...issues Table 51 Adv Status Parameters Menu Menu Display Name Item Display Name Default Setting Range Password Level Adv Status PA Temp 2 VAVBox Out Heat Cool 2 DuctPress1 0 0 5 0in 2 DuctPress2 0 0 5...

Page 56: ...were detected The alarm that was detected most recently is displayed first Multiple occurrences of the same alarm may appear Alarm Clearing Active alarms can be cleared through the keypad display or...

Page 57: ...m Self Contained only When a unit is equipped with the head pressure control option the Water Regulating Valve Problem occurs when the greater of the two refrigerant pressure readings drops below the...

Page 58: ...e Return Air Sensor problem occurs When the RAT Sensor problem occurs the unit continues to operate with the following modifications Cooling Reset and Heating Reset revert to none if they are set to R...

Page 59: ...the pump output is de energized and the valves close If the freezestat contacts are still open the pump output remains energized the valves remain open and the 10 minute timer resets This continues wh...

Page 60: ...red through the unit keypad or via a network signal High Discharge Air Temp If the Discharge Air Temperature is greater than the High Discharge Temperature Limit Default 170 F and the supply fan has b...

Page 61: ...lled water hot water or steam coil the Freeze Fault occurs when the optional freezestat contacts open as a result of detecting an abnormally low water or steam coil temperature while the fans are runn...

Page 62: ...iagram The transition from any operating state to another is graphically represented in this figure With a start up command from an Off State the unit will always go into the Start Up state of operati...

Page 63: ...t is used Zero OA Time is set equal to the time to occupancy when the unit starts so that the OA dampers will open at occupancy time Neither heating nor cooling is provided when the unit is in the Fan...

Page 64: ...s in the Recirculating operating state until the Recirculate State Timer default 180 seconds expires This timer is adjustable from 0 to 30 minutes via the following path Extended Menus Timer Settings...

Page 65: ...ion to Mechanical cooling will occur if all the following are true The Control Temperature rises above the zone cooling setpoint by more that the zone cooling deadband The discharge air temperature is...

Page 66: ...started after airflow is lost The supply fan is controlled by a VFD The airflow switch PC7 is open AND the duct static pressure is less than the duct static pressure setpoint There are no active fault...

Page 67: ...is high enough for operation Compressor operation is not disabled by an alarm condition None Cooling capability is not provided Off Ambient The outdoor air temperature OAT on air cooled units or the...

Page 68: ...t by more than the Heating Lockout Differential Off Network Control Mode is set via the System Menu to auto and the unit is disabled via a network command Off Manual Control mode is set to Fan Only or...

Page 69: ...th compressorized cooling the percentage value changes incrementally based on the number operating cooling stages Determining Heating Capacity Htg Capacity is a status item which indicates the percent...

Page 70: ...work signal The following sections describe the five available Net App Mode selections Note The Net App Mode has no effect on the unit operation unless the Control Mode parameter is set to Auto Off Wh...

Page 71: ...Ovrd The Occupancy parameter indicates TntOvrd when the unit is in the tenant override mode In this mode the unit starts and runs continuously cooling and heating as required to maintain the occupied...

Page 72: ...o a network schedule indicating an occupied period IntSchedule The Occ Src parameter indicates Int Sched when the Occupancy parameter indicates Occ due to the unit internal Schedule OneEventSchedule T...

Page 73: ...s enabled due to an internal optimal start schedule being activated Network Optimal Start Unoccupied operation is enabled due to a network optimal start schedule being activated None The Unoccupied So...

Page 74: ...ed without affecting the regular internal schedule A start date time and an end date time can be set The unit can be scheduled to operate during a specified period by using this feature During the spe...

Page 75: ...ver operate simultaneously A unit configured for zone or space comfort control either operates to maintain the Zone Cooling Set Point using economizer and or mechanical cooling or the Zone Heating Set...

Page 76: ...tomatically reverts from either Outdoor Air or Mixed Air to Return if the Control Type is Zone Not DAT If the Return Air Temperature is not reliable the Control Temperature may then revert to Space as...

Page 77: ...rride Time Increment The button must be held for at least 1 second but not more than 30 seconds The unit then starts and runs in the tenant override mode which is the same as occupied mode except that...

Page 78: ...ation Initiation An analog sensor is mounted in the return duct the space or outdoor to sense Relative Humidity The location is selected by setting the Sensor Location value on the keypad to Return Sp...

