Max Caddy Fine Tuning Advice...

[usernametaken]

That would assume that I am over fired and/or the heat exchanger is dirty. (The latter is unlikely since the unit is brand new.) Stack temps would indicate that I am not overfired. Also, while draft was set initially, draft is not a static setting. It changes all the time. If it didn't, then folks wouldn't have permanent gauges set up so they could make adjustments. I'm guessing my draft was low since I've been getting some decent, albeit sporadic smoke roll in when filling along with my low plenum temps. So, while I agree some further checking is warranted and will be done as soon as the new gauge lands, I would not say the sky is falling just yet. I do appreciate the concern and thoughts though.

 

[usernametaken]

Over-firing is definitely one way to increase your plenum temps! If they still are not not high enough you could always try sticking a leaf blower in your primary air and lettin' er' rip! That may achieve the results you are looking for and could also double as blast furnace just in case you want to start forging your own tools. </tongue firmly planted in cheek>

Like bren said, get your draft in check and leave it there.

I like it! Would you recommend a backpack or handheld? Maybe a little of its 2 stroke fuel oil mix on the fire to get things started off right as well! Now we're talking....

 

[JRHAWK9]

Stack temps would indicate that I am not overfired.

Curious, what are you using as your threshold for the basis of this statement and how are these temps being metered?

 

[laynes69]

Being an owner of the Caddy, you will never hit overfire temperatures in the flue pipe. The furnace's heat exchanger is very effective at pulling alot of btus from the furnace. I have my furnace on a switch. If I dont want smoke when loading, I turn off the furnace (or load on coals only). As for draft, .06 is max and SBI had told me numerous times that .08 is absolute max but okay. Unseasoned wood will kill output greatly! I have the wall thermostat hooked up on my furnace and I open the damper after loading for between 10-20 minutes then lower the temperature of the woodfurnace to close the damper. The furnaces are very capable of putting out alot of heat with a normal draft and good wood. Even though the limit is 200 degrees, I lowered mine to around 150-160. If it bounces there it will close the damper and keep the furnace from going nuclear.

 

[usernametaken]

Curious, what are you using as your threshold for the basis of this statement and how are these temps being metered?

I just send the kids down there and see who can hold their hands on it the longest...

Either that or an infrared thermometer. Whichever strikes me as proper for the day... LOL

I got 375-400 at the very highest today when the stove finally got some decent plenum temps. Before that I would never break 300.

 

[usernametaken]

Being an owner of the Caddy, you will never hit overfire temperatures in the flue pipe. The furnace's heat exchanger is very effective at pulling alot of btus from the furnace. I have my furnace on a switch. If I dont want smoke when loading, I turn off the furnace (or load on coals only). As for draft, .06 is max and SBI had told me numerous times that .08 is absolute max but okay. Unseasoned wood will kill output greatly! I have the wall thermostat hooked up on my furnace and I open the damper after loading for between 10-20 minutes then lower the temperature of the woodfurnace to close the damper. The furnaces are very capable of putting out alot of heat with a normal draft and good wood. Even though the limit is 200 degrees, I lowered mine to around 150-160. If it bounces there it will close the damper and keep the furnace from going nuclear.

Good experience info. Thanks...

 

[laynes69]

I guess what I'm trying to say is that you will overfire the furnace well before any temperature gauge would show overfire. At the same time however, I have pushed my furnace very hard in the past and when the firebox was removed from the jacket, there was zero signs on both the exterior of the firebox or exchanger of any signs of heat (paint looked new). The Caddy lines are very well built, it would take alot to damage one. One thing I like to do when the weather is extremely cold is to mix softer woods like maple with hardwoods. That way you reduce the chances of coaling too much.

 

[JRHAWK9]

Being an owner of the Caddy, you will never hit overfire temperatures in the flue pipe. The furnace's heat exchanger is very effective at pulling alot of btus from the furnace.

I guess what I'm trying to say is that you will overfire the furnace well before any temperature gauge would show overfire.

That's where I was going.......thinking he may be thinking old school and looking for those temps.

I got 375-400 at the very highest today when the stove finally got some decent plenum temps. Before that I would never break 300.

Kinda figured that's what you were doing. Easily double that for internal temps......800° internal is way too hot for these types of furnaces. Forget the IR gun, get an internal temp probe so you know what the actual flue temps are. If I ever saw 800° internal flue temps I'd be panicking, as something is not right. When I run mine hard, I may see mid 500's right after a load, but very briefly before the computer goes to pilot. Heck, my BBQ temp probe is only good up to 579° I believe.

