My pilot goes out when the outdoor temp is below about 5 degrees F

Jim100Flower

My pilot goes out intermittently when the outdoor temp is below about 5 degrees F. My heating guy wants to replace the gas valve and has already replaced the thermocouple. It relights easily with a match.
1. Why would a gas valve turn off the pilot only on cold days?
2. Is it time to replace the boiler? Put the repair money towards a replacement instead.
I have a Burnham 208 165,000BTU out natural gas boiler manufactured in 1983 and put in service in 1986. It runs six zones and provides adequate heat.

Jamie Hall

Two thoughts come to mind quickly here. First, I presume there is a draught hood? If not, could there be a down draught through the stack? The other is... check your inlet pressure. Depending on where you live, your inlet pressure may drop when it gets colder (because of all the demand on the system) to the point where you don't have enough to keep things properly lit.

Fred

You say it's "intermittent" and at temps below 5 degrees. Are you really sure those are the real conditions? I believe it is intermittent but I doubt the area where the boiler is located is 5 degrees. I suspect it is more obvious at that temp because the call for heat is more frequent and that the number of times it fails is probably relative to the number of burner ignitions, regardless of outside temp.
Is the pilot flame a good strong flame? Is the Thermocoupler sitting in the flame like it should (tip about 3/8" in the flame)? Is there a known issue with the chimney (back drafts or other issue)? Are there any indications of moisture or staining on the underside of the boiler block or the burner tube in the area immediately above or around the pilot? Is there a good connection where the thermocoupler connects to the gas valve?
Is this problem new or has it been on-going? If new, has anything changed recently?

Jim100Flower

Jamie Hall said:

Two thoughts come to mind quickly here. First, I presume there is a draught hood? If not, could there be a down draught through the stack? The other is... check your inlet pressure. Depending on where you live, your inlet pressure may drop when it gets colder (because of all the demand on the system) to the point where you don't have enough to keep things properly lit.

Tonight is 6 F and windy. The pilot recently went out.

On top of the cabinet is an exhaust tube with a mushroom cap followed by more sheet metal tubing to the chimney. The mushroom cap has vents beneath. I can hear the wind. More importantly, when I hold my hand underneath the vents, the tops of my fingers get cool. Tonight I think there is a downdraft.

The cabinet is 31" high. I don't know if there is space in there for a draught hood. Could the mushroom cap be a form of draught hood?

If the problem is a down draft, what is the remedy? Wouldn't a new gas valve and a new boiler have the same problem?

I live in a small New England city population 90,000. I believe the pilot outage correlates with high demand on the city gas delivery network.

If the problem is low inlet pressure, what is the remedy? Wouldn't a new gas valve and a new boiler have the same problem?

Jamie Hall

From what you describe, neither a new gas valve nor a new boiler -- unless it was of the power vented variety, rather than atmospheric -- would solve the problem. In fact even a power vented boiler might also suffer: your second to the last paragraph may be the key: low street gas pressure at times of high demand, like cold weather. There is a solution to that, but it is probably not one you can do much about: the New England natural gas distribution network, taken as a whole, is simply not big enough to cope with the demand being placed on it. But nobody wants new pipelines... don't get me going.

Jim100Flower

The new boiler would have an electronic igniter. Wouldn't that just relight the boiler eventually. The condition that puts out the pilot doesn't last forever - I can relight with a match.

Do you think the boiler should be replaced due to age?

BTW, I support new pipelines.

Jim100Flower

Fred said:

You say it's "intermittent" and at temps below 5 degrees. Are you really sure those are the real conditions? I believe it is intermittent but I doubt the area where the boiler is located is 5 degrees. I suspect it is more obvious at that temp because the call for heat is more frequent and that the number of times it fails is probably relative to the number of burner ignitions, regardless of outside temp.
Is the pilot flame a good strong flame? Is the Thermocoupler sitting in the flame like it should (tip about 3/8" in the flame)? Is there a known issue with the chimney (back drafts or other issue)? Are there any indications of moisture or staining on the underside of the boiler block or the burner tube in the area immediately above or around the pilot? Is there a good connection where the thermocoupler connects to the gas valve?
Is this problem new or has it been on-going? If new, has anything changed recently?

