Is there a better replacement for the Empress convection motor...?

[steamguy]

I have an Enviro Empress that's 6-1/2 years old, and it's going on its fourth convection motor. Yep, fourth. The first was replaced under warranty, the second about a year and a half later, the third, two years ago. Looks like they seem to last about two to two and a half years.

This stove isn't abused; it burns about a ton, maybe a little more, a year, and is thoroughly cleaned and all appropriate points properly lubricated every year, with the proper oils. When I pull the convection motors, the bearings are quiet, and run quietly when spun. (Believe me, that's the first thing I check!) So the problem is an electrical one:

What happens with the convection motors is one of the windings quits, and the motor will sit and hum and not start. You can go over to the stove and cycle the (very limited) control all the way through 5, and about the time it gets to 5, the control board will give the motor enough voltage to get it to start and then the motor will run reliably (and quietly) until shutdown.

I'm going to pull the stove this summer and give it a good going-through, at which time I'll replace that blower motor <sigh> again.

So I'm ready to do a little re-engineering on the stove. Does anyone have a good idea as to a good replacement part number for that Fasco blower motor - that won't fail in two years? I mean, really... $200 every couple years...?

Thanks...!

 

[Don2222]

Hello

See my PC - Private Conversation.

 

[smwilliamson]

You sir have a bad control board and its burnin out your motors.

 

[Don2222]

You sir have a bad control board and its burnin out your motors.

Hello

There may be more to it than just a bad control panel. The control panel switches AC voltages to the convection blower through a Triac by biasing the base of the Triac with smaller DC voltages. Basically it acts like a switching relay except the Triac can reduce the 120 vac to lower voltages to reduce the speed of the convection blower when turning it down to lower speeds. Therefore it is unlikely that the control board is burning up the convection fan motor. However the control panel cannot control the AC voltage or current coming into it from the wall outlet. I suggest that you check your wall outlet voltage and maybe put a surge protector or even one of the more expensive line filter that you find on very expensive home theater systems. Most pellet stoves do not take more than 10 amps so 120 vac 10 amp line filter would be sufficient.

 

[smwilliamson]

The trial is modifying the wave and is sending it out of phase causing the motor to overheat, most likely. Somewhat common

 

[steamguy]

...check your wall outlet voltage and maybe put a surge protector or even one of the more expensive line filter that you find on very expensive home theater systems. Most pellet stoves do not take more than 10 amps so 120 vac 10 amp line filter would be sufficient.

Wall power is correct; line voltage at the mains on the (very expensive) surge suppressor is 114 VAC, no DC component, so we're good there. I had an Austroflamm before and the outfit where we purchased it cautioned me that the #1 killer of stoves is surges...

The out-of-phase thing is a possibility; thanks for the lead. I'll put a scope on the output to the motor when I pull the whole thing out in a couple months for a full teardown. $400 is an awful lot to just throw at it as a possible fix.

 

[smwilliamson]

Let us know

 

[steamguy]

The status of things right now:

Well, I'm getting a used blower motor and will keep the one I pull out. I'm going to take it to a local guy who has an electric motor shop and have him look at it.

I'm also giving up on the control board - Enviro doesn't make the control board for this stove anymore, but instead has a unit-replacement. Likely they've realized there's a serious problem.

Addressing the Triac output from an electronics standpoint: it appears that the Triac is controlled through the microcontroller (MCU) that runs all the stove's functions. That MCU should be programmed to pick the proper point on the AC waveform to send turn-on pulses to the Triac; it uses a time-sliced version of the AC waveform to decide when to turn the Triac on and off. If that time-slice is corrupted or programmed incorrectly (which is what I'm beginning to suspect) then the Triac gets turn-on pulses at the wrong time, and they will be mis-timed. The problem isn't the Triac; it's the MCU itself.

Let me be of other service here also: the connected surge suppressor is a Tripp-Lite; I've used them in the past on very expensive video equipment and have never had to have them make good on their guarantee. They are one of the few manufacturers that guarantees connected equipment. You'll fry the surge suppressor (a $90 replacement) before you fry a $90,000 video editing system.

 

[smwilliamson]

The MCU controls the triac and the triac controls the signal and the signal controls the motor.....yeah we got that. So you are not going to buy another board?

 

[steamguy]

I have the upgraded board on order. It's the cost of two motors, what I'd spend in another half-dozen years with this stove.

Are you interested in looking at the motor-control waveform or not? If not, I won't bother with putting a scope on it.

 

[smwilliamson]

No just wanted to make sure you got a new board before you connected another motor.

 

[smwilliamson]

What do you have for a scope?

 

[dhall28]

Are you interested in looking at the motor-control waveform or not? If not, I won't bother with putting a scope on it

personally i'd be very interested in seeing the waveforms from a scope. i always assumed it was some small resisters that just took a little voltage out reducing the rpm, i never knew they did all that with the triacs.

 

[steamguy]

What do you have for a scope?

I have a cheap Leader for "everyday" work (or for whenever I need a scope - which isn't too often anymore) and a Tek 2467B for anything that requires serious horsepower.

