RMD Exhaust Flue

[CoolCampingKid]

Originally Posted by elongest

The 3" duct is really tight but you can move it around a little to get it in there. I looked at 4" duct but I did not think I could get it in there through the top vent. I wanted to route the heat to the vent screen to exit. I tried to get as much air entering the duct as possible. I did not want to increase the draft through the boiler flue. My main starting issue and still is the no or little cooling while on the road.
Eddie

Eddie, Are you running 12 volt or propane under tow? I believe the air flow into the back of the fridge while under tow and on propane may cause the flame to be temporarily be snuffed out ... the system will relight itself as long as the thermocouple is warm enough (I have had this happen with my old 5the wheel in a stong wind while parked) This flickering of the flame will reduce the effectiveness of fridge cooling. I took a piece of sheet metal (about 6 by 6 inches), put a 90 degree bend in it on the bottom inch or so. I used velcro on this piece of metal and attached it as an additional wind block at an angle in the back of the fridge. If I can get a photo to post I will show you a picture. This may solve your underway issue. Bill

[Ron in BC]

I think you're correct Jon, that's one of the things that it does. It also has the effect of cooling the exhaust gases although the people that have had charring may find that hard to believe.

But I believe that the primary function is to act as a regulator to control the amount of air flow and combustion. Too much could blow the flame out and too little could affect efficient combustion. That's why there's guidelines for the placement of draft hoods on hot water heaters.

At any rate, I think that the bottom line is, don't remove it.

Ron

[elongest]

Bill
I made a wind deflector like you describe and installed it. I found a bunch of other things that also could effect the flame so I removed it before the last test run. It is sitting by the trailer ready to reinstall before the next test run. Thank you for the suggestion.
Eddie

[fudge_brownie]

Bill,
I would appreciate it if you could post a photo of the wind deflector that you installed. You must have had a reason to install it, did it do what you intended for it to do?

[elongest]

Made from a piece of Home Depot step flashing. 8"X8" comes bent at 90deg. I trimmed it to fit. Aluminum duct tape will hold it in place to the floor and back wall. This was suggested by an old RV frig. mechanic. I have not tested it yet.
Eddie

[CoolCampingKid]

Originally Posted by elongest

Made from a piece of Home Depot step flashing. 8"X8" comes bent at 90deg. I trimmed it to fit. Aluminum duct tape will hold it in place to the floor and back wall. This was suggested by an old RV frig. mechanic. I have not tested it yet.
Eddie

Nice .... that is basically what I did....it helps block the wind coming into the back of rhe fridge and potentially causing the flame to get temporary snuffed out. So Elongest, did this help at all? Bill

[Parker]

Getting back to the flue topic, I'm in contact with a company in Australia that sells the wall vent kit that Ron posted. The proprietor is traveling right now, but he thought he could probably send one of the kits to the USA. I'll report back on how this goes. Turns out, my son was born very near the company's location. Small world.

I removed the vent cover today to look around in there, and I don't believe it would be that difficult to install a through-the-wall vent kit if the entire vent assembly (the screen, in other words) was removed. It would be much easier to locate where to go through the wall working from above. I'm having second thoughts about trying to fish a piece of metal flex hose up there for fear of blocking one end or the other of the tee. Another approach might be an extension (also a dometic part, hard to find, easily made) to simply raise the tee up above the cooling loop. KountryKamper did something similar as one of his many mods on his smaller fridge installation.

[Kountrykamper]

Originally Posted by Parker

Getting back to the flue topic, I'm in contact with a company in Australia that sells the wall vent kit that Ron posted. The proprietor is traveling right now, but he thought he could probably send one of the kits to the USA. I'll report back on how this goes. Turns out, my son was born very near the company's location. Small world.

I removed the vent cover today to look around in there, and I don't believe it would be that difficult to install a through-the-wall vent kit if the entire vent assembly (the screen, in other words) was removed. It would be much easier to locate where to go through the wall working from above. I'm having second thoughts about trying to fish a piece of metal flex hose up there for fear of blocking one end or the other of the tee. Another approach might be an extension (also a dometic part, hard to find, easily made) to simply raise the tee up above the cooling loop. KountryKamper did something similar as one of his many mods on his smaller fridge installation.

I had a machine shop make mine. They made it out of some scrap they had laying around. Hard to say how much it helped because I did so many other things at that time.

[Parker]

Nice. That's such a no-brainer. Sad that Dometic didn't do that to start with, even if it helped just a little.

[Ron in BC]

Sadder still is them not requiring North American manufacturers to install the exterior vent.

Ron

[ReagentGrade]

Originally Posted by Kountrykamper

I had a machine shop make mine. They made it out of some scrap they had laying around. Hard to say how much it helped because I did so many other things at that time.

Tom,

That looks like an easy install... unless to have to pull the fridge to get it in. I see that you pulled yours. Could you have installed this without that?

Rich

[Kountrykamper]

Originally Posted by ReagentGrade

Tom,

That looks like an easy install... unless to have to pull the fridge to get it in. I see that you pulled yours. Could you have installed this without that?

