DC or AC or Both

bobdog

We're adding on to our cabin and as the current electrical wiring will be either destroyed or new, it will be a good opportunity to determine whether to use AC throughout the cabin, or use DC or a combination of both. I'll open it up for discussion and please tell me of your experiences with what you've done, and the pitfalls and successes I can look forward to. Thanks.

Tim

niel

Re: DC or AC or Both

that depends on you and it would be difficult for me to predict what you will want or need in the future. it doesn't hurt to cover all bases, just in case.

tallgirl

Re: DC or AC or Both

bobdog wrote: »

We're adding on to our cabin and as the current electrical wiring will be either destroyed or new, it will be a good opportunity to determine whether to use AC throughout the cabin, or use DC or a combination of both. I'll open it up for discussion and please tell me of your experiences with what you've done, and the pitfalls and successes I can look forward to. Thanks.

Tim

It's for this reason that G-d invented conduit. Conduit means never having to say "Oops!"

niel

Re: DC or AC or Both

i don't see the correlation and g-d didn't invent conduit. as dc and ac components go it really isn't a good idea to have both in the same conduit and his wiring of another system can be done anytime now or later. the same conduit done later may be difficult to fit heavy gauge wire into so are you telling him to put in a single large conduit as opposed to separate ones? he probably won't even need the conduit as it's a cabin and not a house so what am i missing in your statement?

BB.

Re: DC or AC or Both

How much power? How big of Solar RE system?

If the system stays small (12 VDC)--other than stuff that directly attaches to the battery bank -- it is difficult to get 12 volts to go very far.

Plus, there is the very nice MorningStar 300 watt True Sine Wave Inverter that has both a remote on/off control, plus very little power with no load--perhaps small enough that you can leave it on over night and have true AC lighting (CFL's, LEDs, etc.). As well as small radio, TV, DVD player, laptops, etc.

If you go larger --- 24 or 48 volt--then you can send the DC farther--but do you have any 24 or 48 volt devices to run?

In the end--if you can do everything 120 VAC, you can avoid the problem with 12 volt devices (1 or 2 volt drop, many 12 volt devices don't operate--15+ volts for equalization can kill some 12 VDC car converter type devices).

Look at your needs, your solar RE system, and how an inverter would help (or hurt) your system design (inverters do waste 10-20% of their power--but TSW is better than MSW which waste more power in motors and transformers because of their poor AC wave forms).

-Bill

Mountain Don

Re: DC or AC or Both

I went through several phases when designing our small cabin. At first it was going to be predominantly a 12 VDC system for lights with a 120 VAC for the microwave. That was going to be either inverter run or maybe right of the generator. Over time more and more AC was added until it was a real hybrid. Totaling up the wires required for a split system I found I was spending an extraordinary amount of money on copper!

We ended up with going nearly all 120 VAC. Doing that we are able to use whatever standard appliance we might decide on. It also allow me power tool use as we selected a good sized 3500 watt pure sine wave inverter.

I still have a three fluorescent lights that run directly off 24 VDC. Our battery bank is 24 VDC. That was done in case something happened to the inverter. I also used a solar converters SS 24 to 12 VDC converter to power a 12 VDC water pump.

That's what worked for us.

westbranch

Re: DC or AC or Both

To add a couple more cents worth,

first start with the load and type.

If you have a 'need' for more than just lights Bill is on the money, go AC.
Then decide if you need only (cheap) MSW (basically lights) or (more expensive) TSW (fridge, other motor driven appliances).

Simple, if long wire lengths are involved, AC will be cheaper in the long run.

Then you will have to ensure that the PV side will support what you want it to do...

Eric

BB.

Re: DC or AC or Both

To elaborate on what Eric said about MSW vs TSW...

If you are looking at a 12 volt battery bank--the MorningStar 300 watt TSW inverter is a great way to start. Relatively cheap and very efficient. If you have any electronic items to charge (portable equipment, cell phone, laptops, dvd players, etc.)--not having to worry if the next device you plug in will be the one of the 10-20% of the devices that overheat/fail on MSW is a blessing (especially in a remote location).

You can always get a bigger/cheap MSW inverter to run the vacuum, circular saw, corded drill, water pump, etc. if/when needed (TSW is still better--but not cheap).

However--if you are looking at getting a larger MSW inverter (over ~1,000 watts)--you should be looking at a 24 or 48 volt battery bank too (keep your DC current lower, less money spent on copper, switches, fuses, etc. on the DC side).

A couple of inverter FAQs from our host:

All About Inverters
Choosing an inverter for water pumping

-Bill

solorone

Re: DC or AC or Both

By all means run AC wiring. It would be foolish not to, it would only be a couple 100 dollars to put in the boxes and wire. You could add the panel later. Look to the future, larger family, different needs, a larger solar array. Then there is the unknown future, if you sold the cabin the lack of AC outlets could be a real turn off.

When I built, everyone used DC, I installed AC, but not near enough outlets. Fortunately I can add them as need, but it is a royal pain.

