FireMatic fusible link electrical safety switch:

This article describes the Firomatic Thermal Switch TS-150 series (or other brand) electrical safety switch that uses a spring-loaded fusible switch to cut off electrical power to a heating appliance (boiler, furnace, water heater) in the event of a fire. Synonms: Firematic - Fir-O-Matic - FiroMatic - Fire-O-Matic - thermal switch.

If this thermally-fused electrical FireMatic safety switch "trips" it cannot be simply re-set, it will need to be replaced in order to return heat or hot water equipment to operation.

How & Where do We Install a Fusible-Link Firematic™ type Thermally-Fused Electrical Safety Switch

Where to install the Fire-O-Matic fusible link firomatic thermal switch on heating equipment

Our reader asked:

I don't see any info on the fusible link electrical safety switch. I was wondering why it's required and what is the location normally used?

I know they are above the boiler/furnace but are there any specific dimensions above the burner? - G. P. 12/26/2013

Reply:

Thanks for asking, G.P.. Fireomatic ™ or Firomatic™ (or its successors and possibly other companies) produced a Firomatic Thermal Switch TS-150 series (or other brand) electrical safety switch that interestingly uses a similar spring-loaded fusible switch to cut off electrical power to a heating appliance (boiler, furnace, water heater) in the event of a fire.

Separately, equivalent devices marketed for the same purpose: turning off electrical power to heating equipment in the event of overheating or possibly fire conditions, are sold using a thermally-operated electrical snap switch in place of the original fusible link mechanical device.

These heat-triggered electrical safety switches are usually installed in a junction box close to the heating appliance or within six feet overhead.

The original Fireomatic™ fusible link electrical safety switch is an electro-mechanical switch that was wired "in series" with power to the oil burner and is required by local fire or electrical codes in some U.S. states.

The fusible link melts at (typically) 180-190°F, opening the switch, thus cutting off power to the appliance.

Some sources I found refer to the Fire-o-matic thermal electrical switch as the "New England Safety Switch" as that's where several states required its installation.

I've found references to this thermal safety switch for New Hampshire, Pennsylvania, Rhode Island, Massachusetts. Exact installation specifications for the switch location may vary by local state or provincial codes, so you will want to check with your building department.

Other versions of Fireomatic type thermally-triggered electrical power safety switches use a thermally sensitive snap switch to replace the meltable fusible link to open the switch or cut off electrical power in event of a fire or local overheating near the protected heating appliance.

Examples of Installation Specifications for the Firematic thermally-operated electrical safety switch

(e) An electrical thermal switch fused to break the ungrounded conductor in the main circuit at 165°F, shall be installed in the main power line within six feet over the top of the burner-boiler or burner-furnace.

If the ceiling above the burner-boiler or burner-furnace exceeds 12 feet in height, an additional thermal switch shall be installed on the ceiling and connected in series with the lower switch. - Massachusetts building code:

Oil or gas burners both with fireomatic switches, service switches and emergency switches properly marked and in correct locations. (check with Fire Department if you have any questions at (603) 635-2703); - New Hampshire reference: http://www.pelhamweb.com/planning/PDF%20Forms/ELECTRICAL%20REQUIREMENTS%203-18-02.pdf - quoting:

The Fire-o-Matic thermally operated electrical safety switch is sold mounted in the center of a red-painted rectangular or round steel plate intended to be secured to the top of a rectangular or round electrical box. Other manufacturers may provide similar replacements.

Where to buy a Thermal Cutoff Switch - Sources for fireomatic® type thermal cutoff switches

Start at your local heating equipment supplier. Most HVAC and plumbing supply businesses have or can obtain a fusible link thermal switch, aka the "New England Safety Switch" or a Firematic® Thermal Switch. If you need to contact the manufacturer or supplier for these devices we list those companies just below.

• Inner-Tite Corporation, Holden VA USA produces the Inner-Tite Thermal Cutoff Switch rated at 120V 15A with sub-text imprinted on the product: 12oV-AC-600 VA Pilot Duty (copper conductors only), The Innertit TC-2 # 9501A thermal fuse shown is rated for 165°F
• R.W. Beckett (produces fusible link oil line safety valves, check valves, and thermal switches. - Website: www.beckttcorp.com
  
  Two thermal switches are listed by Beckett:
  • Part # 12527, U.L. Switch for 3/4" and 4" round junction box Firomatic # 91301150
  • Part # 12501, U.L. Switch for 4" square junction box, Firomatic # 91301300

Beckett Corporation describes their thermal switch as follows:

Thermal switches - a safety device which provides added protection to fuel burner installations. it is a thermally operated switch installed in the electrical power line to the burner.

It is normally set at 165 degrees F and remoes power if the ambient temperature reaches this point.

The burner then shuts off immediately.

The thermal switch is usually positioned on the ceiling, close to the burner. It SHOULD NOT be used manually to start an stop the burner motor.

When properly installed, there are no exposed electrical wires or contacts, before or after firing - this is important.

The fusible element is the handwheel of the switch - after it "fires" simply replace the handwheel to restore the switch. Contact ratings are: Pilot 120V, 60 Hz, 360VA, 1/2 horepower, 12volts, 60 Hz.

Excerpt from Beckett's Firomatic Thermal Switches Website: (2025/11/03)

Firomatic® Thermal Switches are temperature actuated safety devices installed in the electrical control circuit of a power burner.

