overfiring

Steve McCarthy_2

I work on house systems, the whole thing, insulation air sealing ventilation and heating systems, so I don't work on as many boilers as a service technician might service. I am surprised at how many boilers I find that are making a lot of CO. When I tear the thing apart to clean them I often find a lot of dirt and dust but the most common cause of the CO is overfiring. Two recent units sent my Monoxer of the scale in less than 5 seconds, After they were cleaned. Timing the gas meter VERY CAREFULLY and repeatedly typically indicates that the boiler is 10 to 25 % overfired. These are 10 to 20 year old boilers. I don't use a pressure gauge, just my CO analyzer and my stopwatch. I want the CO to go away and to eliminate the soot. I always am sucessful but Why are these boilers so often overfired? does something change overtime????
Steve / Starbright Energy Services

Unknown

Check the gas pressure

and make sure it matches what is on the rating plate. Increasing pressure at the regulator is sometimes done by techs who do not know any better. Other than that there is not much that should cause a system to be that greatly overfired.

Just curious tell me how you are Timing the meter?

How are you getting the systems to the correct input?

Mark Eatherton1

Tim...

With all due respect, and I have a LOT of respect for you, increasing the input to a given appliance is not always a bad thing to do. If it decreases the CO and increases the net efficiency of an appliance, is it a "bad" thing? Your statement puts me and a whole lot of other people into the "sometimes done by techs who do not know any better" category.

I understand your back ground, and your training from the industry within, but do you for a minute think that these manufacturers would limit the capacity of their heat exchangers to exactly what is listed? No "margin for error" or "buffer factor"?

I know you copletely disagree with Mr. Davis premise that it is acceptable to increase the input of an appliance over what is listed, and as an expert witness I can understand from whence ye come, but do you really think its all that tight of a factory specification? If it reduces the amount of CO is it still a bad thing to do?

My personal experience has shown me otherwise.

With all due respect, and you deserve a LOT for your contributions to the industry.

I remain,

ME

Mark Eatherton1

Steve,

I your case it sounds as if there is some flame impinging upon the cooled surface, and that is NOT a good thing. Backing the flame down through proper orficing, or other means will take the flame contact away from the heat transfer surface and will substantially reduce the amount of CO produced. Personal experience.

It is important however, that proper draft be maintained through this whole process to make sure that the products of combustion are properly eliminated.

I would strongly suggest that you attend Jim Davis' National Comfort Institute classes on Carbon Monoxide. Its an eye opening experience.

THe more you know, the safer you are.

ME

Boiler Guy

Mark

I agree with your comments.
Couple questions however:
Steve states:"Timing the gas meter VERY CAREFULLY and repeatedly typically indicates that the boiler is 10 to 25 % overfired. These are 10 to 20 year old boilers. I don't use a pressure gauge, just my CO analyzer and my stopwatch."

1 How can a tech accurately determine overfiring without a manifold pressure in the equation?

My experience leads me to believe the manifold pressure stated by the manufacturer(+-10-15%) has been determined through rigorous testing based on the specific appliance's abilty to effectively mix fuel/air to achieve a "clean burn", without excess deleterious products of combustion.

2 Would results of Steve's test procedure not change based on differences in indoor, outdoor temperature, draft and heated medium temperature on any given day?

I still think manifold pressure verification must be factored BEFORE making a final determination.

Curious to see others input.

Unknown

Let me answer some of

these comments:

Steve posted:

Timing the gas meter VERY CAREFULLY and repeatedly typically indicates that the boiler is 10 to 25 % over fired. These are 10 to 20 year old boilers. I don't use a pressure gauge, just my CO analyzer and my stopwatch. I want the CO to go away and to eliminate the soot. I always am successful but Why are these boilers so often over fired? Does something change overtime???? Steve / Starbright Energy Services

Tim posted,

Check the gas pressure
and make sure it matches what is on the rating plate. Increasing pressure at the regulator is sometimes done by techs who do not know any better. Other than that there is not much that should cause a system to be that greatly over fired.
Just curious tell me how you are Timing the meter?
How are you getting the systems to the correct input?


