Enviro Maxx overheating/fire issue

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Hi all, just looking for some advice on a possible problem / safety issue?

Just finishing out 1st season with my Maxx and aside from an occasional flashing #3 issue I couldn't be happier, until this morning. Stove is on a stat and this time of year (auto on/off) and it's programmed to turn on around 5:00am and off about 7:00am - it just kicks on as needed if the house is cold and I usually always wake up warm.

Well, woke up this morning around 6:00am and immediately notice that something doesn't seem 'right' - sorta that new stove 'burn-in' smell in the air - I instantly understand that the stove is running too hot and proceed downstairs to find a very HOT stove, very large flame and seemingly stuck in 'start-up' mode, auger chugging away at heat level #4 (which is correct) and no convention blower operating.

I have a magnetic thermometer on the door which usually pegs out at 450F, it was 700F! I manually hit the off button, then turn it on again which starts the convection blower - I let it run and cool for 20 minutes then shut her down.

I have no idea why the convection blower didn't kick in? This is also the 2nd time in the last month that this has happened. If the stat sent a signal to turn off the stove 'during' the start-up process (before blower starts), would this cause this scenario?

Please advise so I can sleep better at night!
 
A flashing #3 indicates that the Low Limit disc went open. The Maxx doesn't use a seperate thermodisc for controlling the convection blower like a lot of Enviro models do. The low limit disc should have shut the stove down as well but I would suggest jumpering out the low limit and seeing if everything run normally for you, and give it several runs that way while keeping an eye on it. If there is an intermittent issue with the disc I have seen it cause the stove to do strange things. Also check all the wiring make sure everything is tight with no loose connections or rubbed off insulation. And finally Enviro has a two year warranty on the electrical parts on a new stove, if you do need to replace something call your dealer.
 
There is a date on the hopper lid, If its before mid 2009, There was a update on the controll panel. I'm getting old and forgetful, But I recall this as one of the issues of the controller.
 
My Maxx was produced June of 2009 - It was my dealer's showroom model for about 2 years, it was just installed and fired up for the first time last August 2011 so it's still under warranty. I thought I was up to date with all the bugs and changes of this model since it's introduction, but I don't recall ever hearing about this issue. What really concerns me is that it seems the the high temp safety override never kicked in and stopped the auger or initiated the shut-down mode.
 
I wouldn't run that stove unattended. I would also get the dealer to check the high limit switch. Pretty rare to see one stuck closed and not open at 250ºF. But that's what it sounds like happened.

If you don't get anywhere? We can step you through how to test the high limit. I can also post a cheapier replacement part number. But seeing its under warranty, Best to get the dealer in motion. I also sent you a PM.

Keep us posted!
 
Follow jtakeman's advice, a screwed up high limit detection/action system is a disaster just waiting to bite you on the a$$ and burn your house down.
 
** UPDATE: 10/10/12 **

I just wanted to update this thread for archival / search purposes and all, to post the resolution of this issue:

Maxx unit sat dormant for the last 6 months until a couple of weeks ago - sure enough the stove started to exhibit the prior issue where the convection fan wouldn't start once the start-up sequence had finished, I also still received the occasional flashing #3 light which triggered the stove into shut-down mode.

I did have a tech from the dealer come out and check out the stove last April, he tested the high-limit sensor (which was one of my main concerns, thinking that it may not be functioning correctly) and sure enough, it was working fine and activating at the proper temp (200f?).

So anyway, I'm thinking this may be a faulty control board (especially considering I pretty much had the exact same issue with a faulty triac on my 11 year old Enviro Windsor stove, replacing the control board solved that problem) so since it's under warranty, the dealer orders a control board. While I'm waiting on the control board, I was looking through a tech/service enviro manual I found online - I found a reference stating that once the Maxx detects the fire, it will send the signal to the convection blower to turn on. So I'm thinking, this sounds like my problem! Maybe it's a faulty sensor? I decided to jump the low-limit (snap disc?) sensor which is located on the exhaust channel just to make sure it's working. Not sure if this did anything, but just noticed that this caused the convection fan to start right away - seems to be working fine.

Now i'm thinking that although the low-limit sensor is working, perhaps the fire is not getting hot 'enough' to close it at start-up? This would make perfect sense since I often get the flashing #3 scenario. Well, since the installer adjusted the damper with a magnahelic during the initial install, I assumed that everything was set correctly - I never touched the damper.

To make along story short, I just pulled out the damper 1/4", giving the burn-pot a tad more air. The unit fires up 100% of the time (no flashing #3) and I haven't experience the convection blower not turning on at all. So it seems that that for my setup, the unit just needed a little bit more air to close the sensor at start-up, which I think was the root-cause of this big headache?
 
Was the stove set with a magnehelic gauge? If the damper is closed to far heat basically doesn't get to the POF switch to close it. POF is what tells the control to turn on the convection blower and go into run mode. LIke MountainSean said not pulling the POF will flash the #3 fault code. Odd the unit got that hot as they start up in low fire mode. It shouldn't go into run if the POF isn't closed. Which threw me off. But I guess if the hot air wasn't exhausting fast enough the stove could get fairley hot.

