Why does this customer's pilot keep going out?

Joseph_4

I have a customer whose basement was flooded a few times and as a result I moved his gas valves 18 inches off of the floor. It was on a crown boiler where the gas valve is close to the floor. I did this during the summer. he has an indirect fired water heater so it is on the whole year round. I used a 48 inch thermocouple and used couplings to extend the pilot tubing that far. lately the pilot has been going out randomly. I changed the gas valve. the thermocouple is also brand new. it still keeps on going out randomly. attached is a picture of the gas valve high up on the right. if anyone has any idea to share as to why it is going out, it would be greatly appreciated. it can stay on for a month at a time and then go out so the gas pressure seems to be right. the pilot burner assembly is a three-line pilot burner and it is a nice size flame properly hitting the thermocouple. I am thinking of putting it back the way it was but when he floods the gas valve goes under water.
Thanks
Joe

Michael Welch

Was this gas valve previously under water? If so you may want to replace it. It may not be getting good electrical conductivity between the thermo couple and the gas valve. Another possibility I see with the gas valve up that high might be a delayed ignition of the main burner causing it to blow the pilot out.

Zman

The gas valve is not the only part of the boiler that should not get wet. Water is not good for the burners, controls, refractory....
Why wouldn't you install a sump pump or put the entire boiler on a pad? I think you are setting yourself up for a lawsuit on this one.
Carl

j a_2

Oh boy, if that boiler went under water,and it sounds like that is what you said…You are playing with fire…..Do the right thing

Gordy

I think you better put it back the way it was, and get the whole boiler high, and dry. Doing what you are attempting just put all liability on YOU if something happens! I would seriously replace anything that was under water.

Tinman

I agree with Gordy. Put it back the way it was. Put it in writing that your recommendation is to do exactly that. The prudent thing to do is raise the entire boiler, not re-engineer it by raising only the gas valve. And, definitely replace anything that was submerged. Once all that's done, there are only a few things that cause repeated pilot outages.

Tinman

Sometimes, and I'm not suggesting this is true in your case, a customer may try to influence us to do something that we know isn't right because it's so much cheaper. I just bite my lip, shake my head, and politely say "No I can't/won't do that, but here's what I can/will do and it will be the safe way, the correct way."

j a_2

Stephen, You are exactly right……

JStar

If you can't repair a gas appliance safely, you shouldn't touch it at all. If a customer does not want to comply with safety protocol, they should be reported to the local fire department, who will make a free visit to their house and disable the appliance permanently. Saving money is no reason to endanger your neighbor's lives.

j a_2

Why should they come out for free,and why would they listen to Mr. fire guy handyman as opposed to a lic. repair tech...

JStar

A submerged appliance is a fire safety hazard and should not be addressed lightly.

icesailor

You're serious? The AHJ's don't care, nor anyone that has anything to do with the gas delivery. A frugal owner will find someone to try to repair it because you/we are crooks and trying to rip them off.

Tuesday in the Local paper where I lived and worked, there was an item about a house that burned down completely. Someone was an artist and caused something to spontaneously combust. Try explaining THAT to someone. Like a floor sander who doesn't believe that his floor sandings can spontaneously combust inside the trash bags. The smart ones leave them outside. If it weren't for acrylic water based paint, houses would be spontaneously combusting on a regular basis.

unclejohn

Yeah there is a lot of air in that gas line before it hits the pilot. And if that is whats causing the pilot to go out, that means the pilot was lit right before the call for heat which means the gas valve is open maybe a minute before the thermocouple reacts and shuts it all down. I counted 11 burners and there are probably 15-16 total. That's at least a 150k boiler

Joseph_4

it would have been great if I could have responded earlier the boiler did not go underwater. the gas valve and thermocouple are brand new. the flooding was only enough to touch the gas valve on the floor and maybe the first inch of the refractory much lower than the burner tubes. none of the sections were touched at all. . the customer has a sump pump which fails sometimes. if there would be a delayed ignition I would see it every time the boiler lights up and it is lighting off fine. . the fact that the boiler room has flooded this small amount each time is not going to make a customer spend thousands of dollars to move a multi zone boiler to higher ground. it is a pain for him every time this happens for me to keep billing him for replacing a gas valve. does anyone have the reason for why it is randomly going off
joe

Gordy

Is gas pressure constant, or does it fluctuate? Have you checked it?

Still not condoning the modification of 48" . There is a reason it's randomly going out, and that is part of it.

icesailor

Oil burner techs are constantly checking oil pumps for proper pump delivery pressure. I don't see that so much for gas. Why is that?

the first thing I did when I started doing gas service work was go out and buy myself a quality digital gas pressure tester.