Used to do broadcast video repair, but don't do that anymore. Lots of the test gear got sold while it was still of value. Couldn't bear to part with the scopes, though...

 

[steamguy]

Okay, we're back with an update.

First, I wanted to wait until we had a week or so of operation time before I posted,

"FIXED!"

I've had the control board sitting and ready to go all summer, and knowing that the stove had to come ALL the way out for fixes made me wait until the weather moderated. It's been so blasted hot (for our part of the country!) all summer that the idea of sweating (more) over the stove just wasn't one that motivated me to action. I also needed my nephew's help to get the stove pulled, and he hadn't been available.

Here's what I needed to do:

1. Replace the wire and connectors for the combustion blower. The stuff had been overheated and was cooked.
2. Replace the convection blower, it was making noise like it had a bad winding
3. Replace the controller board along with its daughter board, they were suspect in killing the blower motors
4. Clean and oil everything that moves on the stove
5. Annual cleaning teardown for the stove

• I got some high temperature wire from the hardware store - rated to 2100°, along with connectors rated for that temperature. Replaced all damaged wire in the back of the stove. Soldered with silver solder, and insulated with heat-shrink.
• Pulled and replaced the control board. Surprise, surprise: there was a scorched spot under one of the triacs. No schematic for the board, so based on the wire routing it's the one for the convection blower. No surprise, again...
• Pulled the convection blower. Cleaned it out (see next item) and gave it a spin. No noise from the bearings (even with my ear right against it), so I think it's still OK. Cleaned the convection passages, and now all looks pretty good. That particular motor was just replaced only a short while ago, and based on the look of the control board, I'm going to chance it and leave it reinstalled. There's a really good chance that all that noise was due to the bad control board.
• I had a guy out last year to do the cleaning and service on the stove, because we had a coupon from the outfit, and I hadn't had time to do the work. But now I open everything up and find that the guy did a terrible job of resealing all the exhaust-side joints. I had to clean EVERYTHING on and around the stove, inside the firebox and behind the trim (this is an insert) thoroughly because it all had a good coating of ash from the stove. Great - so all this time the carbon monoxide levels in the house were probably elevated because of that guy's incompetence.

BUT!

There is a VERY happy set of results to all this:

• The stove is WAY quieter!! I mean, WAY quieter. This stove was ALWAYS noisy, ALWAYS humming and rattling: sheet metal clattering, front doors rattling; and on higher output levels you had to really turn up the sound system. We always thought it was design or construction flaws in the stove. It turns out that we had several vibration 'modes' or 'nodes' caused by the blower motors not being driven correctly. Now the stove is really quiet - it is a 'hold a conversation' kind of quiet.
• The heat output is FAR better. I mean, when set to its lowest, it's heating about as good as it used to when you had it on level 3 of 5.
• Looking forward to it being up to the task of heating the house this winter. Finally. Just in time for a really cold howler of a winter, too!

Thanks to all the folks here, and thanks to our experts, especially Don, for all the help.

 

[Bioburner]

Nothing like the feeling of doing and getting the job done right yourself!

 

[Don2222]

Good Job Steamguy!

Nice writeup of the issue too!

 

[stovelark]

Hey steamguy- glad you got your issue fixed. 4-5 years back Enviro had a bad bunch of Motherboard triacs that made the voltage supplied to the convex blower unstable, creating a "warble effect" (the blower always sounded noisy, and seemed to indicate a bad convex blower). After going to a customer's house for another noisy blower, I checked the operation of the convex blower with a separate ac line with rheostat, and deduced the problem was in the MB's voltage delivery. That fixed the problem. It showed up on other Empresses of the 2008/09 years, Enviro changed the board's design, no more warblers. I'm sure there is a lot out there still. The new multi fused for each load MBs work very well and the current Empress is generally a very quiet stove. Its still one of my favorite pellet stoves. No stove is perfect. I've heard SMW inform plenty of people here about bad triacs for the MBs, good going Scott. One stove at a time, its all one can do. Good luck to all.

 

[Keifer2669]

Hey guys. I was just reading all the posts here on this convo. I'm having empress convection fan probably myself. Got me thinking it's the control board. If you can read my recent post and give me opinions on the prob that would be greatly appreciated.

 

[steamguy]

Hey guys. I was just reading all the posts here on this convo. I'm having empress convection fan probably myself. Got me thinking it's the control board. If you can read my recent post and give me opinions on the prob that would be greatly appreciated.

Saw it and replied.
Hope it helps you out.

 

[smwilliamson]

thank you very much...i get them wrong sometimes too!

 

[Lfdp13RET]

Ok how about the damn sheet metal rattle? Sounds like the insert, can the stove run without it?

 

[Don2222]

Ok how about the damn sheet metal rattle? Sounds like the insert, can the stove run without it?

I fixed an Empress with a very bad rattle from the convection blower. The screws holding the blower to the bracket are too small for the weight of the blower and easily strip! Just remove the blower and put in larger screws. This is a permanent fix!