Reply
 
Thread Tools Display Modes
 
Old 02-11-2009, 11:11 PM   #11
Bus Crazy
 
Join Date: Jan 2008
Location: Upstate NY (Mohawk Valley)
Posts: 1,096
Re: Electrical system - does this schematic look right?

I like the way you think - but some suggestions:

The five-way switch is very good in one sense - all the inputs should be male, and if they are wired in parallel without a switch, the unused ones will be hot and dangerous. You might want to think about adapter plugs for your cables instead of using so many inputs. When I specify shoreline power for a big truck (command center), I specify 50A 240 volt twist-lock input sockets and males and females on all the cords. I can then have a variety of two-foot socket adapters pre-made to twist onto the far end of the shoreline:

50A 240V 4-pin twist-lock (no adapter needed);
50A 240V 4-pin (campground "50A" or cookstove socket);
50A 240V 3-pin (old cookstove socket - be sure to ground the bus);
30A 240V 4-pin (clothes dryer socket);
30A 240V 3-pin (old clothes dryer socket - be sure to ground the bus);
30A 120V 3-pin (campground "30A" socket - use one phase, or tie both hot inputs to the hot leg)
plus 50A 240V "flying leads" (wires with bare ends) that an electrician can install in a panel

As far as breakers tripping, I think that manufacturer's variations and age will come into play more than anything else, if the values are close. I agree with Ray that the breaker in the house will see a slightly higher load because of the wiring resistance, but I don't think it's enough to sequence the breakers. The things your buddy forgot he has plugged in to the same circuit will probably cause the house to always trip first.

Circuit breakers don't like to trip on a sudden high surge - fuses are better protection. If you put a screwdriver across a live 120 volt circuit, the screwdriver tip will vaporize to keep the breaker from tripping (ask me how I know ). On the other hand, It's my impression that a circuit breaker would probably trip before a fuse on a steady draw just above its amperage rating.

I would probably drop your design down to two feeds, a 20-amp and a 30-amp, with an A-OFF-B switch. (I personally would do 20 and 50, but you are only proposing 120 volt service.) The 20-amp shoreline is more manageable than wrestling (and storing) a long high-current cable. Make up the 20-amp shoreline with 12-2 plus ground cord, and put a 15-amp male on it, so it will go into either a 15-amp outlet or a 20-amp outlet. I think most outlet circuits have 20-amp wiring now, anyway, even though they install 15-amp sockets. I only use 15-amp wiring in a circuit that only has lighting on it.

Carry an adapter from 50 amps to 30 amps for the campground cable. My trailer came with 30 amp only, but since we boondock, I wanted to save weight and storage space. I removed the shoreline, and put in 20-amp wiring just long enough to reach the outside connection. I got a $3.00 "hockey puck" at Camping World that fits into a 30-amp socket, and lets me use a plain-jane outdoor extension cord with 15-amp ends if I need power.

In your design, make sure you open the neutral to the shoreline when you run the inverter or the generator. You don't want to just tie the neutrals together and switch the hots. If you get a quality inverter-charger with automatic transfer, you can simplify by having a two-way transfer between the generator and the shoreline, and then install the inverter between the transfer and the loads. It will also do the job of charger turn-on relay. However, you may also want to have some loads like air conditioning on shoreline or generator only, and others like refrigeration and entertainment on the inverter, so you would have two AC panels, one fed from the generator transfer and the other fed through the inverter.

Happy wiring!
__________________
Someone said "Making good decisions comes from experience, experience comes from bad decisions." I say there are three kinds of people: those who learn from their mistakes, those who learn from the mistakes of others, and those who never learn.
Redbear is offline   Reply With Quote
Old 02-12-2009, 12:12 AM   #12
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Electrical system - does this schematic look right?

Redbear, that's a lot of useful information. I'll have to spend some time considering it all. Thanks!

I believe that, for the sake of simplicity, I'd rather only every have one power source active at a time and only use one AC panel. Pretty much the same reason why I planned to use just one phase, even when connected to a 2-phase source.

I guess it's kind of weird that I want things to be simple in one way, but I'm happy to add unnecessary complexity in other parts of the system. Maybe it's because my only electrical experience is with low voltage DC digital electronics, and I find all this multiple-phase stuff a little intimidating.

