Instruction Sheet Board Style Low Water Cutoff 102-305 SUPERSEDES: REVISION E DATED December 12, 2007 #5401173-REV F PLANT ID 001-3902 US Patents 6,904,800, 7,243,540, and 7,317,993 Other Patents Pending Contact Ratings* Voltage Motor Switch Rating Pilot Rating Full Load Locked Rotor 24 VAC - - 50 VA 120 VAC 7.5 A 43.2 A 125 VA 240 VAC 3.75 A 21.6 A 50 or 60 Hz * 1A resistive at 120 F to 150 F (49 C to 66 C) EFFECTIVE: January 6, 2009 Listings/Approvals: UL GUIDE (MBPR2) for Limit Controls per UL Standard 353 Limit Controls - Component UL GUIDE (MBPR8) Controls, Limit Certified for Canada - Component per CSA Standard C22.2 Delays: Probes: 3 Second Delay on Break, (DOB) 1/2 Second Delay on Make, (DOM) Sold Separately. All Taco probe styles are compatible with LTB Ambient Temperature: -40 F to 150 F (-40 C to 66 C) Probe Sensitivity: Extended operation to 40K Ohms Open Collector Outputs: Maximum current 50 ma @ 5 VDC - 24 VDC Enclosure: None, PCB assembly only. For indoor use only. Mounting holes to permit stand-off mounting on customer supplied plate and housing. Reset: Testing: Configurable as automatic or manual reset style. When a normally closed switch is connected, device will be a manual reset device that looks for opening of reset switch. The LTB is fully compliant with CSD-1 requirements. Externally supplied test switch can be wired in series with probe connection to open probe circuit simulating a low water condition. ** 24VAC to be supplied by an EXTERNAL Class 2 power source. Input Voltage Power Consumption 24 VAC** 3 VA GENERAL The Board Style Low Water Cutoff (LTB) is an advanced, microprocessor based low water cutoff for detecting the presence of water in a boiler. The LTB uses advanced signal processing to identify when the probe signal levels have decreased due to possible fouling. These advanced technologies permit extended operation for probe impedance up to 40K Ohms. The LTB functions longer without requiring probe cleaning, and it functions normally under nonideal installation conditions. The LTB is designed for use with hot water boilers and hot water heating boilers. (See each boiler manufacturers' specifications for recommended minimum safe water levels). During a low water condition, the "Status" LED will illuminate RED. Under normal conditions, it will illuminate GREEN. See "Status LED States" table for details. Installation must be performed by qualified personnel and in accordance with all national and local codes and ordinances. Read all instructions carefully and understand them before starting installation. Save instructions for future use. Instruct user how to test and operate this cutoff device as described in these instructions. Shock Hazard. Disconnect power source before servicing. Serious injury or death could result. Risk of explosion. Not for use in hazardous locations. Serious injury or death could result. The LWCO device must be installed in series ahead of other limit and operating controls installed on the boiler. When installations are complete, check for correct operation of ALL limit and operating controls. Wire insulation must be rated at 167º F (75º C) or greater, over copper conductors only. Use of other wire or insulation types could result in fire causing property damage, serious injury, and death. Foam in boiler or piping can cause improper operation. If the boiler is foaming, shutdown the boiler and clean it per the manufacturers recommendations to eliminate foaming. Failure to do so could result in damage to the equipment and property or could cause an explosion resulting in serious injury or death. For use with hot water boilers and hot water heating boilers only. Use on steam boilers could cause improper operation resulting in property damage, serious injury, and death. Hot or pressurized boiler systems can discharge steam and hot water. Cool boiler system to 80º F (27º C) and to 0 psi (0 bar) before servicing. Failure to do so could result in serious burns. Do not use manual reset low water cutoffs with automatic water feeders. Flooding, equipment damage, and property damage can result. Only use automatic water feeders with automatic reset low water cutoffs.
