What else besides a converter?

[hunter535]

I am planning on installing a WFCO 8945 converter. This unit is a power center, 45 amp capacity with 5 AC branches and 11 DC branches. It also has a built in three stage charger. I don't plan on using all those branches initially but I like to have expansion room for future if it is needed. I am thinking of installing a 30 amp feed power cord either to a inlet plug on the side of my cargo trailer or just wire directly to the converter. I am also planning on installing a 12 volt deep cycle battery either on the tongue (if there is space because this trailer is a v-nose) or inside the trailer in a vented battery box. I would like 2 - 6 volt batteries but they are a bit pricey.
My question(s) is - Is there any other device, component, etc. that anybody might think of that I need to install along with the items that I have listed above?

[madjack]

...the nice thing about a converter, is it covers most distribution issues for both AC & DC...the one thing you NEED to provide is a GFIC somewhere upstream of the converter...if upstream, it will GFIC protect the converter and everything connected to it...possible a 30A inline fuse coming directly off the positive side of the battery to the converter...I know that line is(should be) fused at the converter BUT an inline fuse at the battery(+), protects all your wiring back from there to the conveter........
madjack

[chorizon]

Hunter, sounds like we're at about the same place in our respective builds. I looked real hard at the WFCO 8945, but decided to go with the Parallax 6730. It already has the AC breakers in place, and is ready to plug into the TD. It has the same features as the 8945, but with 3 AC circuits and 5 DC circuits, it has fewer outputs. That is not an issue for me, as its still overkill for my application, and I plan on running alot of electrical circuits in my TD. Also, the 6730 is significantly smaller in size compared to the 8945.

http://www.parallaxpower.com/6700/PPS%206730%20brochure.pdf

P.S. Its priced about the same as the 8945-->~$120-$130.

[Juneaudave]

I couldn't tell how the charger works on the Parallax 6730..is it a three stage charger? The size is appealing...

[chorizon]

I couldn't tell how the charger works on the Parallax 6730..is it a three stage charger? The size is appealing...

From parallax's website:

http://www.parallaxpower.com/6700/011%206700%20001%20Rev%20B.pdf

If you read the section on the battery charging, it doesn't specifically say "three-stage", but it does state that it "will only supply the amount of current allowed or "requested" by the battery."

[wlooper89]

Madjack is right on. I installed a 50A master fuse first thing out of the battery box. Maybe too big but it protects against a major short circuit in the DC wiring. Other smaller fuses are downline. With the type of converter you are getting I believe a Battery Tender is unnecessary. Also any other circuit breaker or fuse panel as they are included in the converter.
By the time I decided on a converter I had already installed a Battery Tender, circuit breaker and fuse panel. Could have saved the expense.

A GFCI is a must and as close as possible to campground power inlet. If you use a 30A campground power inlet, shore power can be split into two 20A circuits right away with a 20A circuit breaker on each line. Two 20A GFCI from Home Depot are much less expensive then the 30A one I ordered online.

Hindsight is great and this is probably my last teardrop, I will just keep working on this one, but everything is good and no major mistakes on the electrical. As long as it is just money one is way ahead.

Bill

[wlooper89]

There has been a lot of discussion about whether to ground AC to the trailer frame. After participating in one of those discussions I decided to ground AC only to the campground outlet.

I believe most trailers have the DC running lights grounded to the trailer frame and to me it seemed better not to have a possible mixture of AC and DC that way. My metal power inlet had a grounding strap attached to the inlet housing that I removed because it was attached to a metal tongue box attached to the trailer frame. I am still not 100% sure what is best in this regard about attaching AC ground to the trailer frame.

Does anyone have thoughts on this or knowledge of what RV manufacturers do about grounding when there is both AC and DC wiring?

Thanks! Bill

[hunter535]

Thanks Madjack for the info on the inline fuse. I am thinking of a 30 amp inline fuse as well. Any preference to either a glass fuse or a blade type?

Chorizon,
The 8945 is probably overkill as far as the amount of circuits I will need/use but I tend to lean towards the Tim Allen train of thought "Bigger is better and you can never have enough power!" Arr! Arr!Arr! I have extra breakers on hand from building my house so not having them come with the converter isn't an issue for me. Thanks for the info on the Parallex 6730. I will check it out.

Wlooper89,
I am planning on installing a GFCI breaker before the converter. Probably overkill since the converter has space for a main breaker but I plan on playing it double safe. My father has an old camper up on the farm that someone drug up in the woods for a camp and the porcupines got intoit and eat away. Not a piece of plywood left but there was a 25', 30 amp power cord along with a double breaker box in pretty good shape. I plan on using it somehow in my build.

I stopped on the way home from work today at a local rv dealer and looked around one of his tow behinds and decided that I like the looks and the functionality of a power inlet instead of pulling out a powercord from a hole in the side of a wall.

Funny that you mention about grounding your AC to the trailer frame with your DC ground. I was thinking of that today.
I am glad you possed the question! I was thinking along the same lines as you that the AC feed is grounded to the connection of shore power, hopefully! I look forward to someone responding with a answer.

[madjack]

...toss a coin...whatever is readily available...if your tow vehicle has mostly blade type, then that might be the way to go.......
madjack

[cokebottle10]

In a 120 volt ac circuit the ground is there (beleive it or not ) to cause a problem. The old fridge that only had two wires and no ground could shock you because it was not grounded. This was beacuse it could have a wire shorted to the case. When you touched the case you would get shocked. But the fridge would keep running. It did not care if the case was hot or not. [old fix: pull the plug out rotate it 180 and plug it back in] If you ground the case and a wire shorts it causes a (problem) overload and trips the breaker or blows the fuse. Now you have to fix the shorted wire. But if has failed safe and you do not get shocked.
Because most things in a house do not conduct electricity the shorted appliance would not be noticed if it did not have a ground.

