Unitary Products Group

Transcription

1 Unitary Products Group Voyager Commercial Packaged Rooftop Applications SUBJECT: Micro Controls with Voyager Ton Packaged Units The purpose of this bulletin is to answer common questions regarding the current Voyager Commercial Micro controls for stand-alone applications. In addition, the information provided will help in better understanding the value that Voyager commercial adds to the Voyager product line. The most frequently asked questions are presented in a question and answer format. Wiring ladder diagrams are included which depict the necessary wiring logic. Reference the most recent wiring diagrams prior to beginning any field modifications and consult local electrical codes for compliance. The Voyager Commercial micro controls has furthered the value of Voyager Light Commercial controls by providing many competitive and innovative product enhancements which are unique to the HVAC industry. It is a second generation of microprocessors which includes VAV capability and expanded constant volume features. Major control features that have been added to Voyager Commercial include, in part, the following: VAV Capability (Inlet Guide Vanes and VFD s) VariTrac Compatibility with TCI (constant volume only, not VAV) Ventilation Override (exhaust and pressurization mode) External auto stop User defined exhaust fan setpoint (0 to 100%) Compressor Lead/Lag Added Fan Failure Switch to UCP Remote Panel provides morning warm up on constant volume and VAV units Remote Panel provides supply air tempering on constant volume units Evaporator defrost controls which respond to coil temperature Two speed exhaust fans and added exhaust capacity Enhanced low ambient head pressure control as standard (cycle condenser fans) Thermal Expansion Valves External High head pressure switches for each compressor Adjustable position on the return air economizer damper In addition Voyager Commercial includes the proven performance and simplicity of the Voyager Light Commercial drum and tube heat exchanger with negative pressure gas valve. American Standard Inc Since The Trane Company has policy of continuous product improvement, it reserves the right to change specifications and design without notice.

2 TABLE OF CONTENTS Page Time Clocks & Start Up VAV Startup Time Clocks with VAV VAV Setpoint Control VAV Changeover Smoke Detection & Ventilation Override Smoke Detector Location Ventilation Override Ventilation Override (Purge) Economizer Control Strategies Energy Management Control Temperature Controls (General) Stand-alone VAV VAV Setpoint Range VAV Conversion Discharge Air Control Varitrac Compatibility VAV & Bypass Outside Air Compensation Compressor Lead/Lag When not to use CTI s Duct Heaters/Perimeter Heat Field Supplied Duct Heater Perimeter Heat Compressor Control Compressor Operation Coil Frost Protection Clogged Filter Switch Two speed Motors Low Ambient Control Cooling to zero Exhaust Fans Independent Exhaust Fans Smoke Purge Building Pressurization Control

3 Time Clocks & Start Up Question - How can the Voyager VAV start without a zone sensor? This is a temporary situation. Answer - LTB1-2 and LTB1-4 must be jumpered to enable the rooftop. It will become disabled when the jumper is removed. The rooftop is equipped with a factory installed supply air sensor and will control to the supply air setpoint. Question - What time clock features are available for Voyager VAV? Answer - A time clock contact can be installed between LTB1-11 and LTB1-12 (similar to light commercial Voyager). When contacts close, the unit operates as described below : Mechanical cooling is disabled, outside air damper will close and the fan goes into automatic mode. Inlet guide vanes (IGV) and boxes are forced opened during transition from occupied to unoccupied occurs. If a sensor is installed in the critical space (i.e. BAYSENS021A or BAYSENS013A (non - programmable)), heating can be enabled. If the zone temperature drops 10 degrees below the morning warm-up setpoint (MWUS) during unoccupied, heating will be enabled (down to a low limit of 50 degrees). If the factory installed MWUS is disabled, the heating default is 60 degrees. A sensor must be provided to enable heating functions. Question - How does the Voyager Commercial VAV control operate in conjunction with Tracer or a remote night set back panel during unoccupied mode? Answer - The inlet guide vanes will close when a transition from occupied to unoccupied cooling occurs. If the zone temperature rises above zone setpoint, cooling will be enabled and operates in constant volume mode (i.e. boxes open & IGV open). If the zone temperature drops below zone setpoint, heating is enabled and operates in constant volume mode. Unoccupied VAV heating and cooling setpoints are only available on Tracer or the remote setback panel. Question - Where does Voyager VAV connect electrically for heating change over, day time warm up or morning warm up? Answer - The boxes need to be wired into the VAV heating relay (VHR) contacts. These are shown on the wiring diagram as an inset. The terminals are LTB3-3,4 &5. Which terminal to use will depend on box type (i.e. normally open or normally closed). 3