I do understand the importance of keeping the shore, generator, and inverter circuits completely separate. I guess that any switches or relays used to switch between these would have to be double pole to switch hot and neutral at the same time? Tying the grounds together is a good idea though, right?
Anomalous is offline   Reply With Quote
Old 02-12-2009, 12:32 AM   #13
Skoolie
 
Ray_WA's Avatar
 
Join Date: Nov 2008
Posts: 193
Year: 1991
Coachwork: BlueBird
Chassis: GMC
Engine: 6.2 liter diesel
Rated Cap: 24
Re: Electrical system - does this schematic look right?

Quote:
Originally Posted by Anomalous
I'm afraid that I like complexity and gadgets though. Automation just appeals to me. I'm the type of person who would enjoy having their entire house wired for computer control. If I design something, I'd like it to be able to operate as independently as possible, with little or no human intervention.
This isn't as hard, or as complex as you'd think. I use X-10 modules in my house and a simple computer script monitors the temperature and decides which heater in which part of the house comes on and when. In addition to the heat control I also have quite a few lights in the house I can turn on/off with a handy little remote control.

-Ray
__________________
Pack up your bus and bug out to the hills!
Ray_WA is offline   Reply With Quote
Old 02-12-2009, 10:40 PM   #14
Bus Crazy
 
Join Date: Jan 2008
Location: Upstate NY (Mohawk Valley)
Posts: 1,096
Re: Electrical system - does this schematic look right?

Quote:
I do understand the importance of keeping the shore, generator, and inverter circuits completely separate. I guess that any switches or relays used to switch between these would have to be double pole to switch hot and neutral at the same time? Tying the grounds together is a good idea though, right?
Disclaimer: I am a radio man, not an electrician, and I did not sleep at a Holiday Inn Express last night. I do NOT have access to a copy of the National Electrical Code, and rely on published summaries and the advice professional electricians. Void where prohibited by law. Your mileage may vary.

Yes, you should use double-pole switching of both the hot and neutral, or three-pole if you wire the bus for 240 volts. I don't see why the grounds would not be tied together. The frames of the generator and inverter would probably be touching the frame of the bus, anyway.

One thing to watch out for is bonding the neutral to ground. The Code allows this in ONE PLACE only in a system. In a typical house with only one power panel, you will see the neutrals (white) in the same buss bar as the grounds (green or bare), and this is the bonding point. If you were to add another panel 'downstream' from this one for the second floor or a barn, there would be two buss bars inside the sub-panel, and the one for all the white wires would be insulated from the box and from the other bar for all the grounds.

I don't know the Code for RV's, whether the RV is considered a sub-feed off the campground system, and uses the bond in the campground, and therefore needs an insulated neutral bus. Or is it considered a unique service with its own bond. I suspect the first. It will work either way, but don't let lawyers know you got it wrong.

A 120/240 volt system with two hot legs is still considered single phase. Maybe I can explain it in electronics terms.

Imagine you are building an RS-232 device, and need a dual polarity 12-volt DC power supply. You find an unmarked unit with red, black, and white wires. You connect the black to ground as a reference, and measure +12 volts on the white wire, and +24 volts on the red one. Not what you were looking for. Then you ground the white wire as a reference, and measure -12 volts on the black wire, and + 12 volts on the red wire. Perfect!

Now imagine instead it's an AC transformer with a 24-volt center-tapped secondary. The secondary wires are red and black, and the center tap is white. You measure 12 volts AC from black to white, 12 volts from white to red, and 24 volts from black to red. Now put the transformer on the power pole, and multiply the voltages by ten. Why use 120/240 volts? Using 240 volts and balancing the load means lower currents for the same load, and less power loss and fire danger due to wire heating.

Imagine you have two 1200-watt 120-volt heaters on your bus that draw 10 amps each. You have a 240-volt panel, and wire one heater to a circuit on the black leg and one to a circuit on the red leg. You plug into a "50 amp" 120/240 volt campground outlet, turn both heaters on, and measure the load. 10 amps on the black, 10 amps on the red, and no amps on the white. Each heater still has only 120 volts across it. You have plenty of reserve power. You disconnect the heater on the red circuit and wire it to another black circuit. Now you measure 20 amps on the black, 20 amps on the white, and zero on the red. If this was a "30 amp" 120 volt campground outlet, you've used most of the available power.

