Relocate the furnace inlet grill and block off that opening?

[John E Davies]

Has anybody tried this? I think that having that huge opening right under the sleeping area is a problem. Could the grill be relocated to the other side of the cabin, under the front dinette seat? Or in the front entry  wall at the fridge? Then the big hole in back could be covered or replaced with a hinged access door. It seems as if the fan noise would be greatly reduced if it was located far away. You would have to install a baffle to keep stored items from blocking it under the dinette, which would reduce the volume a little. I’m unclear about the fridge area, if that could be suitable.

Before I start messing with it, has anybody tried this? Did you do any sound measurements, before and after?

There would be an added benefit - conditioned cabin air would be pulled around the water tanks, helping to keep them and the plumbing a little warmer.

Thanks.

John Davies

Spokane WA

Edited February 12, 2021 by John E Davies

[Galway Girl]

Seems like a great idea John.

I assume that the current grill is essentially the cold air return for the furnace?

CS

[John E Davies]

I do not know any function for this other than feeding cabin air to the furnace. Though it is also an access point. Since there is a round port directly in front, I would probably just make a white plastic cover from a cutting board and screw it down here, with some rubber gasket material to seal it 100%. Somebody sleeping here is literally just two feet away from this noisy thing.

I know a grill could work under the dinette. I do NOT know anything about this wall, is there an adequate space (at least 1” of depth) behind it, and could air travel from there to the under-floor spaces? Is it packed with insulation? Somebody who has removed their fridge can answer this, I hope. It would be extra nice if a huge hole could be cut there without removing the fridge entirely.

I am considering installing a nicer looking grill and having a disposable furnace filter behind it, to minimize dust entry.  .... https://www.amazon.com/HVAC-Return-Air-Grille-Dimensions/dp/B0753HS34R?th=1

Thanks,

John Davies

Spokane WA

Edited February 12, 2021 by John E Davies

[SeaDawg]

Generally speaking, rv 3 way fridges are set up in their own separate compartment,  with one vent low, and one vent high (either in the sidewall, or roof.) That's why the fridge is sealed off from the sink cabinet with the access panel.

I wouldn't recommend cutting a vent in the fridge compartment sidewall, creating a third vent. It could create issues with heat exhaust venting properly. 

I don't know if this is an rvia requirement, (probably is),  but it's in the install manual for the dometic. 

Your other choice, under the dinette, would probably be better. But, I don't know the purpose of the existing vent on a ducted furnace. I've never owned one...

Those of us who have installed 12v fridges have the opposite issue. We need venting to the cabin. 

 

Edited February 12, 2021 by SeaDawg
Typos

[John E Davies]

Thanks very much, but I still don’t get it, all the bad stuff is outside next to the two big vents. I thought that section was completely blocked off, out there, with miles of silver tape and sealers. What has this to do with the inner wall near the entryway? 

I sure would like to see some actual Ollie photos.

BTW I know there is air leakage in my trailer, because dust trickles out from under the fridge (inside) on forest roads.  So it is nowhere close to airtight there. I would love a DC fridge, I am just not there financially, this has been a very expensive winter for me, RV wise....

Thanks. 

John Davies

Spokane WA

Edited February 12, 2021 by John E Davies

[SeaDawg]

The idea, from my understanding,  is to isolate everything in the fridge compartment as much as possible. 

I know I've had cold air come in from outside  around my 3way fridges, too.

The heat from the back of the fridge vents thru the upper vent. 

Adding another vent will (possibly/ probably) cause refrigeration issues, as the proper airflow is necessary to remove the heat and create the cold.

The actual burner (outside) was isolated, in mine.

[SeaDawg]

And, since the compartment is pretty much isolated, it wouldn't function as a return for your furnace,  anyway.

 

Edited February 12, 2021 by SeaDawg
Clarity

[SeaDawg]

I guess the elephant in the room is--what does the furnace grate actually do, in a ducted furnace? 

Edited February 12, 2021 by SeaDawg
Typo

[John E Davies]

17 minutes ago, SeaDawg said:

And, since the compartment is pretty much isolated, it wouldn't function as a return for your furnace,  anyway.

We have ways....! I am unafraid of drilling as many big holes as necessary. But not at the risk of screwing up the fridge. I have never had mine out, despite all the hysterical “service every year!” warnings in the operating manual. I never knew that the inside panel, where the door is, is completely sealed all around its perimeter. In theory, I guess. Mine sure isn’t sealed tight.

