Combustion fan cycles after ignition cycle ends

[Jjirishnh]

Hi I'm new to this forum, and have a Pelpro CC1 pellet stove that is acting up. The stove seems to work fine through the ignite cycle. The igniter glows, the combustion fan runs constantly drawing air through the burn pot, and I get a good flame in the burn pot. When the ignition light on the controller goes out and the unit is running in normal operating mode the combusts fan starts to cycle. Either on to off, or fast to slow it's hard to tell. Regardless the flame in the burn goes high when the fan is running and almost goes to a smolder when it's not running.

I've had problems with the controller and have had it replaced since it was under warranty. I also had to replace the auger assembly including the auger motor because the shaft broke.

I'm thinking there is a problem now with the vacuum switch? The other possibility is that when I replaced the auger motor assembly I didn't get a good seal on everything with the RTV silicone. Any thoughts on this would be helpful.

I am an electrician by trade and have the ability to do some troubleshooting, but have no schematic to go by.

 

[Harvey Schneider]

The vacuum switch usually controls pellet feed. No vacuum no fuel.
I think it more likely that you have either a temperature sensor failure or a limit switch failure.

 

[pell it]

Does it happen on all heat level settings?

 

[Jjirishnh]

Does it happen on all heat level settings?

Yes it happens at all heat settings

 

[tjnamtiw]

I seem to remember this symptom coming up not too long ago. You might want to do some creative searching on here. I'm not sure it was a Pelpro but maybe another brand that uses the same/similar controller. Harvey's right. The vacuum switch depends on the combustion blower. Not the other way around. I would be looking for a bad/poorly seated/corroded snap disk. My stoves have a thermocouple to sense the temperature but yours might have a sensor on the exhaust tubing.

http://www.pelprostoves.com/Troubleshooting/Manuals.aspx

''Upon starting the appliance, the AcuTron control board has a 15 minute “Lighting Mode”, if the stove
exhaust does not reach 120° F in that 15 minutes the stove will shut off. As soon as the stove
exhaust does reach 120° F, the limit switch opens and the AcuTron enters a 5 minute “Safety Delay” mode''
Could be what you are seeing. The fan shuts off, heat soaks in enough to trip the snap disk and start the fan again. After the 5 minute delay, snap disk shuts off the fan.

 

[Harvey Schneider]

I found a wiring diagram in this post.
It may not be right on point, but it does provide a wiring diagram.
F140 turns the convection blower on full.
L250 is an over temperature limit switch
The purpose of L120 is not clear, but I expect that it is used to determine that the fire did not ignite. Shut down if ignition failure.

The problem could be L120 or it could be a mis-wire - blowers swapped.
Of course nothing rules out a control board failure, but it just doesn't seem like that.

 

[Jjirishnh]

From what I've read the L120 is used in the initial startup and monitors if the fire goes out. If the temp doesn't reach 120 in the 15 minute startup the stove will shut down, and if the stove goes out and the exhaust temp goes below 120 the stove will shut down. Do you think I could test this by putting a jumper across the switch and see if that fixes the problem? If it does work with the jumper I would of course buy a new L120 and replace the faulty one.

Thanks for your help

 

[Jjirishnh]

I seem to remember this symptom coming up not too long ago. You might want to do some creative searching on here. I'm not sure it was a Pelpro but maybe another brand that uses the same/similar controller. Harvey's right. The vacuum switch depends on the combustion blower. Not the other way around. I would be looking for a bad/poorly seated/corroded snap disk. My stoves have a thermocouple to sense the temperature but yours might have a sensor on the exhaust tubing.

http://www.pelprostoves.com/Troubleshooting/Manuals.aspx

''Upon starting the appliance, the AcuTron control board has a 15 minute “Lighting Mode”, if the stove
exhaust does not reach 120° F in that 15 minutes the stove will shut off. As soon as the stove
exhaust does reach 120° F, the limit switch opens and the AcuTron enters a 5 minute “Safety Delay” mode''
Could be what you are seeing. The fan shuts off, heat soaks in enough to trip the snap disk and start the fan again. After the 5 minute delay, snap disk shuts off the fan.

Thanks .... After looking at the wiring diagram And other advice I've had here on the forum I think it very well may be the L120

 

[tjnamtiw]

From the description, the snap disk OPENS when it reaches 120 so jumping across it would have the opposite effect. You would want to disconnect one of the leads to see if the fan stays on. Better yet, put an ohmmeter across it and hit it with a Bic lighter to see if it opens.

 

[Harvey Schneider]

Better yet, put an ohmmeter across it and hit it with a Bic lighter to see if it opens.

With power disconnected of course.

 

[Jjirishnh]

With power disconnected of course.

I disconnected power, removed the L120 read it with my meter and it showed continuity. I set it on the glass top of my electric range and turned the burner on med. the device opened I slid it off the burner and after it cooled it closed the switch. I repeated this a few times so it seems this switch is properly operating

 

[tjnamtiw]

Sounds like it. Does it seat well onto the metal surface? You might try some heat transfer grease. If you have a pyrometer, you could check the actual temp at that spot on the pipe.

You said you got a good flame in burn pot so the exhaust path should be good. If it were blocked, then not enough exhaust would be going past the snap disk location and heating it up. Good cleaning?

Are you sure it's a 120 degree snap disk and not a higher rated one? I should say so on the disk. It might be worth the few bucks to invest in a new one.

