Two Speed Combustion Blower Control

 
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coalkirk
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Post by coalkirk » Sun. Jan. 30, 2011 12:52 pm

Finally success. It turns out the first speed controller was infact defective. I ordered one directly from KB and it arrived yesterday. Just installed it, adjusted the trim pot and everthing works as expected. Combustion fan runs full speed when stoking and for 1 minute after stoking (plugged into the Harman distribution fan timer and set for 1 minute) then runs at reduced speed the rest of the time. I'll have to experiment with different speeds to see what works best. Thanks all for your help and advice.
I also installed the muffin fan I bought last year but never got around to using. I cut a round hole in the top of the stoker cover and the fan sits over it. Powered off of the Harmans combustion fan timer so it only runs with the stoker. Before the stoker motor was REALLY hot. Now it is cool. I guess its got to make a difference. Sounds cool when it fires up too.
8-) :oops:

 
titleist1
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Post by titleist1 » Sun. Jan. 30, 2011 1:05 pm

Awesome that is working now. I was worried with your first speed control experience that somehow the Harman relay would be energized via the speed control and full power would be getting to the fan all the time.

I should get some time this week to finally work on it myself. Our church has been hosting a rotating homeless shelter this past week and all my free time had been taken up by the previous weeks prep work and on site time this past week. They move to the next church starting tomorrow night so I'll have some time to experiment later this week myself.

Can you please post a pic of the Muffin fan and how you mounted it? Thanks.

 
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McGiever
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Post by McGiever » Sun. Jan. 30, 2011 3:12 pm

Coalkirk,

Way to go, getting it all worked out! 8-)

With my difficult to burn coal I finally am getting my best burn yet. :!:

I gauge my speed controller adjustments w/ a voltmeter and log the setting for future reference.

 
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coalkirk
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Post by coalkirk » Mon. Jan. 31, 2011 9:19 am

titleist1 wrote:Awesome that is working now. I was worried with your first speed control experience that somehow the Harman relay would be energized via the speed control and full power would be getting to the fan all the time.

I should get some time this week to finally work on it myself. Our church has been hosting a rotating homeless shelter this past week and all my free time had been taken up by the previous weeks prep work and on site time this past week. They move to the next church starting tomorrow night so I'll have some time to experiment later this week myself.

Can you please post a pic of the Muffin fan and how you mounted it? Thanks.
Here it is.
stoker cover.jpg
.JPG | 103.1KB | stoker cover.jpg
muffin fan.jpg
.JPG | 102.3KB | muffin fan.jpg
It's plugged into the combustion fan outlet on the Harman controller.

 
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coalkirk
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Post by coalkirk » Thu. Feb. 03, 2011 9:11 pm

An update on the muffin fan feature. While it has done a fantastic job of keeping the stoker motor cool, it has done an equally fantastic job of blowing coal fines from the area inside the stoker housing into the surrounding area. I have suspended the use of the fan for now. Not cool. I guess oiled coal would eliminate this problem in the future. I hope to buy rice coal in bulk via a tri-axle later this year and from what I've been reading, I'd like to have a load of UAE Harmony delivered. To those who buy coal there, do they offer oiled coal? Thanks.


 
blanchem
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Post by blanchem » Sat. Feb. 12, 2011 1:08 pm

I’d like to make this variable speed modification as well. The link on page one takes you to the KB web page but I did not notice or possibly missed reading any post of what model of the 115v each of you were using? 115v model options are 2.5 amp to 8 amp. I assumed it may not matter as all of these are rated well above the blower motor current draw but I did not know if there was a downside to one having too high of a rating above the operating range. I took the opportunity locally to pick up two surplus, new in box KBWC-16K (6 amp) models. I assume this model will work? Please let me know if that assumption is incorrect.

VF3000 with the current settings as follows… The combustion blower plug is connected to the distribution blower receptacle with extend timer set for six minutes. Pilot timers set for four on and twelve off. So based on my settings the blower is on full speed continuously other than two minutes at the end of each pilot cycle. Stack photohelic .045 and firebox photohelic .04. Combustion blower restrictor plate is open about 10%.

I’m considering the following… Keep the existing pilot timers set to four on and twelve off. I’d like to place the combustion blower existing plug back into the combustion blower receptacle for “normal heat & pilot” full speed blower operation. I would then have the distribution blower receptacle and extend timer available for the addition of the variable control and associated wiring. I would set the blower control to an acceptable level through trial and set the extend timer for eight minutes (or higher) allowing it to run continuously at a lower speed at all times when the combustion receptacle is not energized.

