Sunrader 18' Furnace And Water Heater Replacement

[RunningMan]

hi.

Which unit came with the 18' sunrader and does anyone have suggestions on a more efficient units? the fan on the furnace is about ready to go.

thanks

aj

[zero]

18 foot Sunrader came with a 16K BTU input forced-air propane furnace. Has a usable heat output of 12 BTUs. All the Sunraders I've worked on had Suburban NT-16 furnaces. The NT-16 series is still available new.

If you want a new forced-air propane furnace - the efficiency will be the same now as any that were made in the 70s-80s-90s. 75%-80% efficient.

I know of NO super-efficient forced-air furnaces in the ranges of 16K-30K BTUs that are certified for use in an RV. There ARE a few smaller vented catalytic heaters that run up around 85-90%. Note I'm talking about RV furnaces sold for use in the USA. Europe has RV furnaces that ARE super-efficient - some up to 95% like many are for household heating in the USA.

http://www.amazon.com/Suburban-NT-16S-RV-Furnaces/dp/B001HKT0T4

[linda s]

I have the original docs for my 86 Sunrader. The furnace is a Hydro Flame Excalibur 8500 series, 16,000 btu made by Atwood

The water heater is an American Appliance which is now Suburban. Model now would be an SW4. I thought these were discontinued but more just started showing up online. This is 3 gallons. The 6 gallon is too deep to fit behind your bench seat. If by any possibility you have a wrap around dinette seat instead of the bench on each side, some early 86's did, then you should be able to fit the 6 gallon. Measure yours. Little one is 16 something deep and the bigger one is 19 something deep

Linda S

[RunningMan]

yes linda.. mine is the same.... The atwood hydro flame.

http://www.amazon.com/Atwood-37638-Hydro-Flame-Furnace/dp/B004A30JZE/ref=pd_sim_sbs_263_29?ie=UTF8&dpID=411zjMA802L&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=12MW5QEK5MBMJR3M3FG0

yes it looks like the water i have is a 3 gal. but looks like the 6 gallon would fit

any idea on what euro efficient heater model would fit? or do they make the atwood hydro flame with better efficientcy? the heat loss out of the exhaust is 3x as hot as the air blowing in the camper

[linda s]

Furnaces haven't changed much over the years. The exhaust is hotter because that is the air that was in direct contact with the flame. Air in your camper is fresh blown through the furnace with no flame contact so you don't die in your sleep. The best way to preserve your energy is to insulate by covering those lovely big Sunrader window with something. I use reflectix in cold weather. Cut to size and velcro on so you can slap them up and remove easily.

Linda S

If you look around there are a lot of places you can add insulation. look under your seat tops. Mine had some fiberglass insulation there that had degraded. I added some reflectix behind the rear lower wall and around the furnace. On the other side along the side of the water heater, under the drawer beneath the stove. Lots of places to insulate if you dig around

[zero]

yes linda.. mine is the same.... The atwood hydro flame.

http://www.amazon.com/Atwood-37638-Hydro-Flame-Furnace/dp/B004A30JZE/ref=pd_sim_sbs_263_29?ie=UTF8&dpID=411zjMA802L&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=12MW5QEK5MBMJR3M3FG0

yes it looks like the water i have is a 3 gal. but looks like the 6 gallon would fit

any idea on what euro efficient heater model would fit? or do they make the atwood hydro flame with better efficientcy? the heat loss out of the exhaust is 3x as hot as the air blowing in the camper

The US made forced-air furnaces are all around 75% efficient. The two Sunraders I worked on had Suburban NT-16s - but it makes little difference. Hydroflame or Suburban - same type of design and same efficiency. A 16,000 BTU furnace makes 16,000 BTUs of heat but sends 4000 of it out the chimney/vent. Leaves 12,000 BTUs for heating the inside of the RV which is usually plenty. Plenty of household furnaces still made that way too. Less complicated, less pricey and one more factor. A 95% furnace usually needs a moisture drain. The Euro heaters are completely different but yes - you could make on fit.

[RunningMan]

Furnaces haven't changed much over the years. The exhaust is hotter because that is the air that was in direct contact with the flame. Air in your camper is fresh blown through the furnace with no flame contact so you don't die in your sleep. The best way to preserve your energy is to insulate by covering those lovely big Sunrader window with something. I use reflectix in cold weather. Cut to size and velcro on so you can slap them up and remove easily.

Linda S

If you look around there are a lot of places you can add insulation. look under your seat tops. Mine had some fiberglass insulation there that had degraded. I added some reflectix behind the rear lower wall and around the furnace. On the other side along the side of the water heater, under the drawer beneath the stove. Lots of places to insulate if you dig around

yes i have removed all the batting fiberglass and replaced it with better insulation. i have installed many on demand water heaters and radiant systems in houses.... they are super efficient and the exchanger manifolds use a similar system, but the rv heaters just are not designed well. what would make them better is to use induction of the cold air from outside and have it flow over the exhaust manifold thus pre heating the air and utilizing less flame but yet still have ample hot air blowing in the rv. also to have varied speeds when the unit calls for heat would cut down on noise and fuel and keep the interior temperature balanced.

i see the specs on the new hydro flames use a 2 speed fan and roller bearings on the squirrel fan. this would require a bit less energy to spin it and quieter too

looks like the 4.4 amp 20,000 btu is a def improvement

SKU:

sku #37638

http://atwoodmobileparts.com/atwood-furnace-37638-8520-20-000-btu-4-4-amp/

[linda s]

There was a high efficiency vented catalytic heater made a while back. The website is still active but I don't see them for sale anywhere. Don't know if they are still in business or not. I also can't imagine where you would put one in a tiny Sunrader

http://ventedcatheater.com/6.html

Lots of non vented ones but you have to leave a window cracked. Kind of defeats the purpose

Linda

[zero]

Two examples of European RV furnaces that run at 93% efficiency are the Propex and the Trumatic.

