Running propane furnace using camper batterys

JFET ask:
"Do you find the excess moisture produced by the catalytic heater to be a problem?" I have heard they add a lot of humidity to the air.

We always leave a ceiling vent slightly open or a side window cracked and experience very little overall humidity increase over using the on board propane furnace. Our Camper has a Basement and I run the Furnace with its duct into the basement for a few minutes before going to bed and for a few minutes in the Morning and we have never froze up up with lots winter camping in Temperatures in the teens and even below that. Our Eagle Cap is a great Four Season Camper.

GARY and LAURII

Old-Biscuit wrote:
Your furnace will probably draw 3 amps per continuous hour of use

It will draw 3 amps per continuous minute of use too, and 3 amps per 5 minutes of continuous use.

I think you meant to say 3 amp HOURs per continuous hour of use.

I hope you do your experiments because I'd like to know.

I see the furnace blower problem as very similar to putting in LED lights and solar panels.....increasing efficiency of the systems we all use in our TCs. My furnace system uses a current-sucking blower and plastic corrugated ducting, both very inefficient but cheap to buy and install by the manufacturers.

The Wave catalytic heaters are a good idea but in my situation with a heated basement, not applicable in all cases. I need forced air to keep my TC a 4-season TC.

I'd sure like to hear more ideas on making the blower more efficient.
Here's but one article talking about more efficient blower motors albeit for home furnaces:
ECM motors

My first thought was the PWM might have kept me from removing our furnace. Simply used way too much battery and when 110v still just obnoxiously loud. Our Atwood rated at 55 watts/4.6 amps, the fan roared.
At first the PWM sounds like it might solve both- turn down amp use and slow down so it doesn't roar.
Could be though to keep sail switch open might not be enough to make worthwhile amp wise or quieten? Though for $7 worth the try, but someone needs to do some testing. Other thing to consider is how much (if you can enough to matter) slow down and still draw enough air thru so as not to over heat the exchanger?
Id be measuring temps, amp draw & heating cycles and sheet metal temps of box before mod, Then check afterwards results. Especially box temps- as fan is what distributes the heat it also keeps the sheet metal cool (and why all the safety redundancy on the fan).

We just got back from a 4 day dry camping trip in temps that dropped to the teens at night. Ran the furnace off battery power 24 hours a day, kept the interior plenty warm (75° at the thermostat)to make sure the tanks and lines stayed thawed. Used the genset for about an hour once a day to help top the batteries, and cover higher electrical load during showers/cooking. Batteries held up fine, never died or got below "orange" on our meter.

Ran the heat, hot water heater and fridge on propane for 5 days straight, including while driving....and used 1 1/4 bottles of propane. I haven't changed over to LED yet, but I think that when I do we'll likely be able to camp for about a week in that style of boon-docking, with propane and fresh water being the limiting factor.

BTW, we only used about 1/2 of our fresh water, and had 1/3rd full tanks in the grey and black.

I've had the camper down to -5 overnight, and the heat ran pretty much all night...but the neither the batteries or propane ran out.

Jfet wrote:

Geewizard wrote:
A related question: how do I modify my blower so it's slower? I could go a lot longer on battery if the furnace fan was turning slower, I think. I need an electronic circuit rather than some power-eating rheostat or resistor. Any ideas?

I certainly could build a circuit easily enough but there are probably plenty of cheap 12V PWM speed controller boards out there.

Ok, 20 seconds on ebay, $7 with free shipping (I don't know the quality of this unit though):

http://www.ebay.com/itm/12V-40V-Pulse-Width-Modulation-PWM-DC-10A-Motor-Speed-Control-Switch-13KHz-US-/111324607462?pt=LH_DefaultDomain_0&hash=item19eb76b3e6

Hmmm, that is an interesting idea - I'd never thought of adding a PWM controller - worth thinking about.

Thanks,

Steve.

The issue with modifying the blower to go slower is not enough airflow to close the sail switch. The PWM board will allow you to slow it down to just above the point the sail switch makes.

It also partly depends on the heater capacity, if it is ducted etc. My heater is ducted and small enough to use a lower CFM fan, so it only uses about 4A when running and is very quiet. My inlaws, even with a trailer smaller than mine, have a non ducted unit that uses over 8A when running.

Also, that battery chart really reflects the desire to obtain the maximum number of charge cycles, like 600 or so. For people like us occasional campers, our batteries will never see that many. So if I shorten the life from 600 to 250 by discharging to 30%, so what. I only camp a dozen times a year.

Geewizard wrote:
A related question: how do I modify my blower so it's slower? I could go a lot longer on battery if the furnace fan was turning slower, I think. I need an electronic circuit rather than some power-eating rheostat or resistor. Any ideas?

I certainly could build a circuit easily enough but there are probably plenty of cheap 12V PWM speed controller boards out there.

Ok, 20 seconds on ebay, $7 with free shipping (I don't know the quality of this unit though):

http://www.ebay.com/itm/12V-40V-Pulse-Width-Modulation-PWM-DC-10A-Motor-Speed-Control-Switch-13KHz-US-/111324607462?pt=LH_DefaultDomain_0&hash=item19eb76b3e6

A related question: how do I modify my blower so it's slower? I could go a lot longer on battery if the furnace fan was turning slower, I think. I need an electronic circuit rather than some power-eating rheostat or resistor. Any ideas?

When I lived in Alaska, I did a test one cold night. With the outside temp at -20F and the thermostat set to about 45F, my two 27 batteries lasted all night as did the 30lb propane tank. I was in the nice warm house the whole time though. :)

ggadwa wrote:
Add a WAVE 3 Catalytic Heater to your Camper and you'll never have to worry about battery life overnight again.....and the real benefit is no more Furnace Fan noise on and off all night. We winter camp a lot and absolutely love our WAVE 3 Cat heater that I installed.

GARY

Do you find the excess moisture produced by the catalytic heater to be a problem? I have heard they add a lot of humidity to the air.