Lights flicker when furnace is on

[Casita Greg]

I think that it would be a pretty safe assumption that the two heavy black wires are main feeds to something (what exactly I can't tell from the photos), since they are both heavy wires, black, and are fused. Perhaps you may want to consider installing a small heavy-duty terminal strip. You can find nice ones generally at one of your local boat/marine suppliers. Get one with one large terminal lug for the heavy battery (+) hot leg to connect to, and having several screw terminals, (fused ones are nice,) for distributing battery power to all of your subordinate circuits in your trailer. Run the battery (+) positive to feed the terminal strip, and the battery (-) negative back to the frame ground bolt with the heavy green wire.

[Rick G]

Originally Posted by Casita Greg

Hi Francesca,
From what I was able to trace out from viewing your photos, it appears that your large green wire is your main ground to the frame. It appears that all your other grounds (converter, charger, and 120vac ground lines) seem to eventually terminate (as best I can tell from your pics) into the same heavy green wire connected to the frame (photo #2) where it comes through the floor. This does appear to be the point where all your ac and dc grounds come to one point, which is good. Of course, you would have to check your individual branch circuits to see if any "aftermarket" installations were "shortcut grounded" to the frame elsewhere in your trailer, as mods may well have been made over the years. This would require an actual "look-see" and visual wire trace to ascertain that they were properly grounded to your main ground bus.

I'm not entirely able to make out what the two 15 amp fused circuits go to from viewing the photos, but as far as your trailers' battery ground point goes, if you feel up to making the change, I would offer a suggestion to remove the presently attached battery ground from where it is now on the tongue, and run a new line from the negative terminal back to the ground point shown in your photo (where the big green wire hooks to the frame.)

Hope this helps.

Hi Francesca,

While I agree that having a single ground point for both 110V and 12V circuits is perfectly fine, for a small trailer it is also fine to have your 110V grounded to the trailer frame at the converter and your 12V grounded to the trailer frame close to the battery. This is the factory install way for my 1980 Trillium 4500, and my email to Trillium RV last fall (found on another thread here: http://www.fiberglassrv.com/forums/f...ing-44425.html ) confirmed that it is correct. It is not the only way to do it, but it is not a fault to do it that way.

When wiring a house or large building, it is important to have everything grounded to the same place because real grounds (the kind that are a stake pounded into the earth) vary in their actual level from point to point even around a house and having two different grounds can create a "ground loop". However, the 6 foot or so difference in a trailer makes no electrical difference at all in a metal trailer frame. In fact, I would personally prefer to have the large metal frame of the trailer carry the ground between the two points rather than run a wire back to the ground point, but either way works as long as the connections are good.

To be clear, we are talking about the ground wires, usually green, not the negative (return) wires which are usually white in these trailers. The negative circuit return path must have its own wires, not try to run through the grounding.

My two bits worth.
Rick G

[Casita Greg]

To begin with, while in normal use, your trailer isn't grounded at all unless:

* You physically drive a "ground rod" into the earth and attach a conductor from the frame to it, or to a metallic pipe in the ground, when you get to your campsite in order to physically create a bond between the trailer frame and the ground, or

* You hook up to a shore power source which is equipped with a ground wire (this also rules out being grounded if you are running off a portable generator too, unless you grounded the generator to earth as well.)


While I agree that having a single ground point for both 110V and 12V circuits is perfectly fine, for a small trailer it is also fine to have your 110V grounded to the trailer frame at the converter and your 12V grounded to the trailer frame close to the battery. This is the factory install way for my 1980 Trillium 4500, and my email to Trillium RV last fall (found on another thread here: Trillium trailer 12V wiring ) confirmed that it is correct. It is not the only way to do it, but it is not a fault to do it that way.

Actually, while the automotive industry (including RV and trailer manufacturers) use the vehicle chassis as a "ground" or return path AKA negative ground, it doesn't mean that it is the best design. Steel is a relatively poor choice for conducting electricity when compared to say copper. It takes a whole lot more steel to provide the equivalent reduction in electrical resistance as copper wire. Vehicle frames provide, for the most part, a low enough electrical resistance to get away with using it as a return path. Doesn't mean it is the best way, it means that the industry SAVES MONEY by not providing a negative wire back to the battery for every item.

