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Topic: Adding a Fan Speed Control to my Range Hood

Posted By: Blacklane on 10/28/14 09:10pm

I have a Hengs range hood in my RV. The fan is effective, but sometimes too noisy and powerful, particularly when just venting a little heat and steam from a coffee pot early in the morning. I decided to add a Pulse Width Modulator (PWM) fan control to it. I picked it up from Amazon and it came with a remote control knob.

[image]

The advantage of a PWM controller is that it is much more efficient at reducing power than a resistor pack, since resistors simply turn excess current into heat.

Thankfully, Heng provided a generous wire channel between the front panel and the fan. There is plenty of room for a PWM controller in there.

[image]

PWM controller mounted in wire channel. This particular model mounts with 3mm screws; not provided.

[image]

I mounted the control knob on the front panel. I had to keep it close to the existing fan switch so it would not interfere with re-installing the wire channel.

[image]

Now, I can choose a low, quiet setting for morning coffee and a full-force setting for cooking bacon.

* This post was edited 10/28/14 09:32pm by Blacklane *


Posted By: Son of Norway on 10/28/14 09:38pm

I also installed a PWM on the vent fan in my bathroom. They are marvelous little gadgets with many applications.

Miles


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Posted By: westend on 10/28/14 10:15pm

Link to PWM controller


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Posted By: Wet Coast on 10/29/14 01:04pm

wow, thought of making one of these up myself, but why not support the economy instead. Should also work for dimming lights too eh? Thanks!


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Posted By: tvman44 on 11/09/14 05:25pm

I have been wanting to build a adjustable voltage regulator to control the fan on our vent hood because it is so noisy, ours is a Jensen but is made identical to yours except for the name on the front tag. But like your idea, so I just ordered one on flea-bay for $4.69 with free shipping. It will be coming on a slow boat from China but for that price I can wait another 3 weeks for it. This will make all kind of brownie points with SWMBO. [emoticon] $4.69

* This post was edited 11/09/14 05:32pm by tvman44 *


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Posted By: Carb Cleaner on 11/13/14 04:28pm

Two pairs of wires. One pair 12V hot and neg. in and one pair out? Is it that simple? Do you wire the PWM before or after the fan's switch? Does it matter? Our fan has a two-speed switch.
I really like this idea. Thanks for sharing.


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Posted By: Blacklane on 11/13/14 08:30pm

You do have to isolate the fan negative wire from the group of white negative wires (one to ground, one to light, one to fan), all connected by a wire nut. Then disconnect the black fan wire from the front-panel switch. Now you have the black (+) and white (-) wires that connect the fan to the output of the PWM.

Add a black (+) wire from the switch to the PWM (+) input and a white (-) wire from the white ground wires (-) to the PWM (-) input.

I used crimp connectors and short pigtail wires to make it easier to assemble. If you use wire nuts, be sure to tape them, since wire nuts in RVs tend to vibrate off.

Mount it with 3mm screws and re-assemble everything.

Yes, the switch is still used. Note that the speed control rheostat has to be mounted fairly close to the switch, or the wire channel won't fit back on without bending or cutting.


Posted By: Carb Cleaner on 11/14/14 01:04pm

Very nice. Thanks for the detail. I can do that. Easy peasy.


Posted By: BurbMan on 12/05/14 11:01am

I added a 10W resistor and a 2-position switch to the range hood fan about 5 years ago, now I have 2 speeds, too fast/loud and too slow.

Now that these PWM units are fairly inexpensive, I just ordered the same one that the OP pictured in his post. I also ordered this fan, a 120mm pancake fan rated to move 156 CFM.

[image]

Hoping that this fan motor will be quieter at all speeds.


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Posted By: RV daytrader on 12/05/14 11:09am

Son of Norway wrote:

I also installed a PWM on the vent fan in my bathroom. They are marvelous little gadgets with many applications.

Miles


same here...I had installed a single speed vortex fan in bathroom...WAY more than needed to vent fumes!....with PWM switch you can slow it to almost nothing, or run fast to cool RV.


