| Author | Message | ||
| les marston (Les_marston)
Registered Member Username: Les_marston Post Number: 8 Registered: 1-2010 Posted From: 68.151.248.141 Rating: N/A |
I am sure that this has been talked about before but I am looking for some advice on doing the electrical on our coach. Right now as far as electrical goes it is a blank canvas so to speak. What I want to have is of course shore power and a generator 50 amp 240 volt. It is important to me that the generator is as quiet as possible. Any suggestions? I have an older Trace inverter that is only 110 volt output but does recharge 24 volt house batteries when plugged into shore power. Can I run the inverter to one bus bar of my 240 volt panel thus powering at least 1/2 my AC needs? I have a battery equalizer on the coach that I am told I can charge a bank of 12 volt house batteries off of. Is this a good idea or should I install a separate alternator to produce the 12 volts for my house batteries? I would like any feed back on what others have used for an AC panel As you can tell I have a lot of questions, some of it I have my own ideas on how it be best done but a wise man is he who hears the advice of those wiser still. thanks Les | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 180 Registered: 1-2006 Posted From: 66.218.33.156 Rating: |
For ease of operation, my bus is wired straight 120vac. This means I can run my straight 120vac wired 10kw generator and not worry about "balancing the load" between the two legs of the generator. But this also means that I'm restricted to using just one leg of the 50amp land line. I have found when sitting, 6,000 watts is more then enough to run the bus. I have 3 roof airs (that I can run at the same time), 2 electric water heaters, electric heat in the bathroom. Usually when sitting, maybe on the hottest of days, 2 roof airs are needed, then can also run one water heater at a time, the refer, microwave. I like the arrangement so much, I'm using the same idea on my truck conversion. Good Luck, TomC | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 1108 Registered: 7-2006 Posted From: 75.210.132.147 Rating: N/A |
Interesting comments, Tom....though not sure I comprehend. I'm a floor short of an elevator ride to the top about electrical; having said that, I have wired many projects, including our coach...far as I know, with no problems. BUT. that certainly does not mean I know it all. So, what EXACTLY do you mean "balancing the load between two legs of the generator" (how 'bout the land line?)....which, I think, is what I have always done. If not "balanced"....then what?? Thanx, RCB | ||
| David Guglielmetti (Daveg)
Registered Member Username: Daveg Post Number: 143 Registered: 2-2009 Posted From: 209.77.228.123  Rating: |
on a 240v circuit, there are actually 2 120v circuits. You want to have your various loads (electrical usages) balanced between the two legs, in other words...you want one heater on one leg and another heater off the other, rather than two heaters on one leg and nuthin' but a light bulb on the other...clear?! | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 1109 Registered: 7-2006 Posted From: 75.210.132.147 Rating: N/A |
That's what I thot.....???  Therefore,...the question above! RCB | ||
| Jim Wallin (Powderseeker01)
Registered Member Username: Powderseeker01 Post Number: 67 Registered: 10-2008 Posted From: 208.68.48.77  Rating: N/A |
I set ours up just like a house. 120A panel with load distributed across both legs, generator disconnect, and a 50A shore power connection. I did avoid utilizing 220V appliances so I have the option of using a 30A shore power connection if a 50A option is unavailable, like where we are now. Conduit with 12awg thhn to get hooked up. | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 1219 Registered: 12-2000 Posted From: 74.4.63.215  Rating: N/A |
Here is our way, YMMV. We have a 50 amp, 240/120 volt shore cord going to a 50 amp transfer switch. We also have a 120 volt feed from the generator going to the tranfer switch (with a jumper between the 2 hot terminals). The 240/120 volt output from the transfer switch feeds the main panel. A 30 amp breaker in the main panel feeds the 2500 watt Heart-Interface inverter (as well as 12 volt from house batteries). The output from the inverter feeds a 120 volt sub panel. All circuits that are powered by the inverter are fed by this sub panel. PowerTech recommended wiring our generator for 120 only since we have no 240 requirements. If wired 240/120, they recommend keeping the 2 legs balanced to within 15% to prevent overheating the wiring on one leg. Also the voltage regulator on our generator only monitors 120 volt, so if wired for 240/120, it is monitoring one leg. if that leg has very little load, but the other leg has a heavy load (or visaversa), the regulator may not do its job properly. Jack | ||
