Trailer Electrical System Design

[Craig D. Thompson]

I am beginning a complete refurbishment of my '84 U-Haul CT. (Ok, I have been saying that for a few years now, but I am REALLY doing it now...) The original electric controller (orange box) will be removed and replaced with a new controller/converter/charger (Progressive Dynamics PD4045 looks good).

I have a general idea of the electrical system design but I am not familiar with some of the details.

Are there any good references available that discuss the details of a trailer electrical system design/layout? Books? Web sites? Other?

As always, any help is most appreciated.

Craig T.

[mary and bob]

I put the PD 4045 in our Uhaul and am happy with it. Only issue I had with it, and someone else did too, is a couple of the 12 volt wires were marked wrong. Easy enough to check with a multimeter. You want to eliminate that little breaker/outlet that is original on the end of the upper cabinet and either run the shore power cord directly to the new converter, or to a small breaker box just inside the cord access door and then to the power converter like I did. I have added a few outlets and two 110 lights, plus a couple 12 volt lights. Just try to plan ahead what you want to end up with. The PD4045 instructions may be a little confusing, or perhaps I just didn't read it right the first time, so look them over closely.

[Bob Miller]

Me thinks that by starting out with the PD-4045 you have about 95% of the "Design" issues already behind you. With that box the following issues are already designed in....

1. AC Distribution. Proves a main breaker, a breaker for the converter, a breaker or two for AC circuits and one for the air conditioner if you have one and you are good to go. You will want to use "Dual" package breakers that have two breakers in one to save space. I'd start out by using an "RV" rated shore power cord of either 20 or 30 amps.

2. DC Distribution: You have about 12 fused circuits to go crazy with. You can
a. Fuse the lights into two or more groups so, if you blow one fuse there are still lights on. Separate the inside from the outside light(s)
b. Fuse the water pump
c. Fuse the Furnace by itself
d. Fuse each of the DC outlets you install separately, same reason as #1.
e. Fuse any exhaust fans independently from the lights
f. Fuse Any other special DC accessories and you still have a bunch of fuse lines left for future use.
TIP#1 >>>>> Write down what each fuse goes to as you wire them, it's very easy to forget what goes where.

TIP #2 >>>>> If you use any common ground wires, be sure it is big enough to carry all the loads that will be riding thereupon. I personally run two wires to everything and set up a common ground buss external to the PD 4050.

3. Battery Connections
The internal circuitry on the PD-4045 makes the battery connection very easy. Connect the + side of the battery to the input buss with at least a #10 wire, use #8 if the run is from the tongue. I put a 30 or a 50 amp breaker in that line. You connect the charging line from the TV directly to the + side of the battery as well'
Connect a digital battery monitor at the battery. VoltMinders are great if you can get one.

Connect the (-) side of the battery to the (-) buss in the PD-4045 as well as to the external ground buss mentioned above. Be sure to also connect to the frame so the charging line from the TV will work.

Now all you have to do is identify what are called standard wiring practices, buy a ton of wire, wire clamps, zip ties and terminals of all sorts (only use the kind you crimp with a pressure crimper, (not a $1.98 pliers crimper) and you are in business.

Except for the AC side, where I use romex type products, I don't go crazy on color coding,, it gets to expensive, but I also tag all of my wires at each end with a little zip-tie flag.

Also, never bundle AC and DC wires in the same bundle. Some of our newer electronics don't care for any AC leakage into the DC lines that might occur.

Nuff for now.....

Be sure to add more questions......

[stevebaz]

One of the things that helped me was looking at wiring diagrams from other trailers and alot of diagrams and pictures on this site. Its worth the time to do a google search on this site for more information. The instructions with the PD4045 are dismal and I believe its done on purpose so that people that install these pannels have more than rudimentary knowledge of RV electrical systems. The unit works well for me and I would do it again if I needed to. You should plan ahead before purchase so you order the proper 120 volt breakers you will need. Buying the pannel doesn't include the breakers so order them when you buy the pannel. It doesn,t come with any 12 volt fuses for the branch circuts but they are standard automotive types available at any auto parts and easy to find.

( And yes on my unit there were a couple of mismarked 12 volt branch circut wires. Its not a big deal when you know about it. I checked them and re tagged them.)

[mary and bob]

Thanks Steve, I knew I wasn't the only one with mismarked wires. I bought the 110 breakers at Lowes as they were cheaper there (I think).

[Bob Miller]

Yep, buy the breakers & fuses locally, a lot cheaper. And, if one doesn't know how to install a 120VAC breaker, that's a hint that some outside help needed before going any further

I hope that the point made above is well taken. Looking at other wiring diagrams and reading about wiring isn't the best idea for a novice to learn how to wire. If someone doesn't have basic wiring skills, a bit of help from someone with experience WILL avoid problems down the road.

BTW: Unless the diagram you are looking at is using a PD-4045 or a PD-4060, it may be wired a lot differently. Earlier devices didn't have the plethora of DC circuits or the built in sensing and blocking that the PD products have and the wiring maybe very different to accommodate that system.

Good Luck

[Roy in TO]

Originally Posted by Craig D. Thompson

Are there any good references available that discuss the details of a trailer electrical system design/layout? Books? Web sites? Other?