I see no need to run conduit,(EMT) it can be an option to jump across a difficult area, now, or in the furure, but it will be a nuisance to run EMT to each box. I build commercially, and we often throw in conduits here an there for future use, it is very very cheap and can save a lot of money and misery.

I use a lot of AC lighting, but still have the original 2 tube electronic fluorescent lights over head.

One word of caution, although it will require you to use more wire, I would recommend separating any DC power/outlet circuits from the lighting and switches. If the overhead lights were not wired in with the outlets, I could have easily converted them to AC. I want to keep my DC overheads, there is a bit of security in the fact that the sunlight coming straight out of the light, with no device to fail and cause problems.

halfcrazy

Re: DC or AC or Both

I like ac only it keeps it simple but if it is a smaller system and you want certain things wire them now. I did pull strategic 12 and 10 gauge wires to different areas for future dc use?

And I am with Neil God didn't invent conduit and i would go to all the hardship of running it all through my house. It would be way cheaper to run extra wire in case

GreenPowerManiac

Re: DC or AC or Both

America runs on AC current and almost every gadget or appliance is set up for AC. It's very efficient. DC isn't very efficient unless it's higher voltage. Why would anyone run anything on DC current unless it's mobile and had no choice ?

Why use any inverter when you can hook DC up to a transformer and get 240v in phase ?

Cariboocoot

Re: DC or AC or Both

GreenPowerManiac wrote: »

Why use any inverter when you can hook DC up to a transformer and get 240v in phase ?

I'd like to see that.

The decision between going with a 12VDC set-up or spending the bucks on an inverter is mainly one of what your power requirements are - including how much time you spend there. The DC system will be lower in initial cost (no inverter) but limits what you can plug in - you'll do all your appliance shopping at an RV place, and some of that stuff can be very expensive.

So figure out what you want to run and for how long first, with an eye towards what you might want to add in the future. But be forewarned: once you have electric of any kind, the loads start to increase! So always plan your system for expansion.

bobdog

Re: DC or AC or Both

GreenPowerManiac wrote: »

America runs on AC current and almost every gadget or appliance is set up for AC. It's very efficient. DC isn't very efficient unless it's higher voltage. Why would anyone run anything on DC current unless it's mobile and had no choice ?

Why use any inverter when you can hook DC up to a transformer and get 240v in phase ?

America does run on AC, but 120. I am intrigued by your transformer that will convert DC to 240 though. What is it and does it work with a 12 volt system?

Kamala

Re: DC or AC or Both

GreenPowerManiac wrote: »

Why use any inverter when you can hook DC up to a transformer and get 240v in phase ?

Unless the cosmic axis shifted while I wasn't paying attention (and I do pay attention) such a transformer doesn't exist. Unless that "transformer" is an inverter which "transforms" direct current into alternating current.

Depending on the transformer, if it is connected to even a small LA battery (65AH) it will either do nothing, burn out, melt or explode.

Kamala

niel

Re: DC or AC or Both

sure the transformers exist, but only apply to 120vac already present such as from an inverter that produces 120vac and it can make it 240vac. this means that a transformer alone will not go 12vdc to 240vac.
http://search.store.yahoo.net/cgi-bin/nsearch?catalog=wind-sun&query=transformer&searchsubmit=Go&vwcatalog=wind-sun&.autodone=http://store.solar-electric.com/electrical.html

edited to add
maybe i should have came across this firstly with the fact that you can't use transformers on dc and you had to read the rest of the post? i bolded key parts in the original.

Kamala

Re: DC or AC or Both

GreenPowerManiac wrote: »

... hook DC up to a transformer and get 240v in phase ?

How is this possible?????

bobdog

Re: DC or AC or Both

bobdog wrote: »

America does run on AC, but 120. I am intrigued by your transformer that will convert DC to 240 though. What is it and does it work with a 12 volt system?

GreenPowerManiac I'm guessing misspoke, which we all have done, or he/she is from another planet? Which is it GPM?

BB.

Re: DC or AC or Both

To be honest--I am running towards GPM being a spammer... Enough links to self and others' websites and sort of off-the-wall comments to me more than accidental.

But, frankly interesting enough to read that I have not simply banned him/her.

That's my story and I am sticking with it. :roll:;):D

-Bill

bobdog

Re: DC or AC or Both

BB. wrote: »

To be honest--I am running towards GPM being a spammer... Enough links to self and others' websites and sort of off-the-wall comments to me more than accidental.

But, frankly interesting enough to read that I have not simply banned him/her.

That's my story and I am sticking with it. :roll:;):D

-Bill

Well, I guess a few of us got snookered as we were all looking for this "magic" transformer.

Kamala

Re: DC or AC or Both

BB. wrote: »

... interesting enough to read ...

I agree! GPM seems to be a credible contributor to this forum. I would still like some clarification on the statement that GPM put forth on September 15th, 2009 16:45 PDT.

"Why use any inverter when you can hook DC up to a transformer and get 240v in phase ?"

GPM is either disingenuous, unknowledgeable or joking. I'm hoping it's that later.

Kamala