L.P. Gas Burners

Maurice Pickett

A frequent problem seen in propane fired gas burners is that ignition will occure at the burner orifice and/or in the verturi of the burner rather than at the burner! I have found that in some cases that repositioning the burner by slight rotation or moving the burner laterally will help. It appears to me that the fuel and air mixture and possibly the velocity may be the cause of the problem. The manifold pressure is per specs. which is between 10.0" to 11.0" w.c. I would welcome any suggestions and comments.

Mark Eatherton1

L.P.=

Large Pain at you know where. By it's nature, propane is a troublesome fuel. It's much more dense, and doesn't act like its flaming brothers in the natural gas categories. It is finicky at best, and what works in one case may not work in another case. It is wise to make sure that all pressures are as dictated by the manufacturer. Any changes in the burner position, burner placement, pilot placement or any other "unauthorized" field modifications puts the bill of general liability squarely in your court, which may land you in court. I do however know from whenst ye speaks. I've been there and done that, and told the factory about it later. If they disagree with my modifications, they will state so in writing, and make other recommendations that "should" rectify the situations.

All gas fired appliance manufacturers should be required to field test their appliances at altitudes representing thier potential field applications, including but not limited to sea level, and all the way up as high as it is feasible to build a home (12,000 feet above sea level). This is the true gage of a company worth their salt.

HTP sent their chief engineer out to Colorado for a week with a truck full of fuels (natural and LP) and all of their gas fired equipment for high altitude "light off" and combustion testing, and they learned a LOT.

Maybe I should consider hiring Timmie Mac to come out to Colorado and open a "High Altitude Combustion Analysis/Testing/Training Laboratory"... Look out Leadville (10,430' ASL), there's a new industry headed your way.

Be very careful out there... "Tis a litiguous society in which we live" Author unknown.


PS, Don't forget to derate the orifices for altitude. In 90% of the cases where I see facial flames, the orifices were not properly sized for operation at altitude, dude.

ME

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Sherwin Swords

LP GAS BURNER PROBLEMS.

ALL THAT YOU MENTIONED ARE EXTREMELY IMPORTANT, AND MUST BE SET CORRECTLY TO MANUFACTURERS SPECIFICATIONS. LOOK FOR MIS-ALIGNED BURNERS, MIS-ALIGNED ORFICE, (USUALLY CROSS THREADED). ALSO ORFICES THAT ARE PARTIALLY STOPPED UP. SOME TIMES AT START OF HEATING SEASON, I HAVE FOUND SPIDER EGGS, SPIDERS, BUGS, AND OTHER FOREIGN ITEMS IN BURNER TUBES. IF RIBBON TYPE BURNERS, FOUND IN MOST OLDER UNITS, I HAVE FOUND THE BURER SLOTS HAVE BEGAN TO OPEN UP DUE TO THE PROPANE BURNING AT SUCH A HIGHER TEMPEATURE THAN NATURAL. THIS SLIGHTLY LARGER OPENING, ALLOWS THE FLAME TO BE DRAWN DOWN INSIDE THE TUBE, AND BACK TO THE ORFICE. USUALLY A NEW SET OF BURNERS IS THE ANSWER.

Mark Eatherton1

Welcome to the Wall,

and thank you for sharing your knowledge. Being new to the internet, you probably didn't realize that using all capital letters is reserved for expressing YELLING!.

It's also hard on an old mans eyes like my own. I know, it's hard for us 10 thumbed mechanics to type and have to find the shift key all the time, but do us two favors.

1. Stay here and share your knowledge,

and

2.Please find the Caps Lock key and turn it off as soon as possible before we go deaf and blind...

Thanks for your consideration of your fellow man.

Hope your Thansgiving day was as good as ours.

ME

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Sherwin Swords

ouch!

> and thank you for sharing your knowledge. Being

> new to the internet, you probably didn't realize

> that using all capital letters is reserved for

> expressing YELLING!.

>

> It's also hard on an old

> mans eyes like my own. I know, it's hard for us

> 10 thumbed mechanics to type and have to find the

> shift key all the time, but do us two favors.

> 1. Stay here and share your knowledge,

>

> and

> 2.Please find the Caps Lock key and turn it off

> as soon as possible before we go deaf and

> blind...

>

> Thanks for your consideration of your

> fellow man.

>

> Hope your Thansgiving day was as

> good as ours.

>

> ME

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 88&Step=30"_To Learn More About This Contractor,

> Click Here to Visit Their Ad in "Find A

> Contractor"_/A_

Sherwin Swords

all caps

sorry

Mark Eatherton1

No problem...

We've all made the same mistake at one time or another.

Seriously though, welcome to the Wall.

ME

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Unknown

Propane fuel

All of the above comments hit the nailon he head.

One Item was lefyt out.....

Most propane tane are stored out sidw thwe thew building.
Propane as everyone knows is a liquid fuel. the liquid must evaporate to a gaseous state before being ignited.

