why brown smoke?

[4acrefarm]

I have a home built tube boiler with fan forced induction. the firebox is semi separated from the water tubes. When it is loaded or reloaded it smokes brown. Even when it is only smoking a little it is brown not blue like everyone else. My wood is not as seasoned as i would like it but seams ok, hase small crackes and bark is slightly loose. When I split it it does not seam cold or damp on inside. I have heard it sizzle inside the fire once. The water enters tubes at 60-90* and leaves 120-155*. the fan has 2 speeds it does it on both. I run wide open at all times thanks in advance for any ideas.
Is it the wood?
Is it the water tubes colling it down?
Is it the forced induction?

 

[Gooserider]

I have a home built tube boiler with fan forced induction. the firebox is semi separated from the water tubes. When it is loaded or reloaded it smokes brown. Even when it is only smoking a little it is brown not blue like everyone else. My wood is not as seasoned as i would like it but seams ok, hase small crackes and bark is slightly loose. When I split it it does not seam cold or damp on inside. I have heard it sizzle inside the fire once. The water enters tubes at 60-90* and leaves 120-155*. the fan has 2 speeds it does it on both. I run wide open at all times thanks in advance for any ideas.
Is it the wood?
Is it the water tubes colling it down?
Is it the forced induction?

If you are hearing the wood sizzling inside the stove, it is WAY to wet... It also sounds like you are running your water WAY WAY to cold - you will rapidly rot out your furnace with those return temps - normally you should be running the water IN at about 140*F or higher, and having it come out at around 180-190*F. Look at some of the install threads where they talk about boiler return protection...

I could be wrong, but what it sounds like is happening right now is that your tubes are so cold that your combustion gases are condensing on them, and the corrosives in the liquid are attacking the steel of your boiler, and then evaporating back out taking the metal with it and giving you that rusty brown smoke...

I would say fix the boiler return temps ASAP, while you still have a boiler LEFT....

Gooserider

 

[Duetech]

Gooserider brings light to a serious concern. The temps need to come up if there is not enough air and the temps are not allowed to rise the gasses will be too cold to ignite. If the unit has always done this I would say your air flow is too small or is being restricted and probably not dispersed effctively. Is there a way you can pre-heat your air before it gets to the fire so it will help ignite the gasses?

 

[4acrefarm]

thanks for the input.
I heard sizzle only once but, i am not rulling out green wood.I am ordering a moisture meter today. The return comes right from the radiant so getting incoming temps up may be difficult, I can slow down the flo. The air thatintake is 6 inches from outside of boilerso temps should be ok, I am still planning a warming system for the air. I may also preheat the wood, but that is a hassle. When shot with an ir thermometer the outside of boiler is 550-590*, the pipe is 170-275*. The pipe has a 8' run before entering chimney. Maybe it is this pipe that is rusting. Maybe I should insulate this pipe? What would be the best way? What temp is fiberglass good to?
thanks again.

 

[Gooserider]

thanks for the input.
I heard sizzle only once but, i am not rulling out green wood.I am ordering a moisture meter today. The return comes right from the radiant so getting incoming temps up may be difficult, I can slow down the flo. The air thatintake is 6 inches from outside of boilerso temps should be ok, I am still planning a warming system for the air. I may also preheat the wood, but that is a hassle. When shot with an ir thermometer the outside of boiler is 550-590*, the pipe is 170-275*. The pipe has a 8' run before entering chimney. Maybe it is this pipe that is rusting. Maybe I should insulate this pipe? What would be the best way? What temp is fiberglass good to?
thanks again.

You need to put a mix valve of some sort on the output line to redirect some of the hot water from the boiler output back to the input, so that the input temperature is higher. A Termovar / Ladomat type unit is one (fancy) way to do this, but you could also use a 3 or 4 way thermostatic valve. This will also likely require you to have some sort of mixing or regulating function on your radiant input as well to avoid excess temps in the radiant floor...

Could be your pipe that is rusting, but insulation probably won't help that, and note that it is a code violation to put ANYTHING over black stove connector pipe - however you could replace w/ stainless and insulate that - however the problem right now is that the gases entering the pipe are already to cold...

In addition, I would add that in the case of bad return water temps, the largest point of failure is the point where the cold water return enters the boiler...

Gooserider

 

[ISeeDeadBTUs]

As has been bantered about already . . . .

figure out WHY your output temps are that low. Keep the output above 170 and see if she smokes.

 

[4acrefarm]

thanks for the info. My output temps are low because i have a snap disc that turns on the circ at 150*. I will change this to 180* immediatly. What is the lowest stack temp I should run? Is an ir therometer an accurate way to measure? What kind of mixing valve and how much$?

 

[Gooserider]

thanks for the info. My output temps are low because i have a snap disc that turns on the circ at 150*. I will change this to 180* immediatly. What is the lowest stack temp I should run? Is an ir therometer an accurate way to measure? What kind of mixing valve and how much$?

Yes, upping the circ turn on temp should help. One caution you MAY need to look at, depending on how your system is set up, is to watch the temps on your radiant floors - make sure you don't exceed the maximums for comfort and preventing damage... Optimum stack temps seem to vary, but 3-400*F seems to be a good range, w/ up to 600*F being OK... Best way to measure it is with a probe type thermometer that gets it's reading from the middle of the pipe. Shooting the pipe with an IR unit will work, but the results will probably be 1-200*F low...

However the big thing that you should be worrying about, is your boiler water return temp - If that is low, you will rapidly destroy the boiler, regardless of how other the other temps are. If you get the return temp into the right range, it is quite possible that the other temps will largely correct themselves...

As I said earlier, there are MANY options for how to do boiler return protection, with a wide range of price tags and features. Which one is best can be the subject of a great deal of argument, and will also depend on both how your system is plumbed currently, and how you want to change the plumbing to do the return protection. All work on the basic idea of mixing hot boiler supply water into the return water in order to bring up the return temperature to at least 140-160*F, but how they do it varies.

If you post a diagram of your current system layout, we can possibly suggest some options. Computer drawings are nice, but not essential - making a pencil and paper drawing, and taking a photo of it will do if that is what you feel most comfortable with.

We will be especially interested in the "near boiler" piping - what size and material, where are the pumps, zone valves, and other such fittings. We aren't as worried about the details of your loads and floor loops.

Gooserider