Safety valves. It took me a little while to figure out how they worked, what their true purpose was. But let’s start with the outside of the stove. There’s a “CP” logo. That stands for “Certified Performance” and is a trademark by the Gas Appliance Manufacturers Association (GAMA) that ensures that your stove meets certain high standards, like the stove’s oven/broiler safety systems. My OKM vintage gas stove has safety valves and connected thermocouples for a safer operation of the oven and broiler.
Robertshaw Gas Oven Safety Body & Magnet
Description
The Robertshaw TS Series thermomagnetic safety valves are control valves used to cut off the flow of gas to the burner in the event of a pilot outage. The magnet assembly is energized by voltage generated by a thermocouple that is heated by the pilot flame. When this flame is extinguished, the thermocouple voltage decreases until a spring overcomes the magnetic force and loses off both the pilot and main gas (the older valves just shut off the main burner gas). This control can be used for commercial and residential ovens, infrared heaters, chicken and pig brooders, recreational vehicle gas appliances and many more applications requiring automatic safety valves!
What it means is if, for any reason, the gas flow to the stove stops while the oven or broiler burners were on, in addition to the burners going out the pilot flame would go out. That would cool down the thermocouple probe which sits in the pilot flame. When the thermocouple is not hot enough, it signals the safety valve to close, which blocks gas from flowing to the burners.
Seems silly. If the gas is off, why worry about gas to the burners?
WHY!
Prior to safety systems existing, when these stoves were being produced, gas distribution was not always reliable. Sometimes, the gas supply would die out, shutting off the flames. Then after a little while, the gas would come back on.
Unlike the cooktop burners, the oven burner is hidden. If say, a bread baker were only using the oven at that time the gas supply stopped then started again, she or he might not have realized what happened. It was possible the baker might open the oven to check, realize the flame had gone out and try to relight the manually lit oven with a match.
Without a safety system, the oven chamber could have filled up with a dangerous level of raw gas. Lighting an oven that was already full of raw gas…
With a safety system, when the gas flow to the stove was re-established to the entire stove, the safety valve would have prevented the raw gas from filling up the oven or broiler chambers because the valve closed when the pilot light went out.
THAT WAS THEN. WHAT NOW?
These days, gas distribution is pretty reliable. Most often safety valves can seem to be a problem for three reasons: a) after the gas has been shut off from the stove (so the stove can be safely repaired or relocated), b) when the thermocouple bi-metal’s charge dwindles and dies, c) when the safety valve loses its magnetic charge and cannot stay open.
When my gas stove was moved into my kitchen, I needed to perform a manual reset of the two safety valves so I could test the oven and broiler. When the stove was disconnected from the previous owner’s gas line, that killed the pilot flames which cooled the thermocouples which closed the safety valves.
Each time I worked on my stove’s major systems, I’d shut off the gas to the stove. To restart the oven and broiler burners, I’d have to manually reset the safety valves if I wanted the oven and broiler to auto light again.
LIGHTING THE BURNERS
Lighting instructions on an O’Keefe & Merritt broiler door. They aren’t exactly clear.
The standard process I have gone through to reset a fully functional safety system:
- Made sure the pilot flame is on and the thermocouple probe is in that flame. The heat causes the thermocouple to charge and send a signal to the safety valve. The signal cannot open the safety valve, but it can only keep it open. If the pilot is not lit, I’d light it and wait about a minute for it to warm up enough to signal the safety valve.
- Propped open the cooktop lid to access the safety valve(s).
- Turned on oven/broiler gas.
- Pushed and held in the red button on the safety valve. Pushing the button manually opens the safety valve, allowing the gas to flow to the oven/broiler burner. Once the gas flow reached the burner, the pilot flame would ignite the oven burner.
- Released the button on the safety valve. When everything worked properly, button would return to its original position, but the safety valve would stay open, because the thermocouple sent a signal for it to stay open. Big happy dance.
- If the oven burner shut off after that process, my first hope was the thermocouple signal was too weak to keep the safety valve open. Time for a new thermocouple. Relatively speaking, an inexpensive and easy task. Or the safety was on the fritz. Major $$$ pout!
If you have a multimeter with a DC volt scale, you can use that to test your thermocouple’s charge. When heated it generates a DC voltage of approximately 25 – 30 millivolts.
VARIOUS SAFETY VALVE DESIGNS
There are many different safety valve model for major gas appliances like stoves, water heaters and furnaces, but they all have the same purpose – to prevent unbridled raw or uncombusted gas. Their designs and features have evolved over the years. If you’re trying to find a replacement safety valve for your stove, you don’t have to necessarily get an original unit.
But you do need to make sure the replacement valve meets all the critical requirements. For example, the gas line openings need to be the match the diameter of the gas lines in your stove, it needs to have correct port for the thermocouple, it needs to fit the opening of the previous unit, etc. There are workarounds for most of that, but it involves plumbing adapters, additional gas lines and/or plumbers.
When my old gas furnace safety died, troubleshooting pointed to the safety valve as the trouble. I disconnected it and took it to a local appliance parts shop. Thankfully, the owner recognized my old no-longer-available furnace safety valve and knew which updated model would work.
Below are the safeties I’ve seen in the OKMs I’ve rescued.
There are a few more vintage safety valves posted on TOAC’s website.
Robertshaw Gas Valve 1720-801 Safety Series Gas Valve Head
The Robertshaw® 1720 Series Thermomagnetic Safety Valve is a control used to cut off the flow of gas to the burner in the event of a pilot outage. The magnet assembly is energized by voltage generated by a thermocouple that is heated by the pilot flame. When this flame is extinguished, the thermocouple voltage decreases until a spring overcomes the magnetic force and closes off both the pilot and main gas. This control can be used for commercial and residential ovens, infrared heaters, chicken and pig brooders, recreational vehicle gas appliances and many more applications requiring automatic safety valves.
Features and Benefits
- 300°F (149°C) ambient temperature rated and 350°F (177°C) versions available
- J models available with separate pilot inlet/outlet tube connections
- K models are pilot outlet only
- Compatible with other Robertshaw models such as the BJWA, FD, and GS series thermostats
- RoHS compliant
- Series Application: TS11J J Magnet Head Only – Inlet and Outlet
- Ambient Temperature: 32°F to 300°F (0°C to 149°C)
- Body: Inlet and Outlet NA
- Head Pilot Inlet and Outlet: Kit, 1/8″ Pipe, 3/16″ Tubing, 1/4″ Tubing
- Maximum Pressure: 0.5 PSI
1710-112 Safety Series Gas Valve Body
Safety Series Gas Valves
The 1710 Series Replacement Body is used with the 1720 Series Replacement Magnet Heads in TS Automatic Safety Valve applications. Note arrows showing direction of gas flow.
IMPORTANT NOTICE: When a new 1710 replacement body is ordered a new 1720 safety magnet must also be used. Order separately, see Magnet Heads.
https://www.robertshaw.com/Products/Cooking/Gas-Valves/1710-112/?cat=2147484248
Series Application: 1710 (TS Body) Gas Carrier
Capacity: 106,000 (BTU/HR @ 1″ W.C.P.D.) Natural Gas|171,000 (BTU/HR @1″ W.C.P.D.) LP Gas
Inlet & Outlet Size: 7/16″ Tube