Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×


Reply
 
Thread Tools Display Modes
Old 08-25-2012, 06:34 PM   #81
Senior Member
 
Join Date: Oct 2011
Location: Austin, Tx area
Posts: 126
Yes, very. Isn't dissipation of heat, still dissipation of heat no matter if the system is closed or open?
Well yes, but.
These fridges are really two systems. An ammonia cycle heat pump
which is closed and an "ammonia gas generator" which is an open
system. Open in that it requires outside heat input.
What does that mean? Well........??

The question still remains why on most days/nights my little pop up camper fridge would work well, then with no setting changes, it would start to warm up. Then the following day in most cases it would start to cool down. This was fairly random.
Insufficent data.

The only thing that was not consistent was the weather,

A clue? A data point?

so I'm still unsure why ammonia fridges vary so much in cooling.
I think the amazing part is not that they work so well, but that they
work at all........

cheers,
johnd
__________________
2001 Cherokee CKT27X - 2005 Chev 3500
Sara, John & Crafty Canines - Coco and Cole
---
Medical research shows that men have a "biological clock" too. The older we get, the greater the NEED to drive a TRUCK!
dnaraG_1M is offline   Reply With Quote
Old 08-25-2012, 06:34 PM   #82
Member
 
xf021209's Avatar
 
Join Date: Dec 2010
Posts: 53
Quote:
Originally Posted by Mark S
So after 8 pages of discussion, numerous scientific theory, scores of photographs and even a little bit of debate, the answer to my original question that started this thread, "are two fans better than one" the answer is a definate maybe. I am glad we got that resolved

I added the second fan just above the intake and will know for sure when I camp again at the end of September how it works. I may try moving it up to the horizontal exhaust vent if it's not as good as I hope . Thanks for all the input.

Ps. Man, there are some very intelligent folks on this forum. What a great resourse and source of entertainment.

Mark
I'm with ya Mark on all counts. My personal favorite MAGIC! Really though I think you're right. Because of different configurations, designs, and location of use (altitude, temps, humidity) and other factors and personal experiences, the best method is just try it and see what works and what doesn't. Do let us know what worked for you.
__________________
Todd - 2006 Forest River 27BH (previous FEMA trailer, rebuild in progress.) https://www.facebook.com/media/set/?...1&l=1506dbb708
EPDM Rubber Roof Installation - https://www.youtube.com/watch?v=xbraK...hannel&list=UL Pulled by a 2002 Chevy Avalanche, 496cid Rat motor, 12k Lb. tow package, leveling hitch, dual sway controls & electric brakes.
xf021209 is offline   Reply With Quote
Old 08-25-2012, 06:38 PM   #83
Member
 
xf021209's Avatar
 
Join Date: Dec 2010
Posts: 53
Quote:
Originally Posted by dnaraG_1M
Yes, very. Isn't dissipation of heat, still dissipation of heat no matter if the system is closed or open?
Well yes, but.
These fridges are really two systems. An ammonia cycle heat pump
which is closed and an "ammonia gas generator" which is an open
system. Open in that it requires outside heat input.
What does that mean? Well........??

The question still remains why on most days/nights my little pop up camper fridge would work well, then with no setting changes, it would start to warm up. Then the following day in most cases it would start to cool down. This was fairly random.
Insufficent data.

The only thing that was not consistent was the weather,
A clue? A data point?

so I'm still unsure why ammonia fridges vary so much in cooling.
I think the amazing part is not that they work so well, but that they
work at all........

cheers,
johnd
Great responses and thanks...you're right...not enough data, so much of it is educated guesswork. It's interesting trying to explain to someone how heating ammonia with a flame can cause an insulated box cool down, so yes it's amazing they work at all.
__________________
Todd - 2006 Forest River 27BH (previous FEMA trailer, rebuild in progress.) https://www.facebook.com/media/set/?...1&l=1506dbb708
EPDM Rubber Roof Installation - https://www.youtube.com/watch?v=xbraK...hannel&list=UL Pulled by a 2002 Chevy Avalanche, 496cid Rat motor, 12k Lb. tow package, leveling hitch, dual sway controls & electric brakes.
xf021209 is offline   Reply With Quote
Old 08-25-2012, 06:58 PM   #84
Senior Member
 
onetonford's Avatar
 
Join Date: Oct 2010
Location: Lodi CA
Posts: 1,211
Here is how it was Explained to me.