To be clear, we are talking about the ground wires, usually green, not the negative (return) wires which are usually white in these trailers. The negative circuit return path must have its own wires, not try to run through the grounding.

Just because auto and RV manufacturers do something, doesn't mean it is a good thing to copy. As you mentioned it above in your post Rick, I know you have heard about "ground loops." For those who may not be familiar with this phenomenon, in the audio world it is a nightmare, it causes buzzes, hum, pops and clicks. It comes from small differences in voltage due to poor grounding between devices. Ideally all electrical devices should have the same exact negative ground potential. This is where the negative ground bus comes into play.

In the RV world, since 12V is treated as "low voltage" wiring, the general practice is to have one 8 gauge negative ground wire to exit the converter panel and it meets with all the 12V negative grounds from all the 12V items. Typically the RV manufacturer will bundle all the wires together with a very large wire nut. If you are lucky they may have used a crimp instead. This is garbage, not all the wires will make a good connection. A much better way to do this is to provide a negative bus bar, upon which, each individual wire is physically attached securely to the bar.

A vehicles' 12V wiring is a bit more critical when it comes to voltage drop when compared to 120V. A value of 5% is typically the largest acceptable voltage drop for 120V, but with 12V that is too much of a voltage drop. In a 120V circuit, 5% drop is 6V but 12.5 V circuit, a 5% drop is .625V which is a very large amount of drop when comparing 120V to 12V. (Remember, 12.5 V = good battery, 12V = dead battery)

With 12V wiring it is better to keep your wiring runs as short as possible, and use a heavier gauge wire to keep the voltage drop as little as possible.

[Francesca Knowles]

Here's the wiring diagram Rick posted in the thread at http://www.fiberglassrv.com/forums/f...g-44425-3.html Is the "return wire" the line that leaves the negative battery post, splits to a ground point, and eventually ends up at the negative terminal on the converter?

Francesca

[Casita Greg]

In a word, yes...
Now the long version...
The battery negative lead, which is also hooked to the frame (ground) appears in the schematic to be providing separate grounds for all the various 12 vdc appliances. Whether they are "T tapped" into existing wiring runs, wired all the way back to the converter ground bar, or are just grounded to the frame is not really determinable from the line diagram schematic, as the drawing only represents current paths returning to ground. I can't tell if current is returned by wire all the way back to the converter, or just screwed to the frame as a return leg for the circuit. Either would show up on the drawing as "returning to ground", it's just not clear how they actually accomplished that action. You would have to visually determine if there are indeed separate wires (+ and -) running to and from any appliance and the converter and battery terminals. Although either way will function, using the frame in lieu of an actual return conductor (aka wire) isn't the best way to hook things up (as I mentioned in my previous post). Just tying all these various return leads together is not a good way to do it either. I would suggest installing one common ground bus to terminate all the individual branch circuits to one common grounding point, but this is definely a lot of work which you may, or may not, feel up to undertaking. Not saying that using the frame won't work, it's just not a good way to wire things up.

[Francesca Knowles]

I think dawn is starting to break
I'm going to cogitate on all I (might!) have learned and make an examination of my existing-er-"system".
I'm sure I'll be back in a day or two with more questions...
I'll be most grateful if you stay tuned to this thread!


Francesca

[Casita Greg]

We're here for ya!

[Francesca Knowles]

Originally Posted by Casita Greg

To be clear, we are talking about the ground wires, usually green, not the negative (return) wires which are usually white in these trailers. The negative circuit return path must have its own wires, not try to run through the grounding.

Hello again!

I've actually lost track of who said the above first, but it does seem to be -uncontroversial
I'm still a bit hazy about this- my Trillium has two heavy wires, black and white, that connect from the junction up front under the bench to the converter.
Is the white wire the "return" by which 12v power is-well, returned to the battery? Can I call it a "charging line?
Both my black and the white wires are connected to the converter, which has the Main Trailer Ground connection to the frame.
There is no green wire between these two points.

Am I grounded? (side note: I'M NOT TALKING TO YOU, MOM! )

Thanks for everybody's patient help!

Francesca

[Frederick L. Simson]

Off topic comments have been "Un-approved".

Please, just answer the question (which HAS been done) and move on.