PROBE SPACING REQUIREMENTS Fig. 1 FEATURES & CONNECTOR LOCATIONS Fig. 2 Open Collector Outputs, (Model LTB024A Only) O.C. 24VAC / CONTROL Connector, J3 PIN 1 PIN 2 PIN 3 Status LED 6 J3 3 Header, J4 RESET Connector, J2 J2 24VAC/ CONTROL 5 4 2 1 PIN 2 - Do not mount device with probe angled upward or deposits can accumulate in the probe. - Mount only with probe facing horizontally or vertically downward and maintain 1/4" minimum clearance from electrode and pipe wall. - Failure to install probe as directed can cause improper operation and damage to equipment and property. P Alternate Probe Connector 1 2 3 RESET GND J4 Alternate Chassis Ground Connector Relay J4 PIN 1 Item Status LED 24VAC/CONTROL Connector RESET Connector Open Collector Outputs Bi-color LED status indicator. See "Status LED States" table for details. 24VAC power connections. Probe connection. Connections to Form C relay. Connections to a manual reset switch, if present in system. Open collector outputs are available on LTB024A models for driving remote LED's, relays, buzzers, or other equipment that is powered by DC power sources from 5-24VDC. Status LED States: Mode Color/State Contacts Meaning Steady Green COM-NC Normal Steady Red COM-NO Low Water Condition or weak probe signal Blinking Red COM-NO Control Failure. Lockout in Low Water Condition Steady Off COM-NO No power to LWCO LTB Connectors: Connector Designator LTB Connector Open Collector Connector AMP, MTA-100 Friction Lock Header, 640456-3 Reset Connector J2 AMP, Mini-Universal Mate-N-Lok, 770170 24VAC/Control Connector J3 AMP, Mini-Universal Mate-N-Lok, 770178
RESET Connector - J2 and Alternate Connectors: Position 1 Reset switch 2 Reset switch 3 Chassis GND Connection (alternate) P Alternate probe connection - 3/16" male quick disconnect GND Alternate chassis ground connection - 1/4" male quick disconnect 24VAC/CONTROL Connector - J3: P J2 1 2 3 RESET GND Position 1 Alarm Output, NO relay contact - normally open to COM with normal water level and control operation 2 24VAC Common / Chassis GND Connection 3 Probe connection, electrode 4 Low Water Output, NC relay contact - normally closed to COM with normal water level and control operation. 5 Safety Circuit, COM relay contact 6 24VAC Power 24VAC/ CONTROL 6 5 4 J3 3 2 1 Open Collector Outputs (Model LTB024A only) The LTB024A is offered with open collector outputs for signaling purposes. These outputs can drive relays, LED indicators, or other equipment. When turned on, each output can sync up to 50mA at a voltage from 5 VDC to 24 VDC. The DC supply return must connect to Pin 2 of connector. PIN 1 PIN 2 PIN 3 Pin Number 1 Low Water Open Collector Output 2 DC Supply Return 3 Status Open Collector Output Low Water Status Output Mode State Meaning Status Steady On LTB has power Status Steady Off No power to LTB Low Water Steady Off Normal Low Water Steady On Low Water Condition Low Water Pulsed On/Off Control Failure. Lockout in Low Water Condition Example Wiring of External Indicators Using Open Collector Outputs: Low Water DC Return Status O.C. 5 24 VDC Power Source Current Limit Resistors LED Indicators DC supply return must be connected to open collector connector as shown. Failure to do so could result in damage to equipment or property. Open collector outputs must be externally current limited. Failure to do so could result in damage to equipment or property.