Thanks Fred. I've owned the home for 5 years and the problem has occurred once or twice each year during the coldest weather. This record-breaking cold winter it has gone out 15 times during the coldest weather. I haven't seen it go out during average winter temps. But I'll keep watching because if the problem is, as you propose, not related to temperature but to the number of burner ignitions, then I should see it fail eventually at average winter temperatures.

I think the thermocouple is correctly installed as it was just replaced by heating professional.

Do you think the boiler should be replaced due to age alone?

SeymourCates

@Jim100Flower

The situation with reduced gas pressure will cause the pilot to reduce in size. This puts it in a condition were any downdraft from the chimney when the boiler is not operating could cause it to extinguish. Obviously, the problem is more prevalent in colder temperatures where gas is in high demand.

Ask the heating guy to adjust the pilot flame to a larger size. When the gas pressure drops, the pilot flame will also drop in size. However, starting from a higher initial level could correct this infrequent issue if there is sufficient range in the pilot adjustment.

The problem is unrelated to the number of burner ignitions. The boiler doesn't care about that.

You can also consider the adaptation of an intermittent pilot (spark ignition) to the boiler if the heating guy is competent. I would not replace the boiler.

Jim100Flower

Seymour, thanks, your explanation makes a lot of sense and I can't make sense of the gas valve being the problem.

You say you wouldn't replace the boiler. When is it time to replace? How would I know when the boiler is failing?

SeymourCates

Well, technically, the gas valve is the problem as the pilot adjustment is within the gas valve. However, replacing the gas valve is not the correct answer. It is an answer by an incompetent individual.


Let's understand what a boiler is.

A set of cast iron sections that are bolted together and hold water with a set of burners beneath the cast iron.
Everything else is attached to the outside and is easily repaired or replaced as required (even the burners can easily be replaced). So, provided the cast iron is intact, with no failure due to corrosion, the boiler will shoulder onward without serious issue. If the cast iron fails, you will see water on the floor or you will observe excessive makeup water and excessive moisture leaving the chimney.

Then, and only then, do you replace it.

Gilmorrie

Try adjusting the pilot a bit higher. Make sure the pilot flame envelopes the tip of the thermocouple.

Zman

I think you should check you gas pressure when it is cold outside.

unclejohn

I just wish climate change would hurry up and work.

Zman

unclejohn said:

I just wish climate change would hurry up and work.

It sounds like it is....

HomerJSmith

I hope when you replaced the thermocouple, you cleaned the pilot orifice.

HomerJSmith

Any boiler that old should have the burner tubes pulled out and cleaned and the pilot burner cleaned, too.

HomerJSmith

Make sure that the pilot burner has a good ground to the gas valve.

JUGHNE

Homer, standing pilot with thermocouple needs a good ground?That is new to me.

BobC

A few years ago I noticed a problem with my EZgas burner, on a hunch I checked the incoming gas pressure, it was bouncing between 4 and 8 inches of water when the burner was firing.

i called the gas company and they confirmed my findings. They reamed out the pipe o the street main and came back a day later to replace the pipe from the house to the gas main.

The gas in this area was put in a long time ago, the guys who did the work said it's not uncommon for old gas feeds to fill up with corrosion like mine did.

Check the gas pressure on the input of the gas valve when the boiler fires, if it drops a lot that may be your problem. If your in a low pressure gas zone the street pressure probably drops in times of high usage and that on top of a partially blocked feed could be your problem.

Bob

mchicago

I have a very similar problem. First year in a new to me house. Thermocouple, pilot and gas valve replaced in the beginning of the season. Pilot went out twice last week (never happened before that). Thermocouple seem to be installed correctly - tip engulfed in pilots flame, glowing slightly when burners are off.
Pilot on the water heater did not go out both times and they are on the same gas pipe. I don't seem to have problems with downdraft (or I did not notice any), again water heater shares exhaust and has longer and smaller pipe and did not have problems. I have forced air intake in the basement and turns on when burners are on - it was working during the time when pilot was off and all my zone valves were open. Both time I could relight pilot instantly. Is there anything else in the boiler controls that can turn the pilot off other than thermocouple? Or is this draft\gas pressure\thermocouple problem?

