Fahrenheit Endurance teardown and cleaning

I had a part to replace in my burn pot assembly, so I figured since I had to tear the whole burnpot out, I'd may as well do my end of season cleaning not long before the season begins again. The Farhrenheit has a self cleaning operation that happens roughly every 10 hours of runtime, depending on the fuel you're burning. One of those parts is the upper burn plate (or 'slicer' as the parts diagram states). That piece extends out and keeps the fire going while the lower burn pot goes through the cleaning process. I did the cleaning a couple weeks ago, but figured now is a good time to put all the steps together.

My furnace is an early model, manual ignition unit. The control board isn't very fancy, but everything you need is there. The newer units that are auto ignition have a LCD screen. This one has red LED lights that are used to control the fuel type, manual or thermostat operation, and also to put it into override mode when the pot needs to come out.

I got the furnace used off Craigslist in January, 2013. The previous owner was using it to heat a large farmhouse, and it spent its first three years running on heat level 5. I very rarely ever go above level 3 unless its brutally cold out.

I'll split this into multiple posts as there will be a lot of pics.



Below is how I left the furnace after last season. Short of putting a plastic tub of Dry Rid in it, this is how it was left when it was shut down in April. I know, I'm a bad pellet burner.



The first step I take is to pull the cleaning rod and knock the crud off the heat exchanger tubes. After that, I remove the baffles that sit right below the heat exchanger tubes. The pic below isn't that great. I dropped my phone into the ash once trying to get a good picture. Anyways, the baffles are removed by pushing up on the rear section of the baffle (closest to the back wall), then lifting the front off a couple small pegs that they rest on. There are two baffles, one on the left and one on the right. You'll get quite the snowstorm of ash once you get them on their way out.




No pics of the next step, which is using a paintbrush to sweep the ash off everything so I can see what I'm up against. The pic below is of the upper burn plate/slicer, or should I say, what is left of it. It was pretty worn out when I got it in January 2013, but as you can see it wasn't getting any better with time.


More to come....

 

Below is the burnpot assembly, minus the top section which sits on the pot frame. I had to remove the entire pot assembly, which entails putting the control board into override mode so the actuators can be manually operated. In the pic below, you'll see that the upper burn plate is extended. Between the pot and the back wall is the actuator arm that connects to the upper burn plate. When it's extended, you can twist your arm and fingers into all sorts of unnatural positions to remove the pin and cotter pin that hold the actuator to the upper burn plate. Beer helps, and make sure you have band aids handy. There are two acorn nuts that hold the pot frame to the back wall. Those come out later.



On the bottom of the burn pot is the "clinker cutter". That is used to help break up any clinkers that form if you're burning corn. I've never burned corn, and I found one of the ears of the clinker cutter in the ash pan, so that won't be going back on. Remove the two acorn nuts on the bottom and remove the clinker cutter.



When the acorn nuts are off, the clinker cutter will drop out of position. Notice there are only two "ears" on mine. There are supposed to be three.



The next step is to retract the actuator arm for the upper burn plate and extend the actuator arm for the lower burn pot. Once that is done, you can again twist your arm into a pretzel and remove the cotter pin and retaining pin that hold the pot to the actuator arm. Once that pin is out, retract the arm, remove the upper acorn nuts, then remove the pot frame from the furnace. It's heavy. Be careful.

Once you've lowered down the burn pot, it comes out through the ash pan opening.

 

Here is what is left of the clinker cutter. Since I'm not burning corn, I'm going to leave it out. It was out when I bought the unit, but I reinstalled it just for the heck of it. I could weld the broken piece back on, and will probably do that in case I ever decide to burn corn again. It can be reinstalled without tearing the whole unit apart.



This is an upside down view of the upper burn pot assembly that sits on top of the pot frame (the pot frame is the whole thing I had to remove). This has the plate that the pellets ride down on their way to the fire as well as the air wash assembly. It was pretty dirty.


Below is the real reason I tore it all apart. The old slicer/upper burn plate was very corroded. The new one is what it is supposed to look like. I ordered the replacement directly from Fahrenheit. $27 plus shipping, and it was at my doorstep in a couple days. Great people to deal with over there.



Since I already went this far, I figured there was no reason not to go whole hog and clean the entire unit. On the left side of the furnace under the control board is an access panel that can be unscrewed. Remove that panel, then you'll have an inspection plate you can pull off to gain access to the left side of the exhaust manifold. Remove those four bolts, and you can get in there and clean it up.



Yep. It was dirty. This was from the 4+ tons I burned last season, and the 1.5 tons or so from the first year I used it. It wasn't as bad as it looks in the picture, but it was pretty plugged up. I used my custom scraping tool (a 3 foot section of leftover 1/2" copper water pipe, hammered down to a flat blade on one end) and scraped the crud out. The ash vac made pretty short work of it.

I should add this - up to this point I had the unit plugged in with the combustion blower running. That helps suck the dust outside and keeps the basement cleaner. God knows no wrath like a woman who sees a coating of ash on things in the house. Especially when that coating is on her side of the basement.

 

Say it ain't so....there's such a thing as a "woman cave"????

