Harman Fan Speed

Just curious if anyone has any info on adapting the blower that comes with Magnafire-series to have variable speed. All on or all off is a bit too extreme for me - I'd like to rheostat the blower but wanted to see if anyone has some info before I dive in. Mating it with a thermostat would be even better I guess.. Or are there other blowers with these features that fit a Harman interface? Thanks

I'd say that’s an open field and you can use your technical imagination I do know it is recommended to use a rheostat or fan speed controller as compared to say a dimmer switch, a thermostats a nice idea .
The ideal thing would be a thermostat that varied the fan speed according to temperature and actually worked . Something like the one on my Chryslers climate control or my computers cooling fan . There is a thread on here some where that members are discussing control circuits ya might jump in there the one fellow really seems to know his *censored* .

I don't use a fan speed controller on the Harman, in my situation full speed works fine, if it gets too warm we just shut it off. A speed controller would be a good idea in other situations. Probable a rheostat like the ones for my Alaska. I don't know where to get them, send Matthaus a PM, he can set you up with the info. They have a cord set on them, you just plug it in between the motor and the power source. You can set it up with a t-stat but you need a line voltage t-stat unless you want to go all out and build a low voltage control circuit with a contactor, step-down transformer, etc.

I got this 3-speed blower fan to connect up to my Harman TLC-2000 for $24.00 at Lowes last month...Works great!
(just hook it up to your stove with a few duct fittings)
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Devil5052 wrote:I got this 3-speed blower fan to connect up to my Harman TLC-2000 for $24.00 at Lowes last month...Works great!
(just hook it up to your stove with a few duct fittings)
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Good idea, but since Trey already has the blower he can get the rheostat and have an infinitely adjustable air flow. The thermostat idea is optional, but Trey may be like most of us, we're constantly thinking up new ideas to try, the project is never finished.

What I did on my homebuilt stove was just buy a fan speed controller from the hardware store. About $20, the kind for ceiling fans, not a light dimmer switch. You can get 3-speed or infinite ones. Some have an adjustment for the low end so you cannot turn the speed down so far as to stall the motor out. These switches lower the voltage to vary the motor speed. Some info I read said that the best way to control fan speed was to control the power frequency, instead of the volatage. Something about the motor could overheat. However, at the very low horsepowers these blowers are using, overheating does not seem to be a factor. I've never had a problem.

You need to make sure the motor is a shaded-pole motor, not a capacitor start motor. I'm guessing it is almost definitely a shaded pole, especially if it's the stock motor with the Harman. Most of these low-power blowers are shaded-pole. If not, it will not work.

I just mounted a metal junction box to the back of my stove (with some standoffs to keep the box cool). I grabbed an old power cord from a junk fridge at the dump or some old appliance at the appliance dealer. Run both power cords into the junction box, hook the whites together, switch the black, and ground the box.

Seems to work great. Also thought of mounting a "close-on-rise" thermodisc inline as well, but haven't gotten to it yet. Good luck.

Steinke

An update on this - I was able to easily 'hang' a 2x4 steel outlet box under the small wire box on the outside of the blower motor (it has a std knockout whole on the bottom). I picked up a 3-speed ceiling fan switch at the depot and am using it now. Not happy with it as the 3 speeds don't really work well with this blower motor - found a few variable speed switches that I will try and then update again. Good news is that the depot helped me determine that it *is* possible to control the speed of this thing - now I get to return it to them in the shredded clear plastic packaging meant to deter me from returning it.. :>

Just to finish this thread off, I was able to add a nice speed control to my Harman blower. Now instead of just ON or OFF I have good range and it is quiet enough to hear the TV when needed! If anyone else was interested, I found a good deal on the speed control switch - under $10 delivered. Where else but ebay - cheers:

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How does a speed control switch work? If ya reduce the motor voltage, won't ya burn out the motor? What inside of the controller reduces current without reducing voltage?

I bought a router speed control from a woodworking supply house. DON'T DO THAT. It was a transistorized affair, and it did NOT work with my Harman fan. The fan just made an awful whining noise and wouldn't run at all except at full speed. There was something in the literature that came with my stove warning not to use a solid-state controller, but I didn't know that's what I was getting, so now one of my buddies has a router control.

So then I did like others here -- went to Lowes and got a double outlet box, a heavy duty cord with plug, a standard variable speed fan control, and an outlet. Mounted the fan control and the outlet side-by-side in the box, feeding power through the rheostat to the outlet. The control box plugs into the wall, and the stove blower plugs into the box.

How does a speed control switch work? If ya reduce the motor voltage, won't ya burn out the motor? What inside of the controller reduces current without reducing voltage?

I think that the variable speed switches are in fact varying the voltage. But because the motors are shaded-pole, they can handle it. They may run warmer due to the lower voltage, but I don't think it's all that much hotter with the sub-horsepower motors. I've been running mine that way for months, and I cannot feel the increased heat with my hand.

I don't really understand it completely - if we have any experts about this issue maybe they will chime in. Most of the info I've read says that lowering the voltage on a motor is not a good idea, but all that info usually applies to larger motors that use a capacitor start, which shaded-poles don't have. Shaded-poles have a low starting torque, but it's no big deal for blowers, 'cause there's little torque.

Steinke