| Author | Message | ||
| Christopher Goodwin (Cgoodwin)
Registered Member Username: Cgoodwin Post Number: 86 Registered: 10-2005 Posted From: 63.229.7.19 Rating: |
I am considering connecting my inverter (SW4024) to my starting batteries (2x8d) then connecting my AC units (2x 15k btw) to the inverter so that I can have AC while the bus is running from my 270 amp alternator and will shut them off before shutting down the coach. I have questions. 1) Xantrex manual says to use 0000 cable to connect the inverter to the battery bank, my inverter will be about 15' from the batterys, say 20' for safety. Do I really need 0000 cable? 2) If I need 0000 cable supplying the inverter from the batteries, can the stock alternator cable hold up or will it simply melt when running the inverter. 3) What risks are involved in doing this? | ||
| Nick Badame Refrigeration Co. (Dnick85)
Registered Member Username: Dnick85 Post Number: 155 Registered: 2-2006 Posted From: 70.208.133.237 Rating: N/A |
Hi Christopher, 0000 is a must if you are pulling a A/C load on it. Your manual should also tell you about maximum legenth of the cable run. Usually within 8 ft. The shorter the batt cable runs, the less resistance or power you will waste. Sean can confirm this also.. Nick- | ||
| david anderson (Davidanderson)
Registered Member Username: Davidanderson Post Number: 214 Registered: 2-2004 Posted From: 69.153.67.138 Rating: N/A |
I have a Trace SW2512 and have a 0000 cable from a 350 amp alternator running 22'. I did not run a ground for this as I use the coach body as one making the circuit 44'. A separate ground from the Trace back to the alternator ground would probably be better. I do have a voltage drop of 14.2 to 13.2 at that distance. Therefore, it is just barely enough to keep me in the black while running one rooftop AC. Your 24volt system should work better than 12v. However, don't use less than 0000 and consider running wires both directions. Someone else may jump in and verify this. David | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 605 Registered: 1-2003 Posted From: 67.142.130.48 Rating: N/A |
Chris, From previous threads, I understood you to be connecting the inverter directly to the start batteries for temporary purposes only. Meaning that, at some point, you would put some house batteries in, and they would be located near the inverter. In which case, you really, really want to put the inverter very close to the start batteries for this temporary use. If that's not correct, and you are planning on making this a permanent connection, then I have to advise you that 15-20' is waaay too far away. At that distance, running perhaps 200 amps, you would need 500MCM cables to deal with the heating and the voltage drop. To give you a sense of what that's like, a 500MCM cable can only be bent hydraulically, and even then the minimum radius is over two feet (for THxN; DLO is much more flexible, but hard to find and very expensive). In any case, you can't use anything smaller than 4/0 unless you fuse it at a lower value. Which may work, if you only want to run, for example, 175 amps (not enough to run two A/C's, but probably enough for one). But, as a comparison, I run 400 amp primary fuses. To use, for instance, 2/0, you can only fuse at 300 amps or less (preferably 200), which is less than the maximum capacity of the SW4024. So you will have to dial the settings down accordingly. Lastly, yes, you will need to run wires for both positive and negative. As I am sure you now know, one way around this is to put a set of batteries in place to service the inverter (house batteries). On my system, for example, the house and chassis systems are tied together with only 2/0 cables. But those cables never have to carry the full current capability of either system, and voltage drop is much less of an issue on this type of interconnection. HTH, -Sean http://OurOdyssey.BlogSpot.com | ||
| Jerome Dusenberry (Jerry32)
Registered Member Username: Jerry32 Post Number: 29 Registered: 1-2007 Posted From: 148.78.243.50 Rating: N/A |
That is quite a load to run for possible long periods of time. I would say 100 amps min to 150 amps. depends on how much the compressors run. Don't you have aux power plant and could run that some of the time. Jerry | ||
| Christopher Goodwin (Cgoodwin)
Registered Member Username: Cgoodwin Post Number: 87 Registered: 10-2005 Posted From: 63.229.7.19 Rating: N/A |
This is a short term use, but installing the inverter in the engine bay is also not recommended. In any case if I were to install the house batteries now and run the AC units while driving would it not be only a short time before the alternator was supplying the power to the house batteries to run the AC units? Perpas it would be simpler to just get the genset in place and run the AC units from this directly... What I am searching for is the simplest way to get AC while on the road for a 800 mile round trip. | ||
| Jerome Dusenberry (Jerry32)
Registered Member Username: Jerry32 Post Number: 31 Registered: 1-2007 Posted From: 148.78.243.51 Rating: N/A |
The generator sounds the best overall to me as those alternators can produse the power but assuming that it adds extra wear to it. Hate it when the alt quits. I have my SW 4024+ with the house batteries close by and in banks of 2 with switches for each bank then a tie relay for the engine batteries to connect all together. Jerry | ||
| Ron Walker (Prevost82)
Registered Member Username: Prevost82 Post Number: 324 Registered: 11-2003 Posted From: 208.181.210.47 Rating: N/A |