My boiler had electric ignition which was faulty and it was replaced with standing pilot because technician told me that standing pilot is more reliable. Should I install electric ignition again? I don't feel comfortable leaving my house for more than a day even if issue is not frequent.

Jim100Flower

mchicago, I assumed electronic ignition was more reliable than pilot and reliability is one of the biggest factors when I consider replacing my aging boiler system. I want to go to a beach somewhere and not think about my pipes freezing.

Jim100Flower

Seymour, Gilmorrie, I found the pilot adjustment on the gas valve and am considering giving it a small turn but probably won't. Could I leave myself in a worse position, such as not being able to relight it? Increasing the pilot height makes a lot of sense to me but I'm also skeptical because it was not, to my knowledge, done or suggested by the technician, his trainee, or his boss who he called after he replaced the thermocouple, was packed and ready to leave, and the pilot went out.

I can only see the pilot through the match hole and I'm not sure if I can see the thermocouple. I'm expecting to see something that looks like the tip of a copper wire because the tech showed me the one he removed. In any case, the pilot looks like the letter "U" with a blue flame on either arc and a much lower blue flame in the bottom of the U and occasional orange sparks in the center of the U. The pilot moves a bit from side to side as if there is a cross draft. The height of the pilot is about 1" or 1.5". Does that sound right?

JUGHNE

If you watch the boiler pilot flame while the water heater burner actually kicks on and the boiler pilot goes out or almost out then my guess would be lack of delivery pressure to the house.

As the weather warms up where you are the main pressure may increase as others above have said.

Do the neighbors have the same problem? Calls to your gas company by all of you would document the problem.
The more squeaks from the wheels may get them greased.

Jim100Flower

JUGHNE, the boiler pilot flame did not change when I turned on the HW burner.
One neighbor reported a similar problem on our neighborhood website.
The gas company says they know that low pressure has been happening in my neighborhood during the cold spells. They can increase the pressure at the meter. I will have them do that next time the pilot goes out.
A new theory for why this only happens when it's really cold is that during those cold periods the boiler is running continuously and using up enough O2 in the room to snuff the flame.

Jamie Hall

I very much doubt the new theory. If there is any kind of air flow into that space, you will be getting plenty of oxygen. If their isn't you will be getting a backdraft. It's very likely the low gas pressure.

Jim100Flower

How would could I test if I am getting a backdraft?

j a_2

Jim, are you on low or high pressure? Take a photo of your gas supply line and meter....Have your gas service provider check your pressure, they will do a static and dynamic test...The cold up here in the Boston area has played havoc with low pressure areas...a lot of homeowners and installers will soon come to realize the importance of not installing appliances that require more gas than the gas company gaurentees...round these parts it’s not even 5 inch’s...

HomerJSmith

JUGHNE: Ya, I was thinking of a spark ignition.

HomerJSmith

I don't care if the gas pressure is 2" w/c, if there is lite off of the burners there is enough pressure to keep the pilot operating. If you have a feeble pilot flame or not, I would clean the pilot orifice and then look for other causes if the problem persists .

Jim100Flower

@j a Here are photos of the meter, the boiler supply pipe, and a step-down in that pipe.

HomerJSmith

Wow! That meter doesn't have a regulator with an atmospheric vent? If it is buried under the sno dig it out and put a shed roof over the meter. Dig the meter out anyway and put a shed roof over it.

The size of the gas supply pipe to the meter tells me, no. Where are you in relation to the other gas users on the street gas main, first, middle, last? In our area, the street pressure is 45 psi and reduced down to 7" w/c at the meter.

