Help with building a blower for my insert

[JMF1]

I'm building a blower for my Avalon insert. I want to use muffin fans because of the reduced noise, but I'm not too sure of what kind of speed control to use or where to find the temp switch which turns it on and off. I have 2 A/C muffin fans to use, or should I use D/C fans? Any insight would be greatly appreciated.

 

[begreen]

I investigated this for the blower I made up for our old Majestic insert. In order to use the common fan speed controller that one can get at Grainger or better hardware stores, the motor(s) need to be shaded pole motors. Note that some speed controllers don't work with impedeance protected motors, so watch for this also. And be sure to have heat shielding for the fans and the wiring.

Also note that with a pair of low rpm, axial fan motors you might not have to use a speed controller. Some are pretty quiet:
http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1613538500

 

[GVA]

Yeah go with shaded pole blower motors. Stay away from dc, you will need the addition of a dc drive for each blower making the cost about four times the amount needed to spend.

 

[drizler]

Take off the motor and take it to your local AC motor shop. I just bought one to replace the $300 + one on my furnace blower. They squared me away with a nice dayton for $107. This was a little 50 year old family shop and they had or could get about any motor you would want. I can't tell you what to look up in the phone book as a buddy referred me having used them to replace an odd blower mower on an insert. Try electric motors AC.

 

[Corey]

When I put a blower on my insert, I found there are a couple of things to consider.

1: AC fans will work fine. However, if you plan for frequent or extended power outages, you may want to look at 12VDC fans. You would probably want to use a small switching power supply to drive them, but in a power outage scenario, the fans could be run off a common battery with no power inversion. If you use AC fans, you would then need either a generator or a power inverter during a power outage.

2: A big fan spinning slowly will move more air with less noise than a small fan spinning fast. I cut a hole in the back of my insert to install a 12" blower. It moves several hundred CFM and all you hear is a gentle woosh of air out the vents.

3: A speed controller is a moderate hassle for not a lot of payoff. You either get a large quantity of warm air, or a smaller quantity of hot air. Overall heat output is mainly governed by the fire. A simple on/off switch works about 99.9% as good and is much cheaper.


As far as placement of the temp switch, it depends on what temp it switches at. We had a thread on here last year, and it was updated this year about temp switches, where to get them and how to install. Basically, if you have a "hot" temp switch someplace on top of the firebox may be appropriate. If you have one that is cooler, maybe somewhere on the side would be more appropriate.

Corey

 

[BrotherBart]

When I put a blower on my insert, I found there are a couple of things to consider.

1: AC fans will work fine. However, if you plan for frequent or extended power outages, you may want to look at 12VDC fans. You would probably want to use a small switching power supply to drive them, but in a power outage scenario, the fans could be run off a common battery with no power inversion. If you use AC fans, you would then need either a generator or a power inverter during a power outage.

2: A big fan spinning slowly will move more air with less noise than a small fan spinning fast. I cut a hole in the back of my insert to install a 12" blower. It moves several hundred CFM and all you hear is a gentle woosh of air out the vents.

3: A speed controller is a moderate hassle for not a lot of payoff. You either get a large quantity of warm air, or a smaller quantity of hot air. Overall heat output is mainly governed by the fire. A simple on/off switch works about 99.9% as good and is much cheaper.

As far as placement of the temp switch, it depends on what temp it switches at. We had a thread on here last year, and it was updated this year about temp switches, where to get them and how to install. Basically, if you have a "hot" temp switch someplace on top of the firebox may be appropriate. If you have one that is cooler, maybe somewhere on the side would be more appropriate.

Corey

So your blower assembly is back behind the insert? Survives the heat ok?

 

[JMF1]

Mine is in front under the ashlip. It's 2 fans actually, one on either side of the air control. I am assuming there isn't too much heat down there.

 

[Corey]

So your blower assembly is back behind the insert? Survives the heat ok?

Yep. It is down low, so there is not a lot of heat anyway. The bottom 5-6" of my insert is below the fire. But even with the fire going and the blower off, that is where cool air is pulled in. If the fan was up high, it might me more of a problem. But with the baffling system and firebrick, most of the heat is directed to the front / top of the stove.

Corey

 

[Corey]

Mine is in front under the ashlip. It's 2 fans actually, one on either side of the air control. I am assuming there isn't too much heat down there.

That is where mine would have been. (The two openings on either side of the ash drawer in my avatar are fan inlets) But I couldn't find any 4.5" fans that would move a decent amount of air without a shrill whine. Maybe modern technology has caught up as this was several years ago. That is why I mounted one 12" fan in the back and blocked off about 75% of the openings on the bottom front. This directs the heat out the top vents and out a second vent I cut on top of the insert directly above the firebox. It really turned the insert from a one-room radiant heater into a whole house convection blower.

Corey

 

[BrotherBart]

So your blower assembly is back behind the insert? Survives the heat ok?

Yep. It is down low, so there is not a lot of heat anyway. The bottom 5-6" of my insert is below the fire. But even with the fire going and the blower off, that is where cool air is pulled in. If the fan was up high, it might me more of a problem. But with the baffling system and firebrick, most of the heat is directed to the front / top of the stove.

Corey

Good to know since when I put the 30-NCL freestanding stove into my fireplace that is going to put the blower, mounted on the heatshield, low in the back. I have a little concern about it being back there in the heat. But it shouldn't get as hot as yours does with the shroud. The convection path of cooling air is better with yours though than I think this one is going to be since you have the front intakes.