Thanks for the all comments. Maybe I will wait until I can install a compressor fridge, then I can move the furnace intake at the same time.

John Davies

Spokane WA

[SeaDawg]

We never serviced "every year," either, after the warranty expired. We blew out dust, and removed mud dauber nests,, if necessary,, checked color of the flame,  etc..

Maybe that made us "bad owners", but honestly,  the fridge mechanical systems were pretty reliable. 

[JRK]

The installation of the RV refrigerators and the extreme amount of precaution surrounding the refrigerators is most likely due to the quite large number of fires associated with rv refrigerators, and even a few deaths. Dometic and Norcold have been responsible for numerous fires. RV refrigerator fires have paid for a truck for my business, and has continued to this day. You can google RV refrigerator fires for a detailed explanation or I have attached one of several hundred reports. Dometic and Norcold has paid out millions in claims for their part in causing these fires.

John

RV Absorption Refrigerator Fires.pdf

[DavePhelps]

John,

A bit late to this.... This mod has been on my mind for quite some time! But for different reasons though. The sound deadening potential of moving the cold air return (CAR) away from the furnace unit is one I hadn't thought of, but I think it is a great idea and probably would make a difference deadening the rocket.

I have the Elite. The furnace is under the front dinette seat next to the bathroom wall. The CAR is also right there cut into the seat riser. There has been lots of discussion of ways to heat between the hulls while boondocking and using the furnace. For us Elite owners (don't know about the Elite 2, but maybe similar?), the rear street and curb side between the hull corners are problematic in cold weather. What with the water pump and associated plumbing being on the curb side, and the check valves for water fill, and the exterior shower on the street side, they are relatively exposed. There is no space to run supply ducts to this area, so my thought was why not move the CAR back to the rear of the trailer. This way, when the fan kicks on, conditioned air from the cabin would be drawn down between the hulls at the rear of the trailer and make its way forward to the furnace fan. Even if the return air is not as warm as the supply air, it is somewhat warm and just having the air movement between the hulls would really help prevent any freezing down there. The main issue that has come up regarding this is that the blower could potentially receive less air due to passage restriction and/or have to work harder to get the air, causing overheating and furnace shut down. This is what Jason brought up when I posed him the question, but he wasn't sure. He said he would bring it up during the next design meeting. I don't really see this being an issue as there is lots of free space down below for air to move, just no space for duct work. One other potential drawback that I can think of is the fact that RV furnaces don't filter the return air like our home furnaces do. So whatever return air that makes its way to be blower will be recirculated in to the living space. There is a lot of dust from construction between the hulls. Oliver isn't as tidy as I wish they could be. Don't know if this could be a problem or not. Maybe the slow movement of the return air would not pick up any of the fiberglass dust and all that is down there.

What I plan to do is tape off the current CAR. Cut out the required space in a sheet of cardboard for a new CAR and tape it to the removed rear seat cover (dining table seat, curb side) and see what happens. I'm buying some remote temp sensors (thanks contributors on the forum for recommendations) to place in the furnace compartment and in the rear basement to see if there is any change in temperature. I'm not an HVAC person, but this seems like it's an idea worth pursuing for the cold weather campers out there. I'll post back in a few weeks when I get my test all completed.

Cheers,

Dave

[NCeagle]

On 2/12/2021 at 1:18 PM, John E Davies said:

Has anybody tried this? I think that having that huge opening right under the sleeping area is a problem. Could the grill be relocated to the other side of the cabin, under the front dinette seat? Or in the front entry  wall at the fridge? Then the big hole in back could be covered or replaced with a hinged access door. It seems as if the fan noise would be greatly reduced if it was located far away. You would have to install a baffle to keep stored items from blocking it under the dinette, which would reduce the volume a little. I’m unclear about the fridge area, if that could be suitable.

Before I start messing with it, has anybody tried this? Did you do any sound measurements, before and after?

There would be an added benefit - conditioned cabin air would be pulled around the water tanks, helping to keep them and the plumbing a little warmer.

Thanks.

John Davies

Spokane WA

I thought about trying this before I decided that I needed an independent backup for the furnace that could move conditioned cabin air into the basement.  You probably remember helping me with ideas on implementing the "bilge" fan.  My data shows that the fan works as it pulls the temps across the basement up (with heated cabin air), so I'm pretty sure this idea would work for you with respect to conditioning the basement air in the winter - in fact better since your furnace would be taking basement air and conditioning it rather than predominantly reconditioning cabin air. 

