DC Appliances and Rack/Rails

[SSC00]

While I am considering putting solar on my roof, I have come across several different questions on how I should approach this. Right now, my plan is not extremely set in stone because I am having an energy audit done on my house in the next couple of months so I can make a better game plan on what I should do (like improve my insulation first etc).



For context, I live in a ranch style house in East-Central Alabama and the front of my house is facing in a SW direction and nearly all the front of my house has zero shading and most of the back of my house has little shading. I have an asphalt shingle roof that I replaced almost 4 years ago (I should have done a metal roof but it was my first time and I listened to other people for advice). I also currently do not have a carport and one of my options for installing solar was to build a solar carport to avoid doing anything to my existing roof.



How many appliances in the average house can already run on DC without changing anything? I have heard that existing lights can do this. My house is all LED too. I have also heard that more appliances can run on DC than you think – namely things like the fridge, oven/range, dryer, and heat pump unit (I have a heat pump in my home). I ask because this affects what I do for an inverter. Not saying I will run out and just buy a bunch of specific DC appliances to do this, but it shapes what I do in the future to replace them if/when they fail.



My second question is about racks and rail systems. If I decide to just install on my roof, I will need to figure out what to do with the rack and rail systems and I am unclear about how this works or where to start with looking for what system to use. I am also unsure how the installation process goes and whether or not it will make my roof leak – really don’t want that on what is essentially a new roof. I have found a product that claims to have and adhesive that will perform fine. If anyone here is familiar with this product or similar product, please let me know if it is legitimate. I can easily see how a glue would fail. https://solarstack.com/ -- edit, nevermind on the glue. I have an asphalt shingle roof and its not compatible with this so my question is basically answered on this part. lol

 

[Andrewr05]

From what I've gathered, if your house is already wired for AC then you won't really get any benefits trying to run a whole whack ton of stuff off of DC.
It will be more cost effective to just take the hit on the AC inverters power losses.
Mostly because you can't just run high DC loads through your existing wiring, you'd need to run all new wiring throughout.

In my (admittedly not very knowledgeable) opinion the amount of money you'd save by not running all new house wiring could easily go to another Killowatt of battery storage instead.

 

[LakeHouse]

I have also heard that more appliances can run on DC than you think – namely things like the fridge, oven/range, dryer, and heat pump unit (I have a heat pump in my home).

I don’t know that I believe this, but let’s just look at one of those examples and do a little comparison… Your current oven/range runs off 240vac split-phase power.
I have a 40Amp breaker for the one in my house, so I could in theory safely run 40A * 240V = 9600W through that wiring. If I were to change to DC at, say 48V (48V nominal, so more like 53V from the battery), I can still only safely run 40A, which means my maximum power is now 40A * 53V = 2120W.
If it’s 12V, you’re down to closer to 500W.
Neither of these would be very effective for a range.

Do appliances that run off of DC exist? Yeah probably for many of them, but they’re going to be hideously expensive and any savings on an inverter will easily get eaten up in wiring cost.

 

[CaliSunHarvester]

can run on DC than you think – namely things like the fridge, oven/range, dryer, and heat pump unit (I have a heat pump in my home)

I find it hard to believe that these appliances can reasonably run on DC. I have built a ~1200sqft ummmm... structure.... and decided to wire everything DC. Yes, there are DC fridges but they cost a lot more. Oven/ range on DC??? I didn't find them.
Water heater? Yes, there are DC elements. I think this forum has a separate section for solar water heaters.

More and more small household appliances omit the transformer and are powered by USB. So my structure has USB outlets everywhere. And a dozen of 12V cigarette outlets too.

RVs are usually built as a mixed system. As much as possible runs on 12V DC but certain stuff like microwave, furnace.. only on 120V AC.

I let that be my guidance.

 

[SSC00]

From what I've gathered, if your house is already wired for AC then you won't really get any benefits trying to run a whole whack ton of stuff off of DC.
It will be more cost effective to just take the hit on the AC inverters power losses.
Mostly because you can't just run high DC loads through your existing wiring, you'd need to run all new wiring throughout.

In my (admittedly not very knowledgeable) opinion the amount of money you'd save by not running all new house wiring could easily go to another Killowatt of battery storage instead.

This is true, but when I do this upgrade, i will likely have to replace my heating/cooling system because its not correctly sized. I am also just looking around for the thought process of it. It just seems like it should be possible, but its not. Maybe the market is still too young or something

 

[SSC00]

I find it hard to believe that these appliances can reasonably run on DC. I have built a ~1200sqft ummmm... structure.... and decided to wire everything DC. Yes, there are DC fridges but they cost a lot more. Oven/ range on DC??? I didn't find them.
Water heater? Yes, there are DC elements. I think this forum has a separate section for solar water heaters.

More and more small household appliances omit the transformer and are powered by USB. So my structure has USB outlets everywhere. And a dozen of 12V cigarette outlets too.

RVs are usually built as a mixed system. As much as possible runs on 12V DC but certain stuff like microwave, furnace.. only on 120V AC.

I let that be my guidance.

that is interesting. I haven't come across any appliances powered by USB.

 

[SSC00]

I don’t know that I believe this, but let’s just look at one of those examples and do a little comparison… Your current oven/range runs off 240vac split-phase power.
I have a 40Amp breaker for the one in my house, so I could in theory safely run 40A * 240V = 9600W through that wiring. If I were to change to DC at, say 48V (48V nominal, so more like 53V from the battery), I can still only safely run 40A, which means my maximum power is now 40A * 53V = 2120W.
If it’s 12V, you’re down to closer to 500W.
Neither of these would be very effective for a range.

Do appliances that run off of DC exist? Yeah probably for many of them, but they’re going to be hideously expensive and any savings on an inverter will easily get eaten up in wiring cost.

ok. this is an interesting point on the wiring. that would depend entirely on what DC voltage you use I see. I would imagine that a 48V induction range would be plenty but I dont know. There are already mini split heat pumps that can be run entirely off DC and they aren't extremely expensive, but the options on air handlers are limited because there are only a handful of them. I would imagine that there would be more options that would come about over time though.

 

[CaliSunHarvester]

I haven't come across any appliances powered by USB.

Not fridges. Small stuff like a desk light with built-in wireless phone charger.
A pencil sharpener. An air quality monitor. A water dispenser for 5G water bottles. A radio.
A blue tooth speaker.

That's all that I can remember now.

 

[SSC00]

Not fridges. Small stuff like a desk light with built-in wireless phone charger.
A pencil sharpener. An air quality monitor. A water dispenser for 5G water bottles. A radio.
A blue tooth speaker.

That's all that I can remember now.

ok that is interesting. I have seen some stuff like that before. I think that eventually we will see even more things because it will make sense to have DC appliances for solar homes. I kind of want to mess around with a cheap solar kit to build confidence in how to wire things and get comfortable with the types of equipment. I'm still a little fuzzy on some of the components necessary.