Propex HS2800 10,236 BTUs input and 9553 BTUs output (heat into the cabin). Measures 16 5/8" X 8 1/8" X 4 3/4"

Trumatic E4000 13,364 BTUs input and 12,624 BTUs output (heat into the cabin). Measures 25 3/8" X 11 13/16" X 6 3/8"

The USA Hydroflame 8516 and the Suburban NT16 both have 16,000 BTU inputs and 12,000 BTUs outputs (unless something has radically changed lately).

Both are 18" to 24" long (adjustable).

[zero]

There was a high efficiency vented catalytic heater made a while back. The website is still active but I don't see them for sale anywhere. Don't know if they are still in business or not. I also can't imagine where you would put one in a tiny Sunrader

http://ventedcatheater.com/6.html

Lots of non vented ones but you have to leave a window cracked. Kind of defeats the purpose

Linda

Do you have any info showing those heaters are higher in efficiency then others? I ask because they post no specs that I've been able to find and I sent them several emails on the subject with no replies (a long time ago). If they refuse to post the input and output - how can anyone tell what the efficiency is?

[Maineah]

They claim 100% fuel to heat using a catalytic converter. Not cheap and not small.

[zero]

I kind of wonder why anyone cares about the 75% efficiency of the US furnaces when used for a part-time camping unit. I could see the concern - maybe - if someone was living in an RV full-time in cold winters. But otherwise? The difference is so small - between a 75% and a 95% percent - it's kind of insignificant. At least in my opinion. What I do NOT like is the hot exhaust that can burn a hole in my door if I open it, leave it open and have it against the furnace chimney/vent. I DO like that the RV furnaces are pretty simple. Easy to diagnose problems, easy to take apart, and easy to get parts for. Even for some of the ones made in the 1970s. I wish the same could be said for Dometic refrigerators.

Many brand new propane furnaces made for houses are still 75-80% efficiency. When the higher eff. ones came out in the ranges of 90-95% - they were trouble-prone and complicated. Enough so that many people chose not to use them. I think (hope) they've gotten a lot better and many of the bugs are worked out. Nice thing about them is - the chimney can be plain-old plastic PVC water-pipe and it hardly even gets warm. I just installed a new 95% furnace in my house a few days ago and am hoping they have indeed, gotten more reliable. It is a 105,000 BTU unit and uses 3" diameter plastic PVC for a chimney and 1/2" PVC for a water-drain. My in-laws have one that is 18 years old and it has failed four times, along with needing two new circuit boards. NOT a great record. The new one I just got has a 12 year parts warranty so hopefully it is much better.

[RunningMan]

I kind of wonder why anyone cares about the 75% efficiency of the US furnaces when used for a part-time camping unit. I could see the concern - maybe - if someone was living in an RV full-time in cold winters. But otherwise? The difference is so small - between a 75% and a 95% percent - it's kind of insignificant. At least in my opinion. What I do NOT like is the hot exhaust that can burn a hole in my door if I open it, leave it open and have it against the furnace chimney/vent. I DO like that the RV furnaces are pretty simple. Easy to diagnose problems, easy to take apart, and easy to get parts for. Even for some of the ones made in the 1970s. I wish the same could be said for Dometic refrigerators.

Many brand new propane furnaces made for houses are still 75-80% efficiency. When the higher eff. ones came out in the ranges of 90-95% - they were trouble-prone and complicated. Enough so that many people chose not to use them. I think (hope) they've gotten a lot better and many of the bugs are worked out. Nice thing about them is - the chimney can be plain-old plastic PVC water-pipe and it hardly even gets warm. I just installed a new 95% furnace in my house a few days ago and am hoping they have indeed, gotten more reliable. It is a 105,000 BTU unit and uses 3" diameter plastic PVC for a chimney and 1/2" PVC for a water-drain. My in-laws have one that is 18 years old and it has failed four times, along with needing two new circuit boards. NOT a great record. The new one I just got has a 12 year parts warranty so hopefully it is much better.

yes i agree. the percentage difference isnt a big deal.. i just need a new furnace due to the fan shaft bearing being seized and all the exterior components are a bit corroded... so why not try and find the better model than what was originally.

the 2 stage fan will be quieter along with a more controlled interior air flow/temperature and yes the exhaust would be nice if it was a bit less of a flamethrower.

[Maineah]

I can't sleep through the dang things but usually when it's cold I'm some where there is power and then I just use the electric heater. I did install a computer thermostat and set it at 50 over night and at 68 in the morning. Ever so often it comes on at night and I wake up wondering why I parked at the jet port.