Always trade offs though.  My solution also works in the summer for cool cabin air, but it does absolutely the opposite for noise control!  😃

[Chukarhunter]

 

Great idea.

The idea of relocating the forced air furnace return duct(s) is something I have independently identified as a must do since I have spent many nights recently in temperatures down into the teens and like others don't expect to have to worry about freezing water lines or cold batteries.  The place that Oliver chose to located the single return vent in the LEII is the worst possible place they could have put it.  Besides being the noisiest place, it compromises the function of a good forced air heating system.  Placing the return so close to the supply ducts means much of the heat never circulates in the trailer and instead is drawn under the dinette and back into the furnace almost directly from the supply vents.  Also, failing to have placed a return duct in the bathroom renders the hot air supply vent in the bathroom almost worthless when the bathroom door is closed since pressurization of the bathroom creates backpressure on the supply vent.  Further, with the bathroom door closed, there is insufficient free air flow through the furnace heat exchanger resulting in reduced efficiency, more propane consumption and possible cycling due to the heat exchanger reaching its thermal limit.

So my thought is the most important single thing to improve the heating system in the LEII and significantly reduce any risk of freezing pipes or batteries is to put  a small return vent (4" x 4") in the bathroom as low as possible below the existing supply vent (below the T.P.).  Even with the door closed, the bathroom will now be warm but much more importantly, the warm air in the bathroom will be pulled under the bathroom sink into the hull and flow over all the plumbing lines and fresh water tank to the back where the furnace intake is.  

To complete the job, I think that after removing and closing the approximately 50 square inch return vent under the dinette, it should be replaced with a 16-20 sq. in. return in the bathroom, a second 16-25 sq. in. return under the dinette front side, and a third 12-16 sq. in. return in the rear street side across from the furnace to heat the outside shower plumbing.   This should result an a balanced heating system with fairly constant temperatures throughout the inner space and within all inner parts of the lower hull as well.  Added benefits should be a more comfortable trailer and less propane consumption.

Thoughts about this?

[SeaDawg]

I'm not an hvac contractor,  nor expert, but that really, really seems excessive in a small trailer. To me.

I've always liked the idea of an adjustable butterfly vent, for those of you with the luxury of a bath duct.  We don't have one. I leave the bath door propped open a bit, in cold weather, just to circulate warm air from the main cabin. 

In your shoes, I'd  really like to see a manufacturer schematic, before I started making holes in my trailer, imo.

Rv furnaces draw fresh from the outside, and exhaust to the outside.  I'm not really sure the "return" grate idea is so solid, in rv furnaces. 

That said, I  have a non-ducted, 2008 furnace, that still heats my trailer, and functions well.

[John E Davies]

2 hours ago, SeaDawg said:

 

Rv furnaces draw fresh from the outside, and exhaust to the outside.  I'm not really sure the "return" grate idea is so solid, in rv furnaces. 

Sorry, this is not correct. There are two separate systems operating in a furnace, and never the twain shall meet, hopefully, or you could die... The combustion air comes in from the outside, gets heated inside the burner and then is dumped back outside the trailer. The cabin “conditioned” air is sucked in by way of the grill openings around the furnace housing, it passes over the burner/ heat exchanger, and then is pushed into the cabin by way of the fan discharge opening, and any attached ducts. So one or more return air registers are needed inside the trailer (at least one is specifically required by the installation instructions.)

Getting the air circulation balanced is very important in a home with forced air central heating, and no less so in a trailer. The location Oliver uses in an LE2 is more than a little confusing to me, it just seems so very random and poorly chosen. In addition to silencing the jet engine whine, a remote opening would allow you to line the inside of that inner wall, and the solid cover over the existing grill cutout, with sound insulation, which would further deaden the machinery noises such as the water heater sparking, and the water pump chugging, using this stuff: .... Acoustic foam panels

John Davies

Spokane WA

 

Edited February 19, 2021 by John E Davies

[John E Davies]

9 hours ago, Chukarhunter said:

So my thought is the most important single thing to improve the heating system in the LEII and significantly reduce any risk of freezing pipes or batteries is to put  a small return vent (4" x 4") in the bathroom as low as possible below the existing supply vent (below the T.P.).  SNIP To complete the job, I think that after removing and closing the approximately 50 square inch return vent under the dinette, it should be replaced with a 16-20 sq. in. return in the bathroom, a second 16-25 sq. in. return under the dinette front side, and a third 12-16 sq. in. return in the rear street side across from the furnace to heat the outside shower plumbing.   

