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Cabin fan/diesel heater heat distribution fan speed controller


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@Fah Kiew Tu (since you said you’re installing a Dickinson diesel heater, and maybe a Heatex too?) and anyone else who might be interested - I just tested some cheapie PWM DC motor controls I picked up on Amazon - for a bunch of Hella Jet cabin fans I installed recently, and for two heat duct fans that scavenge heat off my diesel heater in winter (in-line duct fans pull heat into forward and main cabin from the Dickinson Heatex).

The fans are all either on/off - and also surprisingly much louder than I wanted when turned on.  These cheap controllers ($12 for 5!) do a great job - you can dial fan speed *right* back and still keep cool or hot air moving nicely.  Just FYI - these controllers work really well. (Rated 12v/2A/30W)

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  • Jud - s/v Sputnik changed the title to Cabin fan/diesel heater heat distribution fan speed controller

Thanks for that, I'm still sorting the heater. I've fired it once using methylated spirits just to test the flue and general stuff, decided the pipe got waaaaay too hot to use unguarded (this was totally expected, incidentally) so now have made a flue guard from some perforated stainless I had in my scrap pile. We're planning on going sailing tomorrow afternoon because all the wage slaves will have to return to their orofices and leave the anchorages uncluttered *and quiet* again.

Not really cold enough to run the heater yet but - shrug. Might give it a test fire on diesel.

After it's all working fine I'll give serious thought to fans. Otherwise all the hot air will stratify and we'll get that roasted head-frozen feet syndrome I remember so un-fondly from down south.

FKT

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I bought a bag of those.  Put three into cabin fans. One made it about 2 weeks, one a month and the other is still going.  Kinda get what you pay for.  Should note the second failure was a smoke show so be careful. They were all on the same model fan at a low speed.

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2 hours ago, SASSAFRASS said:

I bought a bag of those.  Put three into cabin fans. One made it about 2 weeks, one a month and the other is still going.  Kinda get what you pay for.  Should note the second failure was a smoke show so be careful. They were all on the same model fan at a low speed.

Good to know. I bought them as a bit of an experiment to see how well fan speed could be dialled back, since they’re quite cheap - all those boards are mass produced cheaply and I didn’t figure there’d be much quality difference in them.  Apparently there might be  :-)

Or maybe too high current? One thing I hadn’t really considered was at lower speed and lower voltage current is higher. At low speed I metered voltage at load terminals on the board at 5.5v (instead of 13).  Didn’t check current.  Wonder if, in continuous duty at that voltage, amperage is too high for the boards?  Also hadn’t really considered continuous duty in a hot, tropical environment: i.e., heat dissipation from the units).

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Just make sure you fuse locally very close to load, I would even do both plus and minus.  No worries then. All the ones I put in were at low speed just to circulate air, no ryhme or reason why the two failed and the other is fine all the same fan motor.  I was just tired of dropping big money on fans and having the boards die.  Have tried all the Caframo brands.  It seems like the center button one is lasting the best.  We had a box of the really nice articulated ones that are super quiet and no draw but the boards had all died.

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3 hours ago, SASSAFRASS said:

Just make sure you fuse locally very close to load, I would even do both plus and minus.  No worries then. All the ones I put in were at low speed just to circulate air, no ryhme or reason why the two failed and the other is fine all the same fan motor.  I was just tired of dropping big money on fans and having the boards die.  Have tried all the Caframo brands.  It seems like the center button one is lasting the best.  We had a box of the really nice articulated ones that are super quiet and no draw but the boards had all died.

By “the boards died”, do you mean internal components of the fans?

In my case, the fans are all simply on/off.  No internal speed control circuit boards.  I didn’t like how loud they are at on/high speed.  So I wanted a separate speed controller to dial them back (like you, just for air circulation whether in hot weather or to circulate diesel heater air).  I was going to install the controllers in little “boxes” near the fans with the control knobs accessible.