Mark posted,

Tim...
With all due respect, and I have a LOT of respect for you, increasing the input to a given appliance is not always a bad thing to do. If it decreases the CO and increases the net efficiency of an appliance, is it a "bad" thing? Your statement puts me and a whole lot of other people into the "sometimes done by techs who do not know any better" category.
Mark,

Tims answer

If I read the posting correctly Steve said the equipment was over fired (overgased) and as a result it was sooted up. I did not say it was a bad thing to increase input. It has been my experience here in New England that many times the easiest thing for a service tech to do when faced with a problem on equipment is to screw down on the regulator. This is often done without any testing or any reasoning whatsoever. I was trying to help Steve to find an answer to his dilemma. He stated that he did not check pressure. That in itself makes it difficult to come to any conclusion. I would doubt very much that someone was putting orifices in that equipment that were too large and that would be the cause of sooting.

Mark posted

I understand your back ground, and your training from the industry within,

Tim's answer

I am not sure what my back ground has to do with this as my back round is pretty diverse. As for my training I am not sure what the “industry within” is maybe you can explain???

Mark posted

but do you for a minute think that these manufacturers would limit the capacity of their heat exchangers to exactly what is listed? No "margin for error" or "buffer factor"?

Tim's answer

I also did not claim or say anything about margins built in to equipment by manufacturers there has to be some margin simply because of the variables in the fuel itself.


Mark posted,

I know you completely disagree with Mr. Davis premise that it is acceptable to increase the input of an appliance over what is listed,

Tim’s answer

I DO NOT completely disagree with Mr. Davis on this particular subject and am not sure if I ever gave that impression. I have been careful to point out that just screwing down on a regulator is not always the best thing to do. There are other ways to more effectively adjust input for maximum efficiency and safe combustion. I also understand that by increasing pressure many times with orifices remaining the same size or even reducing orifice size with an increase in pressure changes the “inspiration” of the gas/air mixture. If it is done with test instruments and lowers CO and gives maximum thermal efficiency then I am all for it.

One thing that really bothers me and that is why every time I post something I have to hear about Jim Davis says don’t you people have a mind of your own? Just state what you know and leave Jim out of it.

Mark posted,

and as an expert witness I can understand from whence ye come,

Tim's answer

Before I was ever an “expert witness” I was a service man. I started combustion testing in 1966 and many of the things I have learned over the years have directed my thinking not my possibly being used as an “expert witness”. That in no way sways my thinking as to what is correct. In fact being an expert witness is a pain in the neck. I have two artilces coming out in the HVAC Insider on What is Liability? That is always my concern and many things must be considered when making adjustments to equipment. Not the least of which is having good training and knowing what you are doing.

Mark posted

but do you really think it’s all that tight of a factory specification? If it reduces the amount of CO is it still a bad thing to do?

Tim's answer

I have many times adjusted a regulator to bring equipment to its maximum operating level as determined by combustion tests and other criteria, it is often one of the best things to do when fine tuning a piece of equipment. I also am very aware that adjusting poppet style in line regulators to the maximum of their design is not a good thing and many times it is better to change springs and work from different perimeters. Regulators can act very strange when pushed to their limits. The regulators used in gas valves today “servo regulators” which using working gas are even more sensitive to high end adjustment, in fact the valve manufacturers warn against doing so. I am sure Jim Davis in his classes teaches all about the internal operation of regulators and gas valves.


Mark posted,

My personal experience has shown me otherwise.
With all due respect, and you deserve a LOT for your contributions to the industry.
I remain,
ME

Marks answer for Steve

Steve,
I your case it sounds as if there is some flame impinging upon the cooled surface, and that is NOT a good thing. Backing the flame down through proper orficing, or other means will take the flame contact away from the heat transfer surface and will substantially reduce the amount of CO produced. Personal experience.

