Clean Burn CB 90 HS Burner Trouble (too much mist)

[steamdrum1]

Hello I am new to the forum, glad to be here.  I have used a clean burn cb-90-aa with a CB-90-hs burner for three seasons now with good luck.  I wanted to switch to hot water heat, so found an old US Radiator Cast Iron Boiler.  I made all the adapter plates and necessary conections.  I fired the boiler for the first time last weekend and worked great(for a while) brought the water temp up to 180deg nicely.  After a few hours run time I noticed oil seeping out of the gasket on the burner throat.  On further investigation I found an excessive amount of un burned oil mist in the combustion chamber of the boiler.   I have a glass observation port, and I can see the mist floating down and settling on the floor. When the burner was on the old furnace I ran 1 to 1.5lbs oil pressure and had no problems.  Since the boiler has a much larger combustion chamber I increased pressure to 5lbs.  The flame looks great, plenty of heat, with smokeless combustion, but just large amounts of the un burned oil mist.  I have tried adjusting the compressed air pressure and changing the secondary air on the burner fan, as well as cleaning the nozzle several times with no luck.  The only other change i made is adding a heat exchanger which pre heats the wmo to aprox 160deg just before the burner.  The burner has a 9-5 nozzle, it is the origional one that came with the furnace and has 5,000 odd hours on it  Any help or suggestions would be appreciated. Thanks Bill

[Russ]

Greetings Bill.  Glad you stopped by the forum.

I cant say that I am familiar with your particular burner.  The home made siphon style burners many on this forum have used usually run best around the 8 to 12lbs air pressure.  That's interesting that yours runs so low.  Must a little different style burner.  Do you think you are just pushing too much through he nozzle beings it worked well at the lower pressure?  Also, how long are nozzles typically good for?  5000 seems like quite a few hours, but I could be wrong. 

The other thing I have heard with boilers is that unlike a forced air system where the burn pot can get red hot and burn any residual oil, boilers run much cooler and cant burn off stray mist.  I think some have solved this by putting plates of sheet metal in the burner and they will get hot and help burn all the oil.  I don't remember exactly where I read this, but that might be an option that could help.  Maybe others will have some ideas.

Good luck with your boiler!

[doug]

Bill,

Welcome to the forum. On my boiler I use a piece of 5" dia. x 8" long exhaust pipe to help burn off the unburnt oil mist. The exhaust pipe will be hot enough to burn the oil droplets. The boiler walls don't get hot enough with the water circulation.
Sure would like to see pic of your set up. Let us know how your project goes.

doug

[steamdrum1]

Thanks for the suggestions.  I can definately see how having sothing in the combustion chamber of the boiler to get hot and burn off the mist.  I will try to attach a picture of my boiler, it is a 1930's vintage about six feet long and four feet high.  The boiler came from a small church in the town where I grew up.  Thanks again Bill

[doug]

Bill,

That's one huge boiler. Must be efficent if it didn't take long to come up tp 180*. What are you heating?

doug

[steamdrum1]

Right now it is providing hot water for a heat exchanger in the return furnace duct for the house.  My heat exchanger is an old hydraulic oil cooler off a piece of construction equipment, unfortunately it is not exchanging enough heat so I plan on upgrading to a new exchanger that goes in the furnace plenum.  The boiler is located in my attached garage/shop and the stray heat from the stack and the boiler itself keep the temp at around 50 deg.  I plan on building a better jacket for the boiler so that should cut down on some of that lost heat.  I also put a couple pieces of heavy sheet metal in the combustion chamber over the weekend, and it has solved the mist problem.  A big Thank You for the help guys.  Best regards Bill

[Russ]

Good job Bill.  Sounds like you are getting it all figured out.  Things will really take shape when you get your plenum exchanger.  I bought a 16x18x3.5 exchanger and it keeps up with my boiler well and throws out some nice heat.  Glad to hear you got the mist problem taken care of as well.  Sounds like it is time to put some hours on that thing!