Furnace runs for the first night....then won't start up in the morning?

[Blackwatch]

So I'm stuck with an issue and am about to troubleshoot yet again to fix this problem, but I wanted to see if anyone else could throw in some nuggets of information gold for me....

I went camping on May long and ran the furnace with no issues on my 2006 Forest River Yearling Tent Trailer. It ran all the way through the night, and in the morning I turned it down low to 16C so as not to run my propane and power dry. The next evening, the furnace doesn't work. When the thermostat is turned over to engage the furnace, the blower runs its 20 second cycle to clear the combustion chamber and then turns off. The DSI does not "click" and ignite the burner. I boosted the battery with my truck and that was able to turn over the furnace on the first try and ignite the burners and when I took it off the truck it ran through the night again, but the next day it would not start up again after the burner went out. Long story short, the battery I was using had two broken cells so it would make sense that it had a low voltage issue and was not able to turn the blower to its 75% rpm, not activating the sail switch, etc. Oh and plus the charge (from my multimeter) was showing 11.5 amps during this period.

HOWEVER, after the weekend I replaced the battery with a high quality marine battery and an intelligent charger. Fully charged and ready to go, I took it out again this weekend. First night, no problem. Blower turns over its cycle, burners ignite and we're off to the races. Heat all through the night, and again in the morning I set the thermo to low (not off). Next evening comes around, and NOTHING. Same crap. Blower goes through its cycle and nothing else happens. Multimeter shows a charge of 12.7 amps on the battery. I cycle through numerous times and same cycle happens with no burner ignition. The fix came when I charged the battery to full strength again and, oddly enough, it worked on the second cycle.

I am going to be taking the relay board in to see if its faulty, but I am wondering now if it is a faulty sail switch that isn't getting closed. I just don't understand why it works great for the first night and then craps the bed the next. It makes it really hard to fix things when they work when you test them at home and then they don't work in the field. The wife is not happy.....

Any suggestions?

[caper]

After one night the battery is too low to run the furnace. You might have to go to a 2 battery set up. Or find a way to charge the battery during the day.

[sherdep]

Are you boondocking?
Or hooked to power (110) when it doesn't function the first night and not the 2nd?

It will most likely always work when hooked on power (110v) at home versus not hooked to power.

Caper has a good point

Get a battery disconnect that allows you to either have one battery on at a time or both batteries on or off and maybe a small solar panel to charge each battery indipendantly during the day light hours when not in use if you are not hooked to power (110v)

I am running two 12v batteries and have the disconnect that allows me to use each battery indipendantly or use both at the same time.

[Blackwatch]

After the first night with the new battery it said I had 12.7 amps left on the battery, I would think that it would be more than enough to run. Maybe I'm asking for much, but I would think that the battery would get me through AT LEAST a weekend lol

Having one battery per night for a whole weekend seems silly to run a single tent trailer furnace (not even running any lights or any other draw either). Something just doesn't seem right

Oh and I'm not boondocking (I assume that means hooking up at a powered site?). I'm only using the 12V battery

[Dave_Monica]

The furnace fan is a power hog...the biggest DC draw on the camper. I think what you're seeing is expected with a single 12V battery.

Dave

[Blackwatch]

Really? That really sucks lol I honestly would have thought it would last longer than that. I wasn't sure what the amperage draw from a furnace would be, but I imagine it would be the biggest in comparison.

So I have an idea, would a battery booster pack (like the 800A ones from Can Tire) be good enough to start it over every day and just let the fan do the slow draw from there? Just from the previous experience from needing a boost from the truck and it running all night gave me that idea.

[garbonz]

it don't matter how you get the correct voltage to the furnace as long as you do. You may want to check all the connection both pos and neg to the furnace cause you may be seeing a voltage drop from loose or corroded connections, so the voltage at the furnace under load may be less than the control board and igniter needs.

just a thought

[Blackwatch]

Hmm that's a good point. The pos/neg connections to the battery have some corrosion on them, I did clean them off but maybe I'll change them out to ensure they have the best connection possible. Thanks again for your advice Garbonz!

[mduff]

Originally Posted by Dave_Monica

The furnace fan is a power hog...the biggest DC draw on the camper. I think what you're seeing is expected with a single 12V battery.

Dave

X2 recent experience running the furnace drained the battery each night. We had to run our generator on occasion through the weekend to charge the battery.

[Herk7769]

Watch your light usage.
10 bulbs (5 fixtures) draws the same power as the furnace.

[caper]

The high draw of the furnace will drain the battery in one night. Your 12.7 volt is enough to let the fan turn but it is not turning fast enough to activate the sail switch on the furnace. Most people who boondock (no services) will either go to a two battery (12v) system or change over to 2 6volt batteries. If you run a furnace over night then you will have to find a way to recharge the battery for the second night.

[Blackwatch]

Ahh I see. That really sucks! haha I really thought that it would last more than one night. We don't use any of the lights because we want to keep the battery up enough to run the furnace. Good to know though, that probably saved me a fair chunk of change sending it in for repair.