| les marston (Les_marston)
Registered Member Username: Les_marston Post Number: 9 Registered: 1-2010 Posted From: 68.151.248.141 Rating: N/A |
Hi All Thanks for the info. I am thinking that I will set up something like Jack has done with the shore power and generator power coming into a transfer switch and feeding the breaker panel. I don't have my generator yet so will probably buy a 240 volt just because the hydronic furnace requires 2 110 volt 20 amp circuits. Then tie the inverter into one breaker on one leg of the panel so as to have at least one side of the panel powered when we are on the inverter. What are you using for a AC panel and how do you deal with the no earth ground issue from the generator and inverter?. I assume earth ground thru the 50 amp plug when on shore power. Les | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 1220 Registered: 12-2000 Posted From: 74.4.63.215 Rating: |
Make sure the feed to your inverter is not on the same side you feed the inverter output into. This weill let all the smoke out of the inverter and it will not work once the smoke gets out. We used a standard residential load center. We left the neutral stip isolated from the case and added an additional strip for the grounds that we bonded to the case. The generator, as well as the load center case and ground wires are all bonded to the bus frame. The neutrals remain isolated. The transfer switch switches the neutrals as well as the hots. Although the neutral & ground are bonded at the generator, when the transfer switch switches to shore line it disconnects the neutral from the generator, thereby breaking the generator neutral/ground bond. Jack | ||
| David Evans (Dmd)
Registered Member Username: Dmd Post Number: 424 Registered: 10-2004 Posted From: 173.68.141.245  Rating: N/A |
Really good book you can get here on this site by George Myers on electrical circuits for conversions. george used to be the man at busconversions magazine with the monthly elect. articles. George goes by the codes and gives you alot of options. Pay attention to what Jack wrote about the grounds. VERY important stuff. And dont forget our national treasure, the Archives. | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 1012 Registered: 1-2003 Posted From: 67.142.130.15  Rating: N/A |
That's an enormous generator, 12kW. How did you arrive at this size? You really want to add up all the loads and size this properly; running an underloaded generator is almost as bad as not having enough generator capacity to power everything you need.
If you have a 24-volt bus and a 24-volt inverter, you probably should have a 24-volt house bank, not a 12-volt bank. Use the equalizer to run 12-volt loads, but keep them to a minimum. Lights are commonly available in 24 volt, and some other items are as well. You will need 12 volts for alarms, fans, and some controls. If you are married to having a 12-volt house bank, you probably want a 12-volt inverter-charger, too.
No. What you really should do is have a separate sub-panel for the inverter loads. This is because feeding only half a bus can present a shock hazard, and you will still need an input breaker for the inverter. Also, inverters present specific ground-neutral bonding issues. Typically, the inverter is fed with a branch circuit from the main panel, and inverter loads are served from a dedicated sub-panel.
Buy regular household panels from your friendly home improvement store. I favor QO-series panels from Square-D, because they can also be used for DC circuits; having common breaker types allows for more field-repair options.
Use GFCI receptacles on all outside outlets, as required by code. If all power sources are on board, there is no need for an earth ground.
Indeed, it has. Everything ever typed on this board is in the archives; you might spend some time with the Search page looking for electrical information. For example, there have been extensive discussions of 12v vs. 24v house systems: http://www.busnut.com/bbs/messages/233/5650.html http://www.busnut.com/bbs/messages/233/9518.html http://www.busnut.com/bbs/messages/233/5786.html Grounding of panels: http://www.busnut.com/bbs/messages/11/27283.html http://www.busnut.com/bbs/messages/233/23000.html And the list goes on. I found so many electrical posts for this reply I could not read them all.