Rich

No the fridge has to be pulled and the height if the extension has to allow for you to slide it back in. Probably could have installed it by removing the top vent but that a lot of work in itself.

[elongest]

I did a 1.5 hour test run last week after installing the dryer duct. The outside temp. was in the mid 80's and the frig's performance was improved over my last outing but not great. Today I installed the (metal flashing) flame guard and I put the range hood screen over the air intake vent. I also added a door strap to hold both doors tight to the frame. I did this after remembering a conversation with a couple who had a E-21 with RMD 8555 that was operating satisfactorily. They mentioned they ran a strap across their frig. door and closet door while traveling.
Today the temperature was in the upper 90's an increase of over 10 deg. F. since the last test run. I followed my same path and time. My heat loss was about half as much as it was on my last test run. In all my prior testing my frig. temp. increase was almost always 2X as much as the freezer. Today I had about a 1 to 1 heat loss between the freezer and the frig. I actually had a 1deg F. more increase in the freezer than in the frig.
Now that both doors are strapped tight and the upper and lower section temperature loss is proportional I think loose fitting/sealing doors and air loss was one of my main issues. Once the frig. is loaded I think the thermal mass will greatly stabilize my OTR temperatures.
Eddie
Added pictures of door strap. The white foam block puts pressure on the center where the doors meet. The bottom of the strap is attached inside the lower door and the main part of the strap can be stored out of site. The top clip lives by the tank monitor.

[tractors1]

Originally Posted by elongest

Top install 3" dryer duct exhaust chimney. I installed a 3" semi-rigid flexible aluminum duct over the Flue T then leading to the vent screen. Used the complete hose as compressed as possible for support
Result: hot air exits the tube, cooler air exits over the coils. When the vent top is in place the hot air exits the rear of the upper vent. Seems to really thehelp cool down rate on gas. It also helps on the elec. mode
This is just what I did. Take the info. for what it is worth.

Got my 3 inch hose installed. Took many hours to get the Dometic base off the trailer as ETI used at least a half a tube of sealant. The sealant does clean up with "Goof-off" quite well. Used an oscillating saw with a scraper blade to cut through it first. After 3-4 days in high 80s, low 90s, with the fridge side in the afternoon sun, I'm seeing a 4-6 degree improvement in both fridge and freezer running on electric.

Used a laser thermometer on the "T" before installing the hose and inside the hose after installation. Temps were in mid to high 200s near the "T" on electric, and around 50-60 degrees hotter on propane.

Next 3 days will be 100-107F outside - should get some good data.

PS: I replaced the Dometic base rather than take 2 days to get all the old sealant off that thing. Noticed that the trailer surface is quite flat for mounting, but the Dometic part isn't as it's injection molded so it's distorted. Mounted the new part with 3M RP45 VHB tape and will seal where needed on top of that. Original screws were only 1/2" square drive, replaced with 1 inch #8 truss heads. They were long enough to get all the screws loosely started in the old mounting holes, then snug down the base gradually as in tightening a wheel. No gaps now between the tape and the parts.

[Parker]

Now that you've led the way with this approach, what do you think about just snipping out the wire mesh and installing something afterwards in its place rather than pulling the entire base? That sounds like a ton of work that would lead me to put this job off for awhile. Would this still provide adequate access to install the 3" duct? Thanks for posting....looking forward to more data!

[tractors1]

Originally Posted by Parker

Now that you've led the way with this approach, what do you think about just snipping out the wire mesh and installing something afterwards in its place rather than pulling the entire base?

That might work - but getting the hose to seat down over the "T" required me to make a tool (used a bent aluminum tent pole) for leverage, and the base sticks up quite a bit - dunno if you can get the leverage in that smaller space. I had to lever against the fiberglass shell to get the semi-flex tubing over towards the front of the trailer. It's not so flexible once you've flattened it enough to route it through the tubing on the back side of the fridge. You'd only need to remove the rear side of the mesh, so it would be simple to recover it things don't work for you.

[cpaharley2008]

Do not forget to plug the hole in the bottom of the refer door and a piece of foam inside the freezer door helps. Is your thermistor hanging, that also helps as water in the condensate cup.

[Parker]

Okay. I might consider it. I'm still concerned about how the tee sits within the duct when I read about squashing the tube some to get it to fit over it. What keeps the tee centered in the duct so that either exit doesn't end up sitting against the inner wall?

[tractors1]

Originally Posted by cpaharley2008

Do not forget to plug the hole in the bottom of the refer door and a piece of foam inside the freezer door helps. Is your thermistor hanging, that also helps as water in the condensate cup.

I taped over the hole as a temporary measure & the freezer has the foam. Temps are running 12/36 on electric @ 89F outdoors and fridge side in full sun. Texas fan is off. Gotta find a Torx for the thermistor - think I'll tape it to the underside of the upper shelf.

[cpaharley2008]

I think just hanging in mid airtight below the rear fins worked the best. Also put some foam in the door hole and then tape over it.