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Old 11-23-2010, 10:00 PM   #1
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Not enough heat in back

My cold weather experiments in trailer heat confirmed what I had already suspected from a few late fall camping trips:

There isn't enough heat in the bedroom.

In 15 degree outside temps, running the furnace (only, not any of my electric heat), I recorded these temperatures:

Gaucho 69
Dinette 66
Head 61
Bed 58

Some experimentation showed that it took around 1000 watts (3400 btu/h) of supplemental heat in the bedroom to make things even out. Doing this provided fairly consistent temperatures throughout the trailer.

The 2010 classic 30' has four furnace outlets. Two are near the exterior door, at the end of the galley cabinetry. One is in the head, and one is in the bedroom. I checked temperatures with an IR thermometer which told the story pretty clearly:

Galley outlets - 160 degrees
Head - 134 degrees
Bedroom - 104 degrees

There is also less airflow in the more distant outlets, in part because some of it is redirected through a T fitting in the ductwork to the holding tanks.

Wondering if anyone has figured out a way to run more ducts, or get more airflow, or do something to get more heat to the bedroom without having to rely on shore power.

One thing to consider is that the Duotherm controls won't let you run the rear heat pump and the furnace at the same time. Doing so would be one way to solve this.
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Old 11-23-2010, 10:13 PM   #2
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I had the same issue in my 34'...fixed it by closing one of the two forward facing ducts near the door in the living area...bedroom and bath heat jumped up to a balanced level
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Old 11-23-2010, 11:00 PM   #3
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as i pack for florida i'm taking a 12v computer fan with me. (two in fact. one is for the fridge) what i'd like to do is set it up with a thermostat so it automatically comes on when the temp hits 95 degrees. i suppose i could run the thermostat closer to the furnace and run the wires to the fan through the duct. if it runs when the trailer is closed and the air is off is ok with me since i'm connected to shore power. i hope to try this by mid december. i'll try just the fan first to see how much air it can pull.

oh, i tried blocking one front outlet and i was getting too hot on the gaucho!

someone mentioned that the turbulence from the accordion duct really slows the airflow a lot.
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Old 11-23-2010, 11:12 PM   #4
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blocking one of the front ducts is helpful,

using a small 12v or battery powered fan is another useful trick.

it should be obvious that most of the heating system is very closely aligned to the plumbing.

since there is no plumbing in the rear, warmth is only critical 4 humans.

the overhead ac/heat pump does a better job of warming the rear, simply because the vents throw air better.

the most effective tweak for boondocking is 2 add a small vented plat/cat in the bedroom.

they take up minimal space, use little juice and warm nicely.

IF plugged into shore power, i place a small heating/dryer element in the under bed storage to warm from below...

and use a small (700 watt) oil filled space heater in the bedroom which is very effective.

with twins the catalytic add-on or a fan would be effective.

the entry door is a sieve not a barrier, and the interior framing (along with window frames will ICE UP inside.

so in sub teens temps i park near a windbreak, and cover the door frame with green painters tape or a blanket.

then sleep on the sofa bed, closing OFF the bedroom.

it's a compromise but works.

like many others i stuff all the overhead vents with bubble foil,

maybe u can confirm if this is useful or not with your investigations.

cheers
2air'
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Old 11-24-2010, 04:47 AM   #5
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Quote:
Originally Posted by HiHoAgRV View Post
I had the same issue in my 34'...fixed it by closing one of the two forward facing ducts near the door in the living area...bedroom and bath heat jumped up to a balanced level
I dug through the Atwood manuals and I see that technically the 34,000 btu/h furnace requires at least four outlets. Closing off one of the front outlets would leave only three, which could lead to the furnace overheating and tripping the limit switch.
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Old 11-24-2010, 05:07 AM   #6
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Quote:
Originally Posted by 2airishuman View Post

the most effective tweak for boondocking is 2 add a small vented plat/cat in the bedroom.

they take up minimal space, use little juice and warm nicely.
I've never been much of a fan of the cats.

An alternative to ponder is the smaller unducted furnaces:

Everest Star 7900 II Series Heating System - Atwood Mobile

These draw 1.8 amps and produce 12000 BTU/h.

Quote:

IF plugged into shore power, i place a small heating/dryer element in the under bed storage to warm from below...

and use a small (700 watt) oil filled space heater in the bedroom which is very effective.
When shore power is available I'm using one of these:

Marine/RV HFC Series Portable Desktop Heater

Which sits on the "nightstand" between the twins where it is out of the way of people and linens. Smaller and lighter than an oil-filled and nearly as quiet.

Quote:

then sleep on the sofa bed, closing OFF the bedroom.

it's a compromise but works.
Good alternatives to consider. When boondocking I don't consider it practical to run the heat all night anyway from an amp draw perspective and I have a good sleeping bag for that.

