6.7 Frig Tinkering ideas?

[Klem]

Originally Posted by Ron in BC

The stuff Myron calls "junk too good to throw out" and I call "resource materials"

Getting rid of 126 degree waste heat has to be a benefit. Great work and good solution for hooking up the flue.

Ron

Thank you, There was a person who extended his in an early thread that inspired me too. Thinking HotFishTacos but maybe a nice fellow from Tennessee?

It takes a village ...

[Klem]

Originally Posted by cpaharley2008

Mel,
I'm wondering if the bottom locale of the intake will not have the same effect as the open MaxxFan on the roof has, you may have a reverse pressure situation and the draw may be affected. Perhaps if you turned the vent cover forward to scoop air into the intake while moving?
Then again the faster you go the more air, do you want that to happen? Or is it already facing forward, hard to tell from the pictures?

The simple answer I believe is that I have sealed the 'chimney' top to bottom with sealing tape, silicon, sticky foam, etc. so any positive or negative pressure should not get into the trailer living area.


I just realized the last paragraph is saying I should have blocked off the upper area (seen in my pictures with the plastic conduit for supports). It should be down at refrig top.

I tried to meet or exceed this:

Proper installation requires one fresh air intake and one upper
exhaust vent. The ventilation kits shown in this instruction
manual have been certified for use with the refrigerator

models listed in the Table. For approved vents and refrigerator

vent options, see Pages 12 -16. The ventilation kits must be
installed and used without modification. An opening toward
the outside at floor level in the refrigerator compartment must
be provided for ventilation of heavier-than-air fuel gases. The
lower vent of the recommended kits is provided with proper
size openings. The flow of combustion and ventilation air
must not be obstructed.
The lower side vent is fitted with a panel which provides an
adequate access opening for ready serviceability of the
burner and control manifold of the refrigerator. This should be
centered on the back of the refrigerator.
When installing the refrigerator, the installer must block the
space between the storage cabinet and the top of the
refrigerator, otherwise heat will become trapped in this
space, making the top of the refrigerator hot, thus reducing

the efficiency of the unit.

[NJ Joe]

Any concern with the air that enters through your new bottom vent getting sucked out the side vent when the trailer is underway ?

[Klem]

Originally Posted by NJ Joe

Any concern with the air that enters through your new bottom vent getting sucked out the side vent when the trailer is underway ?

Good question. I won't really know until we take a long trip south in February. Hopefully I have built in the ability to make changes to optimize this air system.

I have thought a lot about the aerodynamics of the top and bottom vent. Some people complain of poor operation on the road and I wondered if there may be some backflow in the stock system.

We have hauled our trailer maybe 900 miles so far and always with the propane turned on with a digital thermometer inside that reads outside. Whenever we stop I have been looking at the temperature obsessively and I don't see any significant changes. I definitely see changes in ambient temperature will change frig temp and increase or decrease the 'power' (1-5 bars) to compensate.

That being said, I built the air box right inside the lower vent so I could fool around with the fan mount angle and design. The 'texas fan' was mounted up in the vent system at a location you would have to cut into the upper vent screen, or pull the refrigerator, to service.

The air box is simply a wooden box that I can slip in a piece of wood, or metal straps, to mount fan(s), create a baffle, or whatever. I was happy to find a protected area of 'disturbed air' for the lower pickup. IF air is sucked out the side vent but it doesn't affect the refrigerator temperature I don't care.

I have sealed all joints with tape, silicon, etc. to insure the air system is 'closed' from the living area. I would hope the Dometic top vent is designed to 'draw' air up the chimney and my additional lower vent should not increase the lower supply to greater then the upper outflow.

If the 3 air vents work unpredictably for any reason I can always add an aluminum sheet deflector to break the draw, but my guess is this will work better then what I had.

Mel

[padlin]

How warm does it get where you are headed?

[cpaharley2008]

Yes, I wonder if you will get any negative air pressure or venturi effect with the air blowing across the bottom under floor vent opening while under tow and sucking air out vs into the unit. In other words a poor chimney draft.

[Jubal]

I believe that any movement of air displacing heat from bottom to top and vice versa would be an improvement on the OE poorly designed and improperly installed refrigeration system.
Mel, I admire your initiative !

[rbryan4]

Originally Posted by Klem

I just realized the last paragraph is saying I should have blocked off the upper area (seen in my pictures with the plastic conduit for supports). It should be down at refrig top.

Yeah, as in this drawing -- where they've added insulation wool to the top of the fridge:

[Klem]

Originally Posted by padlin

How warm does it get where you are headed?

We'll be spending some time in the south southwest, bouncing along the border (US-Mexico). Hopefully 'hot'

[Klem]

Originally Posted by cpaharley2008

Yes, I wonder if you will get any negative air pressure or venturi effect with the air blowing across the bottom under floor vent opening while under tow and sucking air out vs into the unit. In other words a poor chimney draft.

See what you think of this 'logic'...

The air under the trailer should be turbulent (like an airplane with flaps down) and the top should be faster (like the smoother top of a wing). And the top vent should be designed by Dometic to draw air. The side is quite smooth too but the vent is smaller then the top. At this time I can only assume the air is moving up ... but with the weird performance reports I'm not sure.

