Taco LTR Low Water Cutoff for Hot Water Boilers

Instruction Sheet

LTR – Low Water Cutoff for Hot Water Boilers

SUPERSEDES: Revision F Dated December 17, 2012

5401179-REV G PLANT ID 001-3907

US Patents 6,904,800, 7,243,540, and 7,317,993
Other Patents Pending

• Listings/Approvals

  • UL GUIDE (MBPR) for Limit Controls per UL Standard 353 Limit Controls
  • UL GUIDE (MBPR7) Controls, Limit Certified for Canada CSA Standard C22.2

• Maximum Probe Ratings:
  Hot water only – 160 psi (11.2kg/cm2) at 250°F (121°C)

• Probe Sensitivity: 20K Ohms. Extended operation to 40K Ohms.

• Ambient Temperature: 32°F – 120°F (0°C to 49°C)

• Enclosure Rating: NEMA 1 for indoor use only
  Input Power: 1.5 VA @ 24 VAC supplied by a Class 2 power source

• Output Contact: Form B Relay, normally closed (water detected)
  LTR024 Models
  5A @ 24VAC Max Load
  50 VA @ 24VAC Switching

• Reset:

  • Automatic Model: Automatic reset when water level returns to safe level
  • Manual Model: Press RESET Button when water level returns to safe level

• Testing: Integrated test switch for testing safety shutdown

General

The Residential Low Water Cutoff (LTR) is a microprocessor based low water cutoff for detecting the presence to water in a boiler. The LTR 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 LTR functions longer without requiring probe cleaning, and it functions normally under non-ideal installation conditions. The LTR 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.

WARNING

• 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.
• 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.
• 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.
• Shock Hazard. Disconnect power source before servicing. Serious injury or death could result.
• Use only the wiring harness supplied with the control or factory supplied alternates. Use of other wire harness or insulation types could result in fire causing property damage, serious injury, or 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.

Automatic Model: Pressing the TEST button when water covers the probe will cause the LTR to enter a Low Water Condition.
Manual Model: Pressing the TEST/RESET button for two seconds will reset the LTR provided water covers the probe.

LTR Features

controls.
LTR Connector| Power and relay contact connector.
Reset Button| Manual Reset when pressed after water returns to safe level

LED States:

Installation

1. Install the probe above the minimum safe water level, as determined from the boiler manufacturer’s literature. (See Fig. 1)
   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. 2)

4. Hand tighten the LTR into the process connection. Do not cross-thread. Do not use a wrench or other tools to tighten the control.
   

CAUTION

• Do not mount device with probe angled upward or deposits can accumulate on 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.

CAUTION

• Apply Teflon® tape only to the threads of the LTR. Do not use pipe dope or other thread sealants. Damage to the control may occur and result in improper operation.
• Hand tighten the LTR into the process connection being careful to not cross-thread. Do not use a wrench or other tools to tighten the control. Damage to the control may occur and result in improper operation.

Wiring for Boilers with Honeywell Aquastat Models L8124E or L8148E or

Equivalent

WARNING

• Shock hazard. Disconnect power source before servicing. Serious injury or death could result.
• Only use the wiring harness supplied with the control or factory supplied alternates. Use of other wire harnesses or insulation types could result in fire causing property damage, serious injury, and death.

Wiring Instructions

1. Connect the WHITE wire to the Aquastat’s TV terminal.
2. Connect the RED wire to the Aquastat’s Z terminal.
3. Connect the GREEN wire to a ground source that is electrically common to the boiler ground.
4. Unplug the factory wired quick connector from terminal B1.
5. Plug the male quick connector on the YELLOW wire into the female factory wired quick connector.
6. Plug the female quick connector on the YELLOW wire into terminal B1.

Wiring for Boilers with Honeywell Control Center Model R8285 or

Equivalent

WARNING

• Shock hazard. Disconnect power source before servicing. Serious injury or death could result.
• Only use the wiring harness supplied with the control or factory supplied alternates. Use of other wire harnesses or insulation types could result in fire causing property damage, serious injury, and death.

