has anyone ever seen a gas valve fail open?

luketheplumber

I have heard a lot about it happening on water heaters and them going through the roof like on the mythbusters show. But has anyone here ever see a gas valve fail in the open position on any appliance, if so whats the story?

luketheplumber

shoot! how do i move this discussion to the main wall
can I do it of do i need an administrator to do it?

Fred

luketheplumber said:

shoot! how do i move this discussion to the main wall
can I do it of do i need an administrator to do it?

Ask @Erin Holohan Haskell to move it for you. I had a water heater thermostat fail and the water was probably boiling. I heard the water pipes rattle and I though I had an animal running across the pipes in the basement. When I found none, I turned the hot water faucet on, in the basement, it was a steam cloud. Shut the water heater down immediately! PRV hadn't blown yet.

STEAM DOCTOR

Seen a few on boilers.

luketheplumber

> @Erin Holohan Haskell can you help move this?
my mistake

Larry Weingarten

Hi, It’s extremely rare for gas valves to fail open but good plumbing has a lot to do with it. Propane water heaters have a sediment trap built into the gas valve so flakes of rust or other debris cannot get caught in the valve seat. Other gas appliances have a dirt leg the plumber builds. Most plumbers are careful not to use Teflon too close to the ends of threaded pipe, so no fragments of Teflon wind up in the valve. Still, with tank type water heaters, the relief valve is really important. I’ve serviced thousands of heaters and in my area one of forty relief valves is plugged solid. It’s important to test them.

Yours, Larry

retiredguy

I witnessed an older Maxon 3" or 4"motorized gas valve stick open due to a broken bearing on the gas valve release closing mechanism. Nothing happened since there was a second blocking gas valve that was usually required on larger installations. I have seen a few oil valves stick open with disastrous results. In one case, on a brand new H B Smith 4500W boiler installation in a high school, the shock was felt in the whole building and the new boiler was a total loss.

SuperTech

I've never seen it happen. Usually if something fails it's the solenoid burning out and keeping the gas valve closed. Any appliance should have redundant safety's to prevent what was shown on mythbusters. I did have an electric water heater split open like someone dropped a M-80 in it at my house. I've since moved on to using an indirect tank. I've definitely seen plugged relief valves on the job. Testing them should be done annually, but its not because so many would need replacement because they would drip afterwards.

Erin Holohan Haskell

luketheplumber said:

> @Erin Holohan Haskell can you help move this?
my mistake

Yes, I've moved it.

JUGHNE

A memorable gas valve stuck open was an old furnace from the 50's.
The older tenant lady was getting panicky as here house got over 80 degrees. She shut off the power to the furnace which stopped the blower. (this blower was controlled by the old school heat sensitive plenum switch).
That caused the oversized furnace to really overheat.
There was cheap flex duct connected right to the plenum on top of the furnace and it was getting pretty soft.
Fortunately no fire damage.

Large gas trains may have 2 gas valves in series for redundancy.
Many of those have a vent pipe in between the valves with a solenoid controlled valve that is piped outside.

There are plenty of piping diagrams available for Honeywell gas trains for larger equipment.

rick in Alaska

Just an fyi. If you are getting steam out of your faucet, leave the water running, and then turn off the heater. That way the incoming cold water into the tank will help cool it off, and hopefully prevent an explosion.
Rick

Fred

rick in Alaska said:

Just an fyi. If you are getting steam out of your faucet, leave the water running, and then turn off the heater. That way the incoming cold water into the tank will help cool it off, and hopefully prevent an explosion.
Rick

Thanks Rick, That's exactly what I did!

jumper

Interesting that gas doesn't have failsafe like a fuse for electricity.

JUGHNE

Commercial range hood fire suppression systems have a spring loaded cable system. Fuse links are in the potential hot zones and if melted open the pressurized system is energized.
Also there can be a spring loaded normally closed gas valve that is held open by the same cable system.
If the suppression system is set off then the gas valve snaps shut.
It is in the main gas line that feeds all of the under hood appliances.

Also a normally open master relay(s) for the electric appliances that loses it's control voltage if system is set off.

EBEBRATT-Ed

Anything mechanical can fail. Gas valves are very reliable but and dirt or rust can keep it open

EdTheHeaterMan

Several-teen years ago I received a call from a customer about a high gas bill in their unoccupied summer home. I picked up a key from the realty company and went to find the house was 92°F inside when the outdoor temperature was 17°F. I went to the thermostat and found it set for 55° and the indicated temperature was above 90°. went to the furnace room and found the burner and blower operating. When I turned off the switch the blower stopped but the burner did not.

Shut off the manual gas cock, called the customer and got approval for a replacement gas valve. Since the furnace was probably overheated, I also completed a heat exchanger test to make sure there was no crack in the heat exchanger.
That summer we replaced the heater and air conditioning system with high-efficiency equipment.

Big Ed_4

I never seen it happen , me being a old oil guy ..But I can see it happen now , Thanks...

Solid_Fuel_Man

I saw a gas valve leak by on a year old propane range. It was a dual valve one outlet (spud) for the oven bottom burner, and the other spud for the top oven ( broiler) burner. The bottom burner was held open just enough to smell.

I replaced the valve assembly which included the appliance regulator. When I took is to the shop for failure analysis (I was curious!) I found a sliver of aluminum stuck between the soft seat and the bimetal strip. The entire valve was made of aluminum, so my conclusion was that it was leftover from the factory machining process. The manufacturer, GE, warranted it.

