DC-Living, all DC appliances for new Tinyhouse -Offgrid project?

[eXodus]

I've had two Sundanzers (one fridge and one freezer), neither lasted 5 years and the fridge was a mold factory since it wasn't self defrosting. (there's something no one talks about)

Are we comparing apples to apples? All of the "super efficient" DC fridges I've been around aren't self defrosting. In humid climates they easily get moldy in the fridge compartment and build up ice in the freezer. Here's a quick read on why you sometimes notice the sides of your regular fridge are warm. I've heard that 50% of standard fridges energy (KWH)'s is from is self defrosting.

The other one that people loved many years ago was a Sunfrost but they are long gone now last I heard. Crazy expensive and honestly I always thought they were poorly built. Fit and finish were terrible and they too also prone to get moldy. Here's thread on it.

FWIW: The first fridge might be DC but when it fails you'll be replacing it with an AC one because you'll be done with it's poor quality and lack of convenience

I'm looking at the Dometic 12V fridges , those have an automatic defrost cycle. Just didn't find power numbers as quick with Sunstar, Dometic is Swedish and most of their appliances I had in my RVs are rock solid. Got a 20 year old A/C unit from them, 20 year old fridge etc. no issue and I live close the sun in Florida, where those things constantly run.

What plans are you looking for?
I wired the house as any standard AC system would look like.
The appliances were all standard, albeit high-efficiency, units.

The Solar, Inverter, battery, load calculations, size of the house, climate zone, latitude etc.

I used to be an electrician in a former life, I wire the AC side of a house in my sleep, But here to learn about Off-grid solar.

 

[OzSolar]

I'm looking at the Dometic 12V fridges , those have an automatic defrost cycle. Just didn't find power numbers as quick with Sunstar, Dometic is Swedish and most of their appliances I had in my RVs are rock solid. Got a 20 year old A/C unit from them, 20 year old fridge etc. no issue and I live close the sun in Florida, where those things constantly run.

That's a new one for me but most of things are new to me. Where is that model hiding? Google didn't reveal anything for me when I searched for "dometic defrost cycle" other than turn off your unit and open the doors.

 

[AHTrimble]

I'm looking at the Dometic 12V fridges , those have an automatic defrost cycle. Just didn't find power numbers as quick with Sunstar, Dometic is Swedish and most of their appliances I had in my RVs are rock solid. Got a 20 year old A/C unit from them, 20 year old fridge etc. no issue and I live close the sun in Florida, where those things constantly run.



The Solar, Inverter, battery, load calculations, size of the house, climate zone, latitude etc.

I used to be an electrician in a former life, I wire the AC side of a house in my sleep, But here to learn about Off-grid solar.

I went with Victron due to reliability, reputation, capabilities, and programmability...a Tier 1 company...a huge worldwide supplier.
2xQuattro 5kw/120v run in split phase, balanced the load in the breaker panel. 2x150/70 Victron MPPT run in parallel. 1 handles 2 arrays totaling 3035w, the other handles 2235w. One array oriented more to the south, the other more to the SW to maximize production throughout the day.
Revision 2...I went with LifePo4 batteries (48v), a couple from 2 suppliers (2x205ah from Elite, 1x230ah from Trophy). Had Trophy been around when I bought the first 2, I would have gone with all Trophy. The 640ah capacity decision came from experience, 410ah just wasn't enough spare capacity and limited the use of AC's in the summer evenings/nights. If I had another $3500 I would buy a 2nd Trophy 230ah battery.
The load calculations were done based on what I thought would be our usage...and started with a 4kw Magnum. Realized that wasn't near enough. I really oversimplified my needs/wants. We also needed 48v...hence, the first Quattro. Fell in love with AC and running multiple heavy loads at once...hence, the 2nd Quattro.
We live in northern Arizona in the mountains at 5800'. Mild winters, really decent summers...LOTS of sunshine.

When I was planning the system for my house i spoke with a close friend who owned his own electrical company, commercial and residential. He also was a large player in solar in the area...and an instructor at a local technical college. He said to look at the solar side as the "utility company" and treat the house as a standard house for electrical purposes. Why? Because I too was going to go DC on the house side when I first started talking to him about it. Once I got it in my head about the solar only being a source, then it all started to fall together. The main problem I had at first was under estimating our power needs. Well, that and going with SLA batteries at first since LifPo4 wasn't real popular here...also, that's why the Magnum.

