Mystery furnace

[dick kennedy]

I've got my DuoTherm furnace all refurbished and ready to reinstall. It
uses two side by side holes about seven and a half inches apart for it's
intake and exhaust. The coach has two other holes that are a little lower
and to the rear spaced about five and a half inches apart. These are
covered on the outside by a pair of chrome screens.

I thought at first that these were just a mistake made during manufacturing
and didn't pay much attention. Then I noticed that the fiberglass around
the rearmost one looked burned. There must have been another furnace
installed at one time and my DuoTherm must be a second installation.

This raises several questions. The manual says it originally had a solaire.
Is the five and a half inch side by side spacing the footprint of the
solaire? If so did the solaire have an early failure mode which would
warrant it's replacement? Then what might be the vintage of the duotherm?
It's not new but it's in good shape except for the rusted off intake and
exhaust ports. Had I left the duotherm go another couple years the leakage
may have been enough to cause burns like this. Are these coaches old enough
to have gone through two furnaces?

Can anyone shed any light on this?

It's just history but it is interesting.

Dick Kennedy

 

[gene]

Excellent post from a guy "who was there". but tell me, why are you
looking for a used suburban?? do they fit better than a new one ?? and what
are you going to do about the exit pipe differences ??

gene

>On Mon, 19 Jun 2000 22:14

>
>rearmost one looked burned. There must have been another furnace installed
at
>one time and my DuoTherm must be a second installation.
>
>This raises several questions. The manual says it originally had a solaire.
>Is the five and a half inch side by side spacing the footprint of the
>solaire? If so did the solaire have an early failure mode which would
warrant
>it's replacement? Then what might be the vintage of the duotherm? It's not
>new but it's in good shape except for the rusted off intake and exhaust
>ports. Had I left the duotherm go another couple years the leakage may have
>been enough to cause burns like this. Are these coaches old enough to have
>gone through two furnaces?
>Can anyone shed any light on this?
>It's just history but it is interesting.
>Dick Kennedy >>>
>
>Dick,
>
>The Sol-Aire furnace was used on many early GMC coaches. The company that
>built these used to make furnaces for some type of military use. At that
time
>I was working for Duo-Therm, and we could never figure out why GMC chose
this
>furnace when there were a number of RV furnace manufacturers around at that
>time (only 2 left now). It was probably because this was one of the first
>electronic ignition furnaces to be made for RVs.
>
>Sol-Aire had a lot of problems, and service for these was very poor.
>Eventually they went out of business, and parts were no more.
>
>In May, 1984 a GMC dealer from Michigan sent one of his motorhomes to us to
>install a Duo-Therm furnace. I was given the job of writing the instructions
>for removing the Sol-Aire furnace and installing the Duo-Therm. I don't
>recall all the details of this, but I recall that the sloped sides of the
GMC
>were a bit of a problem for installing the exhaust vent. I also recall that
>this coach had a fold-up sofa-bed in front of the kitchen counter, and I had
>to remove it to get the Sol-Aire out of the cabinet.. I also remember
>patching the original vent holes with stainless steel plates. You may very
>well have the motorhome that I did this installation on (?). The dealer gave
>us a copy of the GMC Maintenance Manual, and I have kept it ever since - now
>I use it all the time.
>
>There is more - the Duo-Therm Model 90030, chosen for this replacement, was
>just released in 1984, and used a totally new type of combustion chamber.
>Shortly after this we started having severe problems with this model, and
>within a year we had a major recall on these due to leaking gas controls. I
>can say that this was the worst product that Duo-Therm ever made during the
>26 years I worked there. I have 2 of these in my shop that burned out within
>a few years of use. However, you should not have to worry about fumes
getting
>into your coach if this happens. The large circulating blower runs whenever
>the burner is on, keeping the walls of the heat chamber pressurized, and
if a
>hole develops, air will be blown INTO the burner and out the exhaust. You
>will experience flame outages and popping noises, but fumes won't come out
of
>the chamber into the coach. This model eventually led to Duo-Therm losing
>much of the market share for RV furnaces, and in 1989 they stopped building
>all RV furnaces.
>
>This was my first experience working on a GMC, and I had time to look it
over
>and compare it to other motorhomes that I had worked in. I liked the design
>of the GMC - very modern, sleek look - but I never thought then that I would
>someday own one of these beasts.
>
>Maybe it's true "ve get too soon oldt, und too late schmardt"?
>
>Erv Troyer
>Lagrange, IN
>74 Sequoia (with NO furnace, and looking for a used Suburban)
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/

 

[gene]

Excellent post from a guy "who was there". but tell me, why are you
looking for a used suburban?? do they fit better than a new one ?? and what
are you going to do about the exit pipe differences ??

gene

 

[dick kennedy]

Thanks Erv,

That's interesting history. I hope somebody's keeping an archive of
interesting tid bits. My model number is 69530-064 so it must be a somewhat
later model. The combustion chamber has three sections of burner. My GMC
was a tradein on a Foretravel, so I bought it in Nacogdoches, Tx. I don't
know where it lived before that.

As I said I completely stripped it so I know it's sound. When I mixed the
fiberglass last night I didn't use enough hardener so now it's in the oven.