Let me suggest you pick up a copy of Designing Electrical Layouts for Coach Conversions by George Myers, available right here on this very web site: http://www.busnut.com/epicconversionsupport.html This is a comprehensive treatise on coach electrical systems, and will obviate the need for you to get your own copy of the National Electrical Code, which you would otherwise need. -Sean http://OurOdyssey.BlogSpot.com | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 1111 Registered: 7-2006 Posted From: 75.208.242.186 Rating: N/A |
Good post Sean....as usual! RCB | ||
| les marston (Les_marston)
Registered Member Username: Les_marston Post Number: 10 Registered: 1-2010 Posted From: 68.151.248.141 Rating: N/A |
Thanks Sean I will be ordering the book from George Myers tomorrow Seems I know even less than I thought Les | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1317 Registered: 5-2001 Posted From: 70.101.207.24 Rating: N/A |
Les, the older we get, the more we notice this. Good luck. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1078 Registered: 10-2006 Posted From: 69.19.14.41  Rating: N/A |
Thge biggest question is usually will you have to look at the electric box? If it is down below in the basement , or in the rear of a closet , house stuff is cheap and works fine. If its going to be used for equipment switching ,( not just protection ) the marine units look much nicer in the cabin. FF | ||
| Matthew Shaw (Greentowtruck)
Registered Member Username: Greentowtruck Post Number: 13 Registered: 11-2006 Posted From: 24.113.12.84 Rating: N/A |
I am not trying to hijack but if I read the electrical stuff correctly then the input power should look something like my pic for shore power plus a generator and an inverter. I am having a little trouble wrapping my brain around it but I think I may have it figured. The way I drew the "schematic" no two switch sets could be on at the same time.  | ||
| Jack Conrad (Jackconrad)
Registered Member Username: Jackconrad Post Number: 1223 Registered: 12-2000 Posted From: 74.4.63.215 Rating: N/A |
Matthew, That is similar to our set-up, except we have the inverter input connected to a 30 amp circuit in the main load center. Since our inverter is also a battery charger, this allows the charger portion of the inverter/charger to recharge the house batteries any time we have 120 volt power avaialable (from generator or shoreline). The output from our inverter goes to a different load center (sub panel) that houses the circuit breakers for all the circuits that are powered by the inverter. When we have power from shoreline of generator, the power passes through the inverter to the sub panel, as well as powering the charger portion of the inverter. Just "our way", YMMV. Jack http://i682.photobucket.com/albums/vv186/OBS-JC/OBS%20II%20Electric/33995.jpg (Message edited by JackConrad on February 20, 2010) | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 1013 Registered: 1-2003 Posted From: 67.142.130.48 Rating: N/A |
Matthew, There are a couple of issues with your drawing. First and foremost, grounds must never be switched. All ground wires should be continuous at all times, except, of course, for cord-and-plug connections. Secondly, the method you propose is only allowed if there is a mechanical interlock that will ensure one and only one of the three connections can be made at a time, and the change-over mechanism is "break-before-make." There are ways to do this, but I think you will find most off-the-shelf hardware allows for only two connections, not three. Lastly, having the inverter as a "third choice" rather than a separate sub-panel only works if it is a straight inverter, without a charger. That's one option, but wiring it this way limits you to that type of inverter alone. -Sean http://OurOdyssey.BlogSpot.com | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 935 Registered: 7-1997 Posted From: 99.39.13.50 Rating: N/A |
Matt, The above two posts are exactly correct, one from a convenience and usability standpoint, the other from an electrical safety standpoint. Most all of the RV type inverters have battery charging capability, on shore or gen, which your design would eliminate. These type inverters also have 120 V "pass thru," which eliminates the need for the third set of contacts. So, unless you are planning on staying with a cheap modified sine wave inverter forever, consider running the power thru the inverter to the bus main panel, and switching ONLY the hot and neutral between shore and gen, before the inverter. You do have to make sure the inverter does its own neutral switching, but again, most of them do. This way, you only have to switch two poles between two sources. The shore input ground wire needs to be connected to the chassis, then, as mentioned above, your switching is a whole lot simpler and safer. G | ||
| Matthew Shaw (Greentowtruck)
Registered Member Username: Greentowtruck Post Number: 14 Registered: 11-2006 Posted From: 24.113.12.84 Rating: N/A |
Ok I think I understand. The drawing was just a quick sketch so no interlocks were shown. I will need to get the book, hopefully it has schematics or drawings to show the circuits as I understand them better than just explained in words. I guess I misunderstood where it was said that the neutral and ground should only be bonded at the power source and only one at a time. That is why I had the grounds switched, so I guess it is more research for me. |
