Guide to buying flue gas spill switches on 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 Spill Detector Switch Brands, Choices & Selection Guides

• Also see FLUE GAS SWITCH INSTALLATION & WIRING - web article
• 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
• Field Controls, GAS SPILLAGE SENSING KIT Model: GSK-3, GSK-4, GSK-250M [PDF] [Installation & Operation Instructions], 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 Thermal Safety Switch, FTS-4, 12 or 6A, 120/240A, Setpoint 140 degF., manual reset, used at draft control or draft hood mounting, quicker response time than the Field FTS-6
  • Field Controls Thermal Safety Switch FTS-6, 12 or 6A, 120/240A, Setpoint 180 degF., manual reset, used at draft control or draft hood mounting, used on 14/120/240V heating equipment at larger BTUh ranges over 400,000 BTU/hr.
  • Field Controls Spillage Switch Model GSK-3, 24VA, mV-24AC, Setpoint 180 degF, Manual Reset, used on gas-fired mV or 24VAC heating appliances. This switch is illustrated at above-left.
  • Field Controls Spillage Switch Model GSK-4, 24VA, mV-24AC, Setpoint 200 degF, Manual Reset, used on gas-fired mV or 24VAC heating appliances where a slower response time is required [e.g. where establishing proper draft takes longer]
  • Field Controls Flue Spillage Switch Model GSK-160A, 24VA, 120AC, setpoint 160 degF, automatic reset, used on draft-induced furnaces, activates at 160 degrees F and resets automatically.
  • Field Controls Spillage Switch Model GSK-250, GSK-250M, 24VA, mV-24AC, Setpoint 250 degF, Manual Reset, used on gas-fired steam boilers
  • Field Controls Spillage Switch Model SSK-1, 24VA, Millivolt 24AC, Setpoint 180 degF, manual reset, kit includes 2 switches and hookup wiring.
  • Field Controls Spillage Switch Model SSK-3, 24VA, Millivolt 24AC, Setpoint 200 degF, manual reset, kit includes 2 switches and hookup wiring. This switch is described as the same as SSK-2 kit but the switches are not enclosed in an electrical box.
  • Field Controls Spill Switch Model WMO-1, 10-Amp, 120AC, setpoint 200 degF, manual reset, this switch is deigned for use on power-vented and chimney vented oil-fired heating equipment.
• Tjernlund's Products, Inc., 24SP200 Safety Interlock System (P/N 950-2420) [Installation & Operating Instructions], [PDF] Tjernlund's Products, Inc., 1601 Ninth Street • White Bear Lake, MN 55110-6794 Tel: (800) 255-4208 Website: www.tjernlund.com.
  
  This spill switch has a set point of 200 degF. and includes a manual re-set switch - a red button that pops out if the switch senses flue gas spillage.
  
  In addition to its use on gas fired heating appliances such as furnaces, hot water boilers, steam boilers, this safety interlock system from Tjernlund's is also used on some gas-fired tankless water heaters.
• 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.
• Quadra-fire GB40FS/GB40i Spill Switch Snap Disc SRV230-0071 high limit control: this is an automatically re-setting high limit control used on some heating appliance. It is not a flue gas spill detector.
• Tjernlund Inc., 1601 9th Street, White Bear Lake, MN 55110-6794 USA: Tjernlund provides draft inducer fans used on heating equipment. Website: www.tjernlund.com Email: fanmail@tjfans.com Tel: (800) 255-4208
  
  Technical note: This is not a flue gas sensor switch: separate from flue gas spillage sensors are fan prover safety interlock switches. Quoting from Tjernlund (cited below) in discussing their Fan Prover Safety Interlock Model PS1505,
  
  To satisfy national mechanical codes for oil and gas installations, Draft Inducers must be properly interlocked with burner circuits.
  
  The PS1505 Fan Proving Switch monitors pressure within the Inducer housing to verify Inducer operation. Used in conjunction with the UC1 Universal Control, it assures compliance with codes and simplifies electrical interlock with all 24/115 VAC burner circuits. The PS1505 is not compatible with millivolt gas valves.
• Viessman Manufacturing Co., Inc., "Blocked Vent Safety Switch Installation Instructions for Vitorond 100, VR1 Oil Fired Boilers", [PDF] Viessman Manufacturing Co., Inc., 750 McMurray Rd., Waterloo Ontario N2V 2G5 Canada, Tel: 888-484-8643, Website: www.viessmann.ca, Email: info@viessman.ca
  or
  Viessman Manufacturing Company (US), Inc., 45 Access Rd., Warwick RI 02886 USA, Tel: as above, Website: www.viessman-us.com, Email: info@viessman-us.com
  Excerpt:
  
  Installation of a secondary safety switch is required for oil-fired installations not equipped with a draft hood. This device is designed to detect flue gas spillage from a blocked flue system and/or inadequate draft. ...
  