I'm in Kokomo, In if you get down this way

Dick Kennedy
'75 PB

>On Mon, 19 Jun 2000 22:14

>
>rearmost one looked burned. There must have been another furnace installed
at
>one time and my DuoTherm must be a second installation.
>
>This raises several questions. The manual says it originally had a solaire.
>Is the five and a half inch side by side spacing the footprint of the
>solaire? If so did the solaire have an early failure mode which would
warrant
>it's replacement? Then what might be the vintage of the duotherm? It's not
>new but it's in good shape except for the rusted off intake and exhaust
>ports. Had I left the duotherm go another couple years the leakage may have
>been enough to cause burns like this. Are these coaches old enough to have
>gone through two furnaces?
>Can anyone shed any light on this?
>It's just history but it is interesting.
>Dick Kennedy >>>
>
>Dick,
>
>The Sol-Aire furnace was used on many early GMC coaches. The company that
>built these used to make furnaces for some type of military use. At that
time
>I was working for Duo-Therm, and we could never figure out why GMC chose
this
>furnace when there were a number of RV furnace manufacturers around at that
>time (only 2 left now). It was probably because this was one of the first
>electronic ignition furnaces to be made for RVs.
>
>Sol-Aire had a lot of problems, and service for these was very poor.
>Eventually they went out of business, and parts were no more.
>
>In May, 1984 a GMC dealer from Michigan sent one of his motorhomes to us to
>install a Duo-Therm furnace. I was given the job of writing the instructions
>for removing the Sol-Aire furnace and installing the Duo-Therm. I don't
>recall all the details of this, but I recall that the sloped sides of the
GMC
>were a bit of a problem for installing the exhaust vent. I also recall that
>this coach had a fold-up sofa-bed in front of the kitchen counter, and I had
>to remove it to get the Sol-Aire out of the cabinet.. I also remember
>patching the original vent holes with stainless steel plates. You may very
>well have the motorhome that I did this installation on (?). The dealer gave
>us a copy of the GMC Maintenance Manual, and I have kept it ever since - now
>I use it all the time.
>
>There is more - the Duo-Therm Model 90030, chosen for this replacement, was
>just released in 1984, and used a totally new type of combustion chamber.
>Shortly after this we started having severe problems with this model, and
>within a year we had a major recall on these due to leaking gas controls. I
>can say that this was the worst product that Duo-Therm ever made during the
>26 years I worked there. I have 2 of these in my shop that burned out within
>a few years of use. However, you should not have to worry about fumes
getting
>into your coach if this happens. The large circulating blower runs whenever
>the burner is on, keeping the walls of the heat chamber pressurized, and
if a
>hole develops, air will be blown INTO the burner and out the exhaust. You
>will experience flame outages and popping noises, but fumes won't come out
of
>the chamber into the coach. This model eventually led to Duo-Therm losing
>much of the market share for RV furnaces, and in 1989 they stopped building
>all RV furnaces.
>
>This was my first experience working on a GMC, and I had time to look it
over
>and compare it to other motorhomes that I had worked in. I liked the design
>of the GMC - very modern, sleek look - but I never thought then that I would
>someday own one of these beasts.
>
>Maybe it's true "ve get too soon oldt, und too late schmardt"?
>
>Erv Troyer
>Lagrange, IN
>74 Sequoia (with NO furnace, and looking for a used Suburban)
>
>

 

[ronald b. kazi]

I was told by the folks at Suburban last week that my NT-22 is no longer
supported by the manufacturer. Parts have not been available through them for
this unit since 1997. Many parts, I was told, are available at local service
centers that still have a stock of the older parts. Some things like the control
valve can be retrofitted. I dropped mine off at an RV place last week and am
hoping for the best. If not, it is off to the catalogs. I like the smaller line
of furnaces that Suburban has and will consider mounting it under the couch to
create more cabinet space under the sink for storing Budweisers.

Ron and Julie

> Gene,
>
> I am looking for a Suburban because my coach had one of these originally, and
> the vent plate is still in place. Also, Suburban is still building RV
> furnaces, and I can still get parts. The Duo-Therm I have in my shop is
> running on borrowed time - my friends at Duo-Therm have exhausted their
> supply of stashed parts that I can draw from.
>
> I am looking for a used furnace, because it fits my budget much better than a
> new one. Local salvage stores want $400+ for a new one, and at this time I
> have any number of more important items on the GMC to worry about.
>
> Max at Buskirk-Rush RV tells me that the vent adaptors to connect to the
> angled exterior vent plate are still available. I know some have mounted
> their Suburbans at an angle to connect to the vent plate, but I don't believe
> the furnace is designed to operate like this (in my opinion).
>
> Erv Troyer
> Lagrange, IN
>
> ------- original message ----------
> Date: Tue, 20 Jun 2000 02:36:52 -0700
> From: gene
> Subject: Re: GMC: Mystery furnace
>
> Excellent post from a guy "who was there". but tell me, why are you
> looking for a used suburban?? do they fit better than a new one ?? and what
> are you going to do about the exit pipe differences ??
>
> gene