Tim's answer

Many times reducing orificing means doing things to orifices that in another posting several manufacturers who post here disagree with my methods. Mark how would you reduce orifice size? The problem we all face in this business is being able to solve a problem now versus ordering new orifices, which may take several days to arrive. No one has all the orifices on their truck that would be required to solve every job. Then we have to talk about the coefficient of discharge for different orifices, which can affect flame stability.

Maek posted

It is important however, that proper draft be maintained through this whole process to make sure that the products of combustion are properly eliminated.

Tim's comment

Measuring oxygen, draft and flue temperature along with CO as you make adjustments will bring you into the ballpark.
Be careful that the boiler or furnace itself is not undersized and the overgasing was done to compensate for poor system design.

Dale

Off scale

Interesting, most monoxors go off scale at over 2000ppm, that's really alot of CO for a cleaned and factory design system. I see quite a few propane devices, especially oven burners fired on propane but set to nat gas, that will definately make soot and CO. Also, I don't know where you live but, in Denver and places higher the factory orifices often can't be use but sadly often are used, which will also make too much CO. As to input with any regulator the main determiner of flow or in this case input is the orifice size, the pressure adjustment is fine tuning. If you can afford a monoxor you might as well get some tip drills and a orifice chart and a 0 to 15" magnahelic or a good utube manometer. As to pressure some manufactures of furnaces say to set the pressure from 3.2 to 3.8 inches with the correct orifice so the heat rise is at least higher than the mid point. And, if it's a conversion the burners come with a pretty wide range of orifices.

Sweet_2

Fixing a boiler today

noticed flame burning yellow. Did C.O. test , 2500 ppm. Converted L.P to nat. boiler, not sure when this was done. Cleaned burners, no change. manifold pressure 3.65IWC I to live at 5000+ Ft. Orifices checked out fine for deration adjusted manifold pressure down to 3.00 IWC, dropped co at diverter to 80 ppm. Is this proper procedure or is combustion analyzer the only way to know whats really going on? Thanks

Nick W

draft question for you pros.

a question for the pros.

i know proper draft is required,to remove the combustion gasses.
example:
an atmosferic burner 3.5 wc at -.05 wc draft,meter clocking
ok with rating plate.

if the draft was increased,would more gas flow thru the meter,and would the 3.5 manifold pressure change?

Mark Eatherton1

Possibly my misconceptions...

Tim, It has been a long time since you were posting things that were negative and counter to JD's teaching. It was long before you two had a chance to sit down and have a heart to heart. You were at one time quite dead set against his teachings, I remember it quite well. By gones are by gones. Item by item, let me re-respond so you can see my perspectives.

Tim's answer

I am not sure what my back ground has to do with this as my back round is pretty diverse. As for my training I am not sure what the “industry within” is maybe you can explain???

By industry within, I'm talking about gas utility companies. The one around here likes to keep things turned down to avoid liability. They'll typically set the reg at the meter at 5" WC to be nervous nellies. If you worked under the same rules and guidelines, you would be against turning things up. If my impression is wrong, please accept my appologies. Your background pertains to the same, as an employee of a major gas utlity company, and again, if my preconceived notion is wrong, my appologies.

Tim’s answer

I DO NOT completely disagree with Mr. Davis on this particular subject and am not sure if I ever gave that impression. I have been careful to point out that just screwing down on a regulator is not always the best thing to do. There are other ways to more effectively adjust input for maximum efficiency and safe combustion. I also understand that by increasing pressure many times with orifices remaining the same size or even reducing orifice size with an increase in pressure changes the “inspiration” of the gas/air mixture. If it is done with test instruments and lowers CO and gives maximum thermal efficiency then I am all for it.

Key word "completely". You have disagreed about this particular principle, and again, I may be wrong in my impressions, but I specifically remember you coming to this site and being very upset about some guy traveling the country telling people to turn it up. Regardless, we agree that if properly done, it is an acceptable measure.