Configuring Reset Style: The LTB defaults to an automatic reset control. Upon power up, if the LTB does not detect a manual reset switch between pins 1 and 2 of the RESET connector, J2, the LTB is configured for automatic reset. When water covers the LTB probe, LTB enters normal operation. Upon power up, if the LTB detects a normally closed, manual reset switch between pins 1 and 2 of the RESET connector, J2, the LTB is configured for manual reset. After a low water condition, pressing the manual reset button while water covers the LTB probe resets the LTB for normal operation. Once the LTB is configured for manual reset, it remains as manual reset until it is re-configured. Refer to Fig. 2 for the location of the "RESET" connector, J2, and pins 1 and 2. Re-configuring Reset Style: If the reset style needs to be changed to automatic reset, re-configure the LTB. 1. Unplug the "24VAC/CONTROL" connector to remove power from the LTB. (See Fig. 2 for location of the "24VAC/ CONTROL" connector.) 2. Be sure no manual reset switch is connected to the LTB. 3. Use a small wire to short pins 1 and 2 together on header J4. (See Fig. 2 for J4 location.) 4. Plug-in the "24VAC/CONTROL" connector to apply power to the LTB. The LTB blinks the "STATUS LED" red to indicate that the reset style is erased. 5. Unplug the "24VAC/CONTROL" connector to remove power from the LTB. Remove the wire shorting pins 1 and 2 of header J4. 6. Plug the "24VAC/CONTROL" connector to apply power to the LTB. The LTB powers up and configures the reset style as noted in the "Configuring Reset Style" section. All LTB devices have the reset style configured to automatic reset prior to leaving the factory. Installation: 1. Install the probe above the minimum safe water level, as determined from the boiler manufacturer's literature. NOTE: This may be in a tapping on the boiler or in the boiler supply or return piping. 2. Install the probe to extend into the boiler cavity or piping to make contact with the water. 3. Install the probe so that the exposed portion of the stainless steel is a minimum of 1/4" from any grounding surface inside the boiler (to prevent the probe from shorting). (See Fig. 1) 4. Tighten probe securely with a wrench, using bushing flats provided. Use pipe thread sealant to seal the probe threads. Wiring: 1. Connect OEM provided plugs to the 24 VAC/Control connector J3 and to Reset connector J2. NOTE: In automatic reset applications, no connections to the Reset connector J2 are required. 2. If connections are provided for the alternate probe, install the connection in the spade terminal marked P. 3. If connections are provided for the chassis ground connections, install the connection in the spade terminal marked GND. NOTE: In systems where the AC Common is not connected to the chassis, use one of the alternate chassis ground connections. Refer to wiring diagrams in Fig. 3 and 4. 2. On model LTB024A, connect OEM provided plug to the O.C. connector to provide connections for open collector outputs. 3. Remove outer locknut on the probe. Install the ring terminal connection from the probe connection on pin 3 of 24 VAC/Control connector J3 and secure the locknut over the ring terminal. NOTE: Do not install bare wire under locknut. 4. The LTB design permits relay outputs to be either 24VAC or 120VAC. 120VAC circuits may only be connected to relay terminals on the 24 VAC/Control connector J3. Refer to wiring diagram in Fig. 4. Install probe wiring with ring terminal. Do not install bare wire between probe locknuts. LTB power source is 24 VAC. Do not connect line voltage to pins 2 or 6 on the "24 VAC/Control" connector J3. Use only copper conductors at lease 18 AWG or as required by code. Insulation must be rated at 167 F (75 C) or greater. Failure to wire as shown in these instructions can cause improper operation, damage to equipment and property, or serious injury.
TYPICAL WIRING FOR 24VAC BURNER SYSTEM Fig. 3 TYPICAL WIRING FOR 120VAC BURNER SYSTEM Fig. 4
Dimensions: A 0.78" 0.22" 0.56" B Probe Model Dimension "A" Dimension "B" P8S-1 Standard 1.95" 1.17" P8N-1 Extended Electrode 2.95" 2.17" 3/8" NPT 11/16" Hex Low Water Cutoff Test Button LWCO Ordering L T B 024 S 1 B S A Style Standard Open Collector Annunciators Input Power 024 24 VAC LWCO Type Board Style Probe Probe Only Ordering P 8 S 1 8 Probe Style S Standard Probe Electrode N Extended Length Probe Electrode Process Connection 3/8 NPT Controls Made Easy TACO, INC., 1160 Cranston Street, Cranston, RI 02920 Telephone: (401) 942-8000 FAX: (401) 942-2360. TACO (Canada), Ltd., 6180 Ordan Drive, Mississauga, Ontario L5T 2B3. Telephone: 905/564-9422. FAX: 905/564-9436. Manufactured by POTTER ELECTRIC SIGNAL CO., St. Louis, MO Visit our web site at: http://www.taco-hvac.com Printed in USA Copyright 2008 TACO, Inc.