Wiring Instructions

1. Connect the WHITE wire to the C terminal.
2. Connect the RED wire to the R terminal.
3. Connect the GREEN wire to a ground source that is electrically common to the boiler ground.
4. Unplug the factory wired quick connector from the R terminal.
5. Plug the male quick connector on the YELLOW wire into the female factory wired quick connector.
6. Plug the female quick connector on the yellow wire onto the R terminal.

Alternate Wiring:

24VAC Systems LTR024 Models Only

Wiring Instructions

1. Connect the WHITE wire to the transformer’s common connection.
2. Connect the RED wire to the transformer’s hot output.
3. Connect the GREEN wire to a ground source that is electrically common to the boiler ground.
4. Cut off the quick connectors from both YELLOW wires and strip the wire ends.
5. Open the connection to the other limit controls ahead of the first limit control.
6. Wire the YELLOW leads as shown to connect the LTR’s relay in series and ahead of all other limit controls

WARNING

• Shock hazard. Disconnect power source before servicing. Serious injury or death could result.
• Never connect 120VAC to Red/White leads.
• Only connect 120VAC to Yellow leads.
• Misapplication of 120VAC will damage control.

Wiring Boilers with an Integrated Control Module: On boilers equipped with a United Technologies integrated boiler control module, Taco recommends the use of the “Boiler Module Wiring Harness”. This harness is available from Taco, Part 9300-2715RP.

Wiring Instructions

1. Disconnect the boiler wire harness from the integrated control module.
2. Plug the boiler wire harness connector into the female connector on the LTR wiring harness.
3. Plug the male connector on the LTR wiring harness into the integrated control module.
4. Plug boiler module module wiring harness into LTR.

WARNING

• Shock hazard. Disconnect power source before servicing. Serious injury or death could result.
• Only use the wiring harness supplied with the control or factory supplied alternates. Use of other wire harnesses or insulation types could result in fire causing property damage, serious injury, and death.

Wiring Boilers with an Integrated Control Module and OEM 4-pin Harness:

Wiring Instructions

1. Plug the 4-pin connector on the wiring harness (#1 as shown) into the integrated control module.
2. Plug the 4-pin connector on the wiring harness (#2 as shown) into the LTR.

Testing:

1. DO NOT fill the boiler. Set the thermostat to lowest possible setting and turn on electric power to the boiler. On initial start-up, the LTR indicates a low water condition, which indicates proper function. The “STATUS” LED on the control unit illuminates RED. The burner should not operate without water in the system.
2. Fill boiler with water. Once water covers the probe, the “STATUS” LED on the control turns from RED to GREEN.
3. Set the thermostat to call for heat. Verify that the burner ignites.
4. With the burner aflame, press and hold the test switch while observing the burner and the “STATUS” LED on the LTR. After the “STATUS” LED illuminates RED, the burner turns off.
5. Release the test switch and verify that the burner ignites (provided water covers the probe). The “STATUS” LED on the control unit turns from RED to GREEN.
6. If burner fails to cutoff or relight, see the Troubleshooting section for details. Otherwise, set the thermostat to its normal setting.

NOTE: Once correct operation of the LTR has been tested, test all other safety, limit, and control devices before finalizing system operation.

Cleaning, Maintenance, and Replacement

Test the operation of the LTR annually, or more frequently, by pressing the “TEST” button. The “STATUS” LED should turn RED and the boiler should shut down.
Probe must be inspected every 5 years, (or sooner if “SERVICE” LED turns on), for scale build-up or coating. Clean all oils, fluxes, and scale from probe with a clean rag.
The control unit should be replaced every 15 years. In areas of high humidity, heavy dust, or other airborne contaminants more frequent replacement may be required.

