Hookup procedures for flue gas spill switches to detect backdrafting at gas or oil fired heating equipment.

In this article series we explain the installation, function, & troubleshooting Flue Gas Spill Switches and we provide a Guide to inspecting Furnace or Boiler Flue Gas Spill Switches on gas fired equipment such as heating boilers, warm air furnaces, water heaters.

Flue Gas Spillage Detector Switch Installation & Sources

Watch out:  thermal switches and flue spill detection switches are important safety devices that are intended to reduce the chances of fatal carbon monoxide poisoning in buildings where gas-fired heating equipment is installed.

If you are not trained to make a correct and safe installation of these devices hire a licensed plumber or heating equipment technician who is so qualified. Making a mistake could kill someone. Here is a typical warning from a boiler installation manual:

Failure to follow all instructions can result in flue gas spillage and carbon monoxide emissions, causing severe personal injury or death. - Williamson-Thermoflo GSA Installation Manual Part Number 550-110-738/0319

Watch out:  Because most flue spillage sensors detect heat rather than the specific gases that might be emitted from the heating equipment the safety switch must be matched to the equipment.

[Click to enlarge any image]

Photo: I'm holding the wire connecting the flue spill detector (at the left end of the wire) to the water heater gas valve (not shown).

• The proper operating temperature range 
  
  of the heating equipment, based on temperatures that will be found in gases passing through the heating flue in the area where spillage is to be sensed.
  
  Typical thermal safety switch operating temperature ranges (varying by model) open to turn off the heating equipment at temperatures of 140 degF up to 250 degF depending on the sensor model and its application.
  
  For example a draft-induced heating furnace may use a switch activating (opening) at 160 degF while a steam boiler may use a thermal switch that does not activate until 250 degF.
• The typical flue vent connectors or draft controls:
  
  different mounting locations and hardware may be required on different types of equipment
• The time duration over which the thermal sensor safety switch
  
   (used to detect flue gas spillage) should operate; you don't want a switch that opens (turns off the heater) too soon in a spillage cycle as some spillage is normal at heater start-up in some system designs; nor do you want a thermal safety switch that waits too long to turn off the heater.
• The operating voltage or amperage range 
  
  of the erquipment to be controlled: 12 Amps / 120VAC, 6 Amps 240VAC, or 24VA on 24AC millivolt equipment

Field Controls, for example, offers such devices. The term usually used is "thermal switch" or "thermal switches for oil fired heating equipment".

These flue gas spillage devices sense heat, must be selected for the proper fuel and application (or else your system would be unsafe as it'd not be properly protected), and are sold in both manual reset and automatic reset spill switch sensor switch forms.

Flue gas spillage or thermal switches also vary by their response time. You may have trouble with a too-fast-acting switch if in normal operation there is a brief burst of heat from a barometric damper - as happens on some oil fired heating equipment.

Field Controls Thermal switch models include FTS-4, FTS-6, GSK250-M (for steam boilers), GSJ0160-M for draft-induced furnaces, and about eight other models. You'll see that it is essential to choose the proper thermals sensor switch.

• Contact Field Controls at Field Controls 2630 Airport Road Kinston, NC 28504 Phone: 252.522.3031 Fax: 252.522.0214 sales@fieldcontrols.com Website: fieldcontrols.com Thermal safety switch specifications source: http://www.fieldcontrols.com/thermal-safety-switches retrieved 12 Sept 2015 

Question: where do I connect a spill switch on a gas fired water heater?

2019/11/18 Anonymous asked:

Where do I tie in a spill switch for a gas hot water heater?

Somewhere on the gas valve?

This Q&A were posted originally

at FLUE GAS SPILL SWITCH TRIPPING & RESET

Reply: simple installation instructions for flue gas spill switch controls

Anon

Watch out: if you are not trained and qualified to work on gas heating equipment don't do it as you could cause a fire, explosion, or death.

Yes the flue gas spill switch mounts at the gas vent draft hood and on a water heater, its wires connect to a special connector installed at the gas valve. The installation kit will contain a connector that is installed between the existing themocouple end and its connection point on the gas valve.