This provides additional protection as a control inter-lock. Provided with a thermal link set at 165˚F these devices are normally positioned at the ceiling, above the burner, or where code(s) require.

Firomatic Thermal Switches use the same handwheel / fuselink as used with our manual valves.

A 200˚F handwheel / fuselink may be substituted for the standard 165˚F for higher temperature applications.

Please check AHJ for code compliance before using the higher temperature fuselink.

Firomatic Thermal Switches SHOULD NOT be used to manually start or stop the burner. When properly installed, there are no exposed electrical contacts or wires.

Also see this

Beckett FIRE SAFETY VALVES APPLICATION, INSTALLATION, & MAINTENANCE INSTRUCTIONS [PDF] (at Beckett's Website), (2020) Form No. 62258-001 R00, local copy saved as Beckett-62258-001-Instructions.pdf

• Sid Harvey
• Possible: Olson Manufacturing S95010A Square Fireomatic, http://www.olsonmfg.com, Toll Free: 1.800.255.0074, Email: sales@olsonmfg.com - sold by heating equipment suppliers and online from various sources including at Amazon.com and rexelenergysolutionsusa.com
• Asco Products (Emerson Industrial)
• R.W. Beckett (U.S. & Canada) Firomatic Fire Safety Valves
• ISP Automation (Firematic)
• Webster Fuel Pumps & Valves, a vacuum-activated OSV
• A confusing link that Google searches return but that won't help you with this topic is at http://firematic.com is a fire equipment & truck company

I'm researching the manufacturer & the switch installation instructions and code citations and will add that information here.

The Fire-o-Matic™ fusible link oil line safety valve or OSV is discussed in detail beginning at

at OIL SUPPLY LINE SAFETY VALVES, OSVs - this is a fusible link safety valve on the heating oil supply line; its location is dictated by the physical location of the oil piping, filter, tank, and oil burner.

"Above the burner" is not a specification that pertains to that control. That switch is not an electrical switch, it is mechanical, and it controls heating oil flow not electrical power.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Is there a Fire Safety Valve for my 240VAC Electric Furnace?

In the case of a furnace supplied with 220volts, what would be the proper installation to interrupt both hot legs. I have not seen a 2 pole firomatic On 2019-10-17 by tziobro48@hotmail.com

by (mod) - Find a Firomatic or fusible heating system safety switch for 220V furnace?

Nor have I, TZ. And I'm doubtful of the safety of interrupting just one leg - as could happen- at least in theory - if two separate Firematic Thermal Switches were used, one on each leg. But there may be no alternative; the double-pole thermal swtiches I could find were not for your application.

Nor have I come across a fossil-fueled residential heating furnace whose base electrical power input was 220V.

There are of course electric heating furnaces that use 220V as do some heat pumps;

Give us the brand and model of your 220V furnace and we'll join you in seeing what the maufacturer advises.

Do I "Open" the handwheel on the FireMatic switch to turn on its safety feature?

In the photo above my pencil is pointing to the visible valve stem in an oil valve - telling us that the turnwheel is screwed fully down, the stemp has been lifted, and the oil flow is "ON".

I have a firomatic cutoff switch with the handwheel. Am I supposed to turn the wheel to the open position to activate the safety feature? Power is flowing fine now. I haven’t turned the wheel to open yet. No instructions cane with the switch. On 2019-09-02 by Jim

Answer by (mod) - which way is fire safety switch "ON" ? handle up or handle down?

When the handle is screwed down on a Firomatic OSV or thermal switch then the valve stem is under spring tension and actually the valve has been opened and the stem lifted "up": the safety device is activated.

Both the electrical fire safety valves shown on this page and the actual oil line safety valves described

at OIL SUPPLY LINE SAFETY VALVES, OSVs work the same way and their open/closed direction is opposite that of ordinary plumbing valves.

Details about which way to turn the conventional oil line control Fire-o-Matic switch are

at OIL SUPPLY LINE SAFETY VALVE TURN DIRECTION to OPEN or SHUT 

Power surges are tripping my electric Fire-Matic switch

Almost every time the power flickers it trips my fire matic I have to remove and reinstall it. Is it bad? On 2018-11-27 by Bob

Warning by (mod) -

The description of a thermal firematic switch in the article above explains that the switch responds to heat and at a sufficiently high temperature will open to close the electrical power to your heating system.

It's not clear to me how power series would be causing problems with the switch but that would certainly be worth getting the manufacturer call.

Post a picture of your switch or tell us the brand and model and we can help research the question.

Watch out: if your lights keep flickering the cause of that problem needs to be found and possibly repaired (if it's not the power company) since you could be facing a dangerous electrical failure and a shock or fire hazard.

Who can hook up power to my new heating boiler? What size wire do I use?

I have new heat boiler i want to wire from main box or breaker to firematic then circulator pump whats the wire code 12/2 or 14/2 romex

I live in Providence, Rhode Island; please can you help On 2015-04-27 by vlasimir larrain

Reply by (mod) -

Vlasimir

I'm not sure what help you are asking - it sounds as if you need a licensed electrician to hook up some switch and wiring for you.

Some heating service techs are also able to do that.

You won't need 12/2 wire unless your circuit draws 20Amps. Check your burner motor and controls - I expect they want as 15A circuit.

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Continue reading at OIL SUPPLY LINE SAFETY VALVES, OSVs or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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