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Small Cabin Forum / Cabin Construction / Simple build-- input needed
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Birdman
Member
# Posted: 4 Feb 2021 16:13
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Quoting: gcrank1
Regarding your bike-bats math it looks right but I dont have experience with more than 12v bat-banks so that 48v converted to 12v may be throwing me.
I get the same 48v x 13.5 ah = 648w
x 80% use (and including in that the -2% effic.drop)
is the 520ish w. Now with that divided by 12.5v converted makes for 40ish ah per bat, 80 total usable, IF Im doing this correctly??
Guess that fridge is 12vdc?, some 7.5amps? or? My old absorption cooler is this so I'll use it as an example, if it were 7.5amps you would run the fridge only for 10ish hours. For me that is too high a tariff on my bat-bank so we use an ice cooler. Not a Yeti, but similar (and faarrr cheaper) and used wisely lasts for days. Key for me with bat-bank based power, no matter how it is charged or converted or inverted, is energy conservation first and the new-gen ice chest suits us (and is way cheaper) than a power sucking fridge.
Ie, up your power 'requirements' means upping your system (costs) to accommodate the indulgences. Running the numbers, if we go from a 3amp/hr av. usage (3x24hrs=72 x 3 days=216ah @ 80% dod LFP means I 'need' a 270ah battery; thats pricey for only an av. 3amp draw. Make it 6 and )


Cool looks like we're getting similar numbers so I'm not totally crazy!

I am looking at some sort of portable compressor fridge/freezer combo like the Dometic CFX 75DZW or Whynter FM-62DZ. They draw roughly 60w when the compressor is running, but they are super well insulated and so the compressor doesn't run all the time so once it's down to temp the power usage is around 6-7 watts.

Check out this video. This person runs a similar fridge on a Goal Zero Yeti 1000 (non-lithium) and is able to run the fridge for like 3 days without recharging.

So yea the fridge/freezers are super spendy ($600-800) but the lower power usage will mean I hopefully won't have to upgrade my battery capacity. I'm totally fine with running my generator for the 4-6 hours every other day or just making a run to the bar as needed to recharge the batteries. And that's if I don't incorporate the 300W of solar panels that I have lying around.

gcrank1
Member
# Posted: 4 Feb 2021 17:28 - Edited by: gcrank1
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With a fridge, any fridge, if it isnt running in your absence it takes a fair bit to bring its whole insides down to fridge temp before it just idles along cold. Same thing needs to be done to a fridge as to an ice cooler to pre-chill it; ie, get there, turn it on, fill it with all the frozen/cold stuff you brought and ice bottles/pacs to as full as you can get in then leave it closed as much as possible as long as you can, pref overnight.
I rather hate front door opening for off grid/rv's etc, open the door and all the cold spills out. For on grid no big deal....not so for off grid. Id much rather have a top loading box the the cold stays in and smartly load it for use in order of pulling stuff out.
Fwiw, Ive got a Haier 3.5cf, 120vac, front loader at the cabin, it has turned into a non-running pantry.

Fanman
Member
# Posted: 4 Feb 2021 17:54
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Quoting: Birdman
Fair question! I had actually purchased the diesel heater for another project that I didn't end up using.

I also wanted diesel because it is lower energy consumption than RV style propane furnaces, cheaper than RV furnaces, and it produces dry heat vs wet heat that even vented propane heaters produce.


If you already have the diesel heater that makes sense. But vented propane heaters don't produce "wet" heat, all of the moisture is vented outside. Unvented heaters, of course, are another matter, I would never install one of those.

Quoting: snobdds
Wood stoves work off radiant heat. Diesel and propane work off of convection heat.

You could run a place all day off the propane or diesel and it will never feel warm as none of the indoor furnishings will get warm. It will always feel cold on surfaces. A wood stove heats the objects in the room and for cold snow gear, you want them to dry thru, just not surface dry.


Not necessarily. Yes, you get a lot of radiant heat from a wood stove, but it only heats the objects directly in front of it. There is also a fair amount of convection heating of the air that moves past the stove. Propane heaters may be primarily radiant, primarily convection, or a combination of both.

Our cabin is heated by a wood stove and a coal stove, but our house is heated by three propane heaters, all direct vent: One is a 30,000 BTU propane fireplace that puts out a lot of radiant heat, but also convection from the air moving through internal tubes. Stand in front of it and it's like standing in front of a wood stove. That's in the living room. The others are 7500 BTU wall mounted heaters in the back bedrooms, those are pure convection. The nice thing about them is that none of them require electricity.