Page 79: ...aintain the Reheat Setpoint If the Reheat Type software configuration parameter is set to Standard Heat then the normal heating analog output is controlled to maintain the Reheat Setpoint Cooling Fan...

Page 80: ...nit needs to go into Cooling This reduces opportunity for unit to go into heating or cooling during Dehumidification In the Cooling state the Dehumidification Reheat Setpoint equals the DAT Cooling Se...

Page 81: ...ge Time The Enthalpy Wheel is turned on at minimum speed when The Wheel has been off due to Frosting Condensation for longer than an edited Minimum off Time The exhaust air temperature leaving the Ent...

Page 82: ...s is referred to as the Intersection Point This prevents the wheel from operating under frosting conditions The following describes the details involved in the frost protection function that affect th...

Page 83: ...The Exhaust Fan capacity is commanded to a value above the minimum value Default 5 by a BAS for longer than the Minimum Exhaust Fan Start Time Default 120 seconds OR The Exhaust Fan is Constant Volum...

Page 84: ...nt Limit at the Min Clg Spd For VAV units the Demand Control Ventilation Limit equals the Ventilation Limit times the ratio of the editable DCV Limit to the editable Vent Limit The editable parameters...

Page 85: ...Limit 10 Min OA reset type IAQ VDC Min V mA 0 Max V mA 10 PPM DCV Limit 800 PPM Vent Limit 1000 Min PPM 0 Max PPM 2000 In Figure 9 the Minimum OA Position would vary linearly from 10 outside air damp...

Page 86: ...its These outputs are controlled differently depending on whether the unit is a 100 OA or a Return Air Digital Output The OA damper is driven fully open when the digital output is On and fully closed...

Page 87: ...perating state the outdoor air dampers are modulated as required to maintain the Discharge Cooling Set Point Economizer to Cooling Operating State The transition from the Econo to Cooling operating st...

Page 88: ...hether water flow is established The Bypass Valve is opened in the Fan Only state whenever Waterside economizer is installed AND EconStatus Enabled or Off Ambient AND Control Temperature is greater th...

Page 89: ...he Water Regulating Valve is closed The Water Regulating Valve is set to an editable minimum water regulating valve position MinWRVPos Default 10 The Entering Water Temperature EWT is measured after t...

Page 90: ...h the condenser before a compressor starts This occurs when the following conditions are true Airside economizer position is equal to or greater than 95 open for longer than the cooling stage timer Th...

Page 91: ...The method for deciding which staging sequence is active is described for each compressor configuration below Two Unequal Sized Compressors Two Circuits Three Stages Only one sequence is provided so t...

Page 92: ...set to Auto and neither circuit is disabled the compressor sequence is Std 1 if compressor 1 has fewer hours than compressor 2 and the staging sequence is Std 2 if compressor 1 does not have fewer ho...

Page 93: ...han compressor 2 and the staging sequence is Std 2 if compressor 1 does not have fewer hours than compressor 2 If Circuit 1 is disabled the staging sequence is Std 2 If Circuit 2 is disabled the stagi...

Page 94: ...at disabling and re enabling the compressors or turning the unit off and on may be necessary to cause sequence changes If a circuit is disabled Maximum cooling stages is set to two Any compressor on t...

Page 95: ...it 2 are disabled the staging sequence is Std 1 Only compressors 3 and 4 are used The Compressor Sequence changes based on Run Time only when the compressor stage equals Maximum cooling stages or zero...

Page 96: ...mum cooling stages or zero This means that disabling and re enabling the compressors or turning the unit off and on may be necessary to cause sequence changes If a circuit is disabled Maximum cooling...

Page 97: ...n compressor 2 and the staging sequence is Std 2 if compressor 1 does not have fewer hours than compressor 2 If Circuit 1 is disabled the staging sequence is Std 2 If Circuit 2 is disabled the staging...

Page 98: ...This means that disabling and re enabling the compressors or turning the unit off and on may be necessary to cause sequence changes If a circuit is disabled Maximum cooling stages is set to four Any...

Page 99: ...1 1 3 1 3 5 1 3 5 7 1 2 3 5 7 1 2 3 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 8 Std 2 2 2 4 2 4 6 2 4 6 8 1 2 4 6 8 1 2 3 4 6 8 1 2 3 4 5 6 8 1 2 3 4 5 6 7 8 Std 3 3 1 3 1 3 7 1 3 5 7 1 3 4 5 7 1 3 4 5 7 8 1...

