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Harrysheets · 07-13-2020, 07:27 PM

I am in a few year project to renovate my 1986 29’ Soveriegn and have finally reached the stage of putting things back in. I purchased a new NT-30SP to replace the rusty original and need to put it in before I can continue with new cabinets.
Problem – When I go to slide the vent tubes of the new furnace into the original tubes mounted on my AS they won’t slide in. The diameters of the tubes appear close but the distance between the new tubes appear to grown about 0.23”. (measured 5.205” on old receiving tube vs. 5.48” on new, outside to outside dimension). The tubes appear parallel.

Did Suburban change the centerline of these tubes so you can’t use the old cast external port on a new furnace? I could use the new stamped external vent assembly but I liked the cast original better.

Has anyone experienced the same issue?

I also noticed the new vent assembly exhaust tube is about 10/1000 smaller at the rolled lip and now has a small gasket. This is probably to minimize gases from passing between the pipe joint and reentering the trailer. This might be the reason they are forcing the new assembly.

Scott

dieseleagle · 07-14-2020, 04:59 AM

I've had mine out several times and have never been able to stab the furnace into the escutcheon tubes while they are attached to the trailer. I end up removing the escutcheon, set the furnace in its final location and then stab the furnace from the outside. I think the reason is that the furnace is parallel to the ground, but the side of the trailer is not perpendicular to the ground. There is a slight pitch to it. Its a pain, but it takes less time than the futile effort to get it done from the inside. Good luck.

NikkiCole · 07-15-2020, 07:57 AM

I also am attempting to purchase NT30SP to replace original furnace on my 78 Sovereign. Did have any issues with lining up the original side ducts to new furnace?? All the pics i have found on the new version show that ducts will not be parallel to with old ducts? Seeing as you are addressing this exact issue, i just need some guidance on this before I purchase another furnace that doesn't fit.

thanks!
Nikki

Harrysheets · 07-15-2020, 08:01 PM

After trying to tilt & slide the New NT-30SP into the old vent I determined the issue was the centerline distance between the exhaust and intake vent pipes of the new furnace. It was greater than the 3.5" as specified (3.73”). I decided to use the new stamped vent assembly since the intake pipe was separate and gave some adjustment. Turns out it was this way on the old vent part as well however I did not know this till I pried the old one from the AS shell.

Since the shell is not perpendicular to the AS floor I also struggled as others mentioned with the horizontal alignment of the vents. To make it worse the rear of the furnace sits on the C wall channel forcing to tip back slightly. To reduce this problem I cut the bent over portion of the C channel to get the furnace flatter on the floor. I also notched two millimeters off the bottom of the furnace where it sits over the C channel in the wall. The furnace now sat flat enough to insert and remove from the new vent.

I was also able to use the old intake vent as an adapter into the 2” duct that comes thru the floor below the front of the furnace. This is much more robust than the original coupler. I have yet to connect gas but the furnace is in.

Scott