Quote:
like many others i stuff all the overhead vents with bubble foil,

maybe u can confirm if this is useful or not with your investigations.
I might try that. I suspect that the bubble foil may be more helpful for the A/C in summer since it also helps with the solar gain.
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Old 11-24-2010, 06:49 AM   #7
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I run the MaxAir fan on ceiling fan mode to circulate the warm air downwards. Sal.
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Old 11-24-2010, 11:11 AM   #8
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the small everstar is a nice idea, but it will take up a lot more space than a surface mount cat.

maybe theres room under one of the beds or in the center nightstand for the small furnace.

the cat i like (used for 20 yrs) has both fresh and exhaust venting options...

it's a small company and it takes a good long while to get a unit now...

http://ventedcatheater.com/6.html

and it is true completely shutting off 1/4 ducts is a nono...

but don't forget the 'tank vent'.

take a look at the furnace box and the # of vent connections.

i often place the next meal (a sealed food container) over/blocking the galley vent,

now that i know it's 160 degrees, i can better adjust cooking times.

this seems to kick up flow to the bed room and to the tanks a bit.

have wanted to replace the LONG run of irregular bedroom tubing with something smooth

going south just seems easier.

cheers
2air'
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Old 11-24-2010, 11:58 AM   #9
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If you don"t have a furnace in the rear bedroom. What you have mentioned seems
to me to be the best suggestion!!!
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Old 11-24-2010, 12:04 PM   #10
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2air

I have not measured but I believe from just looking at pics and things think that an Everest Star would fit in the boxed in area at the foot of either bed. You have a twin, right? So there's that box covered with carpet, basically, that has a heat outlet on the curbside, and maybe part of the water heater on the street side. I looked around in the curbside when I had the vent out to paint it and there's nothing in there but empty unused space. Proximity to the bed linens would be a possible safety concern that would have to be evaluated carefully.

People miss the real problem with long duct runs. The loss of heat through the walls of the duct is at least as much a problem or more as the reduction in airflow due to turbulence. These aren't dryer ducts where there's lint and stuff to get caught on the spirals, and even metal ducts aren't smooth enough to produce laminar flow. All it takes is a screw or ridge at a joint to introduce turbulence for the next few feet.

From my measurements (see upthread) the temperature at the furnace is roughly 160 degrees, which if we're shooting for a 70 degree trailer is a delta-T of 90. By the time the air gets to the bedroom it's at 104 giving us a delta-T of 34. So even if the airflow were the same, there would be only around 38% or so of the BTUs delivered.

Unfortunately there isn't room for an insulated duct along the entire length, but it might be possible to wrap portions of the existing duct in fiberglass batting or replace parts of it with an insulated duct. The area in the closet where the ducts cross over the water pump is particularly crowded.
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Old 11-24-2010, 12:20 PM   #11
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no twins here, gotta climb around the queen.

which is why i suggested going with twins as a better layout when u ordered.

in my case i'd really like a street side double bed,

isle on the curb side and a 2nd entry/exit door.

might do this mod someday IF i can sort out better sealing 4 the door.
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i get the non insulated 'heat loss' issue.

my view is that the heat isn't really lost

it escapes into the structural bits and plumbing that runs with the ducting.

it' just doesn't make it to the bedroom living air space at full temp.

real 4 season use is a compromise in these cans or requires upgrades.

especially if off the grid.

cheers
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Old 11-24-2010, 01:49 PM   #12
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Quote:
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no twins here, gotta climb around the queen.

which is why i suggested going with twins as a better layout when u ordered.
4 which I will always be grateful.

Didn't realize that your voice of experience in this area was from the qb side of things.

Quote:
i get the non insulated 'heat loss' issue.

my view is that the heat isn't really lost

it escapes into the structural bits and plumbing that runs with the ducting.

it' just doesn't make it to the bedroom living air space at full temp.
I think most of it does still end up in the living space by indirectly heating the cabinetry, the coat closet, and so on. So, not "lost" in the sense of heating up the great outdoors.

But still it doesn't contribute to heating the bedroom.

Quote:
real 4 season use is a compromise in these cans or requires upgrades.

especially if off the grid.
As others have pointed out the best strategy may be to head south. I have ties to the Minneapolis area which keep a season-long departure from being practical however. And we have winter here, so might as well make the best of it.

In any case EVALUATING these problems in real cold makes measurements much easier to take and makes the benefits and sufficiency of any upgrades more obvious.

The 34,000 btu/h Atwood draws 10 amps and with the electronics insisting on long periods of fan operation both before and after the burner fires, in practice, the blower runs well over half the time in freezing weather. Anything more than an overnight stop without shore power would be asking a lot of the batteries under the best of circumstances.

An advantage of adding an Everest, aside from the matter of heat distribution, would be the relatively lower amp draw, which it achieves because it has no ductwork allowing a much smaller blower motor to be used.

Then again even with the dodgy-est shore power it's still possible to run 750w of electric heat in the bedroom which is probably good enough.
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Old 11-24-2010, 02:14 PM   #13
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Why not just install a second vented gas heater like a Suburban NT30? Those just require a small vent opening in the skin, a gas line, and a 12 volt power supply.

The best change for my trailer I can think of is a new zip code.
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Old 11-24-2010, 03:17 PM   #14
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Here ya go. Just up the road.

NEW READY TO HEAT/ SUBURBAN NT16 SE DIRECT VENT FURNACE 16000BTU

SUBURBAN NT16 SE
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