The temperature that propane is stored at has n effect on the evaporation rate of the liquid.

In the day light hours when the tank is heated by the sun or the rise in temperature evapoate the fuel at a different rate than the night time when the fuel stored in the tank drops in temperature.

In some locations the delta T of between day & night can be from 20 to 70 degrees. The evaporation rate that occurs with the fuel is significant due the Delta T.

Assume the all tests and settings were performed in the day time when the fuel evaporates faster due to the higher temperature of thepropane will not have the same results in the evening the fuel evaporation rate of the liquid is much slower.

When pilot problems and ignition problems occur some liquid propane maybe carried over with gas and strange thing can happen in the chamber or the BTU rating of the fuel.

The most common problem is the building heats better when the sun is out than in the night time when the liquid is colder.

If a propane is protected from the wind and cold the liqid fuel temperature will vary less and the fuel will behave better.

If the tank is kept warm and at the same temperature all the time the burner will perform uniform all the time.

I learned this many years ago when I had to make a designer stove an oven operate.

The sstove and oven combination was imported from France. It never worke correctly from the day of installation.

The only time the stove and oven worked propely was between May and Setember.

Additionally the manufacturer could not make the stove work.

I was in the building trying to correct a long standing heating problem when the customer told me about the stove condition.

The stove condition mademe think about the boiler and burner.

I took abreak from the heating problem and checked out the stove and oven.The flame in the stove and oven was perfect for 10 minites and them the flame dropped out.

I went outside the building and checked the pressure gauge on the tank and it was near 0 psig. I had the customer call the propane supplier the come and check the tank for fuel and possibly replace the gas regulator at the tank.

The propane supplier came to the job and found the tank half full and the prssure regulator to be operating properly.

What I noted was the service technician took out a temperature chart and a thermometer.

He found the outdoor temp. was -10. The chart for this tank at half full indicate that the pressur in the tank should be less than a 1/2 pound.

At that time I asked the technician about the fuel evaporation rates and he explained about the liquid fuel having to evaporate to gas.

He also told me that his company had many calls for empty tanks in the winter because the houses that heated with propane were not suppled sufficient Cubic feet of gas to provide the BTUH to heat the house.

His company never had a stove problem because all the houses in that area had electric stoves.

After he left I conducted a test on the fuel tank.

I put an electric heating blanket under the tank and put 4" of fiber glass isulation around the tank and covered the whole thing with a tarp to prevent the insukation from getting wet.

The building heated much better and the stove worked well enough to cook. The oven did not reach set temperatures to broil. The baking feature on the oven worked O.K.

In the summer I built an insulated shed over the tank and installed a 1000 watt electric heater in the shed. The T stat wa set to 50 degrees.

The folowing winter the bilding heated properly and the fancy stove and oven finally worked correctly.

So when you have propane problems do not discount the temperature of the liquid propane and its relationship with evaporation and cubic foot of gas production.

jake

Mark Eatherton1

Good point Jake...

I remember going to my dads place in the mountains with my wife and sister when it was -20, we couldn't get the furnace to stay lit. Had to sleep together to conserve and share body heat (with our clothes ON thank you...) and pray for warmth. Next morning, the temp rose to ZERO and the furnace started working about half way. Sounds like a good time to invent a resistance controller that could use the tank as the element.

Worked on a job high in the mountains here where an easterner (New Joisy I beleive) built himself a 20,000 square foot home, and speced oil boilers. NO ONE up here installs or services oil, and he paid $10,000 for an environemental study because his home was at the top of a major water shed. When asked why he didn't spec propane, he said "What's that??"

They also make LP tanks for direct burial. Below the frost line, the soil should remain stable enough to keep the gas a flowing.

Good thougts though, we sometimes forget the obvious.

ME

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Unknown

Great story Jacob...but

you can not put propane tank inside and you can not put an electric heater anywhere near the tank. The cure to the low temp problem is to put some alcohol in a drip leg to mix with the fuel when it is real cold.

As to the original problem with ignition I will give an answer in the AM tomorrow as it is late and I am very tired. But please do not start putting electric heaters anywhere near propane.

hr

Cold weather LP

on large commercial boilers in extreme cold you may need a preheater. Years ago at a ski area I worked at we had big LP boilers. Outside in a concrete vault (avalanche proof) were a group of preheaters, The looked similar to large water heater tanks and they were LP fired.

Yes the LP tanks were underground also. Those large Sellers fire tube boilers really misbehaved when the pre heaters went off line. They would backfire and blow open the large steel door at the ends, then set of the LP alarm located at the front desk, and go into lock out. Everyone hated crawling into those vaults to troubleshoot the preheaters.