Glad you figured it out and all is well! Good you updated the cure, very helpful if someone else encounters the same deal. :cool:
 
The stove was set at install with a Magnehelic, which is why I just assumed the damper wasn't the issue. Everything now points to the POF switch staying open, the only thing which I still haven't figure is out is what you mentioned that the stove shouldn't go into run mode if this is the case. Perhaps it's a timing thing whereas the POF hasn't closed yet, the stove sends the signal not to start to convection fan, but before it triggers the flashing #3 the POF closes so the unit just proceeds with the startup/run sequence? This is the only thing I can think of that would make sense?

In reference to the stove getting very hot during low fire mode - the thing is that I had it on a stat set at auto on/off, set to heat setting #4 - this is why the stove became very hot. Convection fan didn't start and startup sequence finished then it reverted back to last heat setting (#4), so the auger was just dishing out the pellets making a very hot environment when there is no convection fan - I'm sure now that if this continued the high limit switch would've eventually tripped shutting down the stove.

Either way, just a simple 1/4 turn of the damper fixed this whole headache! Funny how picky some things can be, and now my kids are not complaining that the house 'is cold' waking up in the morning!
 
Since I have a maxx this was good info. Just to add a note when my Maxx flashes #3 it is out of fuel, or I have it running so low the fire went out and I will find a pile of pellets in the burn pot. Now I no the my POF is working good.
 
** UPDATE: 11/15/12 **

I just wanted to update this thread once again, because looks like I spoke to soon. It seems I did indeed have two issues going on here, although opening the damper 1/4" did fix my flashing #3 problem - I assumed that this fixed the convection blower not starting issue as well, but I soon started to notice that the convection fan was failing to kick in after start up again.

This was about a month ago and my dealer did ended up getting a new circuit board which I switched out last month - My Maxx has since been operating as designed and haven't had any problems (knock on wood). So it appears that the circuit board was faulty after all, in terms of the convection blower operating correctly.
 
** UPDATE: 12/26/14 **

I just needed to update this thread for future reference if anybody was having this issue with the same stove.

Replacing the circuit board last year actually did not fix the issue as it eventually came back - what fixed this issue for me was removing and cleaning the POF sensor on the combustion fan housing - it had carbon crud on it. Once cleaned, I haven't had this issue since.
 
Wow. You replied to my problem. And will take your advice. But your problem was the same as mine. If I didn't check my stove I believe I would of had a fire on my hands. My daughter comes home everyday after school and would turn on the stove 2 hours before get home if this happen when I wasn't home not sure what the out come would of been. I told my daughter 2 days ago not to start the stove with out me being home. I believe fixing the sensor will take care of my problem. But it doesn't leave me with warm feeling. An with a firefighting background.
 
Interesting tread. My Maxx has done the same thing twice. Only the auger was almost not even shutting off. Just keep feeding it pellets. Fan did not start. Did it both times when starting off the season. Last time it did it I had to clean the sensor on the exhaust pipe also to stop a flashing light. Has worked fine both time after a good cleaning. Just because the sensors dirty you wouldn't think it should over heat. I was thinking a bad board as well.
 
This potentially can create an unsafe (and scary) scenario when it happens, I had my blower speed on #4 at the time so the auger was just shoveling pellets into the burnpot like there was no tomorrow. My magnetic temp gauge attached to the stove door read 700f after running in this 'stuck' cycle for 40 minutes and the heat radiating off the stove was ridiculous!

I did discuss this with my dealer at the time who assured me that the high temp sensor was working correctly (after testing it) and that eventually it would have tripped and stopped the auger. I might be wrong, but i think the high temp sensor on a Maxx unit is attached to the hopper housing? So does the unit need an actual hopper fire in order to shut off? It would help me sleep better at night knowing that the safety mechanisims in my main heating device are designed to kick in 'before' a fire breaks out, but i am skeptical at this point.

It seems that this has happened with a few other Maxx owners. Design flaw? I don't know, but Sherwood Industries / Enviro should be made aware of this.
 
This potentially can create an unsafe (and scary) scenario when it happens, I had my blower speed on #4 at the time so the auger was just shoveling pellets into the burnpot like there was no tomorrow. My magnetic temp gauge attached to the stove door read 700f after running in this 'stuck' cycle for 40 minutes and the heat radiating off the stove was ridiculous!

I did discuss this with my dealer at the time who assured me that the high temp sensor was working correctly (after testing it) and that eventually it would have tripped and stopped the auger. I might be wrong, but i think the high temp sensor on a Maxx unit is attached to the hopper housing? So does the unit need an actual hopper fire in order to shut off? It would help me sleep better at night knowing that the safety mechanisims in my main heating device are designed to kick in 'before' a fire breaks out, but i am skeptical at this point.

It seems that this has happened with a few other Maxx owners. Design flaw? I don't know, but Sherwood Industries / Enviro should be made aware of this.
This would scare me. Maybe you have to get someone to define "Eventually?" Seven hundred degrees with no blower running seems like it should fulfill that criteria and shut down the auger.
 
The high limit switch on the stove is a 200 degree sensor that 200 degrees would be reached long before there would be any danger of a hopper fire. The temperature on the door is not an accurate measurement of the temperature in the hopper, but if you are worries about a fire there you could put a thermometer there, just be sure it doesn't end up in the auger. Not to disregard the other issues you are having with the stove, but the placement of the high limit switch is not unusual for stove manufacturers.
 
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