I think this is fine, my only concern is the first bath return seems too close to the existing warm air register. It is certainly best to have the cold air returns very low, because that where the cold air collects, but in the bathroom you have to also worry about water ingress during showers. So I would be inclined to put only one, located up high in the bulkhead wall, as more than one owner have done. That also provides good airflow into the bathroom from the main room when the door is closed and the exhaust fan is running. If you want low returns, they need to have some sort of hood or splash guard over the top.

The others will work, I have already done that, using 4” round vents. I am considering putting one more in the bottom of the closet wall, to draw cold air into that space and then out the closet floor. It would require adding return holes through the floor near the door opening, and adding a screen so you don’t lose any small objects down the rabbit hole. An extra grill up high in the closet wall will let it vent freely in summer and winter - as built it (and the pantry) is a dead end box that traps both heat and cold, and in the closet, any moisture from a damp jacket or shoes.

John Davies

Spokane WA

Edited February 19, 2021 by John E Davies

[NCeagle]

Moving the cold air vent seems like it would work, but I have some data that may work against this concept.  While working on my bilge fan that I installed under the dinette seat, I tested and saw that for the first 15 minutes or so many areas of the basement didn't budge - even with the fan set on high at 350 cfpm.  It took prolonged airflow to get the basement temps and humidity to move in any appreciable way.  I haven't had extreme cold to test in this winter, but the furnace fan never runs for more than about 7-8 minutes when the temps are down around 20F and the cabin is set to 68F.  This may not be enough time to actually accomplish the air mixing you are after.  Just a thought - If you ran some extra duct behind the back storage area and down the street side like several owners have done - and moved the vent / added a few more - that would be the best way to get some additional mixing all around the basement.

Edited February 19, 2021 by NCeagle
wording

[John E Davies]

You need to also consider the benefits of simple convective airflow and how slow air exchange helps to remove stale air from all the dead end compartments. That requires a top and bottom opening in each compartment. Even if that isn’t doing much to move heat under the floor (using the furnace fan) it should help to keep everything at a more consistent  temperature. I normally crack open the closet and pantry doors when running the AC or furnace, but I suspect that would not be needed with two vents in each of those areas.

All this air circulation means you have to be very comfortable cutting lots of holes, and looking at the clutter of  extra grills. Cutting rectangular ones is more work, but a 4” round hole saw makes adding round ones very quick and easy. I personally prefer the appearance of round ones. You still have to deal with dust cleanup. I put down paper towels behind the future hole, and lay a shop vac hose close by while drilling. That helps a little to control the mess and keep the dust out of your lungs. And once you commit and drill that first one, the following ones are a whole lot less stressful. 

John Davies

Spokane WA

Edited February 19, 2021 by John E Davies

[SeaDawg]

9 hours ago, John E Davies said:

. There are two separate systems operating in a furnace, and never the twain shall meet, hopefully, or you could die... The combustion air comes in from the outside, gets heated inside the burner and then is dumped back outside the trailer.

Yes, I should have added the words "for the combustion chamber." That's why a furnace is safer to run than an unvented portable heater, that uses the air inside the trailer for combustion,  and exhausts to the inside.

[John E Davies]

There is a possible excellent reason that the Ollie engineers chose the existing location for the air return in an LE2. I woke up at 4:00AM and it just popped into my head. 

There are a dozen moisture vent/ drain holes in the bottom of the hull, the ones with those cute little stainless steel covers. The covers face rearwards so IMHO when the trailer is moving they will provide a slight suction effect, which is good for drainage. (I can’t imagine another possible reason for taking the time and expense to install them all with rivets. Most manufacturers would not bother.) 

HOWEVER, in addition to letting out condensation or an actual water leak, they will also let air go back inside the outer hull when the trailer is stopped and there is a low pressure created inside, like turning on an exhaust fan with all the windows closed. Duh.

But if you relocate the furnace grill to the far side of the cabin,  you are essentially creating a slight vacuum under the floor with the furnace fan, so air is going to be pulled inside through those holes. A little air infiltration isn’t bad, but on a really frigid day it will also suck in trickles of freezing cold outside air right where you don’t want it, under the tanks and plumbing.

With the existing location there is no suction created under the floor, instead the cabin air enters directly.

