Experience closing off 1 nozzle on larger units

NYEDGE said:

Can those of you that have tried this share some of your experience of what the outcome has been?
I think that the front nozzle would be closed so that the unit has more heating time in the lower box.
Is their any problem with the wood not burning down to coals over the closed nozzle?
Have your burn times been extended while still being able to keep up with your heating needs?

I was thinking of using a wet saw and cutting a firebrick to a wedge shape to insert into the nozzle.
If the nozzle is plugged, do you shut the secondary air going to that nozzle, or just leave it as is?

Thanks.

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I did go down to one nozzle on a EKO 60. I did it mostly due to the fact as I was having a hard time running on two nozzles. I read in another post that you have most of your wood cut at 16 inches so if you do change, you should have any problem just burning on one. All of my wood fits almost directly over the one nozzle so I really don't have any problem with coals over the closed nozzle. As far a extending burn times....this hasn't been a issue as I have allot of storage so I burn full tilt all the time. I did nothing with the secondary air going to the closed nozzle, I just had to adjust the number of turns for the secondary air covers to fine tune. I don't know how much heat you'll need for the pool but this may work after you get it up to temp.

I would be concerned about splitting the ceramic with anything going inside the nozzle. As it heats & expands the plug could drop down & when cooling could crack the nozzle. A piece of steel or brick laid over will do fine, Randy

I just used a fire brick over mine. My problem was like Shannon's I did not have long enough wood to keep both nozzles covered in coals. My splitter will only do a 20" log


Rob

NYEDGE said:

Thanks for the information.
So for the most part you covered one nozzle due to non-constant gasification in both nozzles right?
Outside of that, I guess you haven't had any other benefits?

I will take the advice and put a steel plate over the nozzle when I try to run with only one nozzle.

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Yes that was the reason. As for the steel plate... you might get it to warp then it will lose the seal. If you use steel put a good layer of cold ash over it to protect the steel.

My biomass has just one rectangle hole in the middle about 1 1/2" by around 10" long. Could I block 1/2 the hole? What is the addvantage of a longer burn if you have storage ?

woodsmaster said:

My biomass has just one rectangle hole in the middle about 1 1/2" by around 10" long. Could I block 1/2 the hole? What is the addvantage of a longer burn if you have storage ?

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I've been blocking off about half the slot in my boiler with a plate of mild steel covered with an inch or so of ash. The theory is that by running at a lower burn rate the size of the heat exchange surfaces becomes relatively larger, meaning you can get lower stack temperatures and somewhat better efficiency, which is supposed to amount to 1% gain in efficiency per 35 to 40 degF reduction in stack temperature. But of course it is very important to make sure your stack temperature is hot enough.

Another possible advantage, at least in my particular boiler, is that it brings the nozzle into the center of the firebox and then I can center undersized fuel on top of the nozzle and get steady burns with just the right amount of charcoal left at the end.

And there's the advantage of being able to take fuller advantage of storage because more fuel can be placed in the firebox for the last loading of the burn because the extended burn time means more of storage will be depleted before the last of the fuel is consumed, and therefore you can extend the time until the next burn without idling.

To do it right you would need to make sure the primary and secondary air settings are optimized for the revised burn rate.

Also it seems to me it would be prudent to increase boiler return temperature to be plenty hot so there aren't any cool corners in the firebox for acidic condensation, but I'm merely speculating on this point.

--ewd