Adding a Fan Speed Control to my Range Hood

[Blacklane]

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.



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.



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



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.



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

[Blacklane]

Here you are.

[scotty1946]

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.

[LarryJM]

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.



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

[LarryJM]

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

[BurbMan]

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.

[Blacklane]

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.

[KJINTF]

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

[Danhannah]

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?

[tvman44]

The one I got is rated at 10 amps.

[2112]

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

[All_I_could_aff]

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 .

[tvman44]

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. 🙂 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. 🙂

[RV_daytrader]

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.

[BurbMan]

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.



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