How many older houses now have undersized gas mains? Turn on all the gas and see what you have for pressures. Someone at a boiler school I went to mentioned to the instructor that areas in New York don't have high pressure gas in the street and during peak periods can barely provide enough pressure to systems to keep them running. How would you know if you didn't take the pressure readings?

Gordy

Gas meter btu rating comes into play here maybe.....225k 250k? Or more? That's a big boiler looking at the burner rack. What else is on NG that may come on while the boiler is going?

Tinman

I've seen soft, lazy, dirty pilot flames pull away from the thermocouple when the main burner comes on so if you haven't pulled apart the pilot burner and made sure the orifice isn't slighly plugged or dirty, you should. You would think that the main burner would always relight the pilot, but it doesn't always.

Check line pressure and manifold pressure.

Delayed ignition doesn't necessarily happen each and every time a boiler or furnace lights off. Pull and clean the burners as the other guys have suggested.

Those three simple things may answer a lot of questions.

Ironman

The prudent thing would be to have redundancy with two sump pumps, not re-engineer the gas train on the boiler. From a legal and liability stand point, you totally are responsible for the gas train on that boiler since you re-did it. It's AGA approval is now void and that's your responsibility.

It's a shame that's the way things are when you're trying to be helpful with a customer, but we live in a litigious society. And, quite frankly, it should be so in this case. None of us (except maybe Tim McElwain) is qualified enough to re-engineer a gas train that a manufacturer has designed and had approved.

Ironman

Joseph said:

"it can stay on for a month at a time and then go out so the gas pressure seems to be right."

Joe, no one is trying to be hard on you here, but we're trying to help you see that there are just some things that cannot be done, no matter how good your intentions are.

I gather from your statement above that you did not actually take inlet and outlet gas pressure readings? Please correct me if I'm wrong.

As someone already pointed out, there are many older gas systems that have low pressure zones where the incoming pressure fluctuates greatly. I do work in nearby Staunton, VA which has a low pressure zone in the downtown area. Some of the lines there are over 100 years old. I've seen the incoming pressure fluctuate from a low of 3" to high of 12" depending upon the demand and time of day. You need to check the pressure and see if it fluctuates and if it's a low pressure zone.

BobC

I just had my gas main and meter replaced. The gas pressure at the boiler input was dropping from 8 to a bit less than 5" WC, the output of the valve / regulator was bouncing all over the place. After the work was done the pressure at the boiler input drops from 9.3 to 9" WC.

It's important to measure the gas pressure at the input and output of the gas regulator to be sure it's what you think it is. Also check the input pressure when other gas appliances are firing.

Bob

Tim McElwain

Try doing some troubleshooting:

PROCEDURE FOR TESTING THERMOCOUPLES

I am often asked about troubleshooting a thermocouple on gas systems. This will be a permanent reference that will give a step-by-step procedure.

A thermocouple is a device used to satisfy pilot safety on many 24-volt gas systems. The thermocouple is a device made up of two dissimilar metals. They are joined together at the tip (Hot Junction). When heat is applied to that hot junction a small millivoltage is created. This develops because of temperature difference between the hot junction and what is called the cold junction. The flame has to envelop the upper 1/2" to 3/8" of the thermocouple and the tip should glow a "dull red". If the flame is adjusted to a sharp flame it will glow "cherry red" this will cause the tip to be welded and eventually the thermocouple will fail. The flame should be adjusted to a soft blue flame, not roaring or lifting. The normal millivolt output is 25 to 35 millivolts, on some you may even get up to 35.

The other part of this safety pilot system is the electromagnet (power unit). It is if you will the LOAD and we can say the thermocouple is the SOURCE. The electromagnet is made up of a coil of wire and "U" shaped iron core. When the thermocouple is heated and the millivolts generated the coil will be energized and create a magnetic field. The magnetic field will cause the "U" shaped iron core to be magnetized; it in turn will hold open a seat allowing gas to pass through.

When this system malfunctions it typically causes the pilot to go out and the gas will not flow. The first thing that should be done when arriving at a pilot outage situation is to do some visual checks.

1. IS THE PILOT LIT?
2. IS THE PILOT CLEAN? (NOT YELLOW)
3. IS THE PILOT HITTING THE UPPER 1/2 TO 3/8 OF THE THERMOCOUPLE?
4. ARE CONNECTIONS TIGHT?
5. IS TIP DAMAGED?
6. IS THE COLD JUNCTION BEING HEATED BY THE PILOT OR MAIN BURNER FLAME?

Once those things are addressed it is a good idea to take some millivolt readings. It should also be mentioned that many times it is the policy of some to replace the thermocouple on a call and clean the pilot. It is not a bad thing to do, however it is statistically about 85% of the time it is the thermocouple giving the problem. It is the other 15% of the time that taking readings can solve other problems.