Since up-grading my system with 2nd Quattro and 2nd MPPT and 3rd battery and an additional 1.5kw of Pvs ...not a single issue of any kind.

 

[Lt.Dan]

d love a 700 watt induction cooker. most are rated for more than that. or an electric kettle in the 700 watt range.

I have this Nuwave https://www.amazon.com/NuWave-Preci...-Ceramic/dp/B01CHB1Y22/ref=asc_df_B01CHB1Y22/

It has a 600w option. I've never used it, but at peak output, this thing kicks a$$.

 

[eXodus]

That's a new one for me but most of things are new to me. Where is that model hiding? Google didn't reveal anything for me when I searched for "dometic defrost cycle" other than turn off your unit and open the doors.

Dometic DMC4081 or DMC4101​

Page 15 of the manual:

8.1 Defrosting the Refrigerator
The refrigerator has an auto-defrost feature that will automatically start a heating device to assist defrosting after a certain period of run time.

I got a big RV-Accessory store in my town, and those new 12V fridges look pretty much like regular fridges + a bit thicker insulation. With all the bells and whistles. The RV industry is actually what inspired me to look down the path of DC-Living. The technology of appliances is getting pretty fantastic, just the built quality of the rigs and insulation is mediocre.

 

[efficientPV]

I don't think everyone here is into the spirit of a tiny house. Its like you trying to cram a whole moving truck of furniture into one. Your lifestyle has to more adaptive and custom products have to be made that fit the situation. While not technically a tiny house (900sf) I do have a tiny electrical system by the standards here and I don't feel it limits how I live. It is mostly DC and I have a couple of small inverters that are turned on only when needed. For many years it has run on only a car battery. Near the end of the season last year when the battery was failing, I bought a 50AH lipo to supplement it. I do have a medical device that keeps me alive, it seemed prudent. It was essentially free. I did feel a cosmic angst at becoming one of the big battery people and taking the attitude I could just leave the lights on. For three years I ran my washer directly off PV. This year the weather has been so bad with clouds I had to add a battery to be able to complete a load. Just one from town recycling that maybe had 7AH. It only supplements the panels as needed and provides an additional 150W. I even do all cycles with hot water. Not lacking any of the amenities, the wife had to have a dishwasher. Everything is run off PV except the stove which I found takes 400W to run the oven.

I think the important thing here is knowing technically that it can be done and is extremely cheap to live off PV. While 99.99% couldn't do this, neither could you live in a tiny house. It is not a matter of money. I pay $3400 to have my grass cut just so to be able to move into this squalor. I think I could afford another battery. I like the feeling of living very close to my energy, at least part of the time. Back home the utility with its charts tells me I use way above that of my neighbors.

 

[Doggydogworld]

Dometic DMC4081 or DMC4101​

Where'd you find a DMC4101 for $900? I usually see them "discounted" to about 1500. It's consumption will be much higher than the SunStar you posted, I'd guess at least double. The SunStar has much thicker insulation and lacks a power-sucking freezer defrost cycle.

Meanwhile there are plenty of 10 cu ft 120V refrigerators below $400. That one has a typical rating of ~800 Wh/day. Similar to the Dometic, I bet. Yes, the 120V fridge incurs inverter losses, but the $1000 you save upfront can go toward a nicer inverter with low standby consumption.

I wouldn't apply Dometic absorption fridge reliability to their 12V compressor models. I don't think it'll be worse than the 120V units, but certainly wouldn't bet on it being better.

Even if you buy all these DC appliances, you almost have to have an inverter for random things. Coffee maker, curling iron, shop-vac to clean up after a plumbing leak, mixer to make a birthday cake, etc. Could be a really cheap inverter, but a budget of zero seems unrealistic.

 

[Quattrohead]

The 24k heatpump needs 1300w - so roughly 26A - not a giant cable. I've put it on there - because the 12k is only $200 cheaper and there is nothing in between.

A 24k heat pump is going to be 240v only, 18k is the biggest you can get that will run on 120v.
As for 12 volt lighting you would you lose the ability to use regular switches and especially dimmers, my alternative is going to be a small very efficient inverter just for the lighting circuits if flickering is a problem.

