Suburban NT20S Furnace

[Janets Husband]

I thought I would pass on some interesting information, that I found out about the Suburban NT-xxS model furnaces.
I just purchased an NT-20S unit. While I was reading the installation/Operation/Repair manual, I found out that the only difference between the 12,000BTU, 16,000BTU and 20,000BTU units is about $200 in the price and the burner Orifice used in each.
The parts list shows an exploded view of the furnace with reference numbers for the various parts. It is arranged in three columns, one for each model. A side by side comparison of the part numbers shows that the only difference is the Burner Orifice part number.
I wounder if an Orifice is worth $200. Anyone know what a Burner Orifice costs?
It seems to me that you could buy a 12,000BTU unit and change out the Burner Orifice and have a 20,000BTU furnace. Any thoughts?

[boatdoc]

Originally Posted by Janet's Husband

I thought I would pass on some interesting information, that I found out about the Suburban NT-xxS model furnaces.
I just purchased an NT-20S unit. While I was reading the installation/Operation/Repair manual, I found out that the only difference between the 12,000BTU, 16,000BTU and 20,000BTU units is about $200 in the price and the burner Orifice used in each.
The parts list shows an exploded view of the furnace with reference numbers for the various parts. It is arranged in three columns, one for each model. A side by side comparison of the part numbers shows that the only difference is the Burner Orifice part number.
I wounder if an Orifice is worth $200. Anyone know what a Burner Orifice costs?
It seems to me that you could buy a 12,000BTU unit and change out the Burner Orifice and have a 20,000BTU furnace. Any thoughts?

Hi Gary; Very interesting. I am not sure in this case if the main housing is the same but you can determine that from size of air intake and overall external dimensions. But yes, in many other items with which I am very familiar, that is a common practice. It is called "Marketing Justification" even if only the ID label is different. Often the reason is the cost of tooling duplication, which reduces production costs. After Holidays I will check this out with my supplier. Thanks for the note Gary. Wishing all Forum members happy and safe Holidays. "Boatdoc"

[dwightdi]

This is a pretty common practice by many manufacturers. Most people will not take the trouble of taking appart a brand new unit to do it and many manufacturers will not honor their warrentees if you do it. I think I would do it to save $200. Sometimes there are other changes such as larger blower motors to move more air when the BTU rating is increased in some furnaces.

[Janets Husband]

Originally Posted by dwightdi

This is a pretty common practice by many manufacturers. Most people will not take the trouble of taking appart a brand new unit to do it and many manufacturers will not honor their warrentees if you do it. I think I would do it to save $200. Sometimes there are other changes such as larger blower motors to move more air when the BTU rating is increased in some furnaces.

Nope, All of the part numbers are the same for the 3 models, housings, burner chambers, valves, blower motors and all. Just the Burner Orifice is different.

[markdoane]

Gary,

Suburban has to pay a propane depletion fee to the Federal Government based on their Fleet Overall Combined Orifice Size (FOCOS). Bigger orifice=bigger fee.

Note: this is a fee, not a tax so don't whine to your congress person. By placing this fee on the manufacturer, we can maintain our "No New Taxes" pledge.

Other manufacturers are expected to follow this innovative pass-through pricing structure as soon as new price lists can be printed.

[3Ms75Argosy]

you almost had me going there!

Gary - gee, I wish I would have known that prior to me buying a new furnace. I think I remember I bought the "biggest" one, as it was cheaper by about $50.00 vs. the others. Couldn't figure that one out. I also noted that they all looked about the same.

I too wonder how much an orifice is. Bet CW doesn't carry one - but my local mom/pop RV store probably could order one.

Just a note. The new furnace was almost a plug and play. I had to take off the old exhaust port from the outside and replace it with the new one. I also had to mount the furnace about 1" (can't really remember) higher. I put some 1x material on side, screwed that to the floor, and then mounted the furnace on that.

Also, the new furnace gas hookup was on the right side of the furnace, where as the old one was on the left. I bought a new pre-flared piece of copper tubing (I think about 14" long - measure to make sure. I bought mine with the furnace at the shop- flared while I was there) and used that to make the connection.

No new wiring needed. Even used the existing thermostat.
Happy Holidays!
Marc

[TomW]

Originally Posted by markdoane

...Suburban has to pay a propane depletion fee to the Federal Government based on their Fleet Overall Combined Orifice Size (FOCOS). Bigger orifice=bigger fee.