You need a multimeter with a DC volt scale, as the millivolts generated are DC volts. There are four readings we are going to take they are

OPEN CIRCUIT - this is taken with the thermocouple disconnected and the meter leads attached to the outside of the thermocouple and the other meter lead attached to the tip of thermocouple. The pilot-on-off knob will have to be held manually to take this reading. This measures the output of T'couple the readings must be above 17 to 18 millivolts.

* CLOSED CIRCUIT - This measures the millivolts used by the coil in the electromagnet. A rule-of-thumb is this reading should be roughly half of the open circuit. It is taken using an adapter screwed into the magnet and the thermocouple screwed into the adapter.

CLOSED CIRCUIT LOAD - This reading is taken the same as the previous reading except the burner is now on. With a proper flame this reading should be about the same as the previous reading. With a lifting main burner flame or excessive drafts or chimney pull, this reading may reduce from previous reading (flame being pulled away from the thermocouple). With the cold junction being heated this reading may increase. If the "cold junction" is heated excessively it will break down.

DROP OUT - This is the final reading. It requires the pilot to be blown out. It measures the ability of the magnet to hold under reduced MV input. A good unit should drop out below 6 MV's - normal is 1 to 2 MV's. The allowable "drop out" time is 180 seconds yes three minutes. It is more likely to be a minute and half to two minutes. There will be an audible "click" when the magnet shuts down.

* THE CLOSED CIRCUIT READING REQUIRES A SPECIAL ADAPTER THAT SCREWS INTO THE MAGNET ASSEMBLY TO ALLOW CONNECTION OF THE METER. AN ADAPTER CAN BE PURCHASED FROM ANY ROBERTSHAW DEALER THE PART NUMBER IS 10-038 THERMOCOUPLE TEST ADAPTER.

A normal set of readings

OC- 30 millivolts
CC- 15 millivolts
CC(load) -15 millivolts
DO- 1 millivolt

The best way to be able to diagnose these readings is to use MILLIVOLT CHARTS these can not be displayed here but I can provide them if you e-mail me.

Thermocouples from different manufacturers vary as to their dependability. The only thermocouples I recommend are made by Johnson Controls. The K15 and K16 series are the best. If you are having durability problems then use the K16RA, which is a nickel-plated high ambient or corrosive environment thermocouple. The Husky (K16) will fit most applications and for those that it does not the Slim Jim (K15) will fit.

To repeat the adjustment of the pilot flame to envelope the upper 1/2 to 3/8 of the thermocouple is important, the flame should be a soft blue flame not roaring which will cause the tip to glow a "dull red" versus "cherry red".

The combustion condition (excessive temperatures) in the chamber is also an issue and this will require a combustion test and draft measurement to insure that excessive temperatures are not being applied to the pilot. In some cases on water heaters it may be necessary to alter the pilot adaptation to get better quality performance. This however should not be done unless you have had proper training.

The possibility of the equipment operating in a depressurization environment will certainly lead to thermocouple failure. In addition if the equipment is flued together with a "fan assisted" furnace or boiler this can lead to problems. There are solutions to this also but training is required.

The thing that I find is often a problem is the environment in which the equipment is operating. Many times corrosive chemicals and airborne contaminants are being drawn into the air gas mix and a chemical reaction takes place. This again requires attendance at a training session by a professional combustion person to help you to see the various affects this will have.

Last of all the failure to put all the doors and covers back in place on equipment. The failure to do this will cause an alteration in combustion air and the flame stability is affected.

The design of some equipment is also a problem. When there is high demand for heat (very cold weather) the temperatures that are created in the chamber have an adverse affect on the pilot and thermocouple system. The addition of the K16RA thermocouple can offer some assistance toward extending the life of the thermocouple in this situation.

Insufficient air for combustion and dryers operating in close proximity to equipment also lead to problems.

Last of all and this is not directed at any one in particular but just plain lack of service personnel and installers knowing what they are doing.

Make sure the inlet and outlet gas pressure are according to the rating plate.

My book "Circuitry and Troubleshooting" Volume II addresses many of the things in question here.

RobG

Tim, what effect if any will the modification of the gas train have?

Tim McElwain

If the gas valve is too far away from the burners then the outlet sensing port on the valve will not respond correctly to downstream demand. I was thinking that the tech would eliminate any millivolt or other readings and if needed replace the valve or put the old one back in its previous location.

I just went back in the posting and found the picture that valve is definitely too far away from the burners.

Joseph_4

If Tim says move it back that is the end of discussion for me. ... i appreciate everyone's input.
Joe

RJ_4

Might want to check your flue for possible downdraft issues, Is the flue the right size, is the flue cap intact , is the height of the flue at least 2 ft. above restrictions on roof like parapet walls or roof equip. Also check to see if boiler room has correct fresh/combustion air and is not at any time in a negative pressure