 

[AntronX]

As for 12 volt lighting you would you lose the ability to use regular switches

Regular 120Vac 15A wall switches handle 12V just fine. I switch 18W of bare LED strings (8S4P) at 24V for many years without an issue.

 

[Skypower]

Where'd you find a DMC4101 for $900? I usually see them "discounted" to about 1500. It's consumption will be much higher than the SunStar you posted, I'd guess at least double. The SunStar has much thicker insulation and lacks a power-sucking freezer defrost cycle.

Meanwhile there are plenty of 10 cu ft 120V refrigerators below $400. That one has a typical rating of ~800 Wh/day. Similar to the Dometic, I bet. Yes, the 120V fridge incurs inverter losses, but the $1000 you save upfront can go toward a nicer inverter with low standby consumption.

I wouldn't apply Dometic absorption fridge reliability to their 12V compressor models. I don't think it'll be worse than the 120V units, but certainly wouldn't bet on it being better.

Even if you buy all these DC appliances, you almost have to have an inverter for random things. Coffee maker, curling iron, shop-vac to clean up after a plumbing leak, mixer to make a birthday cake, etc. Could be a really cheap inverter, but a budget of zero seems unrealistic.

Be very careful with the selection of RV fridges. Some models (absorption?) when running on 12 volts consume more energy than several old full sized models. My full size LG isn’t even a factor in my daily consumption because of its efficiency. If they don’t document the 12v draw, perhaps suggested fuse size could yield a clue. As with many devices DC isn’t always more efficient or properly/truthfully disclosed. Spend more on DC appliances or add more panels for more power & AC

 

[Quattrohead]

Regular 120Vac 15A wall switches handle 12V just fine. I switch 18W of bare LED strings (8S4P) at 24V for many years without an issue.

Look if you going to quote me, at least quote the full sentence for context.

 

[AntronX]

Look if you going to quote me, at least quote the full sentence for context.

I only wanted to point out that part to clear a misconception. Regarding dimmers, DC PWM dimmer modules do exist. Small AC inverter for lights can work as well.

 

[irv818]

It would make sense to me to have a small, cheap 12v system to run cheap low power 12v stuff (lights, chargers, even small 12v pumps and fridges). But for all the higher powered stuff I'd rather spend my money on having a back up inverter(for redundancy) and be able to buy and use whatever regular, cheap, easily available AC appliances I want.

Since it's just me here, there's no need to cook big meals, I've collected several of those $10-15 cooking appliances from WalMart -
egg steamer, waffle iron, sandwich press, etc. They use around 350-450 watts @ 120v., so can work from a small cheap inverter.
I use these nearly every day. They're much cheaper and much faster than similar 12v versions.

 

[eXodus]

A 24k heat pump is going to be 240v only, 18k is the biggest you can get that will run on 120v.
As for 12 volt lighting you would you lose the ability to use regular switches and especially dimmers, my alternative is going to be a small very efficient inverter just for the lighting circuits if flickering is a problem.

you are right - a 24k AC heatpump would be 240V and require a bigger inverter then I had in my table. That tips cost scale further towards DC.

24K 48V DC heatpump

Where'd you find a DMC4101 for $900?

Even if you buy all these DC appliances, you almost have to have an inverter for random things. Coffee maker, curling iron, shop-vac to clean up after a plumbing leak, mixer to make a birthday cake, etc. Could be a really cheap inverter, but a budget of zero seems unrealistic.

My local RV store has them as pickup only. They run between $900 and $1100. Shipping is expensive - that's why you see them online for that much.

In my Motorhome I have 3000W AIO. with Solar and batteries, I'm thinking about using that system for the house 120V needs. I know the comparison is not entirely fair Or like you said - just get a cheap $500-700 AIO for running the occasional AC load scenarios.

Looks like the kitchen is going to get a regular 120V AC outlets and the remainder of the Cabin/Tinyhouse (how every you want to call a small dwelling unit) will be DC.

Be very careful with the selection of RV fridges. Some models (absorption?) when running on 12 volts consume more energy than several old full sized models.

