Guess what? Last night the combustion (exhaust) fan died again, with the "other" control box in. I heard a noise, not sure what it was, I then smelled smoke. Ran to the stove, found the fan just barely turning. Unplug the stove, plug it right back in, and just like before, it takes right off. Anyone got a guess now?? Convection fan was running fine, so not an incoming power problem. I don't understand that I remove power and reapply and everything is fine. Motor spins fine, has been running now for the last 10+ hours fine....
QuadraFire convection fan
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SmokeyTheBear
Minister of Fire
B-Mod said:
The thermals on the motor have enough time to cool before you re power the blower so it works.
They tend to thermal off at around 475 degrees or so.
If the impeller blades, cooling fan blades, the area between the impeller and mounting plate, or motor housing is crudded over this can happen.
Also if the cavity has a lot of ash in it, the vent has a lot of ash in it, the venting is not proper for the EVL, or the venting is positioned so that the wind can enter.
Failing motor bearings can also cause this to happen.
I agree with SmokeyTheBear. When you first posted about this I wrote about checking the exh motor because it sounded like the problem to me. It sounded like the bearings or something else internal. When the motor starts turning slow and you unplug the unit from the wall, is there anyway to manually spin the fan blade to see if it is binding? The other thing is putting a voltmeter on the wires to the fan and see if it drops when the fan slows down. If it doesn't drop, then put the meter in-line to measure current. If the motor slows down and the current jumps up then the motor is binding up.
EDIT: The Fasco blower fan in my CB1200 has bushings that I oil. The Fasco comb. fan feels like it has sealed bearings. I have never taken it apart. One thing about sealed bearings is that they are made with grease in them so using oil destroys the grease and makes it worse. I replace the bearings with good quality bearings to keep the noise down when I fix anything with bearings around the house. That is C3 or better quality. I feel it is worth the extra cost.
EDIT: The Fasco blower fan in my CB1200 has bushings that I oil. The Fasco comb. fan feels like it has sealed bearings. I have never taken it apart. One thing about sealed bearings is that they are made with grease in them so using oil destroys the grease and makes it worse. I replace the bearings with good quality bearings to keep the noise down when I fix anything with bearings around the house. That is C3 or better quality. I feel it is worth the extra cost.
Motor is brand new, around a months use tops. Just cleaned the stove a few days ago, very clean. No binding in fan, fan spins free as can be. When the motor is spinning real slow like that, I can spin it by hand easily, no roughness. When I find it turning real slow like that, it could be just the hot exhaust turning it??? Intermittent problems are the worst to fix. I have to be quick as smoke is coming in the house. Exhaust is only 3 foot pipe straight out the back of the stove, no wind at all last night.
Also, stove is running on low, turned it up to medium an hour ago. Just checked fan, electric coil on fan, 72 degrees, large metal core around fan motor, 80 degrees. Barely warm to the touch. I am scratching my head........
Well, that changes things a lot. Since the motor is new then it is highly probable to be good. Since you have the smoke problem then the first thing I would do is make up a cord that I could plug directly into the motor connector. That is, if the motor stops then unplug the unit from the wall and then unplug the exh motor, and then plug in the new cord to the motor providing 115 vac. That way you can get the smoke out. I go a little over board on ventilation......I hate smoke in the house.
I would take a hard look at the motor to wiring harness connector terminals. I would keep a voltmeter attached to the terminals on the motor side so you can watch if the vac voltage to the motor stops when the motor stops. If the voltage stops then it could be the wiring harness / connectors / control box. This is why I said make a cord to clear the smoke because now you have to test at the control box terminals and do it all over again. You could also try wiggling around the connectors and harness while the unit is working to speed up finding the fault. It still could be the control box but I would try to rule out the harness and connectors first.
I would take a hard look at the motor to wiring harness connector terminals. I would keep a voltmeter attached to the terminals on the motor side so you can watch if the vac voltage to the motor stops when the motor stops. If the voltage stops then it could be the wiring harness / connectors / control box. This is why I said make a cord to clear the smoke because now you have to test at the control box terminals and do it all over again. You could also try wiggling around the connectors and harness while the unit is working to speed up finding the fault. It still could be the control box but I would try to rule out the harness and connectors first.
I read your original post again. It sounds like the extra motor cord is not needed because it runs the exh fan once the power is reset.
