Electrical Schema Review/Advice/Questions

[cfiles]

I have read several of the electrical posts, looked at sites, books, etc and I have come up with my "schema". I am very familiar with household electric and mobile electric, but not at putting the two together. I am posting this here for those smarter than me to review. I also have a few small questions that I need answers for.

Here is my schema. Will it work like this?



Questions that I have:
1) Will a 300W inverter be enough? (LCD, DVD, and electric blanket...that is all I plan on running on it)
2) The fuse boxes that I am using are for automobiles. Will that work for the AC side? What kind of fuse should I use (15Amp, 30Amp, ?)
3) Is it worth it to wire the tow vehicle to the battery and charge while I am driving? I have a newer (2005) vehicle that I am sure is smart enough not to charge while off.
4) What do I need to do with the AC ground? I am sure a floating circuit will do and I can just ignore it; am I correct?

Thanks for all of your help in advance.

[jeep_bluetj]

Questions that I have:
1) Will a 300W inverter be enough? (LCD, DVD, and electric blanket...that is all I plan on running on it)

Doubt that 300W is anywhere close enough for an electric blanket. LCD/DVD should be fine, but I'd use a 12v blanket or go direct to shorepower.

2) The fuse boxes that I am using are for automobiles. Will that work for the AC side? What kind of fuse should I use (15Amp, 30Amp, ?)

It will as long as the fuses/holders are rated for the voltage. The common oldschool glass fuses are generally 250v and are used for all kinds of AC uses. I don't recall the ratings for blade style fuses. You can also use a typical home fuse/breaker panel. The rating of the fuse should be based on the max power you can pull on that circuit without burning something up. iow, 14 guage wire is typically used to carry 15A. So you fuse the ciruit at 15 A. If you don't, and pull 30A or so, that 14g wire becomes a heater, which is a bad thing...

With only 300W (3A or so at 120v), use small fuses.

3) Is it worth it to wire the tow vehicle to the battery and charge while I am driving? I have a newer (2005) vehicle that I am sure is smart enough not to charge while off.

Yes. But I never camp where there is shore power, so I'm biased.

4) What do I need to do with the AC ground? I am sure a floating circuit will do and I can just ignore it; am I correct?

GFI. GFI GFI GFI. The you won't need a ground.


I'd rethink the inverter thing. If ALL you want to run is DVD/LCD, get 12V versions. Then no 120V wiring at all. AC/Microwave would require shore power.

[eamarquardt]

I figure on using a second hand laptop for a dvd player. You can get a 12 volt adapter (mine steps up to about 18 volts). As a plus you have a computer to write letters on and do other keen stuff.

An electric blanket uses about a hundred watts (as I remember, don't quote me). I'm not sure what the duty cycle would be, depends upon how much activity is going on between the sheets I imagine. But 100 watts is about 9 or so amps on a 12 volt battery to drive the inverter and the load. This is a big load for the battery. You need to factor this in to the size and number of batteries you install. You can only get about half of the rating of the battery out in useable power (from a 100 amp hour battery you can draw about 50 amp hours).

You also need to have a charger/power source that will put back in the amp hours you need to pump the battery back up, be it a charger, solar panels, or whatever.

The inverter is only a third of the equation you need to work out.

I don't have a lot of time (zero) in teardrops, but I do have a lot of experience in crusing sailboats that are "off the grid" and all of the above applies equally to both in my mind.

I plan on using some sort of propane, kerosene, or whatever space heater and heating the whole tear. Should be much more efficient and reduce condensation to boot. If you do go with an electric blanket, an extra blanket or comforter above it will reduce the electricty required to keep you toasty.

Hope this helps.

Cheers,

Gus

[cfiles]

Doubt that 300W is anywhere close enough for an electric blanket. LCD/DVD should be fine, but I'd use a 12v blanket or go direct to shorepower.

I should have mentioned this...I am adding the AC wiring encase I ever sell this (not that I will for a long time). I do not mind all DC but it is nice to have the AC.

I also do not plan on using the electric blanket unless I am connected to shore power. I am sure my charger -> battery -> inverter setup will allow me to run an AC blanket just fine when the trailer is plugged it. Has anybody tried this?

The whole reason I have this schema in the first place is for ease of use. When I pull up to the site all I want to do is plug in power from the outside and be done with it. When I am without power the converter will kick in and everything will work without issue.

Basically I would like all of the complexity to be done now so I do not have to rewire/re-hook anything when I go out.

[eamarquardt]

Think about installing a simple dual pole dual throw switch to connect the shore power and inverter to the 120 volt recepticles. When you have shore power the switch routes it to the recepticle using one throw. When no shore power, throw the switch the other way, turn on your inverter, and you have 120 volts when needed.

Installing an extra dual pole dual throw switch shouldn't take long and cost more than $5 and throwing two switches shouldn't slow up your transition from traveling to camping more than 10 seconds or so.

I may be wrong, but my logic is irrefutable.

Hope this helps.

Cheers,

Gus

[Miriam C.]