 

[Jjirishnh]

I was going to try lighting the stove with the switch out and see if the issue goes away. At least I'll know if I'm on the right track

 

[tjnamtiw]

That is a good next step IMHO. If it won't start up without the switch being made due to the logic, then you'd have to pull off the common side spade lug and see if the fan keeps going after the initial start up.

 

[Jjirishnh]

That is a good next step IMHO. If it won't start up without the switch being made due to the logic, then you'd have to pull off the common side spade lug and see if the fan keeps going after the initial start up.

Unfortunately the stove acted the same way with this switch removed. It lights fine but when the ignition period is over the combustion fan cycles fast to slow. I'm not sure where to go from here

 

[Harvey Schneider]

Unfortunately the stove acted the same way with this switch removed. It lights fine but when the ignition period is over the combustion fan cycles fast to slow. I'm not sure where to go from here

Some more investigation:

1. Does the fast/slow happen with a consistent timing?
2. How often does it cycle?
3. Are you sure that the convection and combustion fan wiring wasn't swapped?
4. Does the flame size vary with the fan speed?
   Fast = big flame?
   slow = smaller flame?
5. Does the stove get hot enough for the convection fan to go to high speed automatically?

I'm looking for patterns of behavior that may tell us what is happening; fast cycling must be caused by something different than slow cycling, inconsistent timing must have a different cause than clockwork like regular timing, etc.

 

[Jjirishnh]

Some more investigation:

1. Does the fast/slow happen with a consistent timing?
2. How often does it cycle?
3. Are you sure that the convection and combustion fan wiring wasn't swapped?
4. Does the flame size vary with the fan speed?
   Fast = big flame?
   slow = smaller flame?
5. Does the stove get hot enough for the convection fan to go to high speed automatically?

I'm looking for patterns of behavior that may tell us what is happening; fast cycling must be caused by something different than slow cycling, inconsistent timing must have a different cause than clockwork like regular timing, etc.

The timing seems to be irregular. The odd thing is when the fan runs fast the flame is lower but more intense like I'm used to seeing...bright lively flame some sparks flying from the burn pot, with the fan running slowly I get a larger more lethargic flame that seems dirtier in that it produces much more smoke.

I focused on watching the lights on the controller and the auger light flashes. Not sure if that means anything. The only other time I've seen that light flash is if the hopper is open

 

[Harvey Schneider]

The timing seems to be irregular. The odd thing is when the fan runs fast the flame is lower but more intense like I'm used to seeing...bright lively flame some sparks flying from the burn pot, with the fan running slowly I get a larger more lethargic flame that seems dirtier in that it produces much more smoke.

I focused on watching the lights on the controller and the auger light flashes. Not sure if that means anything. The only other time I've seen that light flash is if the hopper is open

Irregular timing would make me look for an intermittent connection or possibly an intermittent snap switch.
Based on my experience in electronics the order of probability of intermittent connections:

1. wiring
2. snap switches
3. internal to motors
4. circuit board connections

I don't know what the flashing light means, there is probably a reference to it in the users manual.

 

[Jeff1978]

It's the control board, The auger light flashes because the combustion fan slows down and trips the vacuum switch which shuts off the auger. I'm on my third control board, First one combustion fan would cycle in feed rates 2,3,4. Same with my second board. Just got a third board in and it does it on feed rate 2. I'm getting frustrated. Right now I've got a acutron 2 control board from my other stove and it works just fine! Today I'm going to try these acutron 4 control boards in my older stove to see what happens,

 

[Jjirishnh]

It's the control board, The auger light flashes because the combustion fan slows down and trips the vacuum switch which shuts off the auger. I'm on my third control board, First one combustion fan would cycle in feed rates 2,3,4. Same with my second board. Just got a third board in and it does it on feed rate 2. I'm getting frustrated. Right now I've got a acutron 2 control board from my other stove and it works just fine! Today I'm going to try these acutron 4 control boards in my older stove to see what happens,

I finally called the company and they told me the same thing. I just swapped the new one in. It seems to work fine in feed rate 2 3 and 4. When I drop the feed rate to 1 the fan cycles as I have described previously. I guess I need to call again.

I saw my style stove in a store the other day and they have changed the controller to one that had a dial instead of the buttons. I wonder if this are more reliable?

 

[Jeff1978]

I finally called the company and they told me the same thing. I just swapped the new one in. It seems to work fine in feed rate 2 3 and 4. When I drop the feed rate to 1 the fan cycles as I have described previously. I guess I need to call again.

I saw my style stove in a store the other day and they have changed the controller to one that had a dial instead of the buttons. I wonder if this are more reliable?

That's enough to piss a guy off, lol. Try turning the trim pod for the fan speed, the little plastic screw on the control board listed "fan". I read in another thread a guy had some luck doing so. I don't know which way to turn it so try it both ways when your on feed level one. That screw only controls the combustion fan on level one anyways, let me know if it stops cycling.

PS I'm still waiting on a call back from pelpro, did you notice the name on the new control board with the dials you saw in the store?

 

[Jeff1978]

Well I figured mine out. I tryed the new control board in my old stove and it worked just fine, at that point i was really scratching my head. Reinstalled it back into my new stove and combustion fan started to cycle in feed rate 2. Now after 3 boards i noticed the trim pod screw for combustion fan is set at almost max (ccw). I put the stove back to feed rate 1 and turned the screw ccw till it stopped and the combustion fan started to cycle. So its something with the position of this screw and the combustion fan cycling . Anyways i turned screw to its middle set point and everything is working fine. I'm satisfied enough, i quit tinkering with it, hope you find success playing with that fan adjustment.