UPDATE: Supplementary Cooling Fans

[JFXG]

A couple of weeks ago I posted about the old noisy cooling fans the PO had mounted in the back space of my Dometic 1292.
Well, I got the job done. Runs nice and quiet but I still am a bit perplexed.


OLD RATS NEST WIRING


SLIGHTLY CLEANED UP WIRING

Yes, I cleaned up some of the wiring, cleaned out some dust and dirt. Looks better, easier to trace.


OLD BANK OF THREE 3 INCH FANS


NEW BANK OF THREE 5 INCH FANS

The new fans are not only far more secure, they run quieter and look a lot nicer (although no one will ever see them). Of the three old fans one was inop, so I have effectively tripled my fan capacity. I reused the same thermal switch, (see pic), but will replace it as soon as I can get a spec. I can only read a few of the ID numbers on the switch body, so I don't know the temp trigger for this. Any one have that knowledge? I know the switch works to some extent because the new fans cycle, but I don't know the desirable temperature point, and I don't know if the temp switch is in the optimum place. I know it was mounted near the top of the tower where you see it, but can't recall if it was on the top level, or one rung down. Would it matter?
But here's the really strange part: before, with two old three inch fans running, my fridge held steady at about 35-38 degrees. With the fans deinstalled for a few days, my fridge held steady at about 35-38 degrees. And now, with three new five inch fans humming away, my fridge holds steady at about 35-38 degrees.
But the service area sure does look nicer!!


John & Diane, fulltiming since '12 02 DS, FL, Cat, '04 Element NHSO RVM103

[BFlinn181]

Much neater than the previous installation. Since 2 three inch fans did the same cooling as the 3 five inch ones, do you think it's more than you need? What's the temperature in the refrigerator if you turn the fans off? One on?

You might be able to save the batteries and have it quieter too!

[JFXG]

When I had all fans out for a couple of days the temps held steady, 35-38. The whole assembly is also on a switch, so I will experiment in the up coming days. We have some mid-90s days coming, so I'll check out just where the edges are.


John & Diane, fulltiming since '12 02 DS, FL, Cat, '04 Element NHSO RVM103

[MtnTrek]

Great right up and illustrations, Thanks.


The box temps are more representative of the units T-stat functioning properly (thermistor, controller) which cycles the concentrators heat source.
The fans you retrofitted deal more with the heat removal efficiency resulting in reduced call for concentrator run time (reduced energy consumption from heat source).
Reduced probability of premature unit failure due to "crystallization" which is common to the demise of absorption refrigeration devices.
In the upper design envelope approx. +100 deg. ambient it will maintain box better.


Happy motoring.

[MSHappyCampers]

Glad you got the problem solved John!

[JFXG]

Originally Posted by MtnTrek

....The box temps are more representative of the units T-stat functioning properly (thermistor, controller)...........

............In the upper design envelope approx. +100 deg. ambient it will maintain box better...........

Thanks for the explanation-- I hadn't really thought it through that way.

Now..... thermistor. I've read that moving the thermistor up or down on the internal fin will change performance. How much movement, and which direction?
Temp switch controlling the fans..... When you say "+100 degree ambient", do you mean that my fans should trigger on at 100 degrees, or at 100 degrees over ambient-- like 170 or so? Thanks!


John & Diane, fulltiming since '12 02 DS, FL, Cat, '04 Element NHSO RVM103

[Lt Dan]

John;
On my old Norcold, the sensor switch was mounted to the condenser fins on the hot side. It was set to come on at 135 degrees. When I replaced the cooling unit with an Amish, they had a mounting spot for the sensor closer to the boiler tube so the fans would come on earlier. The added air flow will make a difference as the ambient air temps rise. You probably have adequate air flow now just due to convection flow as the hot air inside rises out the top.

[MtnTrek]

X2 Lt Dan.


"The added air flow will make a difference as the ambient air temps rise. You probably have adequate air flow now just due to convection flow as the hot air inside rises out the top."
Those klixon switches are spec'd at a set temp. (example 135) so their placement can somewhat adjust the effect desired. No reason to run the fans in cooler ambient temps. they should generally cycle (not literally, but with a delay) with the concentrators heat source causing those tubes to heat up.

I'd leave the evaporator (Cooler) thermistor in the lower fin corner suggested by manufacturer.




(two Rescued Boston "Terrorists") LOL , cute! DW and I got a chuckle.


Happy motoring.