A car has a metal frame. To save money on wire they usually attach one side of the battery to the frame. This is usually the negative (-) and most people call it ground. If a wire shorts out in a car it will most likely hit the frame (ground) and (cause a problem) blow a fuse. Also 12 volts is not enough electric (pressure) to force the electrons through your body and shock you.

In a house 110 volt circuit the "ground" in not designed to carry current. It is there to cause a problem if something shorts out.

In a car with a metal body the "ground" is a use to carry current.

Now we have a TD with a wood box on top of a metal frame. Pulled by a 12 volt dc car and uses 110 volt AC shore power.

Using the frame to carry current in the DC and using the frame to cause a problem in AC would be fine IF:
1.) You use a ground fault device before it is attached to the TD (upstream).
2.) You test the shore power to see if it is wired correctly. You can buy a tester a walmart.
3.) Keep 110 volt AC and 12 volt DC wires separated. As said before "Bad things will happen if they ever cross".
4.) You only connect the AC ground in ONE place on the frame. This will ensure that the frame will not carry current. You have to run ground wires to each of your ac outlets Do not use the frame to gound the 110 AC outlets. You can use the frame to carry the current in the DC circuits. However since we have a wood box for a TD and not a metal car body I would recommend that you run each of your neg 12 volt dc wires back from each of the 12 volts outlets to a common 12 volt ground.

Thanks,
David

[wlooper89]

David,

Thank you. That does shed light on AC grounding. I use a circuit tester that is a compact unit and usually plugged into a more or less dedicated outlet in the electrical compartment. This one is made by a company named Tripp.Lite or http://www.tripplite.com/en/products/mo ... delID=3941
It has three LEDs that in combination detect:

Open Ground
Open Neutral
Open Hot
Hot/Gnd Reverse
Hot/Neutral Reverse
or Correct

I thought this a good precaution since one cannot always be sure the campground pedestal has the correct connections. It also helped me correct a mistake I made in my trailer AC wiring.

Bill

[hunter535]

THANKS David!

That helps explain the grounding issue.

[wlooper89]

I frequently touch the trailer frame because my electrical compartment is a metal box bolted to the trailer tongue and the electrical switches are inside this box. So I may be standing on wet ground while touching the trailer frame.

I know that if AC primary or common is shorted to the metal tongue box or trailer frame nothing will happen immediately if the trailer frame is not attached to AC ground. Also if there is a short of this type and a person touches the trailer frame while standing on wet ground he or she may complete the path to ground. In this case the GFCI if one is installed on the line side would trip and protect the person from a nasty shock or worse.

On the other hand if the trailer frame does have a connection to AC ground and a short between AC primary or common and the trailer frame occurs, then the GFCI will trip immediately and not wait until a person standing on wet ground touches the trailer frame and completes the path to ground.

So perhaps the question: Is it better for a person to complete the path to ground and trip the GFCI or is it better for the grounded trailer frame to do it sooner?

Bill

[cokebottle10]

Just want to pass along some info on GFCI and Circuit breakers or fuses.

When you have a completed AC circuit, current will flow out one wire to a load (lets say a toaster) and back on the other wire. The current loads will be equal on both wires. Lets say 5 amps. When the current flows out one wire it will generate a magnetic field in one direction when it comes back on the other wire it generates a magnetic field in the opposite direction.
These two magnetic fields cancel each other.

This means that if I put a amp meter around one of the wires to read the magnetic field I will get 5 amps. If I put it around the other wire then I would also read 5 amps. But if I put it around both wires at the same time I would read 0 amps beacuse the two magnetic field would cancel each other.

This is how a GFCI circuit works. If both wires have the same load they cancel each other and the GFCI reads 0 amps. If something or someone bleeds some of the circuit off by touching it then the two wires will no longer be equal because some of the current has found another way back bypassing the wire and the GFCI will read circuit. This will trip it off.

Now here is the tricky part. If the toaster is pulling 5 amps and the two wires cancel each other then everthing is okay. If the toaster pull 10 amps but was rated a 6 amps max the two wires cancel each other and the GFCI still thinks that everything is okay. If it pulls 100 amps on both wires and they cancel each other the GFCI will still think that everything is okay. But by now the toaster is on fire. Even if the toaster pulls 1000 amps on both wires and they cancel each other the GFCI will still think that everything is okay. But by now the toaster will look like the sun until one of the wires burn through. Even then the GFCI will still think that eveything is okay.

This my friends is why we also need a fuse or circuit breaker. They are used to limit the amperage that flows through the wire. A 10 amp circuit breaker will open at 10 amps. A GFCI does not care about how much amperage flows through it. It only opens when the current finds another way back (like your body) bypassing the wire.

I hope this helps.

Thanks,
David

[cokebottle10]

Hey Bill,

That tester you showed is the thing to have. I think they should come as standard equment with all campers that use 110 volts.

As fas as grounding the frame. I keep thinking of the old metal case drill without the ground wire or the ground pin cut off. I don't know if I would want to use one outside on the wet ground even if it was pluged into a GFCI. Touching the drill without the ground or touching your frame without the ground would electrically be the same thing.

As far as nuking something using a large converter and big heavy batterys that you would need to maintain and replace after five years. I think that you would be better off with a good 1500 watt generator.

Thanks,
David