Jump to content


Photo
- - - - -

forced air furnace and power


  • Please log in to reply
35 replies to this topic

#1 nico

nico

    Advanced Member

  • Members
  • PipPipPip
  • 30 posts
  • LocationSan Luis Obispo , ca

Posted 26 December 2021 - 05:25 PM

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.


  • 0

#2 SigSanDiego

SigSanDiego

    Advanced Member

  • Members
  • PipPipPip
  • 75 posts

Posted 26 December 2021 - 05:42 PM

My 2021 Grandby with single AGM did same thing.

With 130 frig, basic light use and overnight heater use you’re lucky to get 12-20 hours parked, no engine idle. Got up in middle of night to start truck to get warm. Only took one of these episodes to upgrade to:

- dual 100 Lithium batteries
- upgraded alternator truck wiring gauge
- 190 watt roof solar

We had “battery anxiety” until the above upgrade. No way to live.

We don’t really need the solar in hindsight since our style of camping is to break camp (one full day maybe 1.5 days) before battery depletion. Truck charging is amazing with very little drive time. Wish we did portable panels instead of roof mount solar ( would not have down roof rails either for roof integrity insurance.

Get battery and wire upgrade for sure. Solar is camp style dependent in my opinion.
  • 0

#3 rando

rando

    Senior Member

  • Members
  • 1,638 posts
  • LocationColorado

Posted 26 December 2021 - 05:50 PM

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.

 

Something doesn't sound quite right.    2 AGMs and 160W of solar should be plenty to run the furnace for a couple of days in the desert.   If you battery is at 12.5V, that is around 80% - 90% charged and should be able to run the furnace just fine.   I wonder if there is an issue with either the wiring to your furnace causing a voltage drop, or an issue with the sail switch, which can make the furnace hyper sensitive to battery voltage.   What year is your camper, and which furnace does it have?

 

For comparison we ran one 75Ah AGM battery and 160W solar panel for a year with no power issues, and now run a 150Ah LiFePO4 with the same 160W panel (which is about the same as what you have) and can camp for days with no sun and be fine. 


  • 3

2016 Fleet Flatbed

2016 Toyota Tacoma


#4 Vic Harder

Vic Harder

    Doctor Electric

  • Site Team
  • 4,898 posts
  • LocationCalgary, Alberta

Posted 27 December 2021 - 12:13 AM

+ to what rando said.  I wonder if that 12.5v is with no load on it, or with a load?  In either case, I would suggest getting a battery monitor that can tell you the SOC and that uses a shunt... something like the Victron Smart Shunt.  Do that before you spend a lot of coin on other upgrades so you can be sure you are spending your $$ in the right places


  • 0

#5 nico

nico

    Advanced Member

  • Members
  • PipPipPip
  • 30 posts
  • LocationSan Luis Obispo , ca

Posted 27 December 2021 - 12:17 AM

It’s a 2021 grandby I’m not sure of the heater model I’ll have to find the manuals. The power draws down so fast once we start running the heat. I was very surprised 😯
  • 0

#6 rando

rando

    Senior Member

  • Members
  • 1,638 posts
  • LocationColorado

Posted 27 December 2021 - 02:55 AM

I think the current Dometic furnace draws about 3-4A when running - so a pair of fully charged AGMs (~150Ah) should easily be able to run the furnace for 30hrs or so continuously    With the thermostat cycling on and off, it should last for at least 3 nights without taxing the batteries.   It sounds like you aren't seeing even close to this, so either there is something up with your batteries, or something up with the furnace.  

 

I would follow Vic's suggestion and get a battery monitor, it will make it much easier to track down the issue. 


  • 0

2016 Fleet Flatbed

2016 Toyota Tacoma


#7 Jon R

Jon R

    Senior Member

  • Members
  • 906 posts
  • LocationWashington State

Posted 27 December 2021 - 03:40 AM

The 12k BTU/hr furnace in my 2021 slide in Grandby draws about 3 amps.

Do you have a three way fridge, and if so are you running it off the battery?
  • 0

Jon R

2021 Grandby Slide-in Front Dinette

2021 GMC 3500HD CC LB SRW Gas

1993 Chevrolet K2500 Ext Cab LB


#8 Adventurebound

Adventurebound

    Senior Member

  • Members
  • 110 posts
  • LocationLas Vegas

Posted 27 December 2021 - 04:37 AM

This may sound crazy and i might get flack for this but I don't think it's a power issue. Remove the duct work from your heater to the grate. That 100% solved all my heater problems. Do the opposite of what I did, start with the easy stuff and move to the complicated (expensive) stuff.

Edited by Adventurebound, 27 December 2021 - 04:40 AM.

  • 1

#9 Jon R

Jon R

    Senior Member

  • Members
  • 906 posts
  • LocationWashington State

Posted 27 December 2021 - 07:38 AM

This may sound crazy and i might get flack for this but I don't think it's a power issue. Remove the duct work from your heater to the grate. That 100% solved all my heater problems. Do the opposite of what I did, start with the easy stuff and move to the complicated (expensive) stuff.


One of the functions of this forum is brainstorming with multiple brains. Nobody should give any flack to someone making an earnest suggestion, especially one that says “here’s how I solved my similar issue.”
  • 0

Jon R

2021 Grandby Slide-in Front Dinette

2021 GMC 3500HD CC LB SRW Gas

1993 Chevrolet K2500 Ext Cab LB


#10 Vic Harder

Vic Harder

    Doctor Electric

  • Site Team
  • 4,898 posts
  • LocationCalgary, Alberta

Posted 27 December 2021 - 11:11 AM

This may sound crazy and i might get flack for this but I don't think it's a power issue. Remove the duct work from your heater to the grate. That 100% solved all my heater problems. Do the opposite of what I did, start with the easy stuff and move to the complicated (expensive) stuff.

+1 good idea.  Start with the easy/physical stuff first


  • 0




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users