You can check the supply pressure at the boiler gas valve input with nothing else in the house drawing gas and then with everything drawing gas in the house check the boiler input and compare the readings.

j a_2

Low pressure gas does not need a regulator hence no atmospheric vent...what is the purpose of the roof over the meter? 2 inch’s of gas is useless, and the only ones that can handle that is the gas supplier...jmo

Jim100Flower

@HomerJSmith, you say "The size of the gas supply pipe to the meter tells me, no."
No what?

Jim100Flower

@j a, you say "2 inch’s of gas is useless, and the only ones that can handle that is the gas supplier"
Can you explain what you mean?

HomerJSmith

No--there isn't a regulator with atmospheric vent because it doesn't need on because the incoming pressure is below 10" w/c.

Gee, maybe your gas suppler doesn't pass you gas thru a dryer and there's moisture in the line and meter, who knows?

Since there is no tap off or tee on the meter to check the pressure, check it where you are having the problem at the boiler gas valve as there is usually a 1/8" tap on the gas input. I still say clean the pilot orifice and check the opening with a very fine needle being careful not to enlarge the opening.

I am saying that if you have lite-off of the burner tubes there should be enough gas pressure in the gas valve to keep the pilot operating which leads me to suspect the pilot orifice. You can look at the pilot flame and think it is ok, but it has been my experience that is not a valid assumption and in one case when I cleaned the pilot orifice and dislodged the blockage with a fine needle that the pilot operated as it should and I had consistent burner lite-off and a consistent pilot flame. I learned a lesson that day, it cost me time and money because I had to remove again the burner assembly and thoroughly clean the pilot correctly. The problem posted here almost mirrors my experience.

Old boilers and furnaces need burner tubes cleaned as well as the pilot assembly. Pilot assemblies just get a brush off with a wire brush and are never disassembled and properly cleaned.
It maybe incorrect, but that the way I see it.

The reason for a shed roof is to keep sno from covering the atmospheric vent in the regulator and sending unregulated gas flow into the building.

j a_2

Jim. I suggest, call and speak to your gas supplier ,tell them your issues...and they will direct you....let us know how you make out with them...

rbeck

I also am going with combustion air problems. The colder it gets outside the more often and longer the boiler runs. Therefore more O2 is required. The home owner sys his fingertips are cold when he holds them to the draft hood. The boiler requires 50 cu. ft. of air per 1000 btu's. That would have to be 8400 cu. ft. The question becomes how many c. ft. are we lacking and do we make it up with the combustion air fan or is it also undersized. If the burners starve for oxygen the flames will roll out quickly looking for more oxygen and snuff out the pilot flame.

JUGHNE

Wouldn't the water heater have the same problems?

Jim100Flower

@JUGHNE, the water heater has an electronic ignition. I think it just tries again if it is also going out. We have never been without hot water. Next time I replace my boiler system I want an electronic ignition.

Jim100Flower

@ j a, I will call gas supplier again when the weather gets cold again so they can measure the pressure while I am having problems.

Lance

What happens in colder weather? I get colder. I want warmer. I tighten up the house. Affects the flue draft. Outside flues get colder less negative draft. Or the rarely seen opposite, the boiler runs constant ,draft gets excessive and pulls too much air in burner area and blows out pilot. Exhaust fans run, reverse draft can put out pilot. Competing chimneys looking for air, upper window open, all affect draft. Gas supply at maximum, gas pressure drops. A weak thermocouple can cause intermittent problem. Measure the millivolts and find out what is there with and without controls energized. Bad control valve or poor contacts. Too low return temp, possible condensate drips on pilot. Failing heat exchanger. A poor drafting flue on a cold start may not develop a draft quick enough. The "mushroom" is a draft hood designed to prevent downdrafts from affecting the breech flue gases. It cannot be modified and is a critical component of the boiler. A steady downdraft means your chimney is not working properly. If it does not draft between -.03 to -.05" wc. in 5 minutes or less you should fail the system until corrected.
There are three points to measure draft, the flue; between the boiler breech and the draft hood; and over-fire to properly engineer a working .
A CO detector above the boiler might be a good thing here.