| Author | Message | ||
| john degemis (Degemis)
Registered Member Username: Degemis Post Number: 11 Registered: 3-2008 Posted From: 71.92.155.140 Rating: N/A |
I am just starting to wire the 12 volt systems( lights,camras...)The bus is 24 volt. Can I use the frame as a ground for both 12 and 24 volt?. | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 840 Registered: 10-2004 Posted From: 70.220.127.152  Rating: N/A |
Yes | ||
| FloridaCliff (Floridacracker)
Registered Member Username: Floridacracker Post Number: 382 Registered: 7-2004 Posted From: 24.27.228.156 Rating: N/A |
Yes, But it's a bad idea. Having individual grounds run from a source to each location will ensure the best possible ground and make troubleshooting issues in the future, WHEN they happen, 100% easier. I can't begin to tell you how many ground issues I have tracked down over the years. Usually running a wire directly from the ground source to the application resolves the problem, but actually finding where the ground is lost, can be a bear. I would at a minimum run the ground from the source to a distribution bus, where you can branch out from there. I have three dc distribution points in my coach, this cuts down on the length and size of the wires needed, you can also use relays in your design to minimize the size and length of the wires you have to run on the positive side. Best of luck, Cliff | ||
| Grant Thiessen (Busshawg)
Registered Member Username: Busshawg Post Number: 32 Registered: 10-2007 Posted From: 206.45.93.160 Rating: N/A |
I strongly agree Cliff, finding a bad ground can cause all sorts of issues making it hard to determine where the problem actually lies Grant | ||
| Grant Thiessen (Busshawg)
Registered Member Username: Busshawg Post Number: 33 Registered: 10-2007 Posted From: 206.45.93.160 Rating: N/A |
I strongly agree Cliff, finding a bad ground can cause all sorts of issues making it hard to determine where the problem actually lies Grant | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 841 Registered: 10-2004 Posted From: 216.9.250.28 Rating: N/A |
Cliff maybe I missed something! A ground is a ground period and the poster asked could he use the frame as a ground for his 12v items when his bus is 24v? Though what your saying is correct regarding location of the ground for said items/s, why is it a "Bad" idea to use the frame? Where else are you going to ground? Ace | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 439 Registered: 8-2006 Posted From: 76.91.197.153 Rating: N/A |
Ace, I must have missed whatever it was you missed too. I think I know what he was trying to get at, but it didn't come out right? Of more importance, I hope John understands the necessity of an equalizer when using a 24V house system. Or in other words, just as in the posts on batteries above, not to even try to put all of the house load on the grounded 12V batt. (E me off bd, if you need a detailed explanation.) George | ||
| Ron Walker (Prevost82)
Registered Member Username: Prevost82 Post Number: 371 Registered: 11-2003 Posted From: 208.181.210.47  Rating: N/A |
A ground isn't a ground if the connection is corroded. I agree with Cliff ... I ran all my 12V house grounds back to a grounding block on the panel. I have 4 ground blocks (welded to bus frame) 2 in the rear and 2 in the front. If I have a bad ground I know wher to look. Ron | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 842 Registered: 10-2004 Posted From: 216.9.250.100 Rating: N/A |
Ron I agree but your STILL grounding it TO the frame! Re-read the original question! Ace | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 654 Registered: 11-2005 Posted From: 208.54.200.171 Rating: N/A |
If you have a bad ground on one electrical component it is not a big deal to find out with an ohmmeter or just by jumping the ground to a known good ground. If the whole electrical system goes out you know it is probably the primary battery ground connections. There are numerous ground paths in a metal bus chassis. If you weld a ground buss to a bus chassis you are using the bus chassis for ground. A corroded ground connection is the same on the chassis or a ground buss and requires the same correction? Using a ground buss just means a bunch more wires to corrode and clutter up the system. The only excuse I can see for a ground buss is on a non-conducting frame. My bus is 54 years old with a chassis ground. Almost all my problems have been corroded connections on terminal boards and on a few ground wires, but very few. Of course I don't have all the complications of solenoids and inverter/charging systems either so that makes things much simpler. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 440 Registered: 8-2006 Posted From: 76.91.197.153 Rating: N/A |
Gus, You got it. Running ground busses just takes a lot more wire. A ground wire would have to be run where a light is attached to a wooden interior wall, etc. Of much more importance is proper wiring methods, and FUSING the hot side! Didn't really want to dis the original reply, but. George | ||
| FloridaCliff (Floridacracker)
Registered Member Username: Floridacracker Post Number: 383 Registered: 7-2004 Posted From: 24.27.228.156 Rating: N/A |
Ace wrote: Why is it a "Bad" idea to use the frame? Where else are you going to ground? I will retract my use of the word "Bad" and say "Minimum Acceptable" instead. The frame is just making the ground return to the negative battery post. This could be be done with a wire, never using the frame. Manufacturers use the frame because it saves on wire and is cheaper. It will normally outlast there warranty period, and that is a primary concern for them. My primary concern is long term performance and ease of troubleshooting a problem. There are lots of ways to do this, my experience has shown me that the individual grounds on DC are the "BEST PRACTICE", yes it may cost a little more, but the better option. Best of Luck, Cliff | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 657 Registered: 11-2005 Posted From: 208.54.200.129 Rating: N/A |