You could run 2 parallel 0000 to the inverters. I wouldn't use the start batteries. Ron | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 609 Registered: 1-2003 Posted From: 67.142.130.11 Rating: N/A |
"... would it not be only a short time before the alternator was supplying the power to the house batteries ..." Yes, but the house batteries, being closer and on larger cables, will absorb things like the compressor start-up surge. Also, when the compressor cycles off, the alternator will continue to charge the house batteries at a lower current. So think of these house batteries as a surge tank, or buffer. By having them there close to the inverter, you will smooth out the current-vs.-time graph. This would allow you to use smaller fuses on the tie line (say 200 amps) and larger 400 amp fuses on the mains. You should also set up the tie line to connect only when the alternator is charging. -Sean http://OurOdyssey.BlogSpot.com | ||
| Chris Peters (Chris_85_rts)
Registered Member Username: Chris_85_rts Post Number: 39 Registered: 11-2006 Posted From: 66.194.150.45 Rating: N/A |
Isn't this all about the numbers? A 15k A/C draws about 13A running at 120V. You will thus need 13 * 120 * 2 = 3120 watts from the inverter. Assuming 85% efficiency, you will need 3120 / 0.85 / 24 = 153 A at 24V. Note, at 4000W max output that would be 200A. According to this website: http://www.powerstream.com/Wire_Size.htm 0000 cable is more than enough to handle it. In fact, based on 153 A and the chart provided, you could get by with 00 cable strictly speaking. Now you can calculate voltage drop. At 20' with 0000 cable at 24V at 153A you have 0.308V drop not bad at all. But with 00 cable you have 0.49V drop, still not too bad, but that will increase your current requirements. Now, this was not an attempt to convince you to use 00 cable. It was an illustration of how you should calculate what you need to use and use safely. Personally, I spent my money on a good genset, which I knew I was going to need anyway, and less money on an inverter. I run the genset on the road to power my 2 15K A/C's and have plenty of power left for everything else. I also do not have to worry about idling too long, as that 270A alternator is not going to put out 270A at idle, so you will be sucking your batteries down. Again this was my personal decision. | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 610 Registered: 1-2003 Posted From: 67.142.130.30 Rating: N/A |
"Note, at 4000W max output that would be 200A." Umm, but the maximum output of a SW4024 is 8,000 watts, not 4,000. Which is why I suggest that no way is 2/0 allowable. Presumably, if this is to be a permanent installation, then Chris needs to engineer for the full load his inverter will be expected to carry, not just the specific load of the two air conditioners. In which case, the assumption needs to be in the range of 250 amps @ 24VDC, not 153 amps. The alternator alone will not be able to supply the full 333 amps that the inverter can demand. But there are batteries in the equation, and the combination of alternator and batteries can definitely supply this amount of current. This is why I suggested additional batteries co-located with the inverter, not 20' away. On DC power, 2% is generally considered the maximum allowable voltage drop. So even at 153 amps, 2/0 yields an unacceptable drop. At 250 amps, you are well over the NEC rated capacity of 2/0, and even 4/0 yields an unacceptable drop. You need to go to 250MCM. At the maximum surge rating of the SW4024, drawing 333 amps, you need to go at least to 4/0 even to be legal, and then if you have a 20' run, you need to go to at least 300MCM (although, admittedly, not 500 as I suggested earlier) to be under 2% drop. (2 x 4/0, as suggested by Ron, would also work, but care must be taken to ensure both cables are carrying their share of the load). So I stand by my original numbers, with the one revision of 500MCM down to 300MCM (still a massive cable, and hard to run unless you use DLO). Also, don't forget, you need to adjust all numbers for heat, as applicable. And I would de-rate substantially if the cables will run (1) outside of conduit and/or (2) next to anything inflammable. Remember, electrical overheating is among the leading causes of RV (and home) fires. -Sean http://OurOdyssey.BlogSpot.com | ||
| Kevin Black (Kblackav8or)
Registered Member Username: Kblackav8or Post Number: 65 Registered: 8-2005 Posted From: 24.152.174.198 Rating: N/A |
It would seem to me that running AC through an inverter is very challenging. Seems like a generator or something like this might be a better means to an end. http://www.willisapu.com | ||
| Christopher Goodwin (Cgoodwin)
Registered Member Username: Cgoodwin Post Number: 88 Registered: 10-2005 Posted From: 71.212.51.75 Rating: N/A |
