Hello.
Been looking all over the internet to talk with a fellow Alterna ll owner. Of course only because I have a huge issue.
I am sorry I couldn't have found you sooner, I too experienced a similar issue. Think its been the beginning of my now bigger issue.
Mine is a 2018. Its been a trooper for the most part. Used as my main source of heat. I have had a few minor things, I consider consumables. My big Issue started with a cavitation in feed auger like yours, I found the main carrier bearings on that auger had seized, the auger ran like this for awhile and wore the shaft area, allowing for slop. til it stopped working all together. When I then disassembled it , the rotary gate valve gear motor stripped a gear. I assume because it loaded up and jammed because lower auger wasn't pushing any through. Of course I may have been a contributor, as before disassembly, I noticed motor was not turning, I applied a small pry tool to casing to push through what I thought was a pellet jam and snap.
From this point its been a nightmare. I replaced feed auger, new bearings put a new gear motor to rotary gate valve. All ordered from ISB for my furnace. When it would start up from this point , its first two ignition cycles, the rotary gate valve would jam up and starve the feed auger causing a missed ignition cycle. If I put pellets in the burn pot, and started up it would trick the system and go to a full run cycle. This is where things do not make sense. As long as the furnace demanded heat, and didn't go to a stand by mode, and go to its start cycle, the furnace would work. Unfortunatley The rotary gate valve gear motor was under heavy load and I have blown 2 gear motors so far, funny it never blew a fuse under these loads.
I discovered here that the rotary valve was really turning hard, I removed the rotary valve and bench tested the physical load to turn with a torque wrench, it was past the starting torque rating of 120 inch/lbs of torque the motor supplies. But once motor gets nominal load it reaches 150 inch/lbs which might explain the reason it works after ignition. I then contacted and ordered the replacement ISB part. It has been replaced with an Avery Gleason Model number (902.4)2516-A07261-1444 which is their recommended replacement as they told me they no longer stock the original Merkle-Koreff model number B4415/4415UI . After this I thought maybe there was too much slack in my original Rotary gate valve, so replaced bushings first! The cheaper option. Yeh that made no difference, so ordered new rotary gate valve, ouch! put it in and still no difference, accept this is where I blow another gear motor. It took a week this time. And that's where I am at. Frustrated and unhappy. All through this I have been in contact with ISB's tech, and not getting any answers. So far lots of reciepts for parts, but no answers. I might be a Tim The tool Man Taylor here, but feel the Gate valve motor is to weak and needs more power!! And stamina. I have disassembled the gear motors and there are differences in Gear components, and electric motor windings. The merkle seems a bit beefier and robust. Also couldn't find torque specs. No way to find out now as I can't seem to find a Merkle original replacement. I do know they are both 2.4 rpm
Sorry for the detailed story to date, excited to find a fellow Alterna owner, just putting it all out there if someone else is experiencing the same or has insight maybe we need a dedicated site we could share. I do love the furnace for its last five years of service its been great, super warm and comfy. Don't want to bail on it as I think its really in the gear motor being the issue.
I will mention that one of the first go too's from the tech was the pellets. I have burning the same supplier for 5 years (Shaw Premium) and really not much selection in this area for suppliers, I have been running these in my Pel Pro in the shop no issues. Besides the rotary gate valve is built solid, and looks like it could shred small branches.
I guess I should ask if you have resolved your issue? Hope nothing like mine.
Cheers
Pictures of damaged gear motors, and auger shaft.
photos.app.goo.gl
