Electrically challenged

[cpaharley2008]

Not sure using the trailer as a ground is acceptable. There are shunts available.

[dbailey]

Do I understand correctly that you're using the existing converter->battery wiring rather than using your 4AWG wire from battery->inverter? What's the wire gauge of the existing wire?

Or is this just a test, to make sure the inverter works?

As for the voltage, keep in mind that voltage drop will increase as you increase the load. The fact you see 12.9V is good, but you also need to test it under load.

[MyronL]

Factory installed wire from the battery is 8 AWG. All my wires from the inverter are 4 AWG.

The back of the converter has a machine screw, to which all negative wires converge. A wire from this assembly point goes through the floor and is bolted to the frame underneath. I added my inverter negative wire to that common assembly point. The battery negative pole (8 AWG) wire is also grounded directly to the undercarriage frame.

Yes I have eyeballed all them factory attachments.

[JohnE3]

Myron,

The 8 AWG wire may be (is probably) too small for the 50A fuse. Given the short length, you may get away with it if the temperature rating of the wire (usually written on the wire) is high enough (90C or greater), but there's another problem.

From what I can see in your pictures, you've actually got both the inverter fuse, and the circuit breaker (30 or 40 amps to the trailier Pwr Cntr) connected to that 8 gauge battery feed. Theoretically, you could cause up to 80 or 90 amps to flow in that wire. That would certainly melt even high temperature insulation.

Given that in the best case you are at the very limits of the 8 gauge wire with only the 50 amps, any additional draw from the trailer while the inverter is providing its rated load could spell disaster.

You may want to consider replacing the 8 AWG feed wire from the battery with that 4 gauge, or run a dedicated wire for the inverter. The 4 gauge could be fused for up to 80 amps depending on the temperature rating of the wire insulation.

Cheers,
John

[MyronL]

Wait a minute. The factory decided installing 8 AWG wire is fine throughout. You say because I installed an inverter and used 4 AWG wire, (rated at 600) a bigger, fatter, stiffer wire that will handle a greater load, plus an inline fuse protecting the inverter that will (theoretically) blow sooner than later if there's a meltable surge from I have no idea where, that I should now replace the factory 8 AWG wires with 4's?

Theoretically, with all due respect....I don't think so.

[Jubal]

Myron, have read your owners/installation manual (page 12) ?
The wiring schematic shows the 4 gauge wire connected directly to the battery bank and fused on the positive cable.
The 8 guage cable used by Escape TT between the battery and the converter is adequate for the electronics installed by them. The 8 guage wire is not adequate for the inverter. You cannot splice a larger guage cable upstream of a smaller cable and expect adequate electrons to flow. CONNECT THE INVERTER DIRECTLY TO THE BATTERY BANK WITH YOUR 4 GUAGE CABLE AND INSTALL THE FUSE IN THE POSITIVE CABLE LINE.You have been give good advise from several individuals.

[MyronL]

Installing my inverter

Xantrex ProWatt 600 $184.39
8 feet 4 AWG wire $7.92
4AWG ring terminals $11.86 (copper is expensive)
50 amp fuse & holder $17.78

total spent $221.95

Jubal, I appreciate your input. Do not wish to dispute my helpful friends, However... My logic is as follows: If water flows through a 1/2 inch pipe at a given rate, would not that same water flow more freely and faster if the pipe is 1 inch?
Using that framework, can someone explain how or why one given physical energy source (water) would be different from another...(electricity) ? Seems to me in all cases the bigger conduit means faster, more efficient, not slower.

Is the factory converter any less a consumer of energy than my inverter? 12.9 volts is 12.9 volts any way you run it, right?

[Jubal]

Myron
Once again have you read your owners manual. The information provided is to help you attain success.
Voltage is not the only factor. 8 guage wire resists amperage flow more than 4 guage wire. A single strand of wire has the same voltage a several strands of wire but the single strand will "resist" more amperage flow then multiple strands. This would be a good time for you to pursue basic knowledge of electon flow. Logic does not trumph the proven physical laws of science.
HowStuffWorks "What are amps, watts, volts and ohms?"
This site has a good description using water flow.
Concerning electronics:
Success = priceless
Failure = potentially catastrophic results

[MyronL]

Man I can't believe this subject is up to 68 posts already. Was hoping all answers would stick close to the chase, but what the heck, still fun. Yes I read the manual (see my post #forty-seven and fifty-eight). Hope this string-out is at the very least helpful as a learning tool for others like me.

I will be going out to the trailer with my multimeter to test for amps.

[Brian B-P]

Originally Posted by MyronL

The factory decided installing 8 AWG wire is fine throughout. You say because I installed an inverter and used 4 AWG wire, (rated at 600) a bigger, fatter, stiffer wire that will handle a greater load, plus an inline fuse protecting the inverter that will (theoretically) blow sooner than later if there's a meltable surge from I have no idea where, that I should now replace the factory 8 AWG wires with 4's?

