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Topic: Why my foretravel furnaces don't heat (Read 903 times) previous topic - next topic

Why my foretravel furnaces don't heat

 It's in the fifties here and I am trying work in the coach. Problem is the furnaces won't keep running. They only run for a 3-5 minutes and then shut down on high limit due to lack of air flow and blowing 190* air.. So it's still cold inside, my best guess based on 35 years of HVAC experience is they kept adding heat capacity to the units based on complaints without increasing duct sizes. Best practice would be get get half sizes furnaces and boost efficiency 30-40%
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: Why my foretravel furnaces don't heat

Reply #1 –
They used to short cycle all the time.  Too hot.  Then too cold.  Repeat.

Design requires starting the fan at the same time as the blower in case of a internal leak. 

When the furnace reaches the cutoff temp the flame goes off but the fan continues until the furnace box cools off a bit.

Plus the bedroom furnace points across the narrow hallway if memory serves me.

Part of the natural beauty of the vehicle

Unless the blower motors are bad?  I can't imagine things wearing out after just 28 years. 
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Why my foretravel furnaces don't heat

Reply #2 –
Your furnace action sounds about "normal" to me.  I have never timed our furnaces, but when they run they usually don't stay on long.  They will keep the coach warm on average, but you have to accept fairly wide swings in room temperature.  If we are plugged in to shore power, we prefer to use several small electric space heaters scattered around the coach, and keep the OEM propane heaters in reserve for emergency heat in case of power failure.  The small heaters will do a much better job of maintaining a consistant temp throughout the coach, plus they are quieter, and probably (?) cheaper to operate.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Why my foretravel furnaces don't heat

Reply #3 –
Plus add a small fan up near the ceiling to circulate the air--prevents stratification of the hot air staying up "top" of the cooler air.
Recommend using the furnaces when it gets so cold the water lines might freeze. The furnaces in newer coaches heat the areas/compartments where it is crucial water doesn't freeze and damage things.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: Why my foretravel furnaces don't heat

Reply #4 –
something else going on - I had two furnaces (noisy as hell) in my 1989 OREG, both worked fine - had coach in WI in below freezing weather many times, snug as a bug (of course the single pane windows were not my favorite in the cold with furnaces going)

Tim Fiedler

Sure Start Soft Start

TCER Direct generator-gas-prod 630 240-9139
Gen-Pro
Tim Fiedler    2025 LTV Unity MBL on Order
2000 Chevy Tracker 2 Door Convertible 4WD Now lifted 4.5"
1985 Citroen 2CV6 Charleston
Murphy Rebel on wheels with 175HP Titan
Cessna P337
1980 48' Westport MY (!/4 Share)

Re: Why my foretravel furnaces don't heat

Reply #5 –
Quote from: Caflashbob –
  I can't imagine things wearing out after just 28 years. 

It's that crappy American-made stuff, just don't last a lifetime any more!  My files show our front Atwood furnace was replaced in 07. The rear Atwood I replaced this year, after being "re-built" by a PO. Typical of furnaces to cycle, that's their job, but, something is haywire with a furnace that won't let you just wear a tee-shirt inside!  ^.^d  I don't think it would matter, but has the electronic board been replaced?
1993 U-240 "La Villa Grande"..CAT 3116 w/ Pacbrake PRXB...Allison 3060 6-speed..
Previous: 1983 Airstream 310 turbo diesel, 1979 Airstream 280 turbo diesel
                                      Build # 4297
                                      PNW natives
                      Home base:  'Cactus Hug' (Ajo, Arizona)
                        DW Judy & Chet the wonder dog
                        Full-Timers 'Sailing the asphalt sea'

Re: Why my foretravel furnaces don't heat

Reply #6 –
You are probably correct that furnace is shutting down on high plenum temp.  We found 'dummy' covers for extra distribution hoses.  Removed the closed off covers and added additional outlets which eliminated the high heat shutoff.  We just need to move more air.  Be sure cold air return is open and all heat duct tubes are clear.

Re: Why my foretravel furnaces don't heat

Reply #7 –
I got my furnaces checked today.. The circuit board on the front needed to be replaced. Both on them spit a cloud of crap when given a blast of compressed air.

Picking the repair techs for knowledge... a good blowing out is usually all they need. If there is anything providing resistance to air flow the flame won't stay lit.
Paul
'92 U300 SBID 40'  #3968 "Large Marge"
Detroit Diesel 6v92TA & Allison HT746
'09 Mini Clubman w/ manual 6spd @ 39 mpg
 

Re: Why my foretravel furnaces don't heat

Reply #8 –
batteries low, lowering fan speed causing overheat?

Tim Fiedler

Sure Start Soft Start

TCER Direct generator-gas-prod 630 240-9139
Gen-Pro
Tim Fiedler    2025 LTV Unity MBL on Order
2000 Chevy Tracker 2 Door Convertible 4WD Now lifted 4.5"
1985 Citroen 2CV6 Charleston
Murphy Rebel on wheels with 175HP Titan
Cessna P337
1980 48' Westport MY (!/4 Share)