Merkle-Korff auger motor on Englander 25-EPI keeps burning out

[SmokeyPete]

Hi guys, I'm new to the forum but considering how long I have been aggravating over this issue I feel like veteran.

I bought a used England Stove Works 25-EPI 2 years back as a "project" for $100.
It had some rust so I refurbished the unit with lots of sanding and a few cans of stove paint.
When I first powered it on it ran for about two hours then started popping the 6A fuses.
I got frustrated and went back to oil for the rest of the winter.

This winter I purchased what looked like a very legitimate (though strangely inexpensive) $50 replacement unit on ebay (Merkle brand) and to play it safe, I wired a 4A fuse directly inline with the auger motor itself. The seller has over 16,000 five star feedback on e-bay so I consider them to be a large and honest liquidator that is selling below market price. Merkle Koriff Model B4415 / 4415UI CU-047042 115v Gearmotor

This new motor popped the 4A fuses and I have noticed that the white label and winding on the transformer itself on the Merkle are also getting brown and then smoking the transformer. I disassembled both gearboxes to look for broken gears or lack of lubrication and they both seem perfect.

I did question if these are legit products I am buying but based on the picture and what I have received they seem like perfect OEM replacements.
They are cheap ($50.00) but again, they look perfectly legit. At this point I am not my 3rd auger motor assembly and I have not had more than 6 hours total of heat.

I just picked a bulk package of 5*20 size 1A 250v fuses in hopes that a value that low will save the transformer/motor that moves the auger l since I am beginning to feel guilty since I seem to be becoming the king of RMAs. I will have this fuse sitting in a fuse holder that is inline with the yellow or black wires that go from the control box to the auger motor.

I stuck an inspection mirror down the tube that the auger sits in and I see zero metal burrs or other obstructions. I am missing the ceramic cerra firebrick which I understand does somewhat protect the unit from overheating but for now the unit sits out from the fireplace for troubleshooting so I find it hard to believe parts are warping or affecting the motor that basically sits outside the unit.

Seeing the 0.40A rating on the auger motor itself, is this 1A amp fuse value adequate to protect the transformer or would you suggest a lower value fuse?
I have also checked all the other wires for shorts and found nothing. I have ran and additional ground from the control box to the stove body and verified continuity.

 

[Ssyko]

Hi Pete welcome to the forums.. More than likely what is happening is there is a leaky Triac on your control board that is feeding the auger motor a very low voltage when it is in the OFF section of the cycle, which in turn heats the coil of the motor and over a period of time it will melt down the winding's in the coil. that's when the motor fails and the fuse blows. with your auger motor un hooked take a digital multimeter and check the voltage of the 2 wires that go to the auger. "be careful you are dealing with line voltage" you will see 115-120vac during the "ON" feed and 1- 40vac during the "OFF" feed. if you get any voltage reading when the auger is not supposed to be running your board needs repair or replacement

 

[SmokeyPete]

Hi Pete welcome to the forums.. More than likely what is happening is there is a leaky Triac on your control board that is feeding the auger motor a very low voltage when it is in the OFF section of the cycle, which in turn heats the coil of the motor and over a period of time it will melt down the winding's in the coil. that's when the motor fails and the fuse blows. with your auger motor un hooked take a digital multimeter and check the voltage of the 2 wires that go to the auger. "be careful you are dealing with line voltage" you will see 115-120vac during the "ON" feed and 1- 40vac during the "OFF" feed. if you get any voltage reading when the auger is not supposed to be running your board needs repair or replacement

Thanks Ssyko,

Sounds like you know your stuff. I checked and I seem to have about five BTA12-600BW Triac components on the controller. At this point the leads to the auger are not even showing voltage. I'm guessing that maybe the triodes were on their way out and decided to die when they saw your post.

Since the shipping cost will be more than the actual components, and since I'll need to pull out the board to do a good bit of soldering might you suggest I order any other components for this repair or future repairs? I don't own an Oscilloscope, only a clamp multi-meter without diode check so being a little proactive seems wise.

 

[Ssyko]

You can see the traces at least on the englander boards. I believe its the second triac from the fuse is the upper auger. Lower is the 3rd. The opto’s may have been damaged also. You will need a dmm with diode test to ck the opto’s. The biggest problem ive had with those boards is if it is a large enough short or amp spike it will wreck the eprom. Lets hope that is not your case

 

[SmokeyPete]

The 25-EPI only has one auger.
I assume the self test will still turn that auger though.

I have attached the main picture of the board. Visually it's near perfect except for dust.
The red in the corner is sharpie, not blood so don't be horrified!

Here is my little shopping list so far.
I'm not a Lite-On fan but the part number was closest to what the original Fairchild Semiconductor markings had.

1​	511-BTA12-600BW​	BTA12-600BWRG​	STMicroelectronics​	​	Triacs 12 Amp 600 Volt​
2​	838-3FS-316​	3FS-316​	Tamura​	​	Power Transformers POWER TRANSFORMER​
3​	859-MOC3021​	MOC3021​	Lite-On​	​	Triac & SCR Output Optocouplers Optocoupler TRIAC​
4​	647-UKL1E101KPD1TA​	UKL1E101KPD1TA​	Nichicon​	​	Aluminum Electrolytic Capacitors - Radial Leaded 25V 100uF 10% Low Leakage​
5​	647-UVR1E102MPD​	UVR1E102MPD​	Nichicon​	​	Aluminum Electrolytic Capacitors - Radial Leaded 25volts 1000uF 10x20 20% 5LS​

 

[Ssyko]

yes, the one problem child i still have on my bench, would test all components but still fail in normal operation. but the membrane pad is bad and you can't buy them unfortunately. I tinker with it till frustration then leave it for a while lol. i have had decent luck with the lite on (cross fingers). You thinik the caps are bad or just changing for the cause?

 

[SmokeyPete]

just changing for the cause.
Since Radio Shack is dead and gone it would be nice to have stuff on hand.
I'll let everyone know what happens.

 

[Ssyko]

oh every order i place on mouser or digikey i buy in bulk 10-100ea

 

[ericofmaine]

One thing I did when one of my opto's pooped out was to, after carefully removing it to preserve the solder pads, to solder a ZIF socket on the board in case I ever had to replace it again.

Eric

 

[bill3rail]

Every reply so far is suggesting you inspect the board.

Have you;
A) Removed the auger and totally cleaned the tube to ensure there is no resistance?
B) Realigned to auger to ensure no drag?

Bill

See also:
GA Versus MK Auger motors

 

[SmokeyPete]

Hey guys,

Final wrap up.
I bought a Gleason Avery (GA) to replace my MK auger motor for $100. I additionally spent about $80 on a new soldering iron, board holder, suction tool, magnifier, etc, etc. I then attempted to desolder all of the big black Triacs on the board. Three hours later I had the board reassembled, big blotches of solder, one cracked trace which made me end up having to solder the Triac in from the other side. Like watching This Old House, the videos make it look 10x easier than real life. Lol.

I plugged the board back in, no fireworks but also the board functioned no better than before. I ended up finding a used board out of state on Craigslist. I ended up paying $95. I examined both boards since my Stove was a 25-EPI and the donor unit was from a 25-PDVC. I noticed one jumper for "VAC Bypass" that was on my original broken 25-EPI board but not on the replacement board from the 25-PDVC so I swapped it over.

I crossed my fingers, fired it up and I'm happy to report that about 15-20 bags of Pellets later my house is cozy and warm for my first Central Massachusetts oil-free winter.

 

[Smokinbubba]

Nice work. You lost this dumb civil servant at triac.... either way, you will be happy with the ga motor. They are highly recommended here and i am running one with zero issues.