Based on what I’m reading in all posts I feel I’d be accomplishing the same as those connecting to an additional outlet while guaranteeing my additional blower control circuit will be on the same leg of the 120v as the VF3000. I’d have close to the setup I have now but the blower will be running at a reduced speed rather than the full speed it's currently run now when the VF3000 is in the pilot no feed mode.

I have not started this modification to date so anyone that believes this will not work or any additions they believe I should make please let me know. Although I am a new member I have been reading this forum and incorporating a lot of what I read here for over a year and I am impressed with the wealth of knowledge this forum provides. Thanks!

 
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McGiever
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Post by McGiever » Sat. Feb. 12, 2011 8:42 pm

blanchem wrote:I’d like to make this variable speed modification as well. The link on page one takes you to the KB web page but I did not notice or possibly missed reading any post of what model of the 115v each of you were using? 115v model options are 2.5 amp to 8 amp. I assumed it may not matter as all of these are rated well above the blower motor current draw but I did not know if there was a downside to one having too high of a rating above the operating range. I took the opportunity locally to pick up two surplus, new in box KBWC-16K (6 amp) models. I assume this model will work? Please let me know if that assumption is incorrect.
It's all about the blower amps, as far as not being undersized and overloading the designed capacity of controller.

The different sizes, do the same job @ their rated amperage capacity.
blanchem wrote:VF3000 with the current settings as follows… The combustion blower plug is connected to the distribution blower receptacle with extend timer set for six minutes. Pilot timers set for four on and twelve off. So based on my settings the blower is on full speed continuously other than two minutes at the end of each pilot cycle. Stack photohelic .045 and firebox photohelic .04. Combustion blower restrictor plate is open about 10%.

I’m considering the following… Keep the existing pilot timers set to four on and twelve off. I’d like to place the combustion blower existing plug back into the combustion blower receptacle for “normal heat & pilot” full speed blower operation. I would then have the distribution blower receptacle and extend timer available for the addition of the variable control and associated wiring. I would set the blower control to an acceptable level through trial and set the extend timer for eight minutes (or higher) allowing it to run continuously at a lower speed at all times when the combustion receptacle is not energized.

Based on what I’m reading in all posts I feel I’d be accomplishing the same as those connecting to an additional outlet while guaranteeing my additional blower control circuit will be on the same leg of the 120v as the VF3000. I’d have close to the setup I have now but the blower will be running at a reduced speed rather than the full speed it's currently run now when the VF3000 is in the pilot no feed mode.

I have not started this modification to date so anyone that believes this will not work or any additions they believe I should make please let me know. Although I am a new member I have been reading this forum and incorporating a lot of what I read here for over a year and I am impressed with the wealth of knowledge this forum provides. Thanks!
The theory sounds good to me. :)

 
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Post by qbwebb » Wed. Mar. 23, 2011 10:08 am

Just wanted to say thanks for this post, I recently made this change and it helped my temp spikes + efficiency dramatically.

I was running off 7 on 1 w/ my timers, and combustion blower plugged into the extended timer set for 6 min. My temp would frequently get higher than my stat setting and then the overtemp (set for 180 or so) would dump excess heat produced into the house. My unit is in a detached outbuilding. Now she barely rises 10deg over my aquastat set point and I can run 1min on and 15 off. Nice long smooth output in the idle times, I think I am all set for making DHW all summer :D

I also insulated 90% of my 1" PEX-AL-PEX lines in the basement going to the furnace, the water temp drop when the furnace kicks on is much less dramatic now. I think this is more due to the fact there is live coal on the grates for a much longer period of time now, so when the stoker motor kicks on it doesn't have to push off a full grate of ashes before high BTU output is reached.

I think my next mod will be an aquastat that interrupts the heat call when the water temp gets too low, this should save electric and smooth out dips & valleys even more.

 
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dave brode
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Post by dave brode » Tue. Apr. 05, 2011 12:06 pm

Related babble;

It seems to me that it's about pressure under the grate. Idle mode needs less air, running flat out needs more. Granted, what was written here is a good thing, but less than ideal imo. After an idle period, and the unit gets a call, there will be waste due to the fan speeding up prior to the stoker filling the grate for full burn [air up the flue]. Same deal when it gets off of the stat: Full grate, and fan still slows.