  A field supplied manual reset high limit control must be installed at the outlet pipe of the boiler to interrupt burner operation should the factory supplied high limit control fail.
  
  This field supplied high limit control must be set 20° F (7° C) above the setting of the factory supplied high limit control. The setting of this field supplied high limit control must never be greater than 220°F (104° C)...
  
  If burner lock-out occurs, verify blocked vent safety switch operation first.
• Zoro Tools, Inc., Website: https://www.zoro.com Tel: (855) BUY-ZORO / (855) 289-9676 [Physcial or mailing address not provided - Ed.]
  
  Si necesita ayuda en español, por favor, comuníquese con nosotros por teléfono. Gracias.

Some Spill Switches on Gas or OIL Fired Equipment Include a Reset Switch or Button

Flue gas spill switches normally connect to the gas valve on gas fired appliances and the switch will shut the valve after sensing flue gas spillage such as that which could occur if the flue becomes blocked.

Many flue gas spill sensor switches, such as the Field Controls GSK-3, GSK-4, GSK-250M switches (which operate based on sensing temperatures of 180, 200, or 250 °F respectively) include a manual reset switch.

The manual reset switch is needed because a gas appliance pilot light can turn off for more reasons than a blocked flue or chimney problem that is resulting in dangerous flue gas spillage.

Watch Out: If your gas fired equipment has shut down in SAFETY OFF position it may be due to a re-settable flue gas spill sensor switch that has detected unsafe flue gas spillage.

Flue gas spillage can indicate a dangerous blocked chimney or other unsafe conditions and may also risk potentially fatal carbon monoxide gas spillage as well as other potentially harmful flue gases in the building.

Check with your heating service company - you might think you can avoid a costly heating service call, BUT

BEWARE: because flue gas spillage is very dangerous, including the production of potentially fatal carbon monoxide gas,

don't simply reset the system without finding out what caused the problem in the first place.

Here is a sketch of the Tjernlund Products Inc. Gas Spill Switch which also includes a manual reset button.

Tjernlund's sketch (left) shows the reset button right on the gas spill switch.

MORE SAFETY WARNINGS: in addition to our safety warning above, Tjernlund explains that flue gas safety switches are intended to alert the building occupants to a potentially dangerous condition.

But flue gas spillage safety switches are not a substitute for a regular chimney safety inspection nor do they replace regular heating appliance inspection and maintenance by a trained technician.

Those steps must be taken as well.

Readers should also

see COMBUSTION AIR DEFECTS

where we explain the causes and remedies for inadequate combustion air.

 

Flue Gas Spillage Switch or Thermal Switches Available for Oil Fired Heating Equipment

Reader Question: Can and or should spill switches be installed on a oil fired furnace barometirc damper?

12 Sept 2015 shell@scrantonlink.com said:
Can and or should spill switches be installed on a oil fired furnace barometirc damper?

This question was posted originally at OIL BURNER INSPECTION & REPAIR

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

Reply: thermal switches can protect various types of oil fired heating equipment

Yes, there are flue gas spillage switches designed for the (usually higher) temperature range produced by oil fired heating equipment including furnaces, boilers, steam boilers, water heaters, etc,

and there are thermal spill switches that can be mounted at a barometric damper on an oil fired heating flue.

Most thermal safety switches operate by being wired in series with the electrical power circuit supplying the burner (gas or oil).

When the thermal safety switch has been exposed to a specific temperature for a specific time the switch "opens" to turn off the burner.

The spill switches discussed at the article series beginning at FLUE GAS SPILL SWITCH TRIPPING & RESET discuss both oil and gas fired heating equipment flue gas spillage devices.

...

Continue reading at SPILL SWITCH & COMBUSTION AIR TESTS 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 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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FLUE GAS SPILL SWITCH SOURCES & SELECTION at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING SYSTEMS

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Citations & References

In addition to any citations in the article above, a full list is available on request.

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