Add some heated air off the coils on the back of the frig and it wants to rise ...

I almost sized the lower vent 6" with less obstructions but chose 4" with screen and cover based on my intuition.

Combined with the centrally located airbox I can balance the air flow if needed.

I've spent a bit of time around aircraft but honestly it's a WAG. (wild ass guess) Ideally I should have a fully compliant installation with the larger LS300 side vent. I'm sure it would work better then what I have. But I can't wait any longer for the tooth fairy to fix my refrigerator, we're heading south and Irma loves her fresh fruits and vegetables chill'n in the frig.

Thanks for your thought provoking questions, I'll be pulling the frig one more time to implement a few improvements you all have suggested.

Mel

[NJ Joe]

I think on many trailer designs, the air gets disrupted long before it hits either the top or side vents, and prevents the negative pressure. The vent design from Dometic may be counting on that. Escape trailers may be different in this respect, and not disrupt the airflow prior to the vents. I think something to disrupt the air aft of the vents would help to create a stagnation point at the vent opening. Its possible that doing this for only the side vent would help ensure the air is flowing properly when the trailer is underway.

[Klem]

I just found this on-line.

Is leaving the flue in the area behind the refrigerator in compliance with this? Are 'our' installations in compliance with the Dometic standards in the document below? Do they apply to US and Canadian installations?

http://www.caravanfridges.co.uk/pdf-...ion-manual.pdf

E1.5 Exhaust gas duct and installing the fume flue

The exhaust gas duct system must be made in
such a manner as to achieve a complete extraction
of combustion products to the outside of

living space. The duct system must slope in an

upward direction in order to avoid a build-up of
condensate. The type of exhaust gas duct
shown in Fig. E22 allows the side installation of
the winter cover.

An installation other than described will
reduce the cooling capacity and jeopardise

the manufacturer's warranty/product liability

[tractors1]

I don't consider the rear side of the fridge to be a "living space." ETI appears to seal/gasket the joint between the two. Same as my last couple of trailers.

[gbaglo]

Klem,

I read what you posted before you edited it to tone it down. It still exists.

[Ron in BC]

Originally Posted by Klem

I just found this on-line.

Is leaving the flue in the area behind the refrigerator in compliance with this? Are 'our' installations in compliance with the Dometic standards in the document below? Do they apply to US and Canadian installations?

That info does raise some questions. Puzzled by the requirement that the flue slope upward to prevent condensation (running back and contaminating the burner area) That would seem to imply that one that is short and vertical stands more of a chance of having condesate foul the burner area. It would seem that an insulated exhaust flue would be better, to prevent condensation. But the whole issue is: it's obvious Dometic considers this important but we have short stubby flues dumping out their exhaust gases lower than what the manufacturer seems to be recommending.

Secondly, they seem to be saying that not to use foam type insulation as it's a fire hazzard. Also they recommend the heat deflector shield.

To be honest, I'm really starting to wonder if Dometic needs to look at our installations and say yes or no as to whether they do meet their standards.

Ron

[jamman]

Originally Posted by Ron in BC

That info does raise some questions. Puzzled by the requirement that the flue slope upward to prevent condensation (running back and contaminating the burner area) That would seem to imply that one that is short and vertical stands more of a chance of having condesate foul the burner area. ...
...
Ron

I think they may be saying it has to be upward as opposed to downward. They may not be saying it has to be sloped rather than vertical.

[Ron in BC]

The surprising part of that item is that there's condensate. I've seen lots of that on mid and high efficiency furnaces but I didn't expect that an open flame with a short flue would even have condensate.

I'd like to find a source of the lip seal that fits the groove. The way I read those installation instructions they're saying that the foam ETI uses in that location is a fire hazzard. Or, is there a lip seal and the foam is just added as extra sealing?

Ron

[reace]

Hello Klem,

The information you have posted regarding the vent/ducting for the fridge.

E1.5 Exhaust gas duct and installing the fume flue

The exhaust gas duct system must be made in
such a manner as to achieve a complete extraction
of combustion products to the outside of
living space. The duct system must slope in an

upward direction in order to avoid a build-up of

condensate. The type of exhaust gas duct
shown in Fig. E22 allows the side installation of
the winter cover.

is for a side mount vent. This is where the fridge is ducted and vented through the side of the trailer.

Escape vents the trailers using a roof mount vent. There is low vent on the side of the trailer and an upper vent on the roof of the trailer.

When the poor cooling performance with the fridge arose Escape Trailer Industries recorded and documented in detail the installation method of the fridge and fridge vent sizes used. This is the first place Dometic looked for fault regarding performance failure. Dometic's tech's, then reviewed this information and they could see no fault with the installation as it met all of their requirements.


Reace

[rbryan4]

Glad you addressed this Reace. The fault is not with the install, as you mentioned when I visited.

[Patandlinda]

Thankyou Reace for responding and clearing up things . Puts my mind at ease as I am sure others . It was starting to get a little crazy .