I recently helped demo an air handler that had adjustable switches that sensed pressure on both sides of the filters. I assume that they would alert when pressure drop reached X amount. The switches were adjustable from .01" to 2", and could be wired for NO or NC.

I tried to snag the switches, but the unit was to be saved [stored], as the facility had like units still in use eleswhere. I should have taken them anyway, since it will eventually go for scrap.....

If we could sense pressure under the grate and ramp fan up/down, we could give the fire the air it needs at all times. The question is, what would it cost vs coal savings.

Dave

 
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Post by titleist1 » Sat. Nov. 05, 2011 7:35 pm

I am resurrecting this thread because I finally made up my two speed controller and I believe I smoked the stoker control unit!!! :shock:
I wanted to warn others about my bad experience before they tried anything. I used a KB speed controller.

I drew out the wiring as I thought it should work, a parallel circuit with the fan plugged into a receptacle that is always fed by 75V through the speed control and fed 120V from the Harman combustion blower receptacle whenever the 'stat calls for heat or when pilot mode kicks it on. Figured I would draw it out first so I wouldn't be getting cornfused by designing it while I was wiring it.

I wired the plug cords and receptacle, and tested it by plugging in an extra blower making sure the minimum low speed would still move the fan. Everything looked OK, 75V moved the fan no problem so I moved on to the stoker. I plugged the combustion fan into the newly made receptacle, flipped the switch to send power through the speed control and the blower ran fine on the low speed. I then flipped the switch so there was no power to the speed control, plugged the 120V cord that is to supply 120V into the Harman combustion fan receptacle. It was off at the time the 'stat wasn't calling for heat and it was between pilot mode cycles. I flipped the switch to power the speed control and heard a pop. Quickly flipped switch back to off position.

The fuse was blown on the Harman controller. I have a spare fuse so I replace it, disconnect my 2 speed creation and plug the combustion fan back into the Harman controller. It appears the controller relays are toast. The feed motor LED and relay stay on all the time while the combustion and distribution blower LED’s operate as they should, but their relay’s are always on.

I happened to have a spare Harman stoker controller so I swapped it in and everything is running normally. I think when it gets colder I will simply run the combustion blower all the time as others do. I am wondering why it worked for coalkirk but not me, I must have something wired wrong.


 
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Post by coalkirk » Sun. Nov. 06, 2011 7:50 am

Sounds like something was wired wrong. Also, you need to use the distribution blower outlet, not the combustion fan outlet. Somehow the combustion fan blower and stoker outlets circuits are connected in the controller. When I first tried it I used the combustion fan outlet and it made the stoker motor run also.

 
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Post by McGiever » Sun. Nov. 06, 2011 11:10 am

Hope he heeded the common source outlet warning...if not, he may of put 220 Volts through it. :!:

With my set-up, I have the slower speed run straight from the common source outlet, and then when the controller cycles it picks up a relay and it takes motor/blower to full 120 volts for that cycle and then at the end of that cycle the relay will release and slower speed is again resumed. This all works from a single common power strip.

 
titleist1
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Post by titleist1 » Sun. Nov. 06, 2011 4:56 pm

I did make sure to use the same receptacle as the Harman controller is plugged into knowing the 120V for both needed to come from the same leg so 220V should not have happened.

Here is a quick sketch of the circuit. Let me know what looks wrong.

I wired the hot from the speed controller and the hot from the comb fan receptacle on the Harman controller to the same side of an outlet (brass screw/narrow blade side) and wired the white from the 120 plug and the white from the combustion fan receptacle on the Harman controller to the other side of the outlet. I then plugged the combustion fan cord into the outlet. That outlet should always have the 75V from the speed controller and it should get the 120V when the Harman combustion fan timer kicks on. It seemed the 75V from the speed controller backfed the Harman controller timer relay and caused the issue.
circuit10001.jpg
.JPG | 11.8KB | circuit10001.jpg

 
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McGiever
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Coal Size/Type: PEA,NUT,STOVE /ANTHRACITE
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Post by McGiever » Sun. Nov. 06, 2011 9:21 pm

titleist1 wrote:It seemed the 75V from the speed controller backfed the Harman controller timer relay and caused the issue.
titleist1,

You may be right, wiring looks good to me.

I don't have mine wired with a Harman Controller, and I used a relay in the circuit from my hold-fire timer and that does not allow the back-feed.

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