A larger volumn storage tank sometimes will help vaporize in extreme cold. My construction heater will work on a small barbecue tank until it gets near zero. Then I switch to a tall 125 lb tank. It still will frost a bit but it does keep up.

hot rod

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Jackchips

I concur,

it is a good story with some excellent responses. Hopefully you got a good night sleep Tim and will take us out of suspense and complete your advice.

Unknown

LP Ignition

I fully concur that temperature can be a problem and Hot Rod is right on we have some similar pre heaters in use at some ski resorts here in New England.

Having said that it is also sometimes that furnaces and boilers in order to work in both worlds LP and Natural Gas have burners which by design should work on both. My experience is that they do not. They work very well with Natural Gas but not so well with LP. Some do not have air shutters and this means adjusting primary air is difficult. Many times the manufacturers will ship you air shutters to place on these burners.

The air shutters are important to allow you to adjust the burners for good ignition. That is something that is different on every job and you gain the experince by adjusting many burners until you get each one right. Another way to adjust some of the gun type burners is to look at the bracket holding the manifiold, it will sometimes have slots in the area that the bolts go thru to hold the manifold to the equipment. Loosen the bolts and slide the manifold up or down to get good flame stability. Or on some you slide it in and out. Do this while watching the flame to make sure it is staying stable on the burner, not lifting or floating around.

Another problem is that by design some warm air furnaces have poor light off charcteristics. The solution is to install a step opening gas valve to give a smoother initial light off.

You also want to check to make sure that the gas valves are shutting off fully when the call for heat ends. If they are not they need to be replaced.

The alcohol thing is something we used on natural gas in very cold weather. Taking the drip legs on all your equipment and making the nipple a little longer, put some wood grain alcohol in the pipe it will mix with the gas and keep it from coagulating and even prevent freezing. It will last for a week or two and hopefully by then it has warmed up a little bit. I have also done this on LP gas and it works great with no adverse effects.

LP gas folks will tell you the critical cut off point for them is anywhere below 10 degrees. On large jobs the preheaters are a must in extreme cold areas.

We even had this problem with LP gas fueled trucks back when we drove those at the gas company I worked for. On cold mornings when you got on the freeway and accelerated they would stall out. The fuel lines had frozen. We finally went to CNG vehicles and no problem.

Duncan_2

Backfiring propane burners...

Tim, I'm looking forward to your post on this also, as I've run into some LP fired burners that flash bach to the primary air "shutters". Not outdoor temperature related at all.

It seems to me, the butterfly adjustments at the primary air ports/intakes were one of the few adjustments we could make (along with pressure and orifice size), and now it seems on many boilers, manufacturers have taken that adjustment option away from us too !!! I am NOT impressed with some of the cheesy burner setups on some of the residential copper fin tube boilers I've seen lately!

What is your take on modifying/replacing cheap, stamped stock burner tube racks with something a little more sophisticated, say laser cut burners?

Duncan_2

Yeah, I've seen those, too.

I've heard them called vaporizers. Pretty pricey, but cheap compared to a Boiling Liquid Expanding Vapor Explosion. They have to be super-designed, I'd guess.

I saw one installed on a job with a LOT of undersized, outdoor roof piping which was exposed to outdoor temperatures AFTER the vaporizer. The vaporizer was not much help on those piping legs. Pipes too cold! But the original piping bid was probably the right price. Ouch!

I guess some of the building was served with underground piping, and that part was OK.

Unknown

Some improvements increase sales volume

while some improvements increase costs to the point where sales decrease.

For instance, power steering and automatic transmissions both fall into the first category, while that third headlight that steered around corners probably falls into the second.

It would be very nice to make only the changes that fall into the first category. We have stamped burners, and changed to stainless steel to improve on the steel ones. We provide a way to adjust primary air.

It is very nice to get feedback about products pluses and minuses. Manufacturers want to make products that contractors want to buy. Cost control is very important to our customers. So is quality and consistancy of product. Please comment on these things as often as you like. We do notice and talk about it.

Noel

Unknown

The lack of air shutters is the

biggest problem that I run into. That and the fact that we no longer have cast iron burners on a lot of equipment. They were very forgiving in many a difficult situation. At least with very low pressure you would get a bead of flame on the burner. They also did not cause as many problems when condensate dripped on them.

Pressed metal and other so called modern burners have problems with corrosive environments and contaminated boier and furnace rooms. The cast iron burners would not react as quickly to corrode.

I have some pressed metal burners I use to demonstrate the effects of Fluorocarbons and hydrocarbons they have big holes in them.

A lot of these new burners do not light off very well in LP gas applications. I also find that different LP suppliers have different quality of gas so this is also a problem.

Unknown

Just found my LP gas

installation and service guidebook. Some interesting info.

One thing it mentions in the table for vaporization of aboveground tanks is that at temperatures below -20 the vapor pressure will not be high enough for proper regulator operation. At 60% humidity and below 0 (zero) the BTU /hr drops off drastically.

With underground temps assuming underground temp of 50 degrees, the BTUS do go up at Zero.