A gas refrigerator uses ammonia as the coolant, and water, ammonia and hydrogen gas to create a continuous cycle for the ammonia. The refrigerator has five main parts:

Generator - creates ammonia gas
Separator - separates the ammonia gas from water
Condenser - where hot ammonia gas is cooled and condensed to create liquid ammonia
Evaporator - where liquid ammonia converts to a gas to create cold temperatures
inside the refrigerator

Absorber - absorbs the ammonia gas in water
It works like this:
1. Heat is applied to the ammonia and water solution in the generator. (The heat comes from burning gas, and\or electric heating element in the case of a RV frig.)
2. As the mixture reaches the boiling point of ammonia, it flows into the separator.
3. Ammonia gas flows upward into the condenser, dissipates heat and converts back to a liquid.

4. The liquid ammonia makes its way to the evaporator where it mixes with hydrogen gas and evaporates, producing cold temperatures inside the refrigerator's cold box.
5.The ammonia and hydrogen gases flow to the absorber where the water collected in the separator in step No. 2 mixes with the ammonia and hydrogen gases.

6. The ammonia forms a solution with the water and releases the hydrogen gas, which flows back to the evaporator.
7.The ammonia-and-water solution flows toward the generator to repeat the cycle.
__________________

2001 Ford F-350 DRW 7.3
2011 25 RL Wildcat
former fiver 1976 Fourwinds had for 35 years
onetonford is offline   Reply With Quote
Old 08-25-2012, 07:19 PM   #85
Senior Member
 
Join Date: Oct 2011
Location: Austin, Tx area
Posts: 126
Quote:
Originally Posted by Mark S View Post
Ps. Man, there are some very intelligent folks on this forum. What a great resourse and source of entertainment.
Mark
Indeed there are. The amount of info and help that I have gotten
here is immense. What did I do before the Internet allowed me
to "gather it all in"!!! And nobody, but nobody has anything like
the Herk Information Super Library.

Yesterday, I finally got around to powering up my FOUR fan
array from Allelectronics and I was amazed at how quiet they
are. So......I'm now gonna try to duplicate what ya'll are doing.
The Texas 100+ heat really does a job on my fridge..........


In a less serious vein:
Entertainment??? Oh yes. In my personal case, I know that I
am a great source. Every time we go to leave, my DW just roars
laughing at me.

But then I remember my pants and......................

cheers,
johnd
__________________
2001 Cherokee CKT27X - 2005 Chev 3500
Sara, John & Crafty Canines - Coco and Cole
---
Medical research shows that men have a "biological clock" too. The older we get, the greater the NEED to drive a TRUCK!
dnaraG_1M is offline   Reply With Quote
Old 08-25-2012, 07:24 PM   #86
Mod free 5er
 
Join Date: Mar 2008
Location: Concord, NC
Posts: 24,702
Best and simplest explanation I've seen. Complete with picture of the back of a refrigerator.
Attached Files
File Type: doc Absorption fridge.doc (96.5 KB, 58 views)
__________________
OldCoot is offline   Reply With Quote
Old 08-26-2012, 08:50 AM   #87
Mod free 5er
 
Join Date: Mar 2008
Location: Concord, NC
Posts: 24,702
I just crawled up on the back of our trailer to investigate the possibility of installing another fan under the roof vent for the refrigerator. After removing the top cover, I discovered a molded collar with a screen in it. I will NOT be removing the collar. The chimney uses the back of the trailer as the back side of the chimney which curves at the top with a large hole cut in the ceiling to dump the hot air.

I will add the extra fan beside the one already installed and wire them together. Using a mirror, and looking up from below, there are no baffles or deflectors blocking off from the back wall of the chimney to the back of the refrigerator. It is clear from the bottom of the compartment to the hole in the roof.
Attached Thumbnails
Click image for larger version

Name:	DSC00080.jpg
Views:	79
Size:	32.5 KB
ID:	18703   Click image for larger version

Name:	DSC00081.jpg
Views:	80
Size:	36.8 KB
ID:	18704   Click image for larger version

Name:	DSC00083.jpg
Views:	85
Size:	24.3 KB
ID:	18705   Click image for larger version

Name:	DSC00084.jpg
Views:	88
Size:	54.4 KB
ID:	18706   Click image for larger version

Name:	Looking up the refrigerator compartment.  White surface is back of trailer.jpg
Views:	86
Size:	21.6 KB
ID:	18707  