Cliff, You may be right but my experience with frame grounds has shown no real problems. I have about 22 antique trucks, cars, farm tractors and the bus and an airplane. They all have chassis grounds and none have had any but minor grounding problems. The usual problem is corroded connections. A buss won't solve this problem. My theory is to not to try to solve a problem that doesn't exist. I try not to diss anyone, all I do is post my opinion based on experience when possible. | ||
| H3-40 (Ace)
Registered Member Username: Ace Post Number: 844 Registered: 10-2004 Posted From: 70.220.99.154 Rating: |
I was aways led to believe that a ground of any kind should be as short as possible! Anyone else hear this? Cliff I wasn't trying to argue with you bud, I just didn't understand why a chassis ground was a bad thing when almost everything is just that! A VERY positive ground and a sure thing would indeed be at the negative post of a battery but then you would obviously have many wires going to one post. It's much easier and shorter to ground said item/s right at the chassis, IF it's not, ah-hem, "rusty"! Again the original question was if the poster could ground at the frame for his 12v goodies while his bus was 24v? I said yes. I do it all the time as my bus is the same way! 24 volt system with 12v lights and goodies. My bus has many many grounds right on the chassis. Heck some even look like big bolts welded directly on the chassis for doing a direct ground! I will try and post a pic tomorrow! Unfortunatly, I have to work first but should be home early enough to do it! Ace | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 380 Registered: 8-2006 Posted From: 74.33.36.174 Rating: N/A |
I don't know if all converters do it but all the 12v stuff on a Vogue Prevost when Mitchel was converting them was grounded back to the battery and not the frame mine was anyway and I don't know the reason or purpose but all the grounds were in the house battery compartment | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 659 Registered: 11-2005 Posted From: 208.54.200.129 Rating: N/A |
The only possible problem I could see would be if the 24v system lost all its grounds and was returning through the 12v grounds. Not likely to happen though I've seen grounds returning through speedometer cables and cruise control systems. Gives some interesting symptoms! | ||
| Tony Gojenola (Akbusnut)
Registered Member Username: Akbusnut Post Number: 20 Registered: 11-2006 Posted From: 208.98.151.220 Rating: N/A |
Ground connections to chassis are probably the most common source of corrosion resulting in "bad grounds". This is true because of electrolysis and galvanic corrosion which occurs from passage of current through dissimilar metals. It can also result in similar corrosion at other body and chassis locations in wet conditions. This is precisely why the 4106 and later GM coaches (and maybe earlier ones as well) used a ground lug in each electrical compartment. That ground lug is connected by a heavy copper wire direct to the battery's negative terminal. tg | ||
| Stephen Fessenden (Sffess)
Registered Member Username: Sffess Post Number: 727 Registered: 1-2002 Posted From: 66.38.120.219 Rating: N/A |
GMs have riveted, not welded, frames under the skin. Every rib is a separate piece held to the skin and the next rib piece with a rivet. There would be a greater potential for bad connections through each rivetted connection. Of course the skin is holding it all together electricaclly too. Seems the best of both worlds would be a good chassis ground and a remote ground buss connected to the battery and chassis ground by a heavy wire. That would not be a bad idea in any bus. To make corrosion at the ground buss less likely It could be copper, or plated copper. But no copper in direct contact with aluminum. A lug in each compartment is a buss in each compartment. My bus has a short ground wire to a large bolt welded to the frame, then a ground wire from that bolt to a ground bus at the wiring panel. Some wiring uses the ground buss and some of the original bus wiring is just grounded to the chassis | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1133 Registered: 10-2003 Posted From: 71.58.48.228  Rating: N/A |
Don't forget how many hundreds of rivets that are connecting all the panels together and how tight they are. The amount of corrosion necessary to cause a problem here would render the body ready for scrap. Your ground problems most likely will occur where cables or grounding straps are attached to the body or pass through points on the bulkheads. | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 337 Registered: 10-2006 Posted From: 208.100.193.193 Rating: N/A |
I have found most bad grounds are at the battery connection to the chasis.. As the starter is a big , and perhaps long draw the weakest terminal will get hot. This pushes the wiring apart so the problem grows. Frequently the problem is simply that the ground bolts are iron or SS which are LOUSEY conductors. The cure is COPPER bolts, and washers and a clean ground surface. A copper lock washer will also help to maintain pressure after a heating event. Thats why those star washers are on so much of (on GM at least) the DC circuit connections. FF | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 387 Registered: 8-2006 Posted From: 74.33.46.171 Rating: N/A |
John, I looked at a new Featherlite H45 Prevost with the VIP chassis for motor homes and the 12v is grounded back to house battery bank separate from the 24v starting system and this is the way it came from Prevost I was told so there must be a reason for grounding the systems separate good luck just some info for you |