Birdman
Member
# Posted: 4 Feb 2021 18:04
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Quoting: gcrank1
With a fridge, any fridge, if it isnt running all the time it takes a fair bit to bring its whole insides down to fridge temp before it just idles along cold. Same thing needs to be done to a fridge as to an ice cooler to pre-chill it; ie, get there, turn it on, fill it with all the frozen/cold stuff you brought and ice bottles/pacs to as full as you can get in then leave it closed as much as possible as long as you can, pref overnight.
I rather hate front door opening for off grid/rv's etc, open the door and all the cold spills out. For on grid no big deal....not so for off grid. Id much rather have a top loading box the the cold stays in and smartly load it for use in order of pulling stuff out.
Fwiw, Ive got a Haier 3.5cf front loader at the cabin, it has turned into a non-running pantry.


Yea I'm picturing maybe even running the generator to handle the initial cool down period, and then switching over to battery power to let it sip power from there. Worth mentioning that these Dometic / Whynter are much more efficient than the Haier that you're using. Also much smaller.

Quoting: Fanman
If you already have the diesel heater that makes sense. But vented propane heaters don't produce "wet" heat, all of the moisture is vented outside. Unvented heaters, of course, are another matter, I would never install one of those.


Ah I'm with you now on the vented propane. And again the no electricity use is VERY appealing. Just wish they weren't so expensive! If I didn't already have the ebike batteries and diesel heater, the vented propane route might make more sense.

I think what I'm going to do initially is use the diesel heater as primary heat, and then if I need any supplements then I'll make very limited use a Mr. Buddy heater I have. If that combo still isn't doing it, then I will look at installing the wood stove I've got lying around.

ICC
Member
# Posted: 4 Feb 2021 18:30
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Direct vent propane, no electricity

Birdman
Member
# Posted: 4 Feb 2021 19:11
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You guys really don't like these diesel heaters huh?

ICC that one does look cool!

gcrank1
Member
# Posted: 4 Feb 2021 19:26
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Im allergic to diesel after some heavy equipment time.
Your heat plan sounds, well, sound. Dance with who ya brung first
If you are at all like many/most of us you will not like a genny intruding into your quality cabin time, even a 'quiet' one becomes the dominant sound around.

ICC
Member
# Posted: 4 Feb 2021 22:46
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Quoting: Birdman
You guys really don't like these diesel heaters huh


They have their place. They do seem to require more maintenance like de-coking, than heaters that burn propane. Propane heaters just work year after year. A friend has two Chinese diesel heaters in a skoolie conversion. He is happy enough but does gripe every so often. He had a power glitch a month ago and wasn-t there to catch it. It stopped, overheated with no airflow and lost the control board as it toasted.

I've never had that happen to a propane wall heater as there is no control board. Empire makes Housewarmer and has a couple of similar Empire models that don-t need power either, though a fan for air circulation can be used.

I have a Webasto in a diesel truck that is reliable but cost about 12X the cost of the Chinese copies.

Brettny
Member
# Posted: 5 Feb 2021 05:55
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Quoting: Nate R
How does that mean you can build what you want?

The way I read it is you can build a shed, you just can't stay in it. Also past cabins built or past code violations that didnt end it tearing down the structure dosnt mean that you have a green light. As long as your willing to take the risk. After all it is your risk.

As for running a fridge off solar it's not very difficult and you dont need to spend $600+ on a fridge. I'm running a 120v 4.5cuft mini fridge with separate top freezer off 470w of solar that only get 2.5-3hrs of sun when the leaves are on the trees. My battery bank is 4 gc2 golf cart batteries. I have a 30a rv charger to charge the batteries on low sun days but do plan on adding 2 more gc2 batteries. The key to getting the most life out of a battery bank and running a freezer is a $10 programmable timer that for about 13hrs durring the night I have running the fridge 1hr on 1hr off. It makes quite a bit of difference.

I have about $1200-1300 into my whole system. That's everything. The solar pannels, pure sine inverter, wireing, fuses, 120v charger, battery, epever charge controller, the fridge and even the generator. I bought the pannels, inverter and fridge used.

Becids a bit of power I can tell you that the best thing after a day in the woods is a nice hot shower. A propane on demand hot water heater is possibly the best bang for the buck. Its something i really look forward to at our property.

Birdman
Member
# Posted: 5 Feb 2021 13:10
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Quoting: gcrank1
If you are at all like many/most of us you will not like a genny intruding into your quality cabin time, even a 'quiet' one becomes the dominant sound around.


Yea I hear you there. I'm probably going to get sick of running it and invest more in my solar setup eventually. Luckily the my property runs 500' from North to South, so if I clear the area right I may be able to get enough energy from that to not have to use the generator.

This is the generator I have. Definitely quiet (especially when I have the low energy mode activated) but like you said it sure will take away from that quiet tranquility of being in the woods.