Managing 12 Volts: How to Upgrade, Operate, and Troubleshoot 12 Volt Electrical Systems: Harold Barre: 9780964738621: Amazon.com: Books

[mary and bob]

[QUO a bit of help from someone with experience WILL avoid problems down the road.

I think this advice applies to many of the tasks involved in repairing or maintaining campers, or any type of equipment. Best way to learn, have an experienced person show you. I don't have a lot of faith in you tube video instructions. If you saw it on the internet, is it right??

[Craig D. Thompson]

Thank you all for such great information! Just what I am looking for.

Though not an electrician, I have done my share of electrical wiring so I have no concerns that I can handle this installation.

I am trying to decide where to mount the controller. The logical location is where the original panel was, on the closet wall to the left when entering the door. I am planning to use this for a storage area. The bed stays a bed and I will be putting storage bins under so mounting under a bench is not an option.

I am thinking of mounting the controller in the upper left (street side) corner, just forward of the cabinet above the stove. Is there any concerns about this location? Does the controller put out very much heat? Will I need to cut air vents into the cabinet/box enclosure for the controller?

Keep all the good info flowing!

[Craig D. Thompson]

Oh, and Bob Miller, you wrote :
...(only use the kind you crimp with a pressure crimper, (not a $1.98 pliers crimper)..."

What is a pressure crimper?

[mary and bob]

I mounted my PD 4045 on the vertical surface just forward of where the original power converter was. That puts it somewhat below the small hatch cover that is next to the hatch that provides access to the battery. I reinforced that surface with plywood, cut a couple 2" round holes above & below the converter for ventilation, and also installed a brace. I've also reinforced that whole rear area, which we keep made up as a bed. Under the bed are two storage baskets mounted on drawer slides, so the power converter is not real easy to get at, but so far there have been no electrical problems that required me to get to it. Over 3 months straight last winter plugged in to shore power, running an electric heater, TV, dorm fridge, and 110 & 12 volt lights.

[Bob Miller]

I am thinking of mounting the controller in the upper left (street side) corner, just forward of the cabinet above the stove. Is there any concerns about this location? Does the controller put out very much heat? Will I need to cut air vents into the cabinet/box enclosure for the controller?
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YES. The PD-4050 has to have flow through ventilation or an outside ventilating port.

[Bob Miller]

Originally Posted by Craig D. Thompson

Oh, and Bob Miller, you wrote :
...(only use the kind you crimp with a pressure crimper, (not a $1.98 pliers crimper)..."

What is a pressure crimper?

---------------------------------------------------

Also called a ratcheting crimping tool, it looks like this one:
WESTWARD Crimper, Ratchet, Manual, 10 to 20 AWG - Cable and Wire Crimping Tools - 13H896|13H896 - Grainger Industrial Supply

Pliers type will result in crimps coming loose, it's right in the product guarantee.....

[Spanke]

If possible, I would mount the converter as close to the battery as possible with at least 8 or 10 ga wires going to it, less distance is better.

Just my preference.

Raz where are you?

Spanke

[mrscottyg]

Cooling airflow for the PD-4045 is Front-In Front-Out. In other words, the unit uses the air in the trailer to cool it and then discharges that heat back into the trailer. Here are a few additional recommendations from their Installation Instructions:

The PD4000 series POWER CONTROL CENTER should be installed horizontally (converter section to the left).

Unit is NOT ignition protected. Do not mount in the LP gas or the battery compartment.

The OEM should test the POWER CONTROL CENTER converter under full load conditions in its intended mounting location to
ensure proper ventilation. Failure to provide adequate ventilation will prevent the converter from supplying full output power.

The INTELI-POWER converters are not designed for zero clearance compartments.

The POWER CONTROL CENTER was not designed for wet or damp locations. Install in an interior / dry location.

[Craig D. Thompson]

Are the vents on the left front of the PD4045 both the in and out for the cooling air? Or does the cabinet where the unit is installed need vents? I read the installation & operation guide but do not see this mentioned.

[Bob Miller]

No, air flow is thru the case, in the front and out the back or vise versa. There are several vents at the back as well.

The instructions seem more oriented to OEM users rather than our group. Buit it does say that zero clearance isn't allowed.

[mrscottyg]

Unless the unit in my trailer is unique (which is unlikely), the PD-4045 pulls air in the front and discharges it out front. The back of the cabinet is solid plastic on top, bottom, and both sides, except where wires pass through. You can feel the warm air exiting the cabinet in the front when the unit is charging at full load.

[Bob Miller]

I don't think that your trailer is unique in that sense, but the 2 year old PD-4045 in my Hunter is vented both front and back, suggesting a change in the PD design. If anyone has bought one recently, please chime in as to the venting.

[Carol H]

A question re how much venting is actually needed for the PD. My converter is located in a large rear hatch on the Scamp. No outside vents to that hatch. Only small openings into other inside areas of the trailer where the water and electrical runs through. Would I or should I need to add a larger vent somewhere on the rear bench hatch to the inside of the trailer to give it more ventilation or as the old converter was fine in that location would the new PD be fine there as is as well?