4 Smoke Detection and Ventilation Override Question - Where can I install a smoke detector? Answer - One can install fire stats or smoke detectors on stand alone units at the external auto stop. When immediate shutdown is required, use the external auto stop feature including those systems under Tracer control. Auto shutdown will cause heat and cool Led's to blink. Unit will be reset if contacts close for 5 seconds. There are other locations (i.e. line voltage of transformer), however specifying and locating life safety controls is the design engineer s responsibility. See Figure 1: Figure 1 Question - How does the Voyager Commercial Ventilation override operate? Answer - In order to initiate ventilation override the field supplied "A" contacts must close. After initiation, the ventilation mode is determined by field supplied contact "B". An open circuit between LTB4-3 and LTB4-4 (i.e. B contact open) is exhaust ventilation. A closed circuit (i.e. B contact closed) is pressurization mode. Exhaust Pressurization Heat/Cool OFF OFF Inlet Guide Vanes Closed Open Supply Fan Off On Exhaust Fan On Off Outside Air Damper Closed Open Return Air Damper Open Closed VAV Boxes N/A Open 4

5 Question - My Engineer requires a ventilation over ride sequence similar to the IntelliPak purge. This is the same as the Voyager III pressurization control, however the exhaust fan is allowed to run. What is the best way to modify the unit for Purge operation? Answer - Field install a two pole single throw relay in parallel with the Ventilation Override relay (24 VAC). The relay contacts are wired in parallel with the line voltage XFR exhaust fan contacts. Economizer Control Strategies Question - I have an energy management system. How do I take control over economizer operation? Can this be accomplished by a 24 volt signal to the actuator? Answer - No. This is not recommended for VAV applications. Also it is not possible on constant volume (except with Tracer). A 24 volt signal will not modulate or control the actuator. However, it may be possible to remove the existing micro actuator and economizer controls and add a field supplied actuator for constant volume systems. This actuator (Belimo) has been installed successfully on Voyager Light Commercial units. Temperature Controls (General) Question - I have a stand alone cooling only VAV unit with economizer and power exhaust. What controller should I order? Answer - Standard factory controls (i.e. supply air sensor, discharge air set point, static pressure setpoint, reset setpoint, exhaust fan setpoint, morning warm-up setpont, reset amount, etc) are unit mounted. No other controls are required. At start up a short must be provided between LTB1-2 and LTB1-4. This will enable unit operation. Question - What are the adjustment ranges for Voyager Commercial VAV utilizing the potentiometer inputs? Answer - All potentiometers are rated at 0 to 1000 ohms and 1/4 watt. Values for various features are listed below: Morning warm-up set point - 50 to 90 degrees F Supply air Reset Amount - 0 to 20 degrees F Supply Static pressure set point -.3 to 2.5 inch w.c. Static pressure deadband -.2 to 1 inch w.c. The corresponding resistance vs. temperature or static pressure is listed on the next page. Note: Morning Warmup Set point is identical to Cooling Supply Setpoint. 5

6 Supply Air Cooling Setpoint Setpoint Nominal (Deg F) Resistance (Ohms) Nominal Resistance (Ohms) Setpoint (Deg F) Static Pressure Setpoint Static Pressure Nominal Setpoint(in. w.c.) Resistance (Ohms) Static Pressure Setpoint(in. w.c.) Nominal Resistance (Ohms) Question - Can a constant volume Voyager III be field converted to a VAV unit? Answer - No. Question - Engineer has specified a discharge air controller for Voyager Commercial VAV. Is this possible? Answer - Yes. The standard unit is equipped with discharge air control. However it is not possible to control Voyager VAV with a generic discharge air controller. The VAV unit is not compatible with C.T.I. s similar to constant volume units. Question - Is Voyager Commercial compatible with Varitrac? Answer - Yes. A constant volume unit should be ordered with a TCI interface. VAV units are not software compatible with Varitrac. 6

7 Question - I have a VAV system with constant volume bypass, similar to Varitrac. What control option is recommended? Answer - Order the Voyager III VAV unit without inlet guide vanes. Gas or electric heat units are not recommended for these applications. If the customer prefers their own controls, order a constant volume unit and install a CTI. For cooling only with two stages of control the Honeywell T7075B has been used successfully (Figure 2). Figure 2 Question - Does Voyager Commercial VAV include outside air compensation similar to IntelliPak? Answer - No. Question - Engineer has requested fully alternating lead/lag. Can I do this with the Voyager Commercial Micro? Answer - Yes, fully alternating compressor control is an option. Removing or cutting the wire at J1-7 on the UCP will enable lead/lag. It is advised to consider 1st and 2nd stage capacity control when using this option. As compressors lead/lag, the largest compressor can become 1st stage cooling. 40 & 50 ton systems (units with three compressors) alternate with 3 stages of cooling when the smallest compressor is lead. However when the lead compressor's are the largest, there will only be two stages of cooling. Units equipped with CTI's are limited to two stages of cooling. FIGURE 3 7