Its suprising to me how little safety is built into appliances as compared to commercial redundant gas valves, each tested everytime the burner goes through its pre combustion tests.

AMservices

I had service call 6-7 years ago where a sprinkler head blew off in the middle of the night right next to a Moden heater in a auto body shop.
Thankfully the sprinkler system did its job because it wasn't connected to the alarm system 🤦‍♂️.
The guy opening the shop in the morning only knew there was a problem because there was water all over the floor under the Moden and the heat was off.

First I find the power was off, so I found the breaker and re set power.
Then I go up and the pilot was out so tried lighting the pilot... no gas.
Maintenance man said he shut the gas off from the meter.
So I'm sitting up on top of a 14' A frame ladder waiting for this guy to get back to tell me to try it, when I hear gas filling the heat exchanger.
I had no idea where he was for me to even run to him and say shut it off and I was right there with my BBQ lighter for the pilot. So I Quickly lit the burner before the place filled with gas.
Gas valve was stuck open.
Definitely the closest I've been to blowing myself up.

luketheplumber

Well I'm not sure how many will see this s but I had it happen to myself today. I have a youtube video I filmed of it below.

Hope yall are doing well and thank yall for your stories.

https://youtu.be/UoHbSG4JiIs?si=sKjU1-gxALYSk0np

JUGHNE

Good catch.

Today the larger control systems check to see if there is a flame present before attempting to fire.

I just changed a GV on brand new out of the box HTP water heater.

It threw up the code of "flame present when there should be none". A small flame was standing on the burner.

The piping/dirt trap/inlet screen were perfectly clean.

A new valve solved the problem.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1605607#Comment_1605607

Isnt a manual valve required outside the appliance and isnt the knob on the gas valve a different valve than the operating valve?

mattmia2

I'm pretty sure that isn't the original valve. That is the main job of the relief valve on a water heater or boiler which brings us back to the leave the water feeder on or off question.

EdTheHeaterMan

Avalon NJ Circa,1995 I got a call from a customer that lived in a Philadelphia suburb about the gas bill being too high. Could I go over their the summer home and check it out?

Upon arrival I entered a home that was over 95° inside and the outdoor temperature was about 38°. The thermostat was set to 55°. Found my way to the furnace and it was burning the full flame, so I shut off the main switch. The blower stopped but the flame was still going strong. Turned the switch back on to keep the blower running. Decided to try a percussion adjustment to the gas valve with my metal flashlight…. Still got full flame. Turned the manual gas valve off. Did some heat exchanger testing and determined that the HX was sound. Instructed the customer by phone that the gas valve was defective. Quoted a price to replace it. Everything went well. No damage to the heater or the home. There were some melted candles on the dining room buffet table. Other than that, all good.

Second one: Electrical failure at a church happened at about 10 PM one evening. That was determined by when the clocks stopped. The dual fuel Steam boiler was operating on natural gas at the time. The electrical event may have had something to do with an open ground to the building. Not sure. I got the call at around 12:45 from the Cape May Fire Department, and arrived to the site at about 1:30 AM. The place was light up like daytime. The fire inspector from the building department was on site and we determined that the gas valve must have stuck open at 10:00 PM. The boiler feed pump was inoperable with no electricity. The water level dropped below the save level with a gas flame inside the chamber. Even though there was no electricity for the burner blower to operate, the flame still made steam and eventually cracked 2 of the sections. Steam exited the boiler room of the church and that was when the Fire Department was called. The gas meter valve was cut off and the boiler room door was breached. The boiler room was full of steam. After the room was ventilated, the FD found my number on the boiler and that is when I was called at 12:45.

Once the FD determined the site was safe, I went home, and back to bed. In the following days the State insurance inspector visited the site and I briefed him on our findings and the boiler sections were apart for inspection by then. He read the report of the local fire inspector and agreed the probable cause was the electrical event, and approved the insurance claim. The repairs were equal to a complete boiler replacement and the state boiler insurance program paid for 80% of the job.

So, I guess I had 2 run away gas valves in my career, and both were with run away flames. But no one was injured and no buildings burned down.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1817658#Comment_1817658

So what happens with power open power close gas valves if the power goes out while they are open? I don't know if there are any commercial systems like that or if only old Honeywell systems are like that.

The electrical even could have been a primary wire contacting a secondary wire and burned up or bent something in the valve. Presumably someone opened it up and looked inside.

EdTheHeaterMan

I am not sure that a power close valve would be acceptable for an AGA approved gas valve. All of the residential gas valves have been a fail safe spring action close. They are also redundant gas valves, meaning that there are 2 spring close valves inside them just in case one of them fails.

On some commercial gas equipment, you may find a single standing gas valves in a series of components that includes a pressure regulator and other valves and pressure switches to signal the combustion control that it is safe to operate. The church system had a manual gas valve with a 1/8" tapping that has another 1/8" gas valve. the pilot tube came from the 1/8" valve thru a pilot solenoid valve the on to a pilot burner that was ignited by a 6000 V transformer. The pilot lit the the oil burner flame of the main gas flame. (so you needed to have gas to lignt the oil flame, Dah!) The nfrom the 1-1/2" manual gas valve, you would go to a gas regulator. Next was the primary gas valve, then a Tee to a pressure control Then there was a manual valve just before the gas went into the burner. Maybe if there was a secondary gas valve, that one would have closed… Who knows why the primary valve froze open in the first place?

Valve open without electricity can never be a safe gas valve.