Quoting: ICC
They have their place. They do seem to require more maintenance like de-coking, than heaters that burn propane. Propane heaters just work year after year. A friend has two Chinese diesel heaters in a skoolie conversion. He is happy enough but does gripe every so often. He had a power glitch a month ago and wasn-t there to catch it. It stopped, overheated with no airflow and lost the control board as it toasted.

I've never had that happen to a propane wall heater as there is no control board. Empire makes Housewarmer and has a couple of similar Empire models that don-t need power either, though a fan for air circulation can be used.

I have a Webasto in a diesel truck that is reliable but cost about 12X the cost of the Chinese copies.


Yea I'll definitely consider those if I find the diesel/wood stove/mr buddy combo isn't working out. Lots to like about them, that's for sure!

Quoting: Brettny
The way I read it is you can build a shed, you just can't stay in it. Also past cabins built or past code violations that didnt end it tearing down the structure dosnt mean that you have a green light. As long as your willing to take the risk. After all it is your risk.

As for running a fridge off solar it's not very difficult and you dont need to spend $600+ on a fridge. I'm running a 120v 4.5cuft mini fridge with separate top freezer off 470w of solar that only get 2.5-3hrs of sun when the leaves are on the trees. My battery bank is 4 gc2 golf cart batteries. I have a 30a rv charger to charge the batteries on low sun days but do plan on adding 2 more gc2 batteries. The key to getting the most life out of a battery bank and running a freezer is a $10 programmable timer that for about 13hrs durring the night I have running the fridge 1hr on 1hr off. It makes quite a bit of difference.

I have about $1200-1300 into my whole system. That's everything. The solar pannels, pure sine inverter, wireing, fuses, 120v charger, battery, epever charge controller, the fridge and even the generator. I bought the pannels, inverter and fridge used.

Becids a bit of power I can tell you that the best thing after a day in the woods is a nice hot shower. A propane on demand hot water heater is possibly the best bang for the buck. Its something i really look forward to at our property.


You're not wrong, it's definitely a risk. If I hadn't done all the research into codes and seen how others have faired when dealing with the code enforcement appeals, I wouldn't be doing this at all. If the worst should happen and I get in trouble and can't work with the code enforcement team, I'll probably just look to sell the property at that point and invest the money I get into my other properties. I have another piece of land in town that has a run-down cabin on it that I know is zoned correctly and can have a true house on it, but there I couldn't get away with what I'm trying to do at this property and the cost of adding sewer connections, electricity, and general permitting costs/process is a lot to try and tackle when our goal is to move out there ASAP.

That sounds like a sweet setup! Are those GC2 batteries the Insterstate ones from Costco?

Also 100% agree on the propane on demand water heater. I've looked at a few models and that's definitely on the list. Is there a particular one you'd recommend?

gcrank1
Member
# Posted: 5 Feb 2021 13:52
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Ive got the on-demand, runs on a 20# but it Ive never tried running it on a gravity water bucket, think it says it needs a min. 20psi water pressure. That makes for a complication of setting up a pump and/or pressure tank. Someday....meanwhile,
You can set a 5 gal black bucket full of water in the sun and let the solar warm it decently for an afternoon gravity shower, or a sponge bath. Ive got a D-cell battery operated Coleman shower that you drop the pump in the bucket and a hand-held wand, works great.
You can use a turkey fryer to quickly heat water to add to it for hotter.
The solar bag showers are cheap, last a year or two, awkward to hang, but if you use em to heat the water and dump it in the bucket yer good to go.

Fanman
Member
# Posted: 5 Feb 2021 19:40
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Quoting: Birdman
Also 100% agree on the propane on demand water heater. I've looked at a few models and that's definitely on the list. Is there a particular one you'd recommend?


I've had a bit of experience with them, all propane. Our first cabin had one when we moved in, not sure the brand, never heard of it. That one had a pilot light, no electric. We liked it so much that when we moved into a new cabin that had an ancient 10 gallon electric tank, we ripped it out (along with all of the other plumbing) and put in a Bosch tankless.

The Bosch is interesting, it has no pilot but requires no electric as there's a tiny hydrogenerator inside that generates its own electricity powered by the water flow as soon as you open a tap... you hear the quiet whizzing of the generator, the indicator light goes on, then click-click-click of the igniter, then poof!, the burner lights and you have hot water. But it does require adequate water pressure, I don't recall the exact number. Some times it just doesn't work but then I shut off the water and turn it back on and all is good. It always seems to be finicky at the start of the season, but it's still working after 13 or 14 years. I think Bosch did it that way because their otherwise identical pilot model had an 89% efficiency rating which was below the 90% required for the energy tax credit; the hydrogenerator version has a 91% rating.

At the house, I just installed a Rheem tankless heater. It does require electric, but if I don't have electric the well pump won't run anyway. It's only been running for a week, but so far so good, and it lights with just a trickle of water.

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