 

On the right side of the furnace is a large inspection cover that can be removed to gain access to the combustion blower and the rest of the exhaust manifold assembly. Remove that plate, disconnect the wires from the proof of fire switch, twist your arm to remove the wires from the combustion blower, remove 4 bolts, disconnect the exhaust vent, then remove the whole assembly.

I think the newer units have another plate that can be removed for cleaning without having to pull the whole assembly. DexterDay might be able to confirm that. Either way, this is by far the worst part of the job. I had to disconnect the cold air return and move the furnace a bit to disconnect the horizontal run from the blower assembly.



It wasn't as dirty as I thought it would be inside. Must be the leaf blower helps.




The combustion blower unbolts from the manifold assembly, then the blower can be removed and inspected. It had a bit of crud built up on it.



After cleaning it up, it looked quite a bit better.

 

Spraying a couple of coats of graphite lube on those blower fan blades will help with that build-up.....especially important if it isn't cleaned that often.

 

This was after 60 bags w/ graphite spray on the blades:

 

Since everything is out of the way, its a good time to clean and grease the actuator rods. The grease gets a bit hard and dusty after a season or two. That helps keep things quieter when it does its self clean.



I wiped down the rails that the arms ride on, then put a light coating of grease on them with my finger. I had to move the arms in and out with the control board to get everything lubed up. The bottom one is a PITA, but the upper one isn't bad.




In case anyone is ever looking for the combustion blower specs, here they are:



I hit the entire pot assembly with a wire wheel and cleaned out the holes in the lower pot and the upper pot assembly. The upper holes I'd blocked off with furnace cement when I first got the unit were still plugged (thanks for that tip Dex). That helps direct more air through the bottom of the pot. I gave it a shot of high temp paint when I was done (just because I had it). It looks a lot better now.



To paraphrase the Chiltons auto repair manual: Assembly is the reverse of removal. Retract the rods, put the pot frame on the upper studs, put the acorn nuts on to keep it in place, connect the actuator rod to the lower pot assembly, then the upper pot assembly, then tighten up all four acorn nuts. Below is the reassembled burn pot.

I still need to finish up a few things before the cold really sets in. The ash pan gasket needs replacement, and I need to run the soot eater through the 4" venting. I hope to get that done next week. Time will tell....





Edit: Total cost: $57 and change for the upper burn plate, new gaskets, shipping and MI sales tax. Four band aids, a bit of leftover high temp black and silver paint, some high temp RTV that was left over, approximately three large handfuls of Gojo hand soap, three hours of time and four beers.

 

The finished side of the basement used to be a family room. She runs a business out of the house, and she outgrew the spare bedroom. Half of the basement is set up with sewing machines, embroidery machines, cutting tables, you name it. She brings home a fair amount of bacon, so I was more than happy to let her have it. As part of the deal, I got a pole building. Fair trade....

 

I thought about it, but it was a crappy, rainy day and I didn't feel like going to the store. I had some high temp silver paint left over, so I gave it a quick shot of that. Probably won't make any difference, but it looked nice.

 

Good break down of the unit. I noticed my cutting plate is starting to wear out too. I used white grease on my actuators and replaced my cotter pins with stainless steel wheel bearing cotter pins(hope it works).

 

When I called Fahrenheit to order the parts, I talked to Mark Graham (the head engineer at Fahrenehit), he emailed me the parts diagram so I could identify what version pot I have , and he warned me that the unit I have is a bit difficult to get apart. They made changes in the second run so they come apart easier.

I tried doubling up on the ash pan gasket when I first got the unit, but then I can't latch the ash pan into place. Mine has two small keys on the pan, one on the top and one on the bottom. There isn't a whole lot of room there for a thicker gasket. It seals good once you get it latched, but the bottom one is a bit finicky.

I need to check the door gasket (I thought it wasn't as tight as it should be last season) and also empty out what's left in the hopper and vacuum out the fines. Once that and the venting is cleaned, I should be ready for a test fire.

 

One other difference I just remembered. Only the auto ignition units have a sail switch. The manual ignition units have a thin silicone 'flap' for lack of a better word where the sail switch would be located (right behind the air intake tube), but there aren't any wires that go to it. I believe the sail switch is used to tell the control board on the newer units that there is air flow through the unit. Mine has a vacuum switch, not sure if the newer units have that or if the sail switch replaced it.

 

Wow. Wasn't expecting that. My only hope was that the info would help someone out someday.

 

I didn't see a plate on mine. I did notice that the gasket opening was a lot smaller than the opening in the manifold, and the overhanging gasket was getting caked with ash. I trimmed up the new gasket before I reassembled it so it was the same diameter as the opening. Not sure if that will make much difference, but I figured why not.

That impeller looks like it would move a bit of air. I have the damper on my intake wide open. Let me know how it works for you.

I forgot to mention that I plugged up the three big slots in the burn pot where the clinker cutter would normally pass through. I figure that might help oil more air through the bottom of the pot instead of through the back of it.

I'm starting to get a bit of a trigger finger and wanting to fire it up, but it's nowhere near cold enough out yet.