Wires from the spill switch are then hooked up to terminals on that connector.

Below as a downloadble PDF are example details adapted from the Field Controls SSK-1 or SSK-2 thermal switch installation instructions.

Case 1: Flue gas spill switch connects at thermocouple mount on gas fired water heater

Because water heaters are not operated by an external wall-mount thermostat sporting thermostat wires but instead are controlled by a thermostat built into the water heater body (with no external thermostat wires), to hook up a flue gas spill switch to a water heater a different approach is used.

On a water heater the thermocouple at the gas valve on the water heater is removed; then a special connector or "junction block adapter", also referred to as a "thermocouple circuit" or a "thermocouple adapter" (shown here) used with the spill switch installation kit, is installed at the thermocouple mount on the gas valve, the thermocouple is then connected to the connector, and the spill switch wires also are plugged into the same connector.

A bit above on this page is a sketch showing those details.

Just above is a photo of the Fields Control thermocouple "circut" or junction block adapter.

[Click to enlarge any image]

Watch out: you may not find this junction block adapter in the box with the spill switches you've purchased. It has to be ordered separately.

Some Flue Gas spill switches like the Field Controls switch SSK-shown below will remain OFF until manually reset.

Here is what Field says about installing this type of control

Kit form of GSK-3 or GSK-4 generally used on millivolt water heaters. Can also be used with 24 VAC gas furnaces or boilers.

Kit includes (2) GSK style Thermal Safety Switches, (1) 12-gauge Jumper Wire and (1) 6 ft. length 12-gauge lead wire. SSK-3 switches not supplied with switch enclosures. TCA-1 or TCA-2 Thermocouple Adapter required for 30 millivolt applications.

Before and after adding this safety control on existing appliances, an installation inspection in accordance with the National Fuel Gas Code 54, Z223.1 Appendix H should be performed and a combustion analysis is recommended to determine the operating condition of the appliance.

Case #2: for heating furnace - flue gas spill switch connects in series to thermostat wire

The actual connection of the flue gas spill switch wires can vary but a typical connection wires the switch in series with one of the thermostat wires that connect between the thermostat and terminals on the gas valve that in turn turns opens to provide fuel gas to the gas burner.

(Because the spill switch may affect the small current draw (amps) of the thermostat circuit, it may be necessary also to adjust the heat anticipator in the room thermostat - if one is provided).

Spill Switch Installation Guides & Manuals

• Field Controls FLUE GAS SPILL SWITCH INSTALLATION INSTRUCTIONS SSK1 & SSK2 [PDF] Field Controls, 2630 Airport Road, Kinston, NC 28504 USA Tel: 252-522-3031 Website: www.fieldcontrols.com retrieved 2019/11/18 from original source s3.amazonaws.com/s3.supplyhouse.com/manuals/1261235379215/20731_PROD_FILE.pdf
  
  The junction block adapter used with these spill switches in a water heater installation at the thermocouple mount has to be ordered separately (TCA Adapter-1 pr TCA Adapter-2 Field Part No. 46082700).
• Field Controls FLUE GAS SPILLAGE SAFETY KIT SSK3 [PDF] op. cit., retrieved 2019/11/18 original souirce: https://www.fieldcontrols.com/wp-content/uploads/2019/04/46114900.pdf
• Field Controls, Gas Spillage Sensing Kit, Model: GSK-3, GSK-4, GSK-250M, [Installation & Operation Instructions], [PDF] Field Controls, 2630 Airport Road, Kingston NC 28504, USA, GEl: 252-522-3031, Website: www.fieldcontrols.com
  
  Excerpting and paraphrasing from the company's thermal safety switch product line description:
  
  Field Controls thermal safety switches detect flue gas spillage due to a blocked flue, continuous down drafting or inadequate draft conditions.
  