Let's look at an imbalance. With the second heater back on the red circuit, turn on a lamp with two 60-watt bulbs wired on a black circuit. We measure 11 amps on the black, 10 amps on the red, and 1 amp on the white. The white neutral carries the imbalance caused by the lamp, and insures both sides have 120 volts.

An open neutral is the most unsafe power situation, in either voltage. There are some bad outlets out there in campgrounds. Cut the white wire, and the unbalanced loads in the example above act as a 240-volt voltage divider. This puts 114 volts on the first heater and light bulbs, and 126 volts on the second heater. Turn off the first heater, and without a white wire for balance, the light bulbs get 218 volts and the second heater gets 22 volts until the light bulbs explode, then it gets nothing. In a 120-volt system with an open neutral, nothing works until you complete the circuit from door handle to shoes and through the earth back to the campground neutral bond. This is why I would think you would not tie your neutral and ground together in a bus.
__________________
Someone said "Making good decisions comes from experience, experience comes from bad decisions." I say there are three kinds of people: those who learn from their mistakes, those who learn from the mistakes of others, and those who never learn.
Redbear is offline   Reply With Quote
Old 02-15-2009, 05:35 AM   #15
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Electrical system - does this schematic look right?

Thanks again Redbear for the information. I still have some more reading to do before I'm confident in my understanding of the AC electrical system.

I do have one question regarding the DC system which I haven't been able to find an answer for, and maybe someone here knows. When charging batteries from multiple sources, can you use multiple smart chargers at the same time, or do they end up confusing each other?

I understand that smart chargers, MPPT charge controllers, etc. work by sensing the battery voltage and adjusting the charge rate accordingly. If you mix multiple chargers, do they start sensing each others' voltage and put out lower current because they think that the batteries are more charged than they actually are?

I can imagine a situation where you have a charger for use with shore power/generator, a charge controller for solar, another one for wind power, and maybe also charging from the vehicle alternator as well. It would seem kind of silly to be limited to charging from one source at a time.

I suppose there would be no trouble at all with older 'dumb' charging systems, since they just dump as much power into the batteries as the batteries can absorb. Of course, this has it's own problems, like damaging batteries from overcharging, or using AGM batteries and burning out alternators that aren't rated for continuous 100% load.
Anomalous is offline   Reply With Quote
Old 02-16-2009, 03:06 PM   #16
Mini-Skoolie
 
Join Date: Jan 2009
Location: Prescott, AZ
Posts: 53
Year: 1997
Coachwork: Carpenter
Chassis: Spartan
Engine: Cummins 5.9
Re: Electrical system - does this schematic look right?

I sent an email to batterystuff.com, because they seem willing to answer general battery questions, not just thing specific to their products. This is the response I got:
Quote:
You can charge multiple batteries that are hooked in series with multiply chargers. The chargers only ‘see’ the batteries that are between their poles.

You cannot do what you suggest with batteries is parallel.
Well, that's a little inconvenient. That would mean that in my proposed system, I would have to disconnect the solar panels every time I wanted to charge from AC power (either from the generator or from shore power).
Anomalous is offline   Reply With Quote
Old 02-16-2009, 08:33 PM   #17
Bus Geek
 
the_experience03's Avatar
 
Join Date: Feb 2006
Location: Saint James, MN
Posts: 2,669
Send a message via MSN to the_experience03 Send a message via Yahoo to the_experience03
Re: Electrical system - does this schematic look right?

I think their opinion is that you shouldn't charge batteries in parallel because you run the risk of overcharging one battery while undercharging another which is quite possible, but I think most of those problems are alleviated by getting identical batteries and making sure they are maintained. Your chargers won't really care if one of the other is connected so long as you have diodes installed I suppose. Of course diodes result in about a .5-.7 volt drop which could hurt on the solar side.
__________________
http://farm4.static.flickr.com/3024/...09f20d39_m.jpg
Skooling it...one state at a time...
the_experience03 is offline   Reply With Quote
Old 02-16-2009, 10:13 PM   #18
Bus Crazy
 
Join Date: Jan 2008
Location: Upstate NY (Mohawk Valley)
Posts: 1,096
Re: Electrical system - does this schematic look right?