You said "One thing that really bothers me and that is why every time I post something I have to hear about Jim Davis says don’t you people have a mind of your own? Just state what you know and leave Jim out of it. "

To be perfectly honest with you Tim, prior to meeting JD and learning from him, I was more dangerous doing testing then if I hadn't been testing at all. I went back and looked at some start up records for some appliances I'd commisioned with my new toy (combustion analizer) and there were CO's WAY out in left field, but all my focus was fixed on the "percent efficeiency" figure my tester was spitting out. Thanks to JD educating me, I now know what I'm looking at and what to do to correct it. So in direct response to your question about referring to JD, in my case, you're going to have to get use to it, because he taught me most of what I know. Yeah, I can think on my own, but I'm dangerous, or at least I was until I met JD. Sorry if it upsets you. It wasn't intended to.

If I'd have met you first, and you'd have been my master mentor on CO, I'd be tossing YOUR name around. How'd you feel then? It was just a matter of timing Tim. Timing and location. I'd still love to take your class, and hopefuly some day can make that arrangement. I value your knowledge.

Tim's answer

Many times reducing orificing means doing things to orifices that in another posting several manufacturers who post here disagree with my methods. Mark how would you reduce orifice size?

Tim, I fill with solder and redrill them to the new size. Thats what I've been doing for the thirty years and it's always served me well.

Tim, I thnk we agree on most points, and if I've mistaken your opinion on the other CO expert, than please accept my sincerest appologies. I think that you and I do agree on one thing, and that is to do it right requires more than just the tools. It requires knowledge. The best tools in the world, if improperly applied, are about as useful as dirt.

I'd proven that with my combustion analyzer, and there are STILL a lot of people out there with analyzers that don't know what they're looking at, nor would they know what to do to change the conditions they're seeing anyway.

Thank you for continuing to educate, and I will try and open my eyes wider to see the whole picture.

Respectfuly,

ME

Unknown

Once the pressure

on the regulator is set it will not change unless someone adjusts it. Draft has no affect on it.

The amount of gas flowing from the meter has nothing to do with draft. The draft is created by the height of the vent and Delta "T" (temperature difference). As draft increases or decreses it affects the amount of secondary and excess air that is being brought into the combustion chamber. That is with atmospheric burners which use the air from within the room for combustion.

With forced draft or induced draft the air mix is controlled mechanically.

The only exception to draft having an affect on gas is with a negative pressure gas valve which uses the combustion air blower to create a suction if you will to draw the gas in and mix with the air. Indirectly the flow of gas in this case is controlled by the air flow from the combustion air blower.

The defining difference is atmospheric versus power burners. With both however gas pressure is predetermined by a setting or adjustment and flow through the meter is only as the demand from the equipment makes on the system.

Draft does not affect pressure or flow through the meter. The gas meters job is to measure flow of gas for billing purposes that is it only purpose.

Nick W

thankyou tim.

Unknown

Thanks Mark, I am sure

we are in agreement on many things that Jim teaches. I may only question that many times here on the Wall people only get half the story. That as I am sure you will agree can be dangerous.

Jim and I have discussed many things and slowly find ourselves pretty much in agreement. He can after all sort of irrate when you first come in contact with him.

My utility experiences did not parallel what you see at your gas company. The company I worked for was an innovative company and tested everything and had a very extensive training program. I however learned my combustion knowledge from an engineer from Midco who manufacture the Economite conversion burner. Tom Roche who owned T.C. Roche Inc. was the most knowlegeable combustion person I have ever met. He by the way was the first to introduce to Field Controls and also AGA the concept of barometrics versus draft hoods. When you do a lot of gas conversions you learn a lot about combustion.

I also owned and operated a restaurant service company servcicing roof top and large commercial ovens and commercial cooking equipment.

I have also installed hundreds of FHW, steam and FWA heating systems and have a Master Fitters Liscense in RI so I have a lot of diverse experience. I would say I am not your average run of the mill "gas man".