__________________
OldCoot is offline   Reply With Quote
Old 08-26-2012, 04:06 PM   #88
Mod free 5er
 
Join Date: Mar 2008
Location: Concord, NC
Posts: 24,702
Going to have to remove the existing fan and come up with a dual mount to get both fans mounted side by side where there is room.
__________________
OldCoot is offline   Reply With Quote
Old 08-27-2012, 04:27 PM   #89
Phat Phrog Stunt Team
 
TURBS's Avatar
 
Join Date: Aug 2011
Location: Iowa
Posts: 34,507
Click image for larger version

Name:	ForumRunner_20120827_162554.jpg
Views:	82
Size:	29.0 KB
ID:	18780



Click image for larger version

Name:	ForumRunner_20120827_162608.jpg
Views:	88
Size:	31.0 KB
ID:	18781



With my two fans outside blowing air up the vent pipe and one inside fridge I maintained 32 degrees in my fridge today.
Temp was 91 today with the fridge side in the sun.
TURBS is offline   Reply With Quote
Old 08-27-2012, 04:56 PM   #90
Phat Phrog Stunt Team
 
TURBS's Avatar
 
Join Date: Aug 2011
Location: Iowa
Posts: 34,507
I almost forgot I started the fridge at 6;30 am today and at 4;30 pm this is the temp.
Also note that the a/c was off in the unit today .
TURBS is offline   Reply With Quote
Old 08-27-2012, 05:26 PM   #91
Mod free 5er
 
Join Date: Mar 2008
Location: Concord, NC
Posts: 24,702
Got my two fans mounted and operational, 1) 80mm and 1) 90mm. With both fans going, you can feel the heat coming out of the roof vent. Temp inside frig is holding @ 33° with the control set at 2 and outside temp @89°. Very pleased with the setup. I may bolt a deflector to the outer edge of the fans so the air is directed straight up so it does not deflect off the accumulator and out the lower vent. I want all the air going up the chimney and out the roof vent.
Attached Thumbnails
Click image for larger version

Name:	Dual fans 1.jpg
Views:	88
Size:	43.6 KB
ID:	18786   Click image for larger version

Name:	Dual fans2.jpg
Views:	112
Size:	39.7 KB
ID:	18787   Click image for larger version

Name:	One 80mm and one 90mm.jpg
Views:	112
Size:	37.1 KB
ID:	18788  
__________________
OldCoot is offline   Reply With Quote
Old 08-28-2012, 06:03 PM   #92
Senior Member
 
M109Rrider's Avatar
 
Join Date: Oct 2010
Location: Chesapeake, Va
Posts: 938
At 89-91 degrees could you not get those temps before the fans?
__________________
Jason and Billie
2018 F-250, 6.2L
2011 Prime Time Crusader 320RLT
"PT Crew Member Since 11/2010"
M109Rrider is offline   Reply With Quote
Old 08-28-2012, 06:08 PM   #93
Phat Phrog Stunt Team
 
TURBS's Avatar
 
Join Date: Aug 2011
Location: Iowa
Posts: 34,507
Quote:
Originally Posted by M109Rrider View Post
At 89-91 degrees could you not get those temps before the fans?
1) I could not maintain a temperature .
2) fridge temp ran mostly in the 36 to 38 range

my fridge cooled to 32 degrees in about 9 hours . it could have been less but I only checked when I got home from work .
TURBS is offline   Reply With Quote
Old 08-28-2012, 06:24 PM   #94
Mod free 5er
 
Join Date: Mar 2008
Location: Concord, NC
Posts: 24,702
Quote:
Originally Posted by M109Rrider View Post
At 89-91 degrees could you not get those temps before the fans?
I could get the temps, but the control had to be set @4 instead of 2 and if the outside temp went to the high 90's and low 100, I had to set the control to 5 to hold the frig at around 34°-35°. It just makes the whole system work so much more efficient for our situation. For no more expense and effort to install, I think it it well worth it.

The gas burner just does not cycle as much. As far as saving propane, I imagine it is negligible, but every little bit helps.
__________________
OldCoot is offline   Reply With Quote
Old 08-28-2012, 06:44 PM   #95
Senior Member
 
M109Rrider's Avatar
 
Join Date: Oct 2010
Location: Chesapeake, Va
Posts: 938
Cool, glad you got the results you needed.
__________________
Jason and Billie
2018 F-250, 6.2L
2011 Prime Time Crusader 320RLT
"PT Crew Member Since 11/2010"
M109Rrider is offline   Reply With Quote
Reply

Tags
fan

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by Forest River, Inc. or any of its affiliates. This is an independent, unofficial site.



All times are GMT -5. The time now is 01:29 AM.