Low power and the furnace - a small advisory

[ThunderRoad]

This weekend was our last planned camping trip and I managed to kick it off with a klutzy move.

Friday night the temps got down to about 30 degrees, so we went to sleep with the furnace on and set to 60 just to keep the edge off. About midnight it shut down and all of the rest of the electrical was dead too. No power.

We heated in the morning by turning on one of the stove burners for a while

I felt really flummoxed that a fully-charged battery (even my crappy low-AH one) would be drained after only 5 hours of intermittent use of the furnace. Low and behold, it turns out I had forgotten to turn off the DC power on the fridge when I turned on it's propane after arriving. That explained the rapid power usage at least.

I hooked up the car and let it idle for about an hour as a make-shift generator to get enough power for basic lights and such. We also figured we'd run the furnace (30 degrees outside again) and make the best of it.

So, now that you have the back-story, here's the warning/advisory.

Furnace was purring along great, kicking on for a while, resting a while, and keeping it at a comfy 62 degrees or so. About 3am, the smoke alarm goes off. We leap up, see nothing on fire but can smell the acrid furnace smell like when we first got it (the smoke detector would go off then as well until I had ran the furnace several hours to burn off the oils). I quickly open the roof vent and only then notices that the lights are super dim. Looks like the power drained again.

My thinking is that as the power wound down, the furnace fan slowed down enough that it wasn't getting adequate air flow any longer, and hence the acrid smells. Not sure how hot it would have gotten if we hadn't been woken up.

I want to do a more controlled test at some point to see if I can correlate this behavior to low power, but I wanted to pass along this experience since we're heading into heating season.

At least in the spring I'm planning a power-system upgrade with solar and two batteries, so we'll have more capacity and passive recharging as well.

[bikendan]

you'll be sadly mistaken if you expect a regular vehicle to recharge a battery by idling.
for the majority of tow vehicles, a vehicle's alternator will only trickle charge, at best. that furnace fan was probably draining the battery faster than the vehicle could recharge it.

unless you have a big 1-ton truck(which sometimes have two alternators or have thicker charging wires) or specifically mod your wiring, you can't expect the battery to be recharged that way.
it's also a waste of gas and the poorest way to recharge the battery.

if you dry camp as much as we do, do yourself a favor and at least get the two matching batteries. a solar system will work if you camp out in the open.
for us, we usually camp in wooded parks, so we just use the Honda 2000, along with our two batteries.

[ThunderRoad]

Unfortunately I don't have a voltmeter to get readings (athough I'll get one as part of my power upgrade), but after that one hour charging, I had enough for lights and the furnace for at least 7 hours (didn't turn it on until night).

I know it's not efficient, but it was what I had to work with at the time. My power upgrade will be with twin new batteries, as you recommend.

[VinceU]

Originally Posted by ThunderRoad

This weekend was our last planned camping trip and I managed to kick it off with a klutzy move.

Friday night the temps got down to about 30 degrees, so we went to sleep with the furnace on and set to 60 just to keep the edge off. About midnight it shut down and all of the rest of the electrical was dead too. No power.

We heated in the morning by turning on one of the stove burners for a while

I felt really flummoxed that a fully-charged battery (even my crappy low-AH one) would be drained after only 5 hours of intermittent use of the furnace. Low and behold, it turns out I had forgotten to turn off the DC power on the fridge when I turned on it's propane after arriving. That explained the rapid power usage at least.

I hooked up the car and let it idle for about an hour as a make-shift generator to get enough power for basic lights and such. We also figured we'd run the furnace (30 degrees outside again) and make the best of it.

So, now that you have the back-story, here's the warning/advisory.

Furnace was purring along great, kicking on for a while, resting a while, and keeping it at a comfy 62 degrees or so. About 3am, the smoke alarm goes off. We leap up, see nothing on fire but can smell the acrid furnace smell like when we first got it (the smoke detector would go off then as well until I had ran the furnace several hours to burn off the oils). I quickly open the roof vent and only then notices that the lights are super dim. Looks like the power drained again.

My thinking is that as the power wound down, the furnace fan slowed down enough that it wasn't getting adequate air flow any longer, and hence the acrid smells. Not sure how hot it would have gotten if we hadn't been woken up.

I want to do a more controlled test at some point to see if I can correlate this behavior to low power, but I wanted to pass along this experience since we're heading into heating season.

At least in the spring I'm planning a power-system upgrade with solar and two batteries, so we'll have more capacity and passive recharging as well.

Somethngs wrong with this picture.....You should never have anything close to exhasut or pungent gas from the funace- new, middle, or old or any other appliance. Just so you can sleep, and wake up, you should have someone check it. I would think anyone who services gas home furnaces can run the gas test on this furnace. They've been found cracked before.

[Jeep4Two]

I would also suggest getting this checked. Even if low voltage caused low air flow to the heat exchanger, there should be a high limit switch that would have killed the flame and avoided the overheating.

[RenFaire Camper]

I have to second getting everything checked out. On this weekend trip the temp dropped to the low 40's and I set the furnace to 74 it ran all night and till around 2 on Sunday when I shut it down to cool off before breaking camp and heading home. total it must have run 15 or 16 hours and power was still good. Battery might be getting old or you have a short some place adding extra drain to the battery