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Old 11-23-2013, 10:27 AM   #1
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1990 25' Excella
Pilot Hill , California
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1990 NT-30 K replacement

Anyone have experience replacing a pre 1990 NT-30 K with a newer furnace?

We have a 1990 Airstream Excella with a Suburban NT-30K furnace that is having operational issues. It starts in the morning and sometimes runs for about 3 minutes. Then the burner turns off and after about 16 seconds starts for 7 seconds then off again. On and on and on… Any ideas? Module board? Flame sensor?

The flame sensor seems to be working. When the burner lights I see a few milli volts in series with the circuit.

I called Suburban and they do not offer anything. No parts, no replacement, no recommendation, no part cross reference, just have a nice day and that’s it. Is there a design flaw with this furnace?

I would try a new flame sensor and module board but cannot find a suitable replacement part number…

If it is time to replace the unit what is the recommended replacement? The NT-30 K measures 9.5” H – 12.5 W – 23” D. Suburban NT-30K, Code AKZ, Serial 2157203

The newer NT-30-SP is 12.5 inches high. It will fit in the cabinet but just barely. Will the original exterior holes work or will I need to modify the exterior of the trailer? If a exterior modification is required what is the best way to patch the original holes?

Thanks
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Old 11-23-2013, 10:40 AM   #2
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1993 34' Excella
York , South Carolina
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We just installed a replacement igniter board in a '90 . The fan would come on but no ignition. The board took care of it. Used a Dinasour board, purchased from Randy at Best Converters. About 100 bucks with shipping. model UIB L (universal igniter board, large). Fit right on, just like the original. You will need to pull the furnace out of the housing, only 2 screws. The board is on the right side. We found it easier to slide the furnace back in by pulling off the outside vents, then put them back on the furnace ports with new sealant.

Not sure it will cure your problem but if original, that igniter board is 23 years old.

John
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Old 11-24-2013, 12:54 PM   #3
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1990 25' Excella
Pilot Hill , California
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Furnace Update

Do you think it is worth trying the board suggested and a newer flame sensor that looks identical to my current one?

Or should I just replace the furnace with a new NT-30-SP?

I pulled the whole unit yesterday and cleaned out the gas lines, (from the supply bottles to the furnace), installed a new main gas regulator, cleaned the burner assembly, re-soldered the control board on two questionable connections, continuity checked all the wiring and the sail switch. I also pulled the flame sensor and checked it’s position. The flame sensor seems to be working okay but is getting distorted on the ends over the burner. See attached photo.

When reassembled and installed it fired up correctly and ran great through the first cycle. I turned it off when the thermostat opened. After letting it cool down I started it again. Now it is running 30 seconds on and 16 off.

I hate to spend $120 on a lost cause just to find out it is time to replace the unit.

Thoughts, advice, recommendations?

Anything will help...
Thanks,
Carl
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Old 11-24-2013, 01:08 PM   #4
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1976 Argosy 28
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A new NT30SP is about $600 with shipping from AdventureRV (and available from many other sources, that's just the cheapest one that showed up when I did a cursory search.)

Cranky old furnaces are extremely annoying (says the man with a cranky old NT22 and a new NT30SP).
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Old 11-24-2013, 02:02 PM   #5
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Tough call. I am by no stretch an expert. The new UIB-L fixed us right up, for about a hundred bucks. The combustion chamber itself looked really good, the trailer spent a lot of it's 23 years in Fla so little time on the furnace. We had done some diagnostics and were fairly sure we needed the board. Maybe just a lucky guess.

John
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