People parallel chargers all the time. The response you got by email was the dumbest thing I've heard.

Assume that you have a 24-volt system, and four three-cell (6 volt) batteries in series. They are suggesting 4 chargers, one for the 0-6 volt battery, one for the 6-12 volt battery, one for the 12-18 volt battery, and one for the 18-24 volt battery. Preposterous! If all the chargers were identical, and had the same output, you might save your batteries. But with multiple sources of charging, and wind and solar not constant, you wouldn't have a battery bank for long.

You are correct that the settings of parallel charging sources will interact. The deluxe way to go is to get devices that talk to each other. If you have lots of buxx, an Outback inverter-charger coupled with an Outback MPPT solar controller communicating to each other through an Outback hub and Cat 5 cables will have them work as a team. If you add the optional battery temperature sensor, you will only need one, and they will share that information, too. Add an Outback Mate remote control and run it all from your armchair. That would be my dream system.

I have two off-grid communications sites that have wind, solar, plus backup battery chargers powered by propane gennys, all tied together in parallel. We have strings of sealed cells and do not equalize, so each of the controllers just cuts out when the voltage gets high enough. Each site has a master controller that both opens and closes the solar connection, and sends the start/stop to the genny, so there exists the possibility of coordination in the software. From what I've seen, the software is written to just use independent voltage setpoints like independent parallel controllers would. The wind turbines have independent controllers that just cut out when the batteries reach 2.275 volts per cell. The site controller can report the current, but not control the turbine.

Most wind controllers I've seen just run wide open up to the cutoff voltage, and then either open the feed or bring in a diversion load to draw down the extra power.

The solution is to have all the setpoints chosen carefully so that they don't cancel each other. For example, our settings are staggered, so the wind turbine will cut out before the solar disconnects. Pick only one source for the occasional equalizing charge, either shoreline/genny or solar, wind is probably too variable in most locations. Set the other sources for float charging. How you do it will depend on the make and model of control devices and batteries you use, and will be custom settings just for your installation.

Do your homework (as you have been), and don't get discouraged.
__________________
Someone said "Making good decisions comes from experience, experience comes from bad decisions." I say there are three kinds of people: those who learn from their mistakes, those who learn from the mistakes of others, and those who never learn.
Redbear is offline   Reply With Quote
Old 12-06-2016, 01:23 PM   #19
Mini-Skoolie
 
Join Date: Dec 2016
Posts: 43
No Diagrams

Quote:
Originally Posted by Anomalous View Post
I've been trying to figure out how all the electrical stuff in a bus conversion would tie together. I have a couple different ideas on how it could be done, but I figure I'll start out with the simpler one. I have some plans for a smarter, more complex, custom built system as well, but I want to see if there are any flaws in my basic reasoning before I try to work out all the details on that. So does this schematic of the simpler system look right? Am I leaving out any recommended safety components, or is there anything else that doesn't seem correct?

Comments on a couple of things that might look weird: I want this to be able to work with any power source from 15A to 50A. I also designed it to use a separate inverter and charger, because they're a lot cheaper than the combined inverter/chargers.

Hello,

I'm tackling this issue right now and found your thread. However, I do not see any diagrams. Can you post them again?
PappySki is offline   Reply With Quote
Old 12-06-2016, 01:39 PM   #20
Bus Nut
 
Join Date: Mar 2016
Location: Greater Houston, Tx.
Posts: 386
PappySki
Did you notice the date on the post? They may not be here, now.
good luck
1olfart is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Electrical System Switch Docsgsxr Conversion Tutorials and How-to's 8 03-31-2014 09:31 AM
Just starting: electrical system question BelltownBikes Electrical, Charging and Solar 10 03-18-2013 04:36 PM
My self-designed electrical schematic if anyone's interested MichaTheStoryteller Conversion General Discussions 3 02-28-2013 11:27 PM
interlock panel on electrical system adamanderr Conversion General Discussions 0 04-07-2008 07:59 PM
Electrical System Setup jnizzle Conversion General Discussions 9 01-30-2008 01:00 PM

» Virginia Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 04:25 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.