OK why complicate it at all. If you are using an electric blanket when on shore power, why not put in a breaker box or use a drop cord. Some outlets just like a house will do.
http://tnttt.com/viewtopic.php?t=20164

All these inverters and converters are great if you like spending money and have all your electrical needs on AC or DC only. KISS

[brian_bp]

Many modern battery chargers will complete a charge cycle then shut off. Even if they maintain a float-level output, they may never come back up to a high current to keep up with stuff like the electric blanket without pushing a reset button. Maybe that's okay...

I have heard of people who successfully use their small travel trailers in exactly this way all the time. They are aware of their battery voltage level, and how their charger must be operated.

[eamarquardt]

I agree that 120 volt ac is not a requirement when off the grid. We managed on the boat for years without it just fine. Most anything you can do with 120 volts ac can be done with 12 volts dc using the right appliance. The only thing that I can see 120 ac is essential for is air conditioning. Personally if you need Air, I probably don't want to be there. But I reserve the right to change my mind and create an external AC unit similar to a pet cool but a lot cheaper and more efficient although an AC unit would probably keep me awake and a generator definately would.

I used to run an air compressor while anchored to fill my SCUBA tanks. I usually got shouts and cheers from the other boaters when I turned it off, ha.

Cheers,

Gus





I

[Chuck Craven]

cfiles

1) 300-watt inverter is to small to run a LCD and DVD player together. More like 600 watts should do. Unless the TV is real small, check the total wattage for both units.
2) You don’t need a fuse box for the AC but wire it for 15 amp service. #14 wire at least. Keep it simple: From a 15 amp male bulkhead connector to a GFI outlet input. Then connect the outer outlets to the load side of the GFI outlet.
3) You need a master fuse for the battery, if you wire a charging wire through the tow vehicle put a fuse close to the vehicles battery just in case!
4) Don’t connect the safety ground to the neutral wire at the GFI outlet. You will have problem with any GFI circuit you may plug in to.

Chuck

[cfiles]

Personally if you need Air, I probably don't want to be there. But I reserve the right to change my mind and create an external AC unit similar to a pet cool but a lot cheaper and more efficient although an AC unit would probably keep me awake and a generator definately would.

I am sorry AC = 120v AC not air conditioning in my last post. I do not want to even deal with the prospect of air conditioning. If it is that hot I will stay home or sleep under the stars :)

[cfiles]

1) 300-watt inverter is to small to run a LCD and DVD player together. More like 600 watts should do. Unless the TV is real small, check the total wattage for both units.

I ended up with a 400 watt inverter. All of the electronics I plan on using will be well under that.

2) You don’t need a fuse box for the AC but wire it for 15 amp service. #14 wire at least. Keep it simple: From a 15 amp male bulkhead connector to a GFI outlet input. Then connect the outer outlets to the load side of the GFI outlet.

Okay, what do you mean by 15 amp service? Are you talking about just using a 15 amp breaker? I had planned on putting all the 120 on a single circuit. There will only be three outlets in the entire trailer. One in the cabin, another inside a cabinet in the cabin (same circuit). Then there will be one in the galley, right next to all of the service for the trailer.

3) You need a master fuse for the battery, if you wire a charging wire through the tow vehicle put a fuse close to the vehicles battery just in case!

I am going to put a 30 amp breaker between the battery and the DC fuse box. If I add a charging wire from the tow vehicle (still undecided) I will do the same to the input.

4) Don’t connect the safety ground to the neutral wire at the GFI outlet. You will have problem with any GFI circuit you may plug in to.

Had not planned on it. I figured I would do a basic 2 wire circuit and just ignore the ground completely.

Thanks for all of the help everybody. It has all been very useful. I am going to do a few sanity checks this evening with all of the components and see what happens.

[Chuck Craven]

cfiles
Does this help?



Or is it more
Chuck

[Alphacarina]

Your schematic looks like your inverter output and input are the same - You show them in the same place anyway

Your AC wiring and all your outlets should be connected to your shore power . . . . not to your inverter, as Chuck has shown you in the above drawing. All you need for your inverter output is a single outlet positioned near where whatever you plan to run off it is located - You could even get by with no outlet at all . . . . just plug your TV directly into the inverter when you want to watch it off battery power . . . . or go with an AC/DC TV and maybe then you don't need an inverter at all

We've slept many nights under an electric blanket running off battery power - works fine and you get many nights before you run the battery down. They DO make DC blankets though, so you don't really need an inverter for that

Unlike you, I'll stay home when it's THAT cold, but my tear has gotta have air conditioning because most of the time I want to travel, it's too darned HOT to sleep without it

Don

[Chuck Craven]

You could take a short extinction cord and chop off the male end. Connect it to the inverter. When you want to run the TV / DVD just plug the female connector from the inverter into the male shore power connector and a way you go…. Simple! Easy! No fuss!



Chuck

[Miriam C.]

Had not planned on it. I figured I would do a basic 2 wire circuit and just ignore the ground completely.

Just curious, why ignore the ground?