I figured the same with the sail switch as well, I have been studying manuals for the furnace. I think that the low voltage isn't getting the fan rpm up to its 75% min to engage the switch therefore not turning it over, but turning over when I boosted it.

Thank you for your help everyone!

[bikendan]

Originally Posted by Blackwatch

Oh and I'm not boondocking (I assume that means hooking up at a powered site?). I'm only using the 12V battery

Boondocking is not hooking up to a powered site, it's the opposite.
it's camping out in undeveloped areas, such as deserts and forests, without any developed campsites.
Dry Camping is camping in a developed campground but with NO hookups.

sounds like you're dry camping and yes, using a furnace all nite long can easily drain a regular Group 24 battery.
you didn't say if yours is a true deep cycle battery or not. that will make a big difference also.
many of us that dry camp a lot, put in two deep cycle batteries. and some also get a small inverter generator to recharge the batteries after a few days.

[Blackwatch]

Yeah you bet, after the first one crapped out I went out and got a deep cycle marine battery. It started out with a charge of 13.7A or so and finished the night with around 12.5A. Seemed like it had a lot more to go in the charge before it was even at 75% but it wouldn't get the blower motor RPM up enough to engage the sail switch (or so I believe from what I've read from the manual). Such as it is I suppose.

I recently purchased a 30W Solar Panel from Canadian Tire though and I'm hoping that will work for my purposes. When I tested it, I started off with 12.5A charging for 3 hours on a cloudy day and it brought it up to 12.8A. Doesn't seem like much but that little thing sitting on the roof of my tent trailer for the whole day would get it up (hopefully) enough to engage that old sail switch.

[Fire Instructor]

Originally Posted by herk7769

Watch your light usage.
10 bulbs (5 fixtures) draws the same power as the furnace.

Speaking to various reps at the Camping World / Good Sam Rally, here in Syracuse, and more than one said that they will likely be switching to all-LED lighting within the next two to three years because of this. Apparently, the "flood" of LED availability in the US markets has now made the possible.

[Herk7769]

It is important to remember that voltage and capacity are closely related and fractions of a volt make a big difference. These charts show the relationship quite well.

However, to get a true reading, remember that a charger packs the electrons into the lead plates at a steadily decreasing rate as the battery fills and the electrons stay on the surface of the plate for a good 10-15 minutes after the charger is turned off to finally migrate into the lead. (Called charge equalization)

The effect of this is to give a false (high) voltage reading when the capacity is not really there.

Additionally, the larger the capacity of the battery, the longer it takes to pack those electrons into the lead of a deep cycle battery. It takes a LOT longer to recharge a deep cycle battery than a starting battery because of the thicker plates used to hold all that charge.

The converse is also true, since the plates are thick, it takes much longer to get those electrons out of the lead since they have to migrate to the surface to be released. Deep cycle batteries are ill suited to deliver large amounts of current (by themselves) and for high current applications (like powering an inverter) more than one is required so the current production demand on any single battery is lower. This is called the Peukert Effect and you can see the effect on a 100 Amp Hour battery's ability to produce and deliver current (AH rating) as the demand on the battery increased (amp load).

The depth of discharge between complete recharging also effects battery longevity. The deeper you discharge a battery, the less times you can recharge it before it will no longer take a charge. If you want your battery to last a long time always recharge it completely when the capacity reaches 50% or a voltage of 12.1 volts (Good light "G" goes out).

[ehorn]

I am having the same issue. Worked fine for a few nights now won't ignite. Fan starts then quits. Now I haven't checked my connections to the furnace so hoping that it is something simple. I have 2 145 watt panels, auto transfer switch to a 3000watt inverter/charger that runs our whole rv with 4 120 amp hour sealed deep cycle 12v batteries. So power shouldn't be my issues hoping that a ground got knocked or something just tweaked a little when installing the solar setup. It will not run with the inverter on or off. Anyone else think it will probably just be something simple once I get time to get in there and have a look! Unloading the basement is a lot of work lol.

[ehorn]

Well I figured out my issue. It was the limit switch in the back if the heat exchanger. I simply unplugged both wires and jumped them across each other fired right up. So reinstalled wires and is working just as it should.

[Dave_Monica]

Originally Posted by ehorn

Well I figured out my issue. It was the limit switch in the back if the heat exchanger. I simply unplugged both wires and jumped them across each other fired right up. So reinstalled wires and is working just as it should.

I'm no furnace expert but it sounds like you're bypassing a limit switch which is probably there for safety purposes. I hope someone with more knowledge can chime in...

Here's a link to the Surburban furnace manual which may help...
Forest River Forums - Downloads - Furnace - Suburban furnace troubleshooting

Dave

[ehorn]

I did indeed bypass the switch to see if that was the problem. I stated that I hooked everything back up. I figure by bypassing and rebooking the switch it somehow reset it. Just to reassure everything is hooked back up as it was. No safety issues