Yes my RV absorption fridge is a powerhog in AC mode - takes like 6kWh every day. Double that of my Residential fridge which has double the size. It's great in Propane mode - can go off-grid for 2-3 months on a 30lbs cylinder.

 

[Skypower]

you are right - a 24k AC heatpump would be 240V and require a bigger inverter then I had in my table. That tips cost scale further towards DC.

24K 48V DC heatpump


My local RV store has them as pickup only. They run between $900 and $1100. Shipping is expensive - that's why you see them online for that much.

In my Motorhome I have 3000W AIO. with Solar and batteries, I'm thinking about using that system for the house 120V needs. I know the comparison is not entirely fair Or like you said - just get a cheap $500-700 AIO for running the occasional AC load scenarios.

Looks like the kitchen is going to get a regular 120V AC outlets and the remainder of the Cabin/Tinyhouse (how every you want to call a small dwelling unit) will be DC.


Yes my RV absorption fridge is a powerhog in AC mode - takes like 6kWh every day. Double that of my Residential fridge which has double the size. It's great in Propane mode - can go off-grid for 2-3 months on a 30lbs cylinder.

Yeah, they really shine when on propane

 

[eXodus]

I only wanted to point out that part to clear a misconception. Regarding dimmers, DC PWM dimmer modules do exist. Small AC inverter for lights can work as well.

I have one dimmer in my house, I never use it. Got a ton of light switches for different moods

My 192 sqft RV has a total 12 light switches.

When I want more light - I switch more lights on, less light - less lights on good old digital.

 

[CJM]

I'm looking at the Dometic 12V fridges , those have an automatic defrost cycle. Just didn't find power numbers as quick with Sunstar, Dometic is Swedish and most of their appliances I had in my RVs are rock solid. Got a 20 year old A/C unit from them, 20 year old fridge etc. no issue and I live close the sun in Florida, where those things constantly run.



The Solar, Inverter, battery, load calculations, size of the house, climate zone, latitude etc.

I used to be an electrician in a former life, I wire the AC side of a house in my sleep, But here to learn about Off-grid solar.

https://yugeshima.com/ about intermittend 120vdc Seems to be the solution.…..

 

[CJM]

I don't think everyone here is into the spirit of a tiny house. Its like you trying to cram a whole moving truck of furniture into one. Your lifestyle has to more adaptive and custom products have to be made that fit the situation. While not technically a tiny house (900sf) I do have a tiny electrical system by the standards here and I don't feel it limits how I live. It is mostly DC and I have a couple of small inverters that are turned on only when needed. For many years it has run on only a car battery. Near the end of the season last year when the battery was failing, I bought a 50AH lipo to supplement it. I do have a medical device that keeps me alive, it seemed prudent. It was essentially free. I did feel a cosmic angst at becoming one of the big battery people and taking the attitude I could just leave the lights on. For three years I ran my washer directly off PV. This year the weather has been so bad with clouds I had to add a battery to be able to complete a load. Just one from town recycling that maybe had 7AH. It only supplements the panels as needed and provides an additional 150W. I even do all cycles with hot water. Not lacking any of the amenities, the wife had to have a dishwasher. Everything is run off PV except the stove which I found takes 400W to run the oven.

I think the important thing here is knowing technically that it can be done and is extremely cheap to live off PV. While 99.99% couldn't do this, neither could you live in a tiny house. It is not a matter of money. I pay $3400 to have my grass cut just so to be able to move into this squalor. I think I could afford another battery. I like the feeling of living very close to my energy, at least part of the time. Back home the utility with its charts tells me I use way above that of my neighbors.

Living like plants. https://yugeshima.com/diygrid/solar-only/ Two years ago starting to build my 500sqm offgrid house I hoped it could be my way to go, but allas ended with goodwe, expensive pylontech 5kwh battery. I still try to understand dc.

 

[Checkthisout]

Just go 120V for everything.

You may one day decide that 48Volts DC is better an then all your 12volt stuff has to go a voltage reducer which causes the same losses as the inverter.

 

[CJM]

Just go 120V for everything.

You may one day decide that 48Volts DC is better an then all your 12volt stuff has to go a voltage reducer which causes the same losses as the inverter.

Right you are. But I still try to figure out why I am wrong ? The author Motsenbocker in his 120vdc mancave.