Author Topic: Run Fridge off Starter Batts?  (Read 19305 times)

Offline Nellie Wilson

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Re: Run Fridge off Starter Batts?
« Reply #75 on: January 30, 2010, 04:29:58 PM »
Another...
Had to change a tire... >:(  got to put it on backward... :-\  still trying to fix it on photoshop... ??? ::) ???

Offline Nellie Wilson

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Re: Run Fridge off Starter Batts?
« Reply #76 on: January 30, 2010, 04:33:13 PM »
Another...
Had to change a tire... >:(  got to put it on backward... :-\  still trying to fix it on photoshop... ??? ::) ???

Offline Nellie Wilson

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Re: Run Fridge off Starter Batts?
« Reply #77 on: January 30, 2010, 04:37:52 PM »
This is stupid, but just one more. I'm taking my own thread off topic, but during 'breaks' I'm refreshing my wheels.  A lot more fun and makes for much better 'bus porn.'  ;D 
Had to change a tire... >:(  got to put it on backward... :-\  still trying to fix it on photoshop... ??? ::) ???

Offline Sean

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Re: Run Fridge off Starter Batts?
« Reply #78 on: January 30, 2010, 06:55:42 PM »
Viviane,

I'm not sure where to start here, but I have several concerns about the photos you've posted.

Let's start with the fridge:

  • I do not see a direct outside air inlet for combustion air.  Not a problem until you connect the propane, but once you do, there needs to be a direct source of air in appropriate quantity from outside the rig.  This is usually accomplished with a side vent at or below the level of the burner.
  • I also do not see a vent for the products of combustion, aka a "chimney."  This needs to be a direct vent through the roof at the highest point of the chase, or else you need an air-tight baffle and a side vent at the top just below it.
  • I do not see any escape for an unexpected release of ammonia.  This requires a vent at the lowest point of the compartment directly to the outside.  Usually, this is the same as the fresh air intake for the burner.
  • If the air handler I see in the photos is discharging condenser air into the compartment, this will severely limit the refrigerator's ability to cool.  Condenser air should be discharged directly to the outside environment.

I am also very concerned about the holding tank vent.  This must go through the roof in a direct and continuous manner.  Also, there can be no negative slope as shown in the photo.

I suggest you correct these things ASAP.  The fridge venting issues can kill you.  The sewer vent issue can make you very sick, or in severe cases cause an explosion in the coach.

FWIW.

-Sean
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Full-timing in a 1985 Neoplan Spaceliner since 2004.
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Offline gus

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Re: Run Fridge off Starter Batts?
« Reply #79 on: January 30, 2010, 08:13:29 PM »
Nellie,  I'm not sure I know what I see in the third photo, but the first two tell me you need a vertical baffle within 1" of the condenser coil (I think that's what I see at the top of pic #1?) and also the large coil at the bottom. There is too much space between the wall and coils for cooling air to work properly.

This will put your waste tank vent in its own separate compartment. I don't remember posting about this vent but I may have??

I don't know what I see in the third photo?  If the AC exhausts cold air into the frig chimney that is probably a waste of AC output. However, in addition to what Sean said about decreased frig efficiency, hot exhaust from the AC condenser will most likely choke down the AC and make it overheat unless your frig chimney is very large. The hot exhaust from an AC cond does not have a lot of "push".

I still don't think one 4" vent is large enough, I don't even think two 4" vents will be enough. You need to check the installation instructions carefully. Most RV frige vents, including mine, are much larger than this. Mine is 24" x 5.25" as required by my instructions, so even two 4" pipes will only be appx half this large.

It is probably a good idea if you email me directly with photos, then you can send as many as you like and they will be much larger so I can see what I see!!
                              egusDOTcATcenturytelDOTnet.

Sean,

She said she has two 2" holes in the bottom for intake air and a 4" exhaust hole at the top. It isn't clear to me if the intake is from outside or from the baggage comp but that is a good point about ammonia gas (LP as well).