So maybe they really did choose this spot for a good reason. A lot of “jet engine” fan noise may be preferable to drawing in cold air through the drains. A completely sealed return air duct from a single opening under the dinette would 100% fix that (like in a home HVAC system). It would have to be huge with no restrictions, so I see no way that could work in an Ollie. If you could put one way check valves at the drain holes, they would prevent air entry when the furnace was going, but it would also stop that beneficial movement when you are running an exhaust fan. Or you could crawl outside with duct tape every time it got really cold.... or install those interesting inflatable winter trailer skirts. .... https://www.airskirts.com/

We need to measure those holes and calculate how many square inches they represent, combined. My guess is about 10 square inches, which is pretty big for an active air leak in a small trailer. My other guess is that the average owner camping in moderately cold weather would find that this is a non issue, but one that plans to camp in sub zero temperatures at the ski resort (or Texas during a Polar Vortex) with water in the tanks and lines should avoid changing the furnace vent!

I am half asleep, the actual flow there may be negligible, so this is either complete nonsense or in fact pure brilliance. Please discuss after you have had your morning coffee. Thanks!

John Davies

Spokane WA

 

Edited February 21, 2021 by John E Davies

[Mike and Carol]

Drinking first cup of coffee....

We just finished this odd arctic blast this week.  Temps hit single digits two nights and we stayed well below freezing all week.  Finally, yesterday we hit the 60s and the low last night was 53.  I didn’t winterize 😬, never needed to before.  I did find a couple of gallons of antifreeze at the third Walmart I checked, but could not find a pump.  I put the trailer in the driveway, turned on the furnace and electric heater, hot water tank and put drop lights in the basement and under the bed near the outdoor shower.  Once the weather returned to normal yesterday I checked everything and it appears we weathered this storm with no damage.  I did keep the vents closed and shades down to help retain heat.  Mike

[John E Davies]

OK, maybe I should not type stuff before dawn. I went and looked.....My trailer Hull 217 has 10 scupper drains that I can locate. Each is about 1/2” diameter (it is really hard to tell, they are very recessed), so each one is about 0.2 square inches, or 2.0 sq in for all 10 of them. IMHO that is completely negligible in terms of air leakage, so I don’t think moving the furnace inlet across the hallway will freeze the belly parts at all.

OTH, the open holes do allow dust entry inside, so it would be possible to add some rubber “duckbill” dirt bike airbox drains, as found on a Jeep forum. I added the annotations from that thread description. BTW that is a typo, it should read 1/2” nipple.

p

This would allow water to drip or pour out, and would prevent air and dust from being sucked back inside. I don’t know if those Honda parts are the last ones ever, or if they will be restocked soon. I asked the seller about that, and if he would combine shipping. It would not be a difficult mod, just time consuming, to drill out the rivets, seal the holes, and epoxy in place the nipples. And they would be a little vulnerable to rock strikes or getting knocked off while washing the trailer. (Rock strikes are not an issue for me due to Stone Stomper and other flaps).

John Davies

Spokane WA

 

 

 

Edited February 21, 2021 by John E Davies

[Overland]

I’m just catching up on this - haven’t been too active here the past few weeks.

A vent at the fridge could work, but would probably involve a good bit more work than cutting one at the dinette.  If your trailer is built like mine, there will be two problems with the fridge vent.  First, there is a solid floor underneath the fridge that separates the fridge space from the basement, so you’ll need to cut a hole in that as well (easy enough, and desirable for future maintenance anyway).  Second, there’s a fiberglass ‘baffle’ in the basement area separating the area under the fridge from that under the sink.  You’d have to cut through this as well to get good airflow.  Possible, but it would be little hard to get to.  I’m not sure if the baffle has a purpose - I doubt it and suspect that its just a vestige of construction.   Here are some photos.  The first shows the fridge space with the access hole that I cut in the floor (the small vent on the left is for my fridge).  The second is in the basement area looking toward the fridge from the rear, showing the baffle.  The access hole that you see is directly below the sink and the hose is the fresh tank overflow.  Hope this helps.

[Overland]

Actually, thinking about it, I believe that the standard fridge sits lower than mine - right at the floor?  That’s probably why the ‘baffle’ exists, since it’s just an extension of the rear wall of the fridge compartment.  If so, then you’d be cutting into the fridge compartment.  Perhaps that makes the situation worse, since you’re then dependent on air making it’s way around the fridge to get into the basement.  

Either way, the dinette is certainly an easier solution.

If your weep vents are anything like mine, they’re 90% blocked with fiberglass dust gunk from construction, so probably not much to worry about.

Edited February 21, 2021 by Overland