Page 100: ...at the stage that produces the discharge air temperature that is closer to the setpoint which results in an average discharge air temperature that is very close to the Discharge Cooling Setpoint This...

Page 101: ...idification is active AND Leaving Coil Temp is greater than the Maximum leaving coil Setpoint AND Current Stage is less than the available number of stages The number of compressor stages decreases wh...

Page 102: ...3 The Cooling Interstage Timer has expired DTB Area B Area C is greater than DTA Area A and the discharge air temperature is below the Effective Discharge Cooling Set Point by more than half the Disc...

Page 103: ...t 9 The Cooling Interstage Timer has expired at the same time that DTB Area M becomes equal to DTA Area L Therefore cooling is staged down the Cooling Interstage Timer is reset and DTA is subtracted f...

Page 104: ...e minimum leaving coil setpoint AND Current Stage is greater than 0 Project Ahead This section provides the Projected Control Temperature used to turn on and off stages of heating and cooling for Zone...

Page 105: ...et menu The reset type may be set to one of the following None Discharge Cooling Spt User Adjustable Network Discharge Cooling Spt Network DAT Clg Setpoint when it is valid Space Discharge Cooling Spt...

Page 106: ...fan on each circuit is always turned on when any compressor on the circuit is turned on through auxiliary switches on the compressor contactors The second two fans on each circuit if applicable are c...

Page 107: ...Unit Size CondFanOutputA MCB D07 CondFanOutputB MCB D08 PC13 PC231 Setpoint Differntial Setpoint Differential Setpoint Differential 050 65 5 060 60 5 062 70 5 068 70 5 070 75 5 90 35 075 65 5 85 5 90...

Page 108: ...F If the OAT Compressor Lockout Temperature on units with evaporative condensing is lowered below 40 F it will immediately be set back up to 40 F Condenser fan 1 on each circuit is turned on and off v...

Page 109: ...connected fans to a calculated setpoint The speed varies from a minimum value 25 default to 100 as the sump temperature varies from the Min Sump Temp to the Max Sump Temp setting In addition to the f...

Page 110: ...ut be turned on to open the valve when the sump temperature drops below 35 F the Sump Pump output is to be turned on if both of the following are true Dolphin System Yes The Sump Pump has been off for...

Page 111: ...n the unit heat cool changeover function but the discharge air temperature falls below a minimum discharge temperature limit by more than the deadband The Min DAT operating state prevents cold dischar...

Page 112: ...state the controller activates the units heating equipment as required to prevent the discharge air temperature from becoming too cool if the Min DAT Control Flag is set to yes via the Heating menu T...

Page 113: ...22 EXPB DI_X1 after having it turned on and the FSG is not off on safety lockout the prepurge sequence will start over If an attempt is made to restart the burner by resetting the FSG or if an automat...

Page 114: ...cribed below the gas heat operates the same for both return air units and 100 Outdoor Air units The sequence described in the following paragraphs is initiated for a 100 OA Unit any time during the St...

Page 115: ...EMB X7 is used to modulate the signal between 0 and 100 capacity Return Air Units When the unit enters the Heating operating state the controller first holds the gas valve at the minimum fire positio...

Page 116: ...ax Clg Spt 10 0V An example of discharge temperature reset based on outdoor air temperature is illustrated in Figure 13 Cooling Reset Type Flag is set to OAT in this example When the current outdoor a...

Page 117: ...n a signal provided via a network The choice of control method SF Cap Ctrl may be set to Duct Press or Speed via the keypad After the Supply Fan is started a speed signal of 25 is sent to the variable...

Page 118: ...Position default 5 OR the SAF capacity is below the Minimum Exhaust SAF capacity default 10 The Exhaust Fan capacity is at or below its minimum value Default 5 for longer than the Min Exhaust Fan Sto...

Page 119: ...from its speed when the damper was closed Exhaust fans do not use this feature Fan Tracking Control For units with variable frequency drives the return fan may be controlled such that the return fan...

Page 120: ...k signal The active setpoint is changed whenever either of these values changes so it equals whichever value was changed most recently Speed Control When speed control is selected the fan operates at...

Page 121: ......

Page 122: ...on training or call 540 248 9646 and ask for the Training Department Warranty All McQuay equipment is sold pursuant to its standard terms and conditions of sale including Limited Product Warranty Con...

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