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Posted By: tvman44 on 12/05/14 04:07pm

I just installed the PWM module on our vent hood and DW loves it as much as I do, we can slow the fan down so it is not so noisy. While I was at it I mounted 3 of the 48 LED panels under the trough and also replaced the funky bulb in the fixture with a 48 LED panel, all 4 panels are the bright white. The DW loves the increase in light. I made all kind of brownie points today. [emoticon] I got the PWM from e_bay for less than $5.00 with free shipping, and the 48 LED panels for a $1.50 each & free shipping, so for $11.00 I did this mod. [emoticon]


Posted By: All I could afford on 12/07/14 07:12am

Can any of you tell me what the rated maximum watts or amps is on the PWM. Are year ago I made my own whole house fan in my trailer using a 12 V electric radiator fan that fits perfectly in the one window frame. While the fan is strong enough to blow a newspaper off the countertop on the other side of the camper it is too much for 90% of the time I want to use it. I measured a six amp load on start up and about 4 A running so about 50 W constant .


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Posted By: 2112 on 12/07/14 07:35am

All I could afford wrote:

Can any of you tell me what the rated maximum watts or amps is on the PWM. Are year ago I made my own whole house fan in my trailer using a 12 V electric radiator fan that fits perfectly in the one window frame. While the fan is strong enough to blow a newspaper off the countertop on the other side of the camper it is too much for 90% of the time I want to use it. I measured a six amp load on start up and about 4 A running so about 50 W constant .
That's another good idea.

The PWM controller mentioned above is 10A rated so you are good to go.

I'm going to order 3


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Posted By: tvman44 on 12/07/14 10:53am

The one I got is rated at 10 amps.


Posted By: Danhannah on 12/25/14 01:59am

The thing I would REALLY like to slow down and quiet down is the furnace fan - would this device do that? Or are those fans too big?


Posted By: KJINTF on 12/25/14 10:39am

Typical RV furnace fans draw 6 or 7 amps from 12Vdc power sometimes a bit more
Yes reducing the speed of the motor will reduce the noise
Might not be a good idea - the furnace gets hot and is designed for a specific cfm of air flow - the motor does double duty one circulating inside air and two exhausting the combustion air - BE Careful


Posted By: Blacklane on 12/25/14 08:41pm

Not to hijack this thread, but a better way to reduce furnace fan noise is to reduce the size of the return-air grill. Check the owner's manual for your model, but most have a minimum return air duct size of about 85 square inches, or about 9x9.5 inches. Most furnace grills are more like 12x15 inches. You can put sound-deadening fiberglass insulation inside the grill, leaving the required 85 square-inch opening. You can even paint the insulation black before installing it, so it's not noticeable.

Slowing down the furnace fan can be a bad idea, since the furnace itself needs to be cooled by the air flow. Reducing the flow creates a fire hazard.

* This post was last edited 12/29/14 07:47am by Blacklane *


Posted By: BurbMan on 01/01/15 10:49am

The furnace has a sail switch in the fans air flow, insufficient air flow will not trigger the sail switch and shut the burner down.


Posted By: LarryJM on 01/02/15 04:22am

Danhannah wrote:

The thing I would REALLY like to slow down and quiet down is the furnace fan - would this device do that? Or are those fans too big?


For the safety reasons already mentioned, I would HIGHLY advise not messing with or modifying your furnace fan.

Larry


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Posted By: LarryJM on 01/02/15 04:24am

BurbMan wrote:

I added a 10W resistor and a 2-position switch to the range hood fan about 5 years ago, now I have 2 speeds, too fast/loud and too slow.

Now that these PWM units are fairly inexpensive, I just ordered the same one that the OP pictured in his post. I also ordered this fan, a 120mm pancake fan rated to move 156 CFM.

[image]

Hoping that this fan motor will be quieter at all speeds.


That looks like a killer combo and I bet you will really like it. Good work matching/finding the components.

Larry


Posted By: scotty1946 on 01/05/15 10:31pm

Can you post a drawing or other schematic to show wiring, Im not much of an electrician. The picture is not clear from the angle taken.


Posted By: Blacklane on 01/07/15 06:57pm

Here you are.
[image]


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