Wood Furnace Blower?

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Well, because installing the Daka wood furnace involves such things as building a floating back-draft damper for the gas furnace, and a plenum extension to tie it into the existing ductwork, which means taking down both gas and wood heat at the same time… installation has been put on hold for warmer weather. So this has given me time to walk around it several times in the shop… beer in hand… thinking. It’ll likely be an all-weekend project… heck, just getting it down the basement steps will be a project.

I’m gonna’ do some cleanup and put a fresh layer of stove paint on it before moving it in the house… make it look pretty, at least to start with. Probably build some of the plenum and cold air return beforehand, run the electrical service, and whatnot.

So I’m looking at the twin blowers for it and get to thinking… I’ve got this three-speed furnace blower salvaged from an A/C unit; I was thinking about using it instead of the two Dayton 550 CFM blowers… figure I’d wire it to run low speed on furnace temperature rise, medium speed on heat demand from the thermostat (when draft blower starts), and high speed on duct temperature rise. The thing is… the blower has a 208/230 volt motor, which means running a 240 volt service rather than a 120 volt service, and would involve a bit of re-wiring on the Daka (fan/limit controller and such). And I’d need to modify the cold air filter box, or possibly build a new one. I can see positives to doing this… such as more air flow on demand, quieter operation, longer blower life, and lower power consumption.

The salvaged blower is rated 1.2 amps @ 230 volts (276 watts) but would be less on low and medium speeds; the Dayton’s are rated 2.05 amps @ 115 volts each (471.5 watts total). The salvaged blower turns a larger wheel @ 875 RPM’s (on high); the Dayton’s turn smaller wheels @ 1640 RPM’s. I figure power consumption would be less than half that of the twin Dayton bowers when all said and done… while moving more air at a lower noise level.

So before I go through the work of running electrical service, building a filter box, rewiring, etc… anybody used a larger furnace blower on their wood furnace? Any problems (like over-cooling the firebox)? Anything else I should know, or ain’t thinking about? Opinions, ideas, thoughts?
 
You will have no problems going with a larger blower. Daka has a factory option for a 1580 cfm blower for their furnace. Our old woodfurnace (1500 hotblast USstove) was installed in series, which used the central furnaces blower. I would say somewhere around 1800 cfms. That setup would push 130 degree air from the registers. There's someone on hearth that upgraded his blower on his daka, and he said it made quite a difference. Those furnaces have alot of exposed steel, so there's quite a bit heat transfer.
 
Yeah, there has been quit a few people on here that have replaced their twin blowers (hotblast?) with a real furnace blower. I don't remember anyone complaining about it afterward.

So, I assume that it is the A/C control board that will allow you to use all of the motors speeds? I'd like to do something like this on my Yukon, have the blower start on low, speed up only as needed. I have a friend who is a scrapper, I'm sure he could get me a gas furnace or A/C control board and multi-speed motor on the cheap.

Do you mind explaining the wiring on this? Thanks spidey!
 
Hey spidey if your not going to use the dayton blowers would you consider selling them?

Sent from my HTC Hero S using Tapatalk 2
 
A relay would work fine for no rewiring, as I am sure you already know. If you do find that you are moving to much air, you could install a merv 13 filter to reduce cfm, or damper down the return some.
 
Do you mind explaining the wiring on this? Thanks spidey!

I'll use double pole 24v-120/240 relays to change speeds, some stuff salvaged with the blower, some came with the Daka, and some stuff I just have from "something" else... but who knows what. I even have a 250v/24v transformer if I want to use that instead of the 120v/24v. I'm a pack rat, ya' just never know what you'll need... I even have what I need to run the 240v service including the fuse box/disconnect.

Anytime the temp inside the wood furnace jacket reaches 130[sup]o[/sup] the blower will start on low, fed through the normally closed side of the first relay.
If the thermostat calls for heat the first relay will switch poles, feeding the medium speed through the normally closed side of the second relay if the fan control is seeing correct temps (the dual relay also starts the draft blower).
If temperatures inside the downstream ducting reaches 110[sup]o[/sup], and the thermostat is calling for heat, the snap switch (in the ducting) will feed 24v to the coil of the second relay, causing it to switch poles and feed the high speed.
A thermistor in the top of the wood furnace jacket will not allow 24v to pass from the thermostat unless there is at least 80[sup]o[/sup] air inside... which will prevent the draft blower from starting up on a cold, dead firebox (the fan/limit control prevents anything else from starting).

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anybody used a larger furnace blower on their wood furnace?

I installed a 1/3 Hp 3 speed furnace blower on my Hotblast 1400.
Best thing you can do to a Hotblast furnace.
Quieter , less heat around outside of furnace, fire burns the same
and electric bill is lower.
 
That's a great idea using the thermistor to keep the draft fan from blowing the coals heat up the chimney! I might steal your idea. Even though I have a draft door instead of a blower, if it is open for long late in the burn cycle, it still has the same effect.

Pretty impressive wiring diagram in just a little better than 2 hours! Whatcha use to do that?
 
A relay would work fine for no rewiring, as I am sure you already know. If you do find that you are moving to much air, you could install a merv 13 filter to reduce cfm, or damper down the return some.

I have already turned the speed down with the adjustable pulley. I don't want to go any more, as the blower will just barely keep up when the furnace is on high fire. I'm sure the speed will need to be tuned back up when it's time for the central A/C to be used. I want to switch out the motor to a multi or variable speed to help deal with the cycling on low burn. Start and run on low, then be able to speed up on high burn or as needed (A/C). One thing I wasn't sure of, does it matter if there is power on 2 or more of the speed taps at the same time? (Example, low and med. powered at the same time) Another bonus would be, at least to my thinking, was that the motor would pull less amps at start up on a low speed. It peaks at 25A, runs at 4.8A now (1/3 hp)

Some snap switches and a relay or two was the original plan, was just wondering if a control board from a modern gas furnace would be of any advantage. The other day I had the idea to use the upper control switch from a electric water heater for this project. I have one laying here, and best part is they are adjustable.
 
I put an old furnace blower on my Hotblast last year and it works great. Yesterday I put a used furnace blower (used at $25 local furnace guy) on the Fawcett that i just put in my new shop. It's a 4 speed and was setup for #3, that was too fast, it was cooling down the furnace too quickly. I changed it to #2 and it seems better, less temp swing in the shop. It's a direct drive, my Hotblast one is a belted one, it seems noiser.
 
I have already turned the speed down with the adjustable pulley. I don't want to go any more, as the blower will just barely keep up when the furnace is on high fire. I'm sure the speed will need to be tuned back up when it's time for the central A/C to be used. I want to switch out the motor to a multi or variable speed to help deal with the cycling on low burn. Start and run on low, then be able to speed up on high burn or as needed (A/C). One thing I wasn't sure of, does it matter if there is power on 2 or more of the speed taps at the same time? (Example, low and med. powered at the same time) Another bonus would be, at least to my thinking, was that the motor would pull less amps at start up on a low speed. It peaks at 25A, runs at 4.8A now (1/3 hp)

Some snap switches and a relay or two was the original plan, was just wondering if a control board from a modern gas furnace would be of any advantage. The other day I had the idea to use the upper control switch from a electric water heater for this project. I have one laying here, and best part is they are adjustable.

You can't power both at the same time. They also share the neutral.
 

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