It kind of sounds like a failing part in the control box that is sensitive to incoming line voltage. Do you have a power strip that you could power the unit from? I would try that first. I would still check the harness for rubbing / damaged wiring and also the connector terminals.
EDIT: Post if the exh fans stops on medium. I am wondering if the motor current is right on the border of not being enough for the TRIAC holding current when it is on low. Or it could be the optoisolator is not triggering the TRIAC.
You could get the parts as free samples from fairchildsemi.com. They make those flavors of optoisolator and triacs. You can get up to 10 free samples of each so you could replace them all. Are the triacs part number Q6004 and the optoisolators part number MOC 3020?
It kind of sounds like a failing part in the control box that is sensitive to incoming line voltage. Do you have a power strip that you could power the unit from? I would try that first. I would still check the harness for rubbing / damaged wiring and also the connector terminals.
EDIT: Post if the exh fans stops on medium. I am wondering if the motor current is right on the border of not being enough for the TRIAC holding current when it is on low. Or it could be the optoisolator is not triggering the TRIAC.
You could get the parts as free samples from fairchildsemi.com. They make those flavors of optoisolator and triacs. You can get up to 10 free samples of each so you could replace them all. Are the triacs part number Q6004 and the optoisolators part number MOC 3020?
SmokeyTheBear
Minister of Fire
B-Mod said:
Just so you know motors/blowers have been known to be DOA for all intents and purposes. I had a blown bearing on my exhaust blower in fact of all but one of the problems I had in the beginning a "insert well known previously mentioned in this thread name here" blower was in the loop somewhere.
However loose connections can cause all kinds of "issues". Including messing up the controller if they persist.
Something tells me it is in wiring of the stove, but I don't see anything bad. Doubt the motor, and I have two control boxes, and it did it on both now. Funny all I do is unplug and plug it back in that quick and it takes back off. Convection fan is running fine the whole time. I will shut it down this afternoon and dig into it deeper. Thanks for the idea on the temp cord to get the fan going. I was trying to think of a way to test it, and get the smoke out............
B-Mod said:
You could put a fan dimmer rotary controller on the new cord for the exh if you want to run the exh on "medium speed" or there abouts.
Here are the most like problems;
1) bad connection at motor connector (white plastic)........are the pins pushed in all the way / seated?......I ask because the motor was just replaced...did the problem start then? Take a good look at this as the pins can pop out and be barely touching in the plastic connector.
2) bad connection at the control module
3) new motor bad connection inside the motor.......did the problem start with this new motor?
3) wiring cracked / rubbing
4) incoming line voltage spikes and marginal exh fan part in control box
I know new does not mean it can't fail, lol. After it running for 11+ hours you think it would show up again. When it went down last night, it had been on for about 6 hours. I just wish whatever it was would quit and then I can find it easier, lol............
SmokeyTheBear
Minister of Fire
Wiring problems can be totally unseen.
You might want to make sure that the motors have good grounds and that if they have quick disconnect leads that they have to be forcefully inserted into the receiving connector and are free of any oxidation.
You might want to make sure that the motors have good grounds and that if they have quick disconnect leads that they have to be forcefully inserted into the receiving connector and are free of any oxidation.
Old fan was dieing, was original. Finally died one day. Installed new motor about a month or so ago, everything fine for weeks, till this past Saturday night. Stove died middle of the night. Found it in the am. Stove burn pot had corn in it, unburnt, as the stove must have shut down, then tried to restart, but couldn't as it won't fire on straight corn, and for sure not with a big clinker in it. The other two times now, I happen to catch it, right after it happens...........
Thinking out loud here for testing.
1) if you want to run on medium speed then make cord with a fan dimmer switch to run the exh medium speed. Connect this to the exh motor
2) connect original control box wiring to exh motor to a light bulb instead to monitor what the exh motor would have done during operation. A spare motor would be better than the light bulb because the bulb doesn't have the inductance the motor would.
3) run the unit and check if the light bulb goes out OR run the unit and move the wiring harness to look for intermittent problem
4) If the light never goes out then the problem is probably in the white motor connector, if the motor stops with the new cord then the problem is in the motor
1) if you want to run on medium speed then make cord with a fan dimmer switch to run the exh medium speed. Connect this to the exh motor
2) connect original control box wiring to exh motor to a light bulb instead to monitor what the exh motor would have done during operation. A spare motor would be better than the light bulb because the bulb doesn't have the inductance the motor would.