I don't think this is enough air but it depends on what her installation instructions say.
PD4107-152
PD4104-1274
Ash Flat, AR

Offline Nellie Wilson

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Re: Run Fridge off Starter Batts?
« Reply #80 on: February 01, 2010, 02:31:23 AM »
Sean & Gus -

I’ll try to answer both your posts, as briefly  as possible.

First, to clarify, I haven’t yet cut any ceiling holes; that project (maybe) begins today.

But, per your (and others) much appreciated advice, I’ve enlarged the intake port (in the floor) and installed an air dam. This air dam will send air directly onto the lowest coils of the fridge.

I am also installing a wall approx. 1”-1½” distance from the coils. For safety, I covered the ‘hot’ side (the side facing the coils) with sheet metal.

The 2nd photo (floor vent for fridge) shows the original hole in the floor, which now reaches to (comes directly underneath) the coils & propane burner. And the flow of air is now channeled (as I mentioned) by an air dam.

The 1st photo (“holding tank vent behind fridge”) is self-explanatory. But, as I said, no holes are cut yet. The negative slope disappears (the ‘bend’ is flex hose) once the top pipe is attached and fixed to the roof.

The 3rd photo (A/C vent into fridge chimney) is just that. Only it will now run up and behind the chimney (using flex hose) and channeled in at the very top, just below the exhaust vent.

Okay, clear as mud, I’m sure. When I get the wall installed, I’ll update the photos… and thanks, Gus, for the email offer.
 
BTW, finally found some excellent venting diagrams (by Norcold) … I’ll try to insert the link. Hopefully, they’ll help someone else as much as they’ve helped me.    

Thanks to everyone; you guys are the greatest!

Nellie
« Last Edit: February 01, 2010, 02:34:32 AM by Nellie Wilson »
Had to change a tire... >:(  got to put it on backward... :-\  still trying to fix it on photoshop... ??? ::) ???

Offline Nellie Wilson

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Re: Run Fridge off Starter Batts?
« Reply #81 on: February 01, 2010, 02:47:57 AM »
Sorry -

Couldn't get that link inserted. I'll try again...

http://www.rvmobile.com/Tech/Trouble/vent.htm

Hope it works.

Nellie
Had to change a tire... >:(  got to put it on backward... :-\  still trying to fix it on photoshop... ??? ::) ???

Offline Christyhicks

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Re: Run Fridge off Starter Batts?
« Reply #82 on: February 01, 2010, 08:33:31 AM »
Excellant link, Nellie.  It shows everything SO MUCH BETTER than I could explain. . . I'm glad you found it!

Please forward those to ALL RV manufacturers and conversion companies, ok???  I can not BELIEVE I've seen as many fridges with improper installation as we have when working on factory rv's and conversions!

Sounds like you're moving forward in the right direction now.  Christy Hicks
If chased by a bear, you don't need to run faster than the bear, just faster than your companion!

Offline gus

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Re: Run Fridge off Starter Batts?
« Reply #83 on: February 01, 2010, 03:28:52 PM »
Nellie,

I think you have the situation well in hand now.

That link is essentially the same thing that is in my Norcold installation instructions. I had planned to email you copies if you didn't have them.

The AC vent may or may not help the frig vent draft, depends on its temp I guess. Anyway, it will be interesting to see what happens.

I firmly believe that you need to install a regular RV frig vent which is 24" x 5.25". This is the minimum size you will need for sure now that you are adding the AC vent also. The vent roof covers are low and smooth and designed to use airflow to aid the draft.

When you cut a hole this size you need to install a doubler which is a sort of frame around the hole about 1.5" wide. It is the same thickness and same metal as the roof metal and riveted. Pop rivets will do. It needs to be installed before you cut the hole, this keeps the metal around the hole from buckling and distorting when you cut the hole.

The vent frame may serve as a doubler but I don't think so. It has been too long since I did mine for me to remember for sure.

This doubler is important also because the roof skin is part of the structural strength of the bus body which is much like a walnut shell.