That was an incredibly good post. You sucked me in from the git-go.

Kudos to you sir. I bow to the master story teller.

Tom

[59as]

Want to put my new nts20 furnace in place, 59 tradewind, wondering if up front next to kitchen counter with covering built around or under right bunk looking towards bath would be best. Also should it be raised cannot find install manual and they will not send me a new one only an owners manual.

Thanks

[Janets Husband]

Originally Posted by betsy

Want to put my new nts20 furnace in place, 59 tradewind, wondering if up front next to kitchen counter with covering built around or under right bunk looking towards bath would be best. Also should it be raised cannot find install manual and they will not send me a new one only an owners manual.

Thanks

I would not put a furnace under a bunk. My 64 Overlander and my 77 Minuet has the furnace under the oven in the kitchen. I would not recommend the sleeping compartment. Modern furnaces are very safe to use, but why tempt fate?

By the way "the right bunk facing the bathroom" would be called the "Street Side Bunk" if the bathroom is in the rear. See the problem?
The side reference is when you are parked on a street the right side or the door side is up against the curb, Hence the "Curb Side. The left side faces the street hence the "Street Side". Or use can use SS or CS bunk for short. Much easier to reference when you understand the system.

[Aage]

betsy, where was it originally installed?

[59as]

Hi thanks for lingo info, the original was up front I believe next to kitchen cabinet SS it was not in a cabinet if I remember. It's been 5 years nice Zi started this and really hope to pull it together this fall.

[idroba]

Originally Posted by Janet's Husband

I would not put a furnace under a bunk. My 64 Overlander and my 77 Minuet has the furnace under the oven in the kitchen. I would not recommend the sleeping compartment. Modern furnaces are very safe to use, but why tempt fate?

Both my 74 Argosy 20' and my 71 Airstream Caravel 18' have their furnaces under the beds as they came from the factory. What would be the problem? They are sealed outside air combustion chambers. The cabinets don't get hot either.

[Aage]

Originally Posted by idroba

Both my 74 Argosy 20' and my 71 Airstream Caravel 18' have their furnaces under the beds as they came from the factory. What would be the problem? They are sealed outside air combustion chambers. The cabinets don't get hot either.

1. The gasses could leak, in an extreme example. Witness the problem they had with the xover gasket on the old ones.
2. The noise! I am fairly sure that it would wake up the sleeper above it every time it came on.

Our new one in our 31-footer is at least 8 feet away (in a cabinet under the stovetop, next to the sink) and sometimes wakes me up when it comes on.

[Janets Husband]

Originally Posted by Aage

1. The gasses could leak, in an extreme example. Witness the problem they had with the xover gasket on the old ones.
2. The noise! I am fairly sure that it would wake up the sleeper above it every time it came on.

Our new one in our 31-footer is at least 8 feet away (in a cabinet under the stovetop, next to the sink) and sometimes wakes me up when it comes on.

Airstream has made many mistakes in building trailers in the past. If they placed furnaces under a bed that is a big one. Personally of the hundreds of Airstreams I have seen I've never seen a furnace under a bed, live and learn.

I agree with Aage, these things are noisy and unless you sleep like the dead it will wake you up. Again I will emphasize they are safe but why tempt fate.
I have to ask did you find any duct work? Is there any small 3" holes going down to a tank in the belly? These would be for heater ducts to the tanks. Where is the Gas feed for the heater? These clues will lead you to where it was originally installed. If you can't find any of these clues, install it under the stove and add your ducts fore and aft from there. Good Luck

[idroba]

Originally Posted by Aage

1. The gasses could leak, in an extreme example. Witness the problem they had with the xover gasket on the old ones.
2. The noise! I am fairly sure that it would wake up the sleeper above it every time it came on.

Our new one in our 31-footer is at least 8 feet away (in a cabinet under the stovetop, next to the sink) and sometimes wakes me up when it comes on.

In a space as small as an Airstream, the gases, in a leak situation, would not matter if they were under the bed or a few feet away. They would be mixed with the heating air from the fan and fully cover all of the trailer, not just the space above the bed. They are dangerous, no matter where the furnace is in the rig.

Noise is a very subjective area. Mine, in the Argosy, is a newer replacement, and is much louder than the original one. But, once my brain gets used to it, I never hear it. The sleeping brain simply says "oh that again" and seems to shut it off as an issue. If you let it bother you, however, it will.

BTW, water heaters are in the same situation, under the beds. And they often makes some noise when they run.