Ordering Information:

Replacement Cables:

• 9300-2714RP – Standard Wire Harness

• 9300-2715RP – Wire Harness for United Technologies
  Integrated Boiler Control

• 9300-2774RP – OEM 4-pin Harness

Troubleshooting

plugged into the LTR and wiring is correct. Be sure power to boiler is turned on.
Low water level| Make sure that the water level has reached the LTR probe.
Air pocket at LTR probe| Turn off power to the boiler and slowly loosen, but do not remove the LTR. Allow any air to escape until water seeps past the LTR’s threads. Promptly re-tighten the LTR and apply power to the boiler.
Dirty probe| Fluxes or oils used during the construction of the boiler or installation of system piping can coat the LTR probe, preventing signals from being received by the LTR. Add a cleaning solution, (such as water and trisodium phosphate or consult the boiler manufacturer), to the system. Heat and circulate this solution for at least one hour before draining and completely flushing the system with clean water. Remove the LTR and thoroughly wipe it with a clean rag. Refill the system and test for proper operation.
Improper ground| Make sure the green ground wire is electrically common to the boiler. Install the green ground wire to an unpainted/uncoated surface.
Improper wiring| Check all wiring to the LTR and refer to the wiring diagrams. Using a multi-meter, verify that incoming power is 24 VAC.

Failed control

| If the “STATUS” LED blinks RED, the safety circuits in the LTR have detected a failure in the control. To remove any temporary conditions, unplug the LTR connector. After 30 seconds, plug in the LTR connector. If the “STATUS” LED continues to blink RED, the control must be replaced.
Boiler will not shutdown| Shorted probe| Turn off power to the boiler and remove the LTR. Verify that there is at least 1/4″ clearance from all metal surfaces to the metal probe on the LTR. Metal from the boiler or piping must not come in contact with the metal probe on the LTR.
Improper wiring| Check all wiring to the LTR and refer to the wiring diagrams. Using a multi-meter, verify that incoming power is 24 VAC.
Amber “SERVICE” LED is on| Dirty probe| Deposits form over time in the system and can coat the LTR probe, preventing signals from being received by the LTR. Remove the LTR and thoroughly wipe it with a clean rag. Refill the system and test for proper operation. It may be necessary to clean the boiler and piping as noted above.

Limited Warranty Statement

Taco, Inc. will repair or replace without charge (at the company’s option) any product or part which is proven defective under normal use within one (1) year from the date of start-up or one (1) year and six (6) months from date of shipment (whichever occurs first).

In order to obtain service under this warranty, it is the responsibility of the purchaser to promptly notify the local Taco stocking distributor or Taco in writing and promptly deliver the subject product or part, delivery prepaid, to the stocking distributor. For assistance on warranty returns, the purchaser may either contact the local Taco stocking distributor or Taco. If the subject product or part contains no defect as covered in this warranty, the purchaser will be billed for parts and labor charges in effect at time of factory examination and repair.

Any Taco product or part not installed or operated in conformity with Taco instructions or which has been subject to misuse, misapplication, the addition of petroleum-based fluids or certain chemical additives to the systems, or other abuse, will not be covered by this warranty.

If in doubt as to whether a particular substance is suitable for use with a Taco product or part, or for any application restrictions, consult the applicable Taco instruction sheets or contact Taco at [401-942-8000]. Taco reserves the right to provide replacement products and parts which are substantially similar in design and functionally equivalent to the defective product or part. Taco reserves the right to make changes in details of design, construction, or arrangement of materials of its products without notification.

TACO OFFERS THIS WARRANTY IN LIEU OF ALL OTHER EXPRESS WARRANTIES. ANY WARRANTY IMPLIED BY LAW INCLUDING WARRANTIES OF MERCHANTABILITY OR FITNESS IS IN EFFECT ONLY FOR THE DURATION OF THE EXPRESS WARRANTY SET FORTH IN THE FIRST PARAGRAPH ABOVE. THE ABOVE WARRANTIES ARE IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR STATUTORY, OR ANY OTHER WARRANTY OBLIGATION ON THE PART OF TACO.
TACO WILL NOT BE LIABLE FOR ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES RESULTING FROM THE USE OF ITS PRODUCTS OR ANY INCIDENTAL COSTS OF REMOVING OR REPLACING DEFECTIVE PRODUCTS.

This warranty gives the purchaser specific rights, and the purchaser may have other rights which vary from state to state. Some states do not allow limitations on how long an implied warranty lasts or on the exclusion of incidental or consequential damages, so these limitations or exclusions may not apply to you.

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

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References

• Fire Alarm Resources | Download fire alarm documents
• Taco Comfort Solutions | Leader in Hydronics and Pump Solutions

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