Now I’m wondering if I should get slightly better quality controllers —probably go with higher current rated ones, with the hope that they’ll last longer under continuous use (as compared to the 2A rated ones I got as a cheap experiment.)

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The best thing is a simple ceramic variable resistor, it fails to open so you just get full speed in the fan. It's what Dickenson uses on the stove fans. The electronic ones have many bits to fail and can be a dead short.  The Caframo fans were all too fancy auto off timers multi speed etc and the open voltage to the fan turns it into a jet engine. If the fan you are controling has a low open voltage speed you will probably be ok as the controller is doing alot less work.

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1 hour ago, SASSAFRASS said:

The best thing is a simple ceramic variable resistor, it fails to open so you just get full speed in the fan. It's what Dickenson uses on the stove fans. The electronic ones have many bits to fail and can be a dead short.  The Caframo fans were all too fancy auto off timers multi speed etc and the open voltage to the fan turns it into a jet engine. If the fan you are controling has a low open voltage speed you will probably be ok as the controller is doing alot less work.

Thanks - makes way more sense.  Simple - just found some nooner.  Just drops voltage at resistor- extremely unlikely to short closed (as the fancy electronic, component-laden shit may well, you noted - esp. if cheap Chinese stuff).

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When I made my cabin fans (cheap 12v brushless muffins in a teak frame) I ended up making them 2-speed with a single-pole double throw (center off) small switch and a simple (and very cheap) single-value resistor.  Used a pot just to decide the right value for the resistance.  Never found a need for more variability.  Plus, nothing to fail, especially if you coat the connections with something appropriate.  

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54 minutes ago, jamhass said:

When I made my cabin fans (cheap 12v brushless muffins in a teak frame) I ended up making them 2-speed with a single-pole double throw (center off) small switch and a simple (and very cheap) single-value resistor.  Used a pot just to decide the right value for the resistance.  Never found a need for more variability.  Plus, nothing to fail, especially if you coat the connections with something appropriate.  

Yeah, I thought of doing that earlier - I don’t need variable speed - it’s just that a pre-made controller or pot is an easy plug and play solution.  (Bloody Amazon and cheap Chinese goods make it way too easy.)  

I figured out I’d need a 20 ohm resistor to get a decent, mellow low fan speed...but then I’d have to do more work to put it all together for 8 fans :-). With the basic cheapie PWM controllers (or variable ceramic resistor), over-spec’d for wattage rating they’re still really cheap, and just need to plug the wires in: done. (Will do some kind of conformal coating or neutral silicone to keep out moisture/salt.) Fingers crossed that they last...I agree two-speed system by using a resistor is way less to fail.  Maybe I’ll revisit that plan...don’t really want to think about fan control drudgery ever again :-) :-)

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jamhass approach is a good one as two speeds are probably fine, you can get horrible noise, electrical and audible at certain speeds so best to do some trial and error for a value.  The good thing on amazon is super cheep boxes of ferrites too.

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32 minutes ago, SASSAFRASS said:

jamhass approach is a good one as two speeds are probably fine, you can get horrible noise, electrical and audible at certain speeds so best to do some trial and error for a value.  The good thing on amazon is super cheep boxes of ferrites too.

Why would you need more than one? 

Cute pets though.

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On 4/5/2021 at 12:13 AM, Ishmael said:
On 4/4/2021 at 11:38 PM, SASSAFRASS said:

...  The good thing on amazon is super cheep boxes of ferrites too.

 

Why would you need more than one? 

Cute pets though.

image.png.f7c3954e2c702e90a121248d9d76f579.png

 

Incorrect

Those are ferrettes

Do not use in 12V applications

FB- Doug

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I guess you could try wrapping all your wiring in ferrets but not sure it would help the noise. Maybe a bit smelly too.  They were our first potential bad pet choice before a capuchin.  Thankfully neither happened.  The Panama swap cat might be part ferret though as he dives into the bilge at any chance and is a major pain to get back out.

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