My original background was coal boilers and furnaces (worked as a helper with an installer) in Western PA at the age of 14 years old until I was 17 and joined the Navy. Nine years in the U.S. Navy working in electronics. While on two destroyers almost all my off hours were spent in the boiler rooms and engine rooms (600 pound steam systems). I was the only electronic technician to ever qualify on the evaporators (converting salt water to fresh water)on board a destroyer.

I would love to have you attend classes sometime.

Unknown

Sweet, the combustion analyzer will

confirm that your adjustments are correct. There are by the way correction factors for inputs relative to alttitude. Just making adjustments with out testing is dangerous.

Steve McCarthy_2

overfiring

So.. It seems that I am the only one repeatedly finding overfired boilers? Must be a fluke.

I am sure that if I measured gas pressure, I would find that these boilers have a higher than specified pressure. My goal is not to verify gas pressure specifications. My goal is to reduce CO to the 1 ppm to 15 ppm range. When I find a big CO problem, I tear it apart, clean it, check the chimney, make sure that the area containing the unit is not depressurized and put it all back together and fire it. I then verify draft with instruments (digital presure gauge), check CO again and usually find it still is a significant problem. I then make sure nothing else in the house is using gas if its natural gas (even pilot lights) and then I time the gas meter for 2 cu. ft. of usage and then I repeat the timing for another 2.( i use a stopwatch)
I have never found an underfired boiler, maybe because of my limited experience.
When I find it is overfired, I reduce the gas pressure. It may take two or more adjustments but I verify that the final firing rate is at or just below the rating plate AND that the CO is close to Zero.
Some folks mentioned increasing the gas pressure and firing rate to eliminate CO. If the unit is 25% overfired,how can increasing the gas pressure possibly fix the CO problem.
If the unit is propane fired (and the rating plate lists that it was delivered for use with propane), I simply reduce the pressure until the CO problem goes away. I also verify visually that ignition and shutdown are instantaneous.
I am sure that in the unit that I found recently that was 25% overfired that impingement was a contributing factor.
Do folks see a problem with not measuring gas pressure. I see it as one extra thing to set up for and measure. I know a lot of folks were trained to measure gas pressure and maybe now they have this primal urge to measure gas pressure but in most cases, not all, but most, my Monoxer and stop watch work well for me.
How many of you find new units right out of the box with gas pressure right on and no CO ????

Steve

Unknown

Steve to talk to you

in a realistic way I need to know your location? It may have something to do with finding everything overfired.

It would also help if you could explain how you figure out input after clocking the meter. Does the meter have AMR (automatic meter reading) device on it. If it does that can cause your calculations to be off.

Taking gas pressure is important for many reasons not only to determine correct input. You should measure inlet and outlet pressure on the gas valve. You should also test pressure at the meter. This will determine if pipe sizing is correct. If you are in a low pressure area the older cast iron systems in many large cities across America it will confirm problems with pressure in the gas main. I have a full procedure for sale that teaches this entire process.

You may have misunderstood the statement that increasing pressure when already overfired is a solution. That is incorrect, it is best to start with the BTU input as listed on the rating plate, fire it at that and then test. If you are still a little underfired then you can adjust pressure (increase) until you obtain the best combustion analysis with low CO and good draft and flue temperature above 300 degrees net. This is what was being referred to.

The urge to test pressure is not a primal one but very necessary as I hope you can see. Pressure by the way on LP gas are critical. You want to be operating at inlet of 11" W.C. and 10" W.C. outlet. Watch out for LP companies that jack the pressure up on second stage regulator in order to keep from increasing pipe or tubing size.

Have you ever been to any combustion classes?

Equipment direct out of the box is not supposed to be all set. That is why it has to be set up by the technician in the field.The problem is that many installers do not know how to set up a boiler or furnace.

Nick W

Not my question!

Something is amiss, as I did not submit this question or the thank you.