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hiskid1973 01-17-2007 01:20 AM

Mobile Home Furnace..Update..Hey Carrierman
Ok..Here is the latest..Service man came today..Swapped out the .6/80s nozzel with a .5/80 and I think he said "a" He said Miller's used to use that nozzel than changed recently. He added a an inline filter because of the nozzel size..Everthing ran fine..I didn't restart when the house called and they sent him back.It was a bad nozzel.
Now here is what he says..My old moc 80 used to kick out 120/140 d. air out..It would come on burner would run about 1.5 min with fan on then shut off and restart burn about two min later and santisfy the stat... He says it was the high limit kicking a was how it was supposed to run, cycling like that...

It is running at 82% eff. The hi limit kick was at 140 deg when he left..It was about 42 out and it was doing great..Runs 3x per hour.

I feel much better now it's not running on the high side 180-200 deg..I's more like the old furnace.. Now it's 2 am ( I have fibromyalgia and have major sleep/sleep loss probs.) and it's 19 d. with a slight breeze and was wanting to run a little more that 3x /hr so i moved the hi kick to help it out..Latest 5am 18 degrees only 4-5 minutes off time instead of 7 and itdoes about three 1-2 minute burns over a 13 minute run..How does this compare with other furnaces?

Should I just put it back to the 160 fac. setting and let it go..I have the fan at the med setting as the low setting doesn't move much air...Also if I want to get a part say this hi limit switch, how can I find this miller # 626436 to the generic Honeywell #..

Thanks for your patience and understanding.
God Bless..k

Christopher 01-17-2007 11:21 AM


I am not sure that I follow everything that you have written but know this: Your furnace should never cycle on high-limit. High-limit is a fault condition, not an operating condition.

During the heating cycle, the burner should run continuously. If your furnace is an oil burner, adjust the blower speed so that when the burner is running continuously, the air temp at the supply plenum never exceeds 140 deg. F. Fan on at 120, off at 100.

Gas furnaces are designed to run at lower temperatures. Set fan speed for a 120 deg. F supply plenum temperature.


#CARRIERMAN 01-17-2007 01:25 PM

Hi kiskid1973

Put your high limit back at the 160 degree where it was originally.
If the limit continues to trip, you will need to tune her down a little more. But before you do I would reccomend turning the blower speed up one to see if that eleviates the rest of the problem. However if the blower being sped up is too noisy, definatley tune it down one more size. Let me know if you need any further assistance.

Good luck

hiskid1973 01-17-2007 01:47 PM

Thanks Rusty.So you can get under .5 gph nozzels? I don't know if I should get another tech from another dealer. The last bill is into the Feb. budget already. I have the fan set at med, so I will reset to 160 d. and put it to Hi..Thanks..k

#CARRIERMAN 01-17-2007 01:51 PM

Hi hiskid1973

Sounds like your getting there, let me know if you need any further help.

Added information: There is a .40/80 available through Johnstone supply. Part number is L37-104, I am sorry I would have got this for you earlier but we have been busy here.

Good luck

hiskid1973 01-18-2007 12:50 AM

Ok Rusty..Here's the latest..Fan is on Hi.. The sounds between speeds make no difference..It's in a closet and just covered by a louvered door..I do notice a little whistling in the bath vent..The cycle time comes down to 9 min to complete instead of 13...The furnace is coming on every 18 min instead of it's at 19 degrees outside..

The burner still only runs 2 min then I hear a click with the blower runninig and another 2 min burn, that the stat stops if it warmer out or shuts off before stat when its cool. This happens wherever the hi limit is set.. It almost seems like the 2 minute burns are hardwired in unless the new looking fan switch is defective.. Now it's a little later and I am noticing the 2 "burns in a cycle go to a short 3 till the stat kicks..I do notice the hi temp heat loss but feel more comfortable that it's hi temp when there is no humidity call hit 140 deg.....Another thing I forgot to mention is the nozzel below the shutters that sprays 60 degree water in for humidity.. It's been averaging a fifteen minute burn cycle with one 2 min burn, 1-1.5 burn and stat santisfy 5 min off next cycle at 18 degrees..Thanks again.Kim
Anyway thanks for your input..God Bless.Kim

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