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 > Furnace low voltage limit

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GregA

Montana

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Posted: 09/17/20 05:16pm Link  |  Quote  |  Print  |  Notify Moderator

Hey All,

What do you suspect the lowest voltage is that I need to "ignite" my furnace?

Everything about my furnace works great on shore power or above 12.1V. Under that, the sail switch does not seem to close and I get no ignition (only blower activation).

Does this seem right? I thought I should be able to ignite much lower than 12.1V. YEs I know 10.5 is the bottom limit.

Thanks!

jimh425

Western MT

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Posted: 09/17/20 05:27pm Link  |  Quote  |  Print  |  Notify Moderator

I've never had a fail to ignite because of voltage, maybe someone has a number in mind, or it could be furnace specific. My furnace is a Suburban.


'10 Ford F-450, 6.4, 4.30, 4x4, 14,500 GVWR, '06 Host Rainer 950 Dbl Slide, Torklift Talon tiedowns, Glow Steps, and Fastguns. Bilstein 4600s, Firestone Air Bags, Hankook DH-01 225/19.5 Fs, Curt front hitch, Energy Suspension bump stops.


brholt

Seattle

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Posted: 09/17/20 05:39pm Link  |  Quote  |  Print  |  Notify Moderator

May be your sail switch or you need to clean the blower.

Does the furnace come on, blow, then stop blowing? In that case the sail switch is not allowing the furnace to run as it thinks there is insufficient airflow.

In our case below 5,000 feet no problem.

At 6,000 ft with a fully charged battery no problem.
However, if the battery is discharged some the furnace shows the above behavior. If I start the truck then it gets enough voltage to spin the blower fast enough for the sail switch to allow ignition. (Used remote start on the truck several weeks ago at Mammoth campground In Yellowstone when the cold front mover in.)

Above 7,000 ft our furnace will not ignite.

Old-Biscuit

Verde Valley

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Posted: 09/17/20 07:00pm Link  |  Quote  |  Print  |  Notify Moderator

Low DC Voltage will cause fan RPM to be low and not move sufficient airflow to move sail switch 'paddle' and close the micro switch

More common issue is dirty/stuck sail switch 'paddle'
Fan gets DC Voltage when t-stat closes
NOTHING else is going to happen until airflow move sail switch paddle and closes it

So clean the paddle ...check that is not hanging up on casing and that micro switch closes

All good.....then Low DC Voltage is suspect

What brand/model is YOUR furnace?????

* This post was edited 09/17/20 10:48pm by Old-Biscuit *


Is it time for your medication or mine?


2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
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Off the road still Debt Free Jan. '14

GregA

Montana

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Posted: 09/18/20 09:04pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks for all the replies. Its an Atwood furnace and brand new. I took the sail switch out and it was clean as a whistle and "looked" fine. Intersting comment about Yellowstone as I am in Gardiner :-) Most of my camping is above 6000ft for sure.

Back in 2010, I had a Halmark pop-up and NEVER had this issue. I consitantly camped at elevation in the WINTER.. Never a problem.

Cheers-Greg

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