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2002sheds · 03-07-2018, 09:05 PM

Hi All,
In yet another departure from my normal "replace the rear floor of our 1970 Ambassador" thread, I have a question or two regarding the furnace.
The only markings I can find so far indicate that it is a Suburban furnace. Where do I look to identify it more specifically?
I have been reading as many posts as I can about this topic (identification) and the furnace in general. This unit looks to be in very good condition -- fan bearing looks good, virtually no rust found so far, and even the rubber is still pliable. It spent its life in California, and likely did not get much use before the mud daubers and mice moved in..
I am tearing this apart with the intention of finding faults with this unit, and so far cannot find any. Obviously, before using the thing I will have it verified at the local shop, and also have a functioning Co2 monitor in the AS.
What else should I be looking for? And again, how do I identify which model it is? I have not seen a plate anywhere (yet).

Thanks,
David

Lumatic · 03-07-2018, 09:52 PM

If it is original it is probably a NT30. Did you take off the front cover?

Old furnaces tend to look OK, but do you really want a furnace pushing 50 years old in your living space?

It may be very difficult to find any RV technician to even look at it for liability reasons. Also parts are not available.

You need a CO detector not a CO2 detector. Personally, I would not sleep in a trailer that also does not also have a propane detector and smoke alarm.

Not that difficult to install a new Suburban. The air intake and exhaust are the same configuration. The biggest problem will be fabricating a new plenum. So much easier to use.

2002sheds · 03-08-2018, 07:53 AM

Hi Lum,
Thanks. I did start to tear it apart, but maybe I have not gotten far enough. I will try to find an image of the NT30 to confirm.

Thanks!
David

mandolindave · 03-08-2018, 08:12 AM

I can not answer your question on location of model number. But….

1. Visually inspecting motor bearings is not enough. I say, briskly spin the fan manually. It should spin for almost a minute.

2. The early 70s era furnaces are not made any more. The replacement is "almost " the same, but requires a little jerry rigging to install.

3. Having your old furnace taken out, rebuilt, and reinstalled will cost enough to make you consider putting in a new one. Maybe the safest bet anyway.

These are just opinions based on my experience. Please correct me if I am wrong.

2002sheds · 03-08-2018, 08:59 AM

Hi Man,
Thanks. I don't even know how to visually inspect a bearing :-) but I will be removing it, cleaning it or replacing it, depending on the condition of the rest of this thing. The fan did spin freely after the mouse nest was removed.
Time and a much closer further inspection will determine if this furnace is in as good of condition as it appears. And I understand that looks can be very deceiving, so I am approaching this with the view that it probably will fail, rather than pass. It is a matter of where, and how minor/major the fail is...

Thanks,
David

Lumatic · 03-08-2018, 10:18 AM

Quote:

Originally Posted by 2002sheds

Hi Man,
Thanks. I don't even know how to visually inspect a bearing :-)
Thanks,
David

The bearing and the motor are a sealed unit.

2002sheds · 03-08-2018, 10:25 AM

Hi Lum,
Thanks. I only got a cursory glance at it yesterday. Good to know.

Thanks,
David

switz · 03-08-2018, 10:37 AM

The big issue for safety would be "ANY" cracks in the heat exchanger due to age linked metal fatigue.

2002sheds · 03-08-2018, 10:42 AM

Hi S,
Thanks -- that is one of the big ones I am looking for... the next step will be to find some time to get further inside this thing. So far, I have only had about 10 minutes on it. The "radiator" hose between the sides is pliable (I would probably still replace it with something from an automotive supply place) and the fan spins freely. All other bets are off until I get a good look at the heat exchanger.

Thanks,
David

Lumatic · 03-08-2018, 02:21 PM

Quote:

Originally Posted by 2002sheds

Hi S,
TThe "radiator" hose between the sides is pliable
Thanks,
David

that "hose" is the crossover tube. Deterioration of the crossover tube let carbon monoxide into the trailer and was the reason the NT28 furnace was recalled.

Dingo Girl · 03-08-2018, 02:37 PM

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2002sheds · 03-08-2018, 09:36 PM

Hi Lu, Din,
Thanks. Lu, I'm pretty sure that it is radiator hose. I just need to keep looking to find it... just kidding. i didn't have the terminology memorized when I responded to Switz.
Dingo, thanks for the pic. I will try to find the badge tomorrow.

Thanks,
David

guskmg · 03-09-2018, 01:00 PM

In 1974 I witnessed an emergency crew extract 3 people from an 1972 Airstrem with a cracked heater plenum. The father, a smoker, was unconscious, the mother was concious , but dazed. A baby, laying near the floor was OK. I would never use an old furnace for the above reason.
guskmg

Dingo Girl · 03-09-2018, 02:23 PM

I'm not putting my old one back in.
Too rusty & too scary.
I had it bench tested & it worked fine but I don't trust it.