This is common practice on airplanes which have the same stressed skin.

I doubt the bus will fall apart if you don't install a doubler but it is a good idea!!
PD4107-152
PD4104-1274
Ash Flat, AR

Offline Nellie Wilson

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Re: Run Fridge off Starter Batts?
« Reply #84 on: February 01, 2010, 05:31:31 PM »
Gus -

You have been right on from the very start... and this from a guy who (at first) didn't even know a vent was required  :)) I'll even install that 'doubler" thingy-do (I even have a riveter... God knows I need it :)).

And thanks to Christy and Sean (and a whole bunch of others) that have offered their time and guidance. As Howard (Roman) might say, "I'm an idiot." But with friends like you, I'm getting (slowly) smarter.

I'll keep you informed... whether you like it or not.  :)

Nellie
Had to change a tire... >:(  got to put it on backward... :-\  still trying to fix it on photoshop... ??? ::) ???

Offline gus

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Re: Run Fridge off Starter Batts?
« Reply #85 on: February 01, 2010, 06:40:16 PM »
Nellie,

When I got the bus in '06 I knew nothing about RVs or buses.

Thanks to this board and a bunch of digging I got it done. I hate to think what I would have done without this board and "the other one"!

We were all "idiots" at first, no sin in that.
PD4107-152
PD4104-1274
Ash Flat, AR

Offline buswarrior

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Re: Run Fridge off Starter Batts?
« Reply #86 on: February 01, 2010, 08:01:15 PM »
Does my post back in page 2 make more comedic sense yet?

"Nellie, install that fridge properly and stop screwing around, "

I got no idea...

happy coaching!
buswarrior
Frozen North, Greater Toronto Area

Offline Barn Owl

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Re: Run Fridge off Starter Batts?
« Reply #87 on: February 01, 2010, 10:24:45 PM »
Throwing in my experience with a 3-way. My refer does a good job over time with 120v and can do a great job (freeze everything...oops!) with propane. Going down the road I thought 12v would be useful to save propane but I was wrong. 12v is just not enough to keep the frig cool. I wound up keeping it on propane because it just worked better than the other modes. While in Las Vegas during 100 degree plus days even the propane struggled. My unit is an old Dometic manual type built in 1979. When it goes I have a good used 12v compressor type to go in it's place.
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Offline Nellie Wilson

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Re: Run Fridge off Starter Batts?
« Reply #88 on: February 02, 2010, 02:51:19 AM »
from BusWarrior
Quote
Does my post back in page 2 make more comedic sense yet?

Hi BW -  :)

Actually, it made sense back then... I just didn't get it. if you check page 3 you'll see my 'admission of ignorance' - always a bitter pill to swallow.  :-[

BarnOwl: Thanks for sharing your BTDT info. Based on all I've heard, I'm going to 'quit screwing around' :-* and go strictly with 120VAC and (eventually) propane. But propane can wait until I get a larger 'chimney' (and some $$).

Still, after a year with no fridge at all, this feels like luxury! And I can keep using ice-packs for going down the road. Heck, until last week, that's all I had. So you see, just like 'The Jeffersons,' I'm still... Movin' On Up.  ;)

Nellie

Had to change a tire... >:(  got to put it on backward... :-\  still trying to fix it on photoshop... ??? ::) ???

Offline gus

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Re: Run Fridge off Starter Batts?
« Reply #89 on: February 02, 2010, 10:02:17 AM »
Nellie,

You still need a chimney, even with only 120vAC, since the frig system uses a boiler no matter what the power source.

The chimney draft pulls in cool air to cool the two sets of coils, the upper coil being the one that removes heat from inside the frig.

The only real difference between AC and LP is that AC has no toxic exhaust gases, it just heats the boiler with a hot coil instead of a flame.

However, during cold weather it will operate well. I know because we did it for a while before we knew better. It did give off some nice heat into the bus though!

Hot weather is another story, I don't know how it will do then but my guess is not very well.
PD4107-152
PD4104-1274
Ash Flat, AR