Fire is suffocating... Please Help [Solved]

[reubendog]

I have a Greenwood Aspen 175 boiler, which has been working excellently for a little over a year.... until now.

The furnace will hold its heat ONLY when there is very little load (i.e. just domestic hot water). As soon as a load is applied, the temperature drops and the fire chokes. I say chokes because when I open the door, there is no more flame, and the only way I can get the fire going again is to remove all the unburned wood (it's virtually full) and rake the coals. Once the coals are exposed to fresh air for a few minutes, the flames rush back to life.

More details...
The ash is clear from the main wood chamber, secondary burn chamber and the back chimney chamber.
The fan motor is running, but doesn't seem to be pushing much air?

My local dealer guy vaguely suggested drilling a 3/8" hole in the top of the fan manifold (to increase air flow and reduce "gumming up" of the damper). Has anyone had a similar experience, with (I hope) a successful solution?

Please advise, my pool is getting colder and colder and colder, PLUS I have to heat my house on oil (ARGhhhhh)

Thank you in advance

 

[ISeeDeadBTUs]

I know nothing about the Aspen . . .

What I know is a fire takes fuel and 'air'. If the fuel is dry, then I'm gonna say its air.

Flap/fan working?
Is the draft the same as it used to be?
With little to no heat load, will the unit come up to operating temp?
Describe the output fropm the stack . . .

EDIT: I just reread your OP . . . kill the heat exchange at the pool and see what happens!!

 

[stee6043]

Are you throwing green, unseasoned wood on those coals? Are you throwing in large splits or some smaller splits?

 

[reubendog]

I'm using unseasoned wood, but it is reasonably dry (was in lumber yard for about a year) - this is also the same type of wood that I burnt all last year with not a problem. I usually burn birch and pine.

I have had to rekindle the fire with very small splits to get it going and up to temperature (with very little load). I have tried small split wood, even just the pine alone. When I take the load off, it seems to be able to handle things OK and it gets up to temp. When I apply a load, the temp drops very quickly, sometimes below the set point of my oil burner.

 

[hkobus]

Reubendog,

Welcome to the forum, good to see more ontarians here. I have no experience with your brand boiler, but I have burned many different types of wood in my Eko 40 gasifier. The gasifiers like wood dry, when you burn wet or unseasoned wood the burn loses the energy it takes to evaporate the moisture first. Any time that happens you will have a hard time yielding good heat.
I also googled you boiler and found some interesting sites you may want to check out, the unit seems to have some maintenance issues and has some air inlets that plug.
I agree with the above post in turning off the pool load to see if it would build heat, but it sure sounds like you may have some airflow and maybe heat exchanger tube cloging going on.
If you can't find the google results feel free to PM me and I will send you the links, just hate to post negative links without knowing the full extend of it, but they may help you on the way to trouble shoot this.

Also, when you say from the lumberyard, is this short cut 2X4 etc or split tree wood. Was it split just now or this spring?

Good luck,

Henk.

 

[reubendog]

Hey Henk,

I certainly appreciate that wet wood doesn't burn very well, as the water needs to evaporate before the wood will burn properly. The wood I'm using isn't wet, though. I probably used the wrong term "lumberyard". The trees are forested and limbed in the bush, then accumulated in the foresters yard for several months before being sold to the consumer (me). I get 12-14' lengths of full circumference tree (pine and birch, but mostly birch). Most of the wood I leave unsplit, as that has given me the best results in the past for burn time. I honestly don't believe this to be a fuel issue, as the wood this year is of even higher quality than last year's crop, which burned A-OK all year long. I also believe this to be an air issue (although I've never considered heat exchange tube clogging).

I've PM'd you to get those sites you mentioned. I've searched many places, but I find more info about the original Greenwood furnaces, rather than the newer Aspen models, which were acquired by the company and use a different setup. I will say that Greenwood has been pi$$ poor about customer service. I called 4 days ago, left messages with no response. I even called the "emergency" number with no response (I have call display, so I know they didn't just call and not leave a message). Even the local dealer I purchased it from can't get through! (He's just as stumped as me, btw)

Looking closer at the back of the unit, there is a fan motor that injects air into the chamber. A solenoid charges an electromagnet that pulls open a plate above the fan blower to allow air into the fan. This functions normally. I still don't get it.

Thank you, everyone for your help so far.

 

[reubendog]

Additional note: When all loads are removed, the fire gets to full temp (I have it set at 180F). Domestic hot water alone will also maintain this temp. The pool load reduces the temp to 150F and below VERY quickly. There is also a thermostatic valve that prevents water less than 140F from circulating back into the boiler from the house.

The output from the stack appears normal (not overly smoky, but enough to know that wood is being burned)

 

[Gooserider]

Don't know about your specific boiler, but some generic ideas....

Seems like time to to think about the old "Fire Triangle" - Fuel, Air, Heat... Fuel doesn't sound like it's an issue, (Though wood doesn't dry very well until it's cut to log length and stacked, so it may be wetter than you think...) so look at the other two factors...

Air -
Have you checked to make sure the fan is tightly secured to the motor shaft?
Is the fan and it's associated ductwork clean?
Have you verified that all the air controls open the right amount when they get a call for more heat?
Have you made sure there are no blockages in any air passages?
Have you verified that the call for heat is actually getting to the controls?

Heat -
Have you checked your actual return temps to make sure that your return protection system is actually doing the right thing?
If you are returning very cold water, in addition to the potential corrosion issues, it can pull the heat out of the fire and cause it to die...
Have you tried raising the return water temps and / or the max boiler temps?
Do you have any delay between cranking up the boiler to let it get a fire going well before starting your load circs?

Gooserider

 

[reubendog]

[SOLVED]

The furnace is now working normally again! (Actually, better than it has in weeks)

The grating between the main wood chamber and the secondary burn chamber had become clogged in places that can't be seen. Greenwood manual says to "simply rake the ashes from the main chamber through the grating". Well.... little clinkers get stuck, then ash builds up around them, and WHAM! no more air circulating to the lower chamber. After doing this I checked the flue tubes at the back of the unit, and they were clear.

I can now put a full load on my furnace (pool and house heat) and the water never drops below 168F. Woo Hoo!

Thank you all for your assistance (and a special NO THANK YOU to Greenwood "Customer Service") who still hasn't answered my calls).

 

[ISeeDeadBTUs]

[SOLVED]

a special NO THANK YOU to Greenwood "Customer Service") who still hasn't answered my calls).

Congrats on burning again!

You were kidding about Greenwood Customer Service, were you not? Even when the company existed, their customer service was non-existant. Now with the company gone . . . 'did 'ya think it was gonna get better?? :lol: