Cast Iron Combustion Chamber Sidewall WetPack

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Old 05-18-08, 03:15 PM
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Cast Iron Combustion Chamber Sidewall WetPack

I want to install a new Beckett AF or AFG burner into my American Standard boiler and I do not want to damage the boiler with one of these hotter running burners . The American Standard boiler is from the early 1970’s (model 1B J1 ) It does not have a door to gain access to the combustion chamber. It has a removable, diagonally mounted, bolt-on pouch plate. An old, non-flame retention, ArcoFlame oil burner that originally came with the boiler is suspended from a bracket just above the pouch plate.

When I cleaned the boiler last, I removed all the sheetmetal to examine it’s construction. It is made of cast iron. It looks like it is composed of four cast iron subsections that are held together in compression by some very long bolts that go from the front to the back of the boiler. With the pouch plate removed, I can see inside the combustion chamber. There is a refractory target at the rear of the chamber and some refractory material on the front. This all appears to be in good shape. The bottom of the chamber is covered with granular refractory material. The sides of the chamber are exposed cast iron as is the top where the exhaust passes through the cast iron “fingers” up to the flue pipe.

I bought a Lynn wetpack kit to cover the bottom of the chamber. My concern is with the exposed cast iron sidewalls. Do I leave them bare or should I cover them with some of the wetpack material. If I leave them bare as they are now, I get maximum heat transfer from the flame, through the cast iron sidewall into the water on the other side of the cast iron. If I cover the sidewalls with the wetpack, I protect the sidewalls from the hotter flame but the wetpack may act as a thermal insulator reducing the heat transfer to the water.

I am not experienced in this area and hope that some of you pro’s could give me your thoughts on the matter.

Also, I have both Beckett AF and AFG burners in my possession. They are identical except for the fan, plastic air guide and the igniter gasket. I intend to install one and use the other as a parts machine as necessary in the future. Someone told me that since this will be going into an older boiler, I would be better off installing the AF since this operates at a lower static pressure than the AFG. Is this sound advise?

Thanks for your input, Bruce
 
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Old 05-18-08, 04:41 PM
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Wet Pack

I believe Lynn makes a wet pack chamber for this boiler which can be installed thru the burner opening. As for burner choice, I don't think it would make much difference.
Just FYI: Most of these boilers I've seen with Becketts have AF burners.
 
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Old 05-18-08, 04:49 PM
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Hello, and welcome to DIY,

The combustion chamber is there to protect the appliance and to aid in proper combustion.
Obviously the front covering is to protect where the burner is mounted and to help protect the end cone of the burner. Occasionally you need to add an end cone protector to keep the extreme heat from melting the end cone.
The back wall is a target wall which once again helps protect the back from overheating, but it is also a large contributor to aiding in proper combustion.
The bottom is basically the same.

But the sides usually depend on the appliance.

A warm air furnace or a dry base boiler will always have side protection, but most wet based cast iron boilers I have seen or worked on replacing chambers have a target wall, a front wall, and a bottom blanket coming up about 1/4 max up the sides. Exactly for the reason you said. Best heat transfer. If the Lynn package doesn't tell you different that is what I would do.

Remember, The walls are cast iron and full of water, and the older cast iron was thicker than todays.
 
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Old 05-18-08, 05:19 PM
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I checked the Lynn website and with Patriot Supply and they did not have a kit specifically for this model boiler. Besides, these kits include both target and front refractory panels. Those were not damaged in my boiler. All I needed was the Kaowool blanket for the floor which is in a crumbled condition

My main concern is the side walls of the chamber. Having never seen inside any other boilers before, I do not know if they should be bare cast iron or if they should be protected by the Kaowool or some other ceramic coating. Do you know if other boilers with cast iron walls run with the metal exposed??? The bare walls have been fine using the original non-flame retention burner but with the hotter Beckett burner, I do not want to damage something… On the other hand, I do not want to degrade the boiler efficiency by insulating the walls if it is not necessary.

The distance between the flame and the sidewalls of the chamber will be much greater than the distance between the flame and the floor. Obviously the protective Kaowool is necessary for the floor but I just don’t know about the sidewalls. The combustion chamber is approximately 20 inches wide, 22 inches high and 12 inches deep. I will be using a .85 GPH 70 degree nozzle. ( I am downgrading from a 1.0 nozzle that has been used in the past with the old burner. Based on previous burner run times, that nozzle was probably overkill for my heat load).
 