Yes.

The factory decided that 8 AWG wire was suitable for the amount of current which could be drawn by the DC distribution panel which is located with the converter. You have installed an inverter which can draw much more current, and bypasses the fuses of the panel, so you have greatly increased the possible load on the wires from the battery and invalidated the factory's choice.

I don't see anything wrong with that; you just need to finish the job and modify all of the affected components as appropriate.

Originally Posted by MyronL

My logic is as follows: If water flows through a 1/2 inch pipe at a given rate, would not that same water flow more freely and faster if the pipe is 1 inch?

Using that framework, can someone explain how or why one given physical energy source (water) would be different from another...(electricity) ? Seems to me in all cases the bigger conduit means faster, more efficient, not slower.

Yes, I agree, that analogy is valid. Bigger pipe or bigger cable doesn't cause problems and does reduce flow restriction and energy loss due to resistance.

Originally Posted by MyronL

Is the factory converter any less a consumer of energy than my inverter? 12.9 volts is 12.9 volts any way you run it, right?

The factory converter is not a consumer of DC power at all; it consumes AC power (and we have not been talking about the AC wiring here) and produces DC power from it. The consumer is the set of equipment (lights, pump, fans, electronics...) which are connected to the DC distribution panel which is located with the converter.

If the converter is the model listed in the 19' features list, it can put out up to 55 amps, so that's that maximum current which would be pushed from the converter to the battery through that 8 AWG cable.

Yes, the factory DC panel (with its attached circuits) is a less a consumer of energy than the inverter. 12.9 volts is still 12.9 volts, but the panel is limited to it's fuse rating (presumably something like the 55 amps converter output), and the inverter could use 60 amps, and is fused for 80 amps. Power is potential (in volts) multiplied by current (in amps); energy is power accumulated over time. Perhaps more importantly, the 8 AWG factory cable is being asked to handle the converter output or DC panel loads, plus the inverter load; it doesn't matter which is greater, but it does matter that they are adding up.

In your home kitchen, an electric can opener and a microwave oven are both provided with 120 volts, but the while the opener uses a few watts the microwave typically uses 1400 watts. If you wire a kitchen to run only can openers, you will need heavier wire if you add a microwave. If you wire a trailer to run up to 40 amps of lights and fans then add an inverter which can can use up to 60 amps, you will need heavier wire.

If you supplied the inverter from a circuit in the original DC panel, the original fuses would protect the wiring... but you would not be able to run the inverter anywhere near full load.

By the way, I was looking for an authoritative source of maximum current draw by the inverter, and I noticed that the Xantrex manual covers all PROwatt SW models (from "660" to "2000") with the same recommendation for input wiring (which is nonsensical). 4 gauge may be larger than required for the 600 model.

[dbailey]

I wonder if we are misunderstanding each other...

Myron, the concern we have is on the flow of power between your battery and your inverter when you have a large load on the inverter. Is any of it passing through the 8AWG wire?

What I think you are saying is that the electrical connection from battery to inverter is a mix of 8AWG and 4AWG wire -- 8AWG at the battery, and 4AWG from the midpoint to the inverter.

If that is true, you do have a serious problem. 8AWG wire is only rated for 24A power transmission. If you have a 600W draw on your inverter, it's going to need over twice that. The 8AWG wire will get hot. I don't know how hot, but it wouldn't surprise me if it was wire-melting hot. It will almost certainly be "burn the insulation and any other nearby plastic" hot.

Or do you have 4AWG wire all the way from the inverter to the battery and the 8AWG wire, originally installed all the way to the battery, now only goes between the pre-existing electronics (converter) and a midpoint on the new 4AWG run you've put in? If that's the case, then I think you're safe.

[Brian B-P]

Originally Posted by MyronL

Yes I read the manual (see my post #forty-seven and fifty-eight).

So you know that at full load (which you might never use) the inverter will draw 60 amps and blow the 50 amp fuse in the wiring you've added, right? The AGU fuse holder looks like a good design - it's just not enough capacity for the peak current that might flow in normal operation of the inverter.

I'm guessing the fuse holder is this one: Lightning Audio 4ga or 8ga AGU In-Line Fuse Holder The web page does not specify a current capacity, but if it allows more than 50 amps, why not put in at least a 60 amp fuse (which happens to be the highest in the Littelfuse AGU line)? Of course, if you never use more than about 500 watts, the 50 amp fuse will never blow so maybe it's not a problem.

[thoer]

All this is making me appreciate the simplicity of only running AC devices when plugged into shore power....