EDIT....572°

 

[brenndatomu]

Stack temps would indicate that I am not overfired.

Bad data. Flue temps don't necessarily follow firebox temps. Plus external pipe temps only loosly reflect 50% of the internal temp.
The one time that I have had the Kuuma's high temp alarm go off (internal firebox temp) the internal flue temp was absolutely fine, on the lower side of normal even. So that absolutely aligns with what the designer/owner of the Kuuma furnace line told me when I said I was monitoring internal flue temp, he said "so?"
Not sure why you are being standoffish here...you came here asking for advice from people that give their many combined years worth of wood furnace experience to you for free, nothing to gain or lose here...but you do.

 

[usernametaken]

I'm not standoffish at all. I just don't jump to worst case scenarios but will certainly consider all that was posted. It's no different than the RV forums. Tow 1lb over your trucks published limits and your destined for a fiery death along with every one you ever loved. Either that or you'll cause an accident that you survive and get sued for everything you own and end up living under a bridge. So, while all this is possible along with the possibility that My draft might be too heavy, it might be something else entirely. Perhaps, my installer did a bad draft test. Perhaps the fact that he did it early in the fall under completely different environmental conditions skewed it a bit. Perhaps it was set perfectly and I over drafted this morning. All possible and when my gauge lands in a couple days, I'll know for sure. All I know is I'm certainly not worried about a fiery death caused by either my increased draft or certain tow ratings... If I die, you can certainly say "I told you so" though...LOL.

Really though, I appreciate all the thoughts and info. It's a great recipe of valid concerns, ideas, personal experience, and a bit of worse case scenario topped with a sarcasm glazing. About what I expected asking a question on a forum. Thanks again everyone and have a Merry Christmas. I'll post back my results when the Dwyer is in... if I make it until then...

 

[brenndatomu]

That would assume that I am over fired and/or the heat exchanger is dirty. (The latter is unlikely since the unit is brand new.)

How long have you been fired up now? A week? More? Have you looked at the HE tubes yet?
When I was running the Tundra furnace here, I found that cleaning my HE tubes weekly made a noticeable difference...and that is with burning 4-5 year CSS wood...buildup occurs much faster if burning marginal wood.
And I don't recall the exact number, but one of the manufacturers that participate on here said one time that xx thickness (it wasn't much) of buildup (soot/fly ash, or creosote if things aren't going well) is a pretty effective insulator...in terms of extracting maximum BTU's anyways...not so much if we are talking about house insulation

Also, while draft was set initially, draft is not a static setting. It changes all the time. If it didn't, then folks wouldn't have permanent gauges set up so they could make adjustments.

You are right, draft changes all the time...but the baro adjustment sets max draft, and shouldn't change, or at least not unless your chimney completely overwhelms it.
And I don't run a manometer full time so that I can make adjustments as needed...once its set, you shouldn't have to change it, unless you want to raise/lower it inside of the -0.04" to -0.06" window for some reason.
The reason I run one full time is just to check that everything is working properly after each time I load...make sure the baro door is not sticking a bit (it happens) or the chimney cap is getting plugged (have had that happen too...years ago) etc.
Bottom line is, the furnace is working better for you now, great. Most likely, based on what you have said, you are not over firing, hopefully not anyways. And as Laynes69 said, these things are pretty tough, so hopefully it would take a bit of abuse if it does turn out that your draft is too high now.

Edit: Never been compared with an RV'er before...I feel so...dirty now... (JK)
Oh, and I never said anybody was going to "die a fiery death", just that you could damage your new machine if you aren't careful about setting chimney draft (blindly adjusting the baro)

Merry Christmas man!

 

[usernametaken]

I've had it up and running about a month or so now. I never thought about early cleaning of the heat exchangers. I was just going to do it annually like the manual stated but if it's a good idea, I'll do it sooner rather than later. Thanks for that tip! I'll dial back the draft until the meter arrives. Brown Santa should have it here in a couple days. I certainly don't want to do any long term damage so I'm not completely cavalier about the dangers posted above. I'm just trying to weigh the odds and make this sucker work. That said, I won't likely get it 100% dialed in until next year when I have my wood properly stored and dried all summer. This year was a cluster getting everything done so things are currently less than ideal....

 

[sloeffle]

What kinda MC are you seeing from a fresh split face on a piece of wood ? Have you tried burning any bio bricks ?

