35 replies to this topic

[nico]

The fridge runs off battery only.

Edited by nico, 27 December 2021 - 03:17 PM.

[Jon R]

So a two way compressor fridge. I asked because the three way fridges (propane/120vac/12vdc) use a lot of power when operated off the battery.

[Jkron]

So I am learning the nuances of my new grandby flatbed. I spent two nights in the desert recently with low temps and my heater was real finicky. I did not realize how much power the heater fan draws and even though my batteries were at 12.5 ish volts, i could not get the heater to work and my kids were freezing. I had to trouble shoot everything before realizing it was a power issue and had to run the truck intermittenly for the rest of the trip which was kinda annoying. SO moving forward i am trying to determine what this system needs (at least in the winter time) to have enough power that I dont have to run my truck constantly to charge up the batteries. I am currently running the dual lead acid batteries with a 160 watt solar panel. I am open to adding another panel but im not sure this will do the trick in the winter time. I imigine the 160 watt panel will be adequate in the summer (albeit we probably wont need the heater in the summer/fall).  i had another camper owner tell my to jsut get a small heater such as the mr buddy heaters but that seems kinda dangerous to run in the camper if it fell over or something. maybe that could be an emergency measure but again I can always run the truck for 20 minutes or so. Open to suggestions.

 

I am willing to bet it is the foil ducting on the front of the furnace causing your issue. I will assume the issue you were experiencing is the furnace would turn on, but would fail to ignite? And after you started your truck, it was able to perform and ignition cycle?

 

The furnace blower motor draws the most power for the appliance, and it sends air through the combustion chamber and through the heat exchanger and out the exhaust. In order for the furnace to move into the ignition cycle, it needs to prove draft, (adequate venting) and it uses a sail switch to close a contact to prove draft. With that foil ducting on, its just restrictive enough to limit air flow from the blower motor to close the sail switch. When you started the truck, the voltage increased, allowing the blower motor to ramp up its RPMs and close the sail switch.

 

I would try removing the silver foil duct. Its 4 screws on the face, and just pop it off. I had to do this on both of my flatbeds. I have a 2021 Hawk UTE with lithium, and when I got into some elevation, I still had a problem even with the batteries at 13.4V. Once I removed the ductwork, it went away. I think it is an issue with how the furnace is mounted on the newer flatbeds, and its lack of "make up air" since it is pretty closed off, and the blower needs to work hard to pull in make up air for combustion and to blow across the heat exchanger. 

[Jon R]

Jkron - Are you saying the furnace gets its combustion air from inside the camper rather than from outside?

Edited by Jon R, 28 December 2021 - 06:51 PM.

[Jkron]

Jkron - Are you saying the furnace gets its combustion air from inside the camper rather than from outside?

 

Sort of. It pulls air from essentially a concentric vent around the exhaust vent. But I have found that having ventilation inside the furnace cabinet can help as well. On some of the later FWC's they added a small louvered vent on the side of the furnace cabinet to help, but it depends on the floor plan. The flatbed floor plan kind of closes off the furnace cabinet area, it is not as open as some other floor plans. 

 

I would remove the interior ducting, as this is what I have done. Most of the issues with the furnace are related to air flow. That little bit of ducting restricts just enough to give issues sometimes, especially as battery power depletes. You can also remove the exterior cover, which can help in a bind. I had to do that at over 10k feet, since the air was thin. 

[rando]

These furnaces are so cheaply built that they use the same motor for the blower fan and the induction fan.   If you choke the blower fan side with small vents, you slow the motor a little and that also slows the induction fan?  Coupled with lower voltage and you may not activate the sail switch.    Some (@Charlie maybe?) one also figured out that the problem is exacerbated by the orientation of the furnace - mounted in portrait orientation the sail switch is also fighting gravity.  I think there was a fix where you increased the area of the sail slightly - but find the original discussion of this before trying this. 

 

Next time you have this problem, take a look at the LED on the furnace circuit board, if it is flashing once then it is a sail switch problem.

[Jkron]

yea, they do share the same blower motor assembly to handle intake and exhaust. its a crappy furnace, no doubt about it. You can tweak the sail switch slightly, but its only a little but before you run into issues with it contacting. Crappy furnace, and poor installation considerations just equal it not working. The small bit of ductwork should not need to be removed in reality, but the blower motor is just barley capable of running the system through its proving stages, so here we are with removing the ductwork to get it to work. 

 

I am working on a diesel heater conversion, and gathering a parts list along with some instructions, since the only way to solve the furnace issues is with replacement at this point. 

[Colorado Mark]

I'm with a couple others.  I don't think its a power problem.  I just went camping a while back and ran 4 days in below freezing temps with 2) 12V AGM & 160W panel.   12V, 85L compressor fridge.   It was even overcast & snowing day 2 and barely got any charging from the panel.

 

Saw battery voltage drop to 11.9 at worst.

 

Zero issues other than running out of LP in one tank in the middle of the night on day 3.  Should have topped it off.  Was only about 1/2 full.

 

I did have some problems earlier (about a year ago) and did like others suggested.  Remove the foil duct and just use the entire front grille.

 

So far, so good.

[Dphillip]

I suffered several years with intermittent heater problems, failure to fire until I removed the foil duct hose and cut out about 6 inches of excessive hose. The air from the hose now has a more direct path through the vent rather than making a slight turn. This simple task completely eliminated my problem. No more sleepless nights wondering if the heater is going to work.

[wicked1]

I noticed the furnace drains my battery surprisingly fast, too. 
I have 3 solar panels (two on top, and a portable), and am almost always at 100% charge by sun down.  Even on the shortest day of the year under clouds!  I am a very light sleeper, and get the fridge very cold during the day, and turn it down at night.. In the cool weather, it doesn't run at all, all night.  So, furnace is the only thing drawing power.
I noticed that running the furnace just a few times over the night.. when I wake and am freezing I turn it on for a while.. Then turn it off and go back to sleep.  That happened maybe 3 times one night, and my battery was down 20% by morning. 

It's fine..  My 3 panels will fill my 200ah battery the next day.  But it's relatively a lot of power usage!  (I haven't noticed how much power it pulls, since I have only run it at night, but I'll do a test later.. 2015 fleet flatbed)