Help me with ideas, variable speed furnace blower, Junk Yard Wars style

[brenndatomu]

I really don't like how my whole house wood furnace blower cycles on and off constantly during the first hour or two of the burn cycle, and then not run at all during the last 3 or 4 hours of the burn cycle. I mean it does a pretty good job of heating the joint, but I think it could do better with a variable speed blower that had a target duct temp it was aiming toward. I have the adjustable pulley on the blower motor set to run at a minimum speed now to help with the cycling, I really can't go any slower or the blower wouldn't be able to keep up with the oil burner, on the rare occasion that it runs. I guess I should say that this is a Yukon Husky wood/oil combo unit. Anyways, my idea is to come up with a automatically variable speed blower arrangement (on the cheap) So it appears there are several ways as to how this is accomplished. I found this fan controller for greenhouses that may have possibility http://www.ebay.com/itm/121221129954?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT but I'm not sure it would handle my 1/3 HP motor start up load. (belt drive blower)
I could get a surplus DC motor, but how to control it exactly? A cheapy PLC with a thermocouple input running a DC controller of some sort? Where to access this stuff on the cheap? Old treadmill? Washer/dryers? Used CL furnace with variable speed blower? I thought I'd throw this out there, see what ideas some of you fellow tinkerer types have?

 

[STIHLY DAN]

Do you want variable speed or multi speed? Don't think variable would work to well. Why not a fan center to a multi speed, high for the oil call, low for the wood fan.

 

[brenndatomu]

I was thinking variable speed. What would the issue with variable be? In my mind, that would be the ultimate solution...
I thought of using a multi speed as you say, wire in a snap switch for lower speed, factory limit switch to kick it in high. My main concern with this was making sure that both parts of the motor winding could never be powered at the same time, maybe a DPDT relay could solve this issue. The other thing is, I couldn't find an affordable 120v multi speed belt drive type motor, it would be easier/cheaper to swap out my blower with a direct drive blower, I have a friend who is a part time scrapper, I'm sure he could find one for me eventually since he also works part time for a local HVAC guy.

 

[STIHLY DAN]

I am not even sure they have a variable speed with a belt. VFD ya. Whats your frame size? I'm sure I could grab one.

 

[brenndatomu]

Ya, I would think most variable speed blowers are direct drive...unless I DIY one!
I thought of a VFD, but I am only familiar with those on three phase, can they be used on 120/240?
Frame size, do you mean the current motor, or the blower frame size?

 

[brenndatomu]

Hmmm, I may have just solved this issue...register cover booster fans. I bet a couple of those will accomplish my goal. I see some of them even have built in "thermostats"
Fleabay, here I come!
I thought of duct boosters before, but I have rectangular ducts, so the fan-in-a-can seemed a PITA to install, register fans...duh!

 

[STIHLY DAN]

Ya, I would think most variable speed blowers are direct drive...unless I DIY one!
I thought of a VFD, but I am only familiar with those on three phase, can they be used on 120/240?
Frame size, do you mean the current motor, or the blower frame size?

Motor frame. I have not herd of register fans, Will they pull enough to not over heat the furnace?

 

[brenndatomu]

Furnace blower will remain untouched so no risk of overheat as it can still kick on and do its things as needed. I have the blower running at about 50% CFM right now compared to when in A/C mode so I have plenty of duct capacity to make up for the lil bit of restriction that these fans may cause when the furnace blower is running.The register fans I have found are rated at 40-130 CFM depending on fan speed and brand/model, so I think a couple of these around the house will do the trick, we gonna find out soon! I'll keep ya updated...
Thanks for your participation and offer to help

 

[Buzz Saw]

I thought of a VFD, but I am only familiar with those on three phase, can they be used on 120/240?

120v input 230v 3phase output. might work for what you have

http://www.automationdirect.com/adc...l)/GS1_Drive_Units_(120_-z-_230_VAC)/GS1-10P5

 

[brenndatomu]

120v input 230v 3phase output. might work for what you have

http://www.automationdirect.com/adc/Shopping/Catalog/Drives/GS1_(120_-z-_230_VAC_V-z-Hz_Control)/GS1_Drive_Units_(120_-z-_230_VAC)/GS1-10P5

Very interesting, I'll hafta file that one in the memory banks. Thanks!

 

[NE WOOD BURNER]

I run an oil FHA furnace and a fisher granpa with a plenum. I shut off the oil and use a temp switch on my fisher plenum It has worked very well for cheap money. my cold air return is above my fisher so I cut a door so the cold air dumps on my fisher. I find the cold air pushes my heat better than the fan in the furnace trying to pull and then push the hot air.

 

[brenndatomu]

Just an update, I received my 2 register booster fans a few days back, they are working very well. The furnace blower runs less often, the house temp is a lil more even, and my real goal...to be able to capture the heat from a smaller fire that may not be hot enough to actually kick the furnace blower on. Goal achieved! With the warmer temps recently (well, warmer than polar vortex anyway) I have been able to heat the house with burning 5-6 average size splits per day. I do get quite a bit of heat to the house just from gravity flow but these fans seem to be the solution for efficient heating on those "in between" days and capturing all the available heat as the fire dies down the rest of the time. Even though these fans will be running most of the time, they only pull 20 watts each running full bore, much better than the 5-600 watts that the furnace blower uses, not to mention the 2000 watt spike each time the blower starts up! Only negative is that one of the new fans is a lil noisy, the other is much quieter for some reason, air flow seems about the same, dunno, not too worried about it since we don't spend a ton of time hanging out in the "noisy fan room"

 

[NE WOOD BURNER]

They make booster fans that get installed in the duct work also. I had one installed to boost to second floor and used a separate temp switch to control that one. I felt it was silent as it was under the first floor. I choose not to use the register type so that I would not hear the fan.