  With the safety switch wired in series with the burner circuit, the switch will de-energize the heating appliance gas or oil burner or burner control once it senses the spillage of hot flue gases. These spillage switches are available for both gas-fired and oil-fired heating equipment.
• Field Controls GAS SPILLAGE SENSING UNIT GSK-160A (with automatic reset) [PDF] retrieved 2019/11/18 original source: https://www.fieldcontrols.com/wp-content/uploads/2019/04/46561800.pdf
  
  Excerpts:
  
  Installation of a spillage SAFETY Switch is recommended for LP and Natural gas fired systems with gas barometric draft controls. This device is intended for installation on a double-acting barometric draft control (such as the Field Controls model MG-1) that is installed in the venting system of an 80+ efficiency rated, fan-assisted gas-fired appliance.
  
  It is designed to detect flue gas spillage caused by a blocked flue system and/or inadequate draft. This device MUST be installed by a qualified installer in accordance with the manufacturer's installation instructions.
  
  Watch out: Wiring MUST be in accordance with the National Electrical Code and applicable local codes. Before and after adding this safety control on existing appliances, an installation inspection in accordance with the National Fuel Gas Code 54, Z223.1 Appendix H should be performed and a combustion analysis is recommended to determine the operating condition of the appliance.
  
  Watch out: CAUTION: Disconnect Electrical Power When Wiring Spillage Switch
• Field Controls FTS-6 THERMAL SAFETY SWITCH [PDF] Exerpt:
  
  Designed for use on large gas furnaces and boilers. Can be mounted on Draft Hood or double-acting Barometric Draft Control (both brackets included). Manual reset. For use on 24/120/240 Volt equipment over 400,000 BTU/hr.
• Field Controls THERMAL SAFETY SWITCHES CATALOG [PDF] (2008), Op. Cit., retrieved 2019/11/18 original source: https://www.fieldcontrols.com/wp-content/uploads/2019/04/4326TSSwitchesSS.pdf
• Tjernlund's Products, Inc., 24SP200 Safety Interlock System (P/N 950-2420) [Installation & Operating Instructions], [PDF] (1997) Tjernlund's Products, Inc., 1601 Ninth Street • White Bear Lake, MN 55110-6794 Tel: (800) 255-4208 Website: www.tjernlund.com.
  
• Tjernlund Products provides instructions for the installation and use of their controls, including the WHKE Millivolt Interlock Kit for use with their UC1 Universal Control, MAC1E or MAC4E auxiliary controls for gas fired equipment. Contact Tjernlund Products at tjernlund.com or at 800-255-4208.
• Also see FLUE GAS SPILL SWITCH SOURCES & SELECTION

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Question: The thermal couple adapter on the flue gas spill switch doesn’t fit my model.

2020/04/29 Anthony said:

Is there another way to install a spill switch? The thermal couple adapter doesn’t fit my model.

Illustration: a flue gas spill swithc installation kit distributed by Zoro, cited

at FLUE GAS SPILL SWITCH SOURCES & SELECTION

Moderator reply:

Thanks for a helpful question, Anthony. Apologies that I'm chicken to bet your life on a guessed-answer.

Let's start by identifying the brand and model of your gas fired heating appliance.

Then we can find the manufacturer's technical help support line and give them a call to get an authoritative answer.

FYI, yes, there are indeed add-on flue gas spillage safety switches, typically relying on wiring in to the electrical wires controlling the gas burner operation. Click on any of the several Field Control flue gas safety switch installation guides given as downloadable PDF files at the end of the article above on this page.

Check with your manufacturer about approval.

Below is a typical flue gas installation switch kit

 

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Continue reading at FLUE GAS SPILL SWITCH SOURCES & SELECTION or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• BACKDRAFTING HEATING EQUIPMENT
• COMBUSTION AIR DEFECTS
• COMBUSTION AIR REQUIREMENTS
• CARBON MONOXIDE - CO
• CARBON MONOXIDE INSPECTION
• CARBON MONOXIDE WARNINGS: HOME HEATERS
• GAS DETECTOR WARNINGS
• FLUE GAS SWITCH INSTALLATION & WIRING
• FLUE GAS SPILL SWITCH SOURCES & SELECTION
• FLUE GAS SPILL SWITCH TRIPPING & RESET
• FLUE SPILL SWITCH & COMBUSTION AIR TESTS
• THERMOCOUPLE REPAIR / REPLACEMENT

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