2002sheds · 03-13-2018, 11:48 AM

Hi All,
Okay, deeper in... Everything is looking good so far, although I still have not found the plate with any model info on it. I have only found a sticker that says "Suburban".
I have taken apart the fan assembly and removed the main burner to allow better access/visibility inside. So far, no visible separation, cracks, etc. I have also gotten to know some of the components, including the ignition system. In my experience, the piezo electric ignition always generates a spark as one part snaps past another. In this case, the lever that activates the Clevite piezo "box" ignitor just moves back and forth.
This seems strange to me because these (piezo) ignitors will reportedly go 10,000 times or so before quitting. There is no indication that this furnace has even been used 100 times (which, considering our climate, is very possible). I read some info on Google Patent about a safety feature on (possibly) this device which prevents it from firing unless a latch is moved (although I do not see any latch -- at least not yet). Not sure if I am barking up the right tree here, but thought I would ask if there is something to the startup process that includes two steps for the ignition, or should pushing that rod result in a "snap" every time? It is easy enough to replace this with a manual or battery-operated ignition system, but I like knowing how things work, so I am checking it out.
Regardless of appearance, I will be taking it the unit to our local service center to verify or disprove what I find.
And whether I buy a new furnace or not, the coach will be equipped with screens over the intake and exhaust ports on the outside, and a carbon monoxide monitor inside.

Thanks,
David

Dingo Girl · 03-13-2018, 04:05 PM

Just added carbon monoxide detector to the list.

Lumatic · 03-13-2018, 05:03 PM

Quote:

Originally Posted by Dingo Girl

I'm not putting my old one back in.
Too rusty & too scary.
I had it bench tested & it worked fine but I don't trust it.

I think you made a good decision for peace of mind and ease of use and serviceability. Waking up dead would ruin my day.

I replaced my NT28 with a new NT30. I took the old base and used it for a plenum so I could reuse the ductwork connections. Raised the new furnace an inch or so with lumber so that the outside air inlet and exhaust holes line up. A new furnace does have a parasitic small 12v draw.

The cheapest source I found was Palomino RV, but you have to know exactly what you want to order.

I am sure there are threads on the subject.

2002sheds · 03-13-2018, 06:42 PM

Don't wanna lose the thread, so re-posting....

Hi All,
Okay, deeper in... Everything is looking good so far, although I still have not found the plate with any model info on it. I have only found a sticker that says "Suburban".
I have taken apart the fan assembly and removed the main burner to allow better access/visibility inside. So far, no visible separation, cracks, etc. I have also gotten to know some of the components, including the ignition system. In my experience, the piezo electric ignition always generates a spark as one part snaps past another. In this case, the lever that activates the Clevite piezo "box" ignitor just moves back and forth.
This seems strange to me because these (piezo) ignitors will reportedly go 10,000 times or so before quitting. There is no indication that this furnace has even been used 100 times (which, considering our climate, is very possible). I read some info on Google Patent about a safety feature on (possibly) this device which prevents it from firing unless a latch is moved (although I do not see any latch -- at least not yet). Not sure if I am barking up the right tree here, but thought I would ask if there is something to the startup process that includes two steps for the ignition, or should pushing that rod result in a "snap" every time? It is easy enough to replace this with a manual or battery-operated ignition system, but I like knowing how things work, so I am checking it out.
Regardless of appearance, I will be taking it the unit to our local service center to verify or disprove what I find.
And whether I buy a new furnace or not, the coach will be equipped with screens over the intake and exhaust ports on the outside, and a carbon monoxide monitor inside.

Thanks,
David

2002sheds · 03-14-2018, 12:42 PM

Hi All (or Any

,
There is no identification on this furnace beyond it saying Suburban. There may have been a badge, but it is gone and only holes in the case remain.
At this point (and through the help of this forum), I am pretty sure that it is one of the dread NT-22 units. I am proceeding with caution, although all components so far (including the treacherous crossover tube) are fine. As I am putting things back together, I am using all new exhaust gasket material and the highest temperature Permatex where appropriate as an added precaution/sealant.
I still have the question about the igniter. I may be one of the few people that has ever bothered to take one of these apart, but I cannot figure out what EVER made it snap or click... there is a lever that is actuated by the push rod, but it does not seem to have anything broken off not does it seem to contact anything that would "snap" against the container with the crystals inside.
I did get a tiny shock when cleaning the dead spider away from the part with the crystals in it. I was using a screwdriver and must've generated enough friction...
I still may junk this whole thing, but I would sure like to know how this part igniter worked. Do they all "snap"?

Thanks,
David

2002sheds · 04-03-2018, 07:29 PM

Hi All, Anyone,
The furnace is back together and ready for its bench test. Replaced any gaskets and also added a thin layer of Form A Gasket as added insurance. Bought a grill-type battery operated electronic igniter and Carbon Monoxide detector with a readout in ppm in addition to the alarm feature. Hope to test it tomorrow.

David