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Old 05-18-08, 05:25 PM
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Plumbingods,

I am glad to hear that based upon your experience, older cast iron boilers do not usually have side wall protection. I will do what you suggest and run the Kaowool blanked across the entire floor of the boiler and extend it up the sides only about 4 or 5 inches. Thanks !!!
 
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Old 05-18-08, 06:43 PM
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The bottom of a wet base boiler usually has less of a water jacket than the sides also.

On a dry base boiler everything you are heating is above the combustion chamber and there is no water jacket at all so a complete chamber is needed to protect the appliance, aid in combustion, AND help to direct the heat upwards for heat transfer.

As for as your nozzle is concerned, that needs to be determined by the max. btu input rating of the boiler. Since it appears that you have a used burner you are putting in, you will need to check the oil pump pressure.
In the past 10 yrs +/-, burner manufacturers have been suggesting to increase the pump pressure to 140psi instead of 100psi for smoother light offs and operation. I do not have the chart with me but if you put a .85 nozzle with 140psi, it is approx equivalent to 100-110gph. So if your pressure is 140 you will need to go with an even smaller nozzle. Most new burners are coming through at 140psi now.

You may also need a universal burner flange so the burner does not stick into the chamber, or you will melt it off. It should usually set about 1/4" back from the chamber wall.

Most beckett burners seam to work well with 80* hollow nozzles, but can use between 60*-80* Hollow or solid patterns.
If you have an oil supply store I would go over these questions with them. Also make sure you put in a new nozzle and filter before firing boiler.

I hope this helps you.
 
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Old 05-18-08, 09:25 PM
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plumbingods

I intend to use the Beckett AF and keep the AFG for parts. It was used but purchased from a professional who completely cleaned and inspected it. The strainer and electrodes are new. I connected it to AC power on the bench and it runs with a good spark. The electrodes are properly set. The burner head size (F3) and static plate were correct for the nozzle I was planning to use. I will install a new nozzle when I finally get the burner installed. My oil tank filter was changed last month.

Regarding the Nozzle: The old ArcoFlame burner currently installed in the boiler has always used a 70-degree nozzle so I thought it best to stick with the same angle when I install the Beckett. Five degrees difference on either side is not much but American Standard may have been concerned with flame proximity to the side walls or floor of the combustion chamber when they specified 70-degrees so I wouldn’t want to press my luck with the wider angle flame.

Regarding nozzle flow rate. I am very glad you mentioned that. I had not considered pump pressure differences. I have not run the burner yet with oil so I do not know what the pump is actually set at. The Beckett sticker says 100psi but I will have to check that. Being a used burner, this could have been changed, especially since you indicate that the burner operates better at 140psi. I do have some .75GPH nozzles on hand if needed. And if I end up with the smaller nozzle, I also have an F0 head and the larger static plate needed for the smaller nozzle.

I have a universal flange and will recess the burner head from the inside wall by ¼ inch per your instructions.

The real fun will come when I have to make the adjustments on the new Beckett. I have an old Honeywell Combustion Analyzer from the early 1980s. I am not too sure of its accuracy. My old burner was indicating a net stack temp of 460 degrees, 10.75 percent Oxygen with an efficiency of 75 percent. The unit also has a built in smoke checker that was giving me a 1.5 to 2 smoke spot number. My boiler/burner combination is 35 years old so I don’t imagine I could have expected much better. I will be curious to see if and how the Honeywell works with the Beckett when I get it installed. I may have to call in a professional before the next heating season to check over my work and make the final adjustments.

Anyway, thanks again for your help.
 
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Old 05-19-08, 05:09 AM
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Hello again,

It sounds like you have everything in check.

As far as the 70* nozzle is concerned, nozzle flame angle and pattern is derived from the combustion chamber, so you may need to try a few different nozzles to make it run smooth.

FYI I have almost never used a 70* nozzle. That's not to say you won't need one.

One more thing, In some of the older burners it was ok to have a smoke reading of 1 or ... because of the large passageways in the boiler. but you should strive for a 0 to a trace smoke with the new burner.

Even though you still have the old boiler with the large passageways, the newer burner is designed for tighter boilers which require a smoke of 0 to a trace, (hard to tell the difference), or they will plug up. The cleaner you run the burner, the less soot buildup and better heat transfer = better efficiency. But do not get too clean as you will start to loose efficiency in another way and possibly be blowing out the spark so the burner won't light. You need to find the "SWEET" spot.
 

Last edited by plumbingods; 05-19-08 at 05:24 AM. Reason: wording
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