8 Question - When should I not use a C.T.I.? Answer - Voyager Commercial VAV will not work with a C.T.I.. Also vendor thermostats which use Triac outputs have created some problems. A C.T.I. will limit Voyager to two stages of cooling. Duct Heaters/Perimeter heat Question - How can I connect a field supplied duct heater to a cooling only Voyager Commercial unit? Answer - There is an isolated heat circuit on electric/cooling units, similar to Voyager Light Commercial, where a 75 volt/amp transformer can be added to accommodate additional power requirements and duct heat (figure 19). Field wiring and connectors must be provided as shown below. (See Figure 4) Figure 49 Question - I have a cooling only unit with perimeter heat in the zone. How can I enable fan operation when heating is required? Answer - Cut the wire going to J1-20 (See figure 4) on constant volume systems. If the unit is VAV, a zone sensor must be added. Compressor Control Question - How does the Voyager Commercial 40 and 50 ton units accomplish 3 stages of cooling? Answer - 1st stage is the smallest compressor (about one third of total capacity). 2nd stage de energizes 1st stage and enables the two manifolded compressors (about two thirds of total capacity). 3rd stage enables the smallest compressor. Question - What is the major difference between Voyager Light Commercial and Voyager Commercial compressor control? Answer - Voyager Commercial is equipped with direct sensing Froststats on each compressor circuit. 8

9 Fan Control Question - I have a customer who is currently using the clogged filter circuit on the Voyager Commercial micro. While he is satisfied that the micro will indicate a service problem, he is concerned that a broken belt or any fan failure may lead to compressor failure. Is there a way to lock out the unit in the event of a fan failure? Answer - Yes. This is a standard feature on Voyager Commercial. If the supply fan is enabled and the fan failure switch opens for more than 5 seconds then the supply fan is disabled and locked out, requiring a manual reset. The appropriate diagnostic will be communicated to Tracer and the Service LED will blink. Question - Is it possible to control a two speed motor with Voyager Commercial controls? Answer - No. The two speed option was removed with compressor lead/lag. However it may be possible to use inlet guide vanes (i.e. two position) in a constant volume application. Low Ambient Control Question - I have a computer room application which will require 100% of rated capacity at 0 F. Can this be accomplished with the Voyager Commercial micro? Answer - Depending on unit size, nominal capacity is 80 to 95% at zero degrees ambient. Since Voyager Commercial is equipped with either three or four condenser fans, additional head pressure control is not typically required. Head pressure control is accomplished by cycling two condenser fans based on outdoor temperature. This control will typically provide a minimum 198 psi head pressure which equals the control provided by add-on head pressure controls. The typical cycling sequence includes disabling compressors for 3 to 7 seconds in order to prevent condenser fan windmilling. Below is a typical condenser cycling schedule: 27.5 ton to 30 ton: 1st stage cooling - 3rd condenser fan is off when outdoor ambient is less than 90 F 2nd condenser fan is off when outdoor ambient is less than 70 F 2n stage cooling - 3rd condenser fan is off when outdoor ambient is less than 60 F 2nd condenser fan is off when outdoor ambient is less than -10 F 9

10 Exhaust Fans Question - A customer has independent exhaust fans. Can he utilize any of the micro features to control a separate power exhaust? Answer - Yes. The unitary economizer module (U.E.M) has a 24 Volt DC output which is utilized with the standard power exhaust (do not exceed 75 milli-amps). The same connection points may be utilized. The exhaust fan output will energize based on exhaust fan setpoint (i.e. 0 to 100%). The exhaust set point (i.e. on/off control) is adjusted by a 0 to 1000 Ohm potentiometer. The wiring interface will require ordering two BAYSENS016A thermistors. While the thermistor is not utilized the accompanying wiring harness and plug is. See the below wiring diagram. Question - I have a smoke purge sequence which will require the exhaust fans to go from low speed (factory setting is low speed) to high speed. How can I accomplish this with ventilation override? What is the exhaust fan capability in this mode? Answer - Add a field installed 24 VAC relay with contacts rated for line voltage ("R" 4PDT) in parallel with the ventilation override relay and wire as shown below. Exhaust fans will exhaust approximately 12,000 CFM on high speed and 10,000 CFM on low speed at zero return static pressure. 10

11 Question - Is Statitrac building pressure control available for Voyager Commercial? Answer - No. However some offices have used variations of the control shown on figure 5. Figure 5 11