[dbailey]

I've done a bit more reading, and now I'm less sure of whether or not it's a problem running 50A through 8AWG wire. The sources (I've seen it repeated in many places) that indicate the maximum capaity of 8AWG wire as 24A all note that it's a very conservative number. The same charts show the maximum capacity for 14AWG wire as 6A. I know house wiring allows 15A on 14 gauge wire. Is house wiring on the AWG scale? I think so... Is AC vs DC relevant for amperage rating? I don't think so...

And, I'm seeing lots of different numbers for current capacity from lots of different places.

And, Brian indicated that Escape used 8AWG wire for the converter, with a 50A fuse. So they seem to think that 49A won't overheat the 8AWG wire.

So, I'm no longer sure whether 8AWG is sufficient for 50A or not. Were it me, I'd play it safe. Either have somebody that I trust knows what they're doing install the inverter (or at least give me advice), or go with the worst case and use 4AWG where I might need 50A.

[MyronL]

My 4AWG wire runs from the inverter to that machine screw where the red wires converge in my picture. No farther. If that is a bad idea I will change it and continue the inverter line out to the battery. I really do not want to do that. Dbailey, might an option be to reduce its inline fuse (AGU fuse holder) to say, 30 amps?

On Page 2 of my users manual, "Comprehensive Protection" states the inverter automatically shuts down if the battery voltage drops below 10.5 V. or if the input voltage rises to more than 15.5 V. , or, if AC output overloads attached to the inverter exceeds its operating limits. Converter installed fuses max out to 50 and my in-line inverter fuse is a 50. How could I not conclude no wiring changes are needed?

It is the AGU 4ga input fuseholder and yes I deliberately chose the 50 over the 60 amp fuse. I cannot imagine using the inverter simultaneously for anything fuller than my laptop and a camera battery charger and (this is a real stretch)my 19 inch tv.

Corrales Dave loves his Cappuccino machine but me, I'll be sticking to my propane-fired Melita.

[JohnE3]

Myron,

It is incorrect to state that the fuse is protecting the inverter; the fuse and circuit breakers protect the wire. Furthermore, the water pipe analogy does not work here.

The 8 gauge wire will happily provide as much current as you need, however it will heat up like the element on a stove. The current rating of a wire is intended, more than anything else, to limit the temperature so that it will not exceed the rating of the insulation. That is evident in the excerpt from the National Electrical Code table (attached) which shows current varies with insulation temperature rating.

This is a good site with ampacity ratings more appropriate to the PVC insulation that is likely in the trailer, and taking into consideration resistance for long runs: Amps and Wire Gauge - 12V Circuit

So when the inverter is drawing its maximum current (50A as limited by the fuse) the power distribution panel may draw up to say 40A (as limited by the circuit breaker). The 8 gauge wire will supply 90 amps. The wire will get hot, because the total protection (fuse and CB) are too high to prevent the wire from getting hot.

Hot wires are bad... unless it is a stove element.

[dbailey]

Originally Posted by MyronL

Converter installed fuses max out to 50 and my in-line inverter fuse is a 50. How could I not conclude no wiring changes are needed?

This is really what's making me think those conservative capacity charts I was looking at are *way* too conservative...

So, I'm thinking you may be right. But, I lack confidence.

If anybody can educate me, I'd appreciate it...

The chart where I got the 24A number for 8AWG wire (reproduced in many places) can be seen here: American Wire Gauge (AWG) Cable Conductor Size Chart / Table -- that site notes that "The current ratings shown in the table are for power transmission and have been determined using the rule of 1 amp per 700 circular mils, which is a very conservative rating" (emphasis theirs). Now, I have no idea where that rule comes from. But judging from the fact that it rates 14 gauge wire at 6A, when we know housing code allows 15A in 14 gauge wire, suggests that their "very conservative" is far too conservative to be useful in this instance.

Now here Ampacity Charts is a chart that says if your wire is rated to 75 degrees C you can put 50A over an 8AWG wire. I don't know if I'd want to let the wire get that hot. If you restrict it to 60 degrees C you're limited to 40A. This seems to be in the standard that Escape has designed towards. Still, I find it a little concerning.

[padlin]

Myron
Just trying to figure this out for myself, can you tell me the distance from the converter the batteries?

Doug
I may be missing it but I don't see where the distance of the run is used on either of the 2 charts you mention.

[KarenH]

Originally Posted by thoer

All this is making me appreciate the simplicity of only running AC devices when plugged into shore power....

...or not having any at all.

[JohnE3]

Doug,

The ratings on the "ampacity charts" link are out of the NEC.

NEC treats 14 through 10 gauge as special cases, and they are quite conservative. Also, the expected wire length in a building is considerably more than a trailer, and I expect the NEC ratings consider voltage drop as well.

However, the quality/temperature of the insulation will vary. I would not be supprised if the (probably) PVC wire insulation in a trailer is on the low end of that scale. Conservative is prbably a good thing.

But even if you would go with the 50, or even 55 amps on 8AWG, Myrons installation is still a concern.

John