3) run the unit and check if the light bulb goes out OR run the unit and move the wiring harness to look for intermittent problem
4) If the light never goes out then the problem is probably in the white motor connector, if the motor stops with the new cord then the problem is in the motor
Ok, just did it again. This time was a little different. When I run my stove I just set stat on max (always on) as I am burning straight corn. I went to shut stove down, turned stat all the way down. Walked out in the garage, brought in some corn, and looked and fan was turning slow. Un hooked motor and hooked up fluke meter. 40vac. turned stat back on, still 40vac. Plugged in motor and it took off. The slow turning is the motor going slow, no power=no fan turning. Took some v readings at fan, low=40v, med=38.5v, high=122v. These are with fan disconnected. No loose wires or connection, wires come out of motor, no connections on motor. Wiggled everything, no drop outs. Aurgggggg......
B-Mod said:
And you unplugged the wiring harness to exh motor connector and looked a the male & female pins to make sure they are fully seated?
Where exactly did you take the voltage measurement? Before or after the white motor connector?
Did you try giving the motor a swift hit with a wooden handle while it was turning slow to see if maybe it is an internal connection?
Do you have a power strip that you could put on the input power?
Next time it happens I would try to measure the voltage on the motor side of the connector with the connector plugged in. You can probe from the wire side. Then I would probe at the control box. The problem with disconnecting is that you haven't said you looked into the connector to verify the pins are in good shape and full seated. By design they mate trying to push each other out of the connector to make a firm connection. If the retainer legs bend then the connection becomes bad.
If the connector seems fine and you probe at the motor side when it fails again and the voltage is bad then it points to the control box. I know it sounds odd that both do it but if the above checks out then that is all I can think of. At that point I would order the free samples from Fairchild and you would have them with their 2 day shipping.
EDIT: Is that a typo for low=40 vac med=38.5 vac? Was med actually higher or lower than low?
SmokeyTheBear
Minister of Fire
B-Mod said:
I'd have expected the medium to have a higher, not lower voltage. What's up with that?
SmokeyTheBear said:
I agree. When I was watching the speed of my exh fan on low/med/high the speed seems to double roughly. I would have expect around 35vac, 70vac, 120vac respectively.
Ok, I can make the issue happen all the time now, apply power and take it away, a few time and it happens. Doesn't matter if it is at the motor or at the receptical that I remove power at, it does it at both. Really weird. If I measure at wires feeding motor, with no motor, I get 40vac, now connect motor and stick probes in connector, motor running, I get 114vac. I forgot to do mediums voltage but it does spin just 100 rpm faster. I am going to see if I have a motor speed controller here and see if I can get the motor to do this hooked up to a speed controller.
The weird voltage reading must have something to do with the type of speed controller in the quad brain box that is fooling my fluke digital meter?
B-Mod said:
Actual no. It is the nature of a triac. It needs a minimum holding current which the motor provides, but your meter doesn't. That is why the voltage is lower with the meter.......the triac isn't staying on. You need to make the measurement with the motor connected or another "like" load.
Did you tap the motor when it is running slow?
B-Mod said:
Not really weird if a triac is failing. The change in voltage (on/off) could be triggering a failure mode. Usually they fail off. I mentioned a power strip and voltage spikes earlier.........you are essentially doing a modified test of that and it is failing that test. I was thinking over a period of 24hrs you are getting random voltage spikes which is normal for wall vac.......but a failing triac wouldn't deal with it.
SmokeyTheBear
Minister of Fire
Motor is fine, starts right up when powered up by a fan speed controller set at the same RPM as stove in low, which is 2175 RPM. I lowered it to about 1900 RPM and still started fine. I wired a bathroom exhaust fan into the stove it started every time, but it started at full speed as best I could tell, no matter what the stove was set on, as it is a different type of motor and size. I have a UPS I can plug into the stove, the batteries are shot, but it would clean up the power? What do you think? Hard to imagine both boxes have bad triac's, maybe they just are not quite in spec, with the fan?.........
SmokeyTheBear said:
Living room recpts. but nothing is on that circuit, newer house 10 years old......
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