 

[usernametaken]

I have not burned any bio bricks. I did a couple test splits and saw 15-20% but that could be skewed as I'm sure I grabbed the lightest pieces off the top of the pile before bringing the whole supply inside for the winter.

 

[sloeffle]

Take this for what it is worth. IMHO - I think you are fighting with wet wood. Having to leave the damper open to sustain temps at 300ish is a tell tale sign. As I stated before you should be able to leave the damper open for 20 minutes, close it, and still maintain temps around 350F. I'd be interested to know what the MC is from a split from in the middle of the stack. I keep my wood in totes and I wrap the top to about half way down with shrink wrap in July in order to keep my wood dry.

We use to heat our house with an EPA approved catalytic wood stove. The first year we had the stove, I fought with wet wood and it made it really hard to keep are fire going. Like you, I always had to have the flaps in the front open and the heat output wasn't very good.

 

[usernametaken]

I agree. I think MC is one of my issues right now. The only reason I don't think it's my only issue is this. When I had an absolutely raging fire about an hour or two in with smaller splits... let's just say, no moisture left whatsoever... I was still seeing less than stellar plenum temps until I upped the draft.

 

[maple1]

Factory recommendation is only clean HX tubes once a year?

 

[usernametaken]

Factory recommendation is only clean HX tubes once a year?

That's what the manual says...

 

[brenndatomu]

Whoever wrote that manual obviously hasn't ever heated their personal residence with one...

 

[usernametaken]

Howdy boys and girls. Just wanted to post an update in case anyone was interested. Dwyer Magnehelic is installed. I also called PSG one more time to ask them to expound a little further on the correct draft as the last gent I talked to there made it sound less critical than the manual states. I was told that yes, the .04-.06 stated in the manual is ideal. However, if I'm finding I'm getting smoke roll in or cooler burn temps, .08 is fine as well but is near the max they would be comfortable recommending. With my baro set at the spot my installer left it, I was around .04-.05. When I dial it all the way back to it's lowest point, I hit .07-.08. Cap it with foil and I go up to a strong .10-.12 (all depending on stack temp.) So, even capped, it's not way outside spec but higher than it should be. I'll experiment this year a bit but as I said earlier, this year is not how the rest of my years will be. Next year will be when it gets dialed in 100%. Again, thanks for all the thoughts. Oh, and I forgot to ask about the more frequent HX cleaning. Not that I don't believe you are correct... I just want to hear what they have to say... I'm sure it will be political and something to the effect of: "It certainly can't hurt..." Anyways, I'll hit them with an email about it and see... I did remember to ask about flue temp though. They told me 900 degrees is the max their furnace can safely handle.

Happy New Year all....

 

[usernametaken]

One year update on the Max Caddy. I found a few issues that were causing my less than optimal performance last season. One, as I mentioned earlier in the thread was MC of my wood. I knew that going in... The second was an area of my home we call the "bonus room." It's about 900 sq/ft over our garage that serves as my daughters play room and our home theater area. When building, my insulator's spray foam rig failed in spectacular fashion and as to not hold up my drywall hanger, we went with fiberglass and reflective insulation on my knee walls which wasn't what it should have been. This summer I cut scuttles in the garage ceiling, pulled down the fiberglass and had all the knee walls sprayed with closed cell. That got me a better vapor barrier and much better insulation. That was half the puzzle. On top of that, I have a ton of ductwork in my attic outside the envelope that was wrapped in R8 by my HVAC installer. R8 is pretty weak so I had the foam insulator spray all my ducts with 5-6" of open cell which made a huge difference in heat loss on my long run outs. It also raised my return air temp a lot which keeps the Caddy's plenum warmer thus letting it kick up blower speed as designed.

So, bottom line, 3 issues corrected and man what a difference. The knee walls aren't HVAC/wood furnace related but were 1/3rd of the problem. MC and duct insulation also made a huge difference to the Caddy's performance though. I now have my baro set at .06 as specced by the manufacturer and with the temp dropping to around 20 last night here, the Max is easily keeping the house at the temps set on the thermostats. Heck, it was actually too warm in my BR last night and didn't drop below 70 until after 4am despite the thermo being set at 67. It never got to 67 either. It was still 68 after an 8.5 hour burn when I got up to fill the furnace this morning. Now, I realize we have colder temps on the horizon and things change when the ground freezes. However, I'm now VERY confident that the Max will handle my needs without issue. I wanted to post this update in case anyone else finds themselves with less that stellar performance from a Max Caddy to give them a couple places to fine tune...