OK, So I need to mount the inverter very close to the batteries, right above them would be optimum. Once I do this what gauge cable should I run from the alternator to the batteries, this is a 15' run minimum as the nearest bay is about that far from the alternator. My real issue is that I am still unsure of the management of real estate in the bays and on this trip I only need the AC units to function while driving so I am looking for a short term solution. It seems that the best option is to install the genset and plug the AC units into it for this trip. Today I mounted the second AC unit and connected the two with PVC outdoor rated conduit filled with 10g wire along the top of the bus between the two roof top hatches (which I had to make from scratch, wood base, 5052 aluminum tig welded covers, gasket from the original hatches) from the rear hatch I will drop the wire into the bus and down a wall in conduit and into the plumbing chase from the engine bay to the first cargo bay where I plan to mount the generator tomorrow. Each AC unit will have its own supply plugged into the respective 27amp 110vac breaker protected outlets on the genset (Honda ES6500 6.5kw gas genset converted to Propane). The propane bottles will be in a plywood box with ventilation through the bus floor, the genset will be in another box with a 110vac fan sucking air in and blowing it out through the floor of the bus. 5 days to departure, Seattle to Boise, 100F+ weather, the cascades and the blue mountains.... | ||
| John MC9 (John_mc9)
Registered Member Username: John_mc9 Post Number: 452 Registered: 7-2006 Posted From: 66.217.102.126 Rating: N/A |
Re: "I need to mount the inverter very close to the batteries, right above them would be optimum. " Optimum for a large amount of acid fumes on it's circuit board? Sparks from a fuse or breaker detonating the hydrogen? Call me crazy (everyone else does), but personally, I'd use another bay/area... | ||
| Christopher Goodwin (Cgoodwin)
Registered Member Username: Cgoodwin Post Number: 91 Registered: 10-2005 Posted From: 71.212.51.75 Rating: N/A |
Point taken. Near the battery bank but isolated from it, battery compartment ventilated. I have seen many battery explosions and fires in nearly 30 years as a mechanic, the typical one is during sudden load (starting) or while removing jumper cables. When wet cell batteries get low they off gas hydrogen like the hindenburg, a spark or arc is all that is needed for a lovely explosion spraying acid everywhere. Too bad AGM cells are so expensive.. | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 611 Registered: 1-2003 Posted From: 66.82.9.58 Rating: N/A |
Chris, With batteries near the inverter, I would wire using 4/0 from the batteries to the inverter, and you can probably get away with 2/0 from the chassis system (alternator) to the house system, with a 200a fuse. Mind you, you will still need separate start batteries with this arrangement. Starter current is immense, requiring 4/0 all on its own. That being said, if all they are doing is starting, you can get away with pretty small batteries. We start Odyssey with a pair of Group 65's. -Sean http://OurOdyssey.BlogSpot.com | ||
| Chris Peters (Chris_85_rts)
Registered Member Username: Chris_85_rts Post Number: 40 Registered: 11-2006 Posted From: 66.194.150.45 Rating: N/A |
This is a great discussion, lots of numbers. I am curious about a few things. 1) The tie line between the chassis system and the house system being sized lower (200A) than the current the chassis system could possibly provide (270A). Is the presumption here that the house batteries will always provide the bulk of the current needed, and the chassis system will only need to supplement? It concerns me that if the house batteries are nearly dead, one might start the coach, rev up the engine, and turn on the A/C's. The nearly dead house batteries would want to draw current from the chassis system to charge, but the 4024 would also be wanting currnet, the chassis system would try to provide the full 270A it can, and you'd blow the fuse (to protect the wire from buring up if it was 2/0). So you just blew a fuse to save a few bucks on 2/0 versus 4/0 cable? 2) According to the Trace manual, the max DC required current is 360A with a shorted output. Hopefully that will never happen. The DC required at full rated power is 200A. But then we have a surge capabilty of 333A. In general is wiring designed for surge, or continuous? I am guessing the numbers we see for wire ratings are continuous. If we could dig a bit deeper, you could probably find ratings for wire under surge of a given duration. I would think the surge requirements for the SW4024 would be short in duration or the thing will shutdown. Interestingly enough, in looking at the SW4024 manual on line I could find no dicussion of the surge rating, Amps or Duration. Basically they recommend 4/0 cable, and a 400A fuse for any installation less than 10'. They don't even discuss greater than 10' for the 4024. They mention 20' for the 48V inverters, but again that uses 4/0 cable. Seems they assume here that no one is going to typically use larger than 4/0 cable. 3) Also I think it is important that you run your cables in "free air". Also, the manual has a long discussion on inductance, and recommends the supply and return cables be tied together as closely as possible. | ||
| James Stacy (Jimstacy)
Registered Member Username: Jimstacy Post Number: 77 Registered: 1-2001 Posted From: 75.40.255.157 Rating: N/A |
Christopher, Perhaps the best kept secret in wet cell maintenance is the Hydrocap, a catalytic replacement battery cap (one per cell). This cap, when properly sized for the application, recombines the gasses into liquid and returns them to the cell. Results: No corrosive vapors in the battery area. Almost zero water use. Check every 6 months w/probably no usage. Helps keep impurities out of cell. Probably saves about the $7 cost the first year in distilled water saving in high usage applications. A really GOOD product. I have no connection with this company other than being a happy customer for nearly ten years. They are in Miami, 305-696-2504. Jim Stacy | ||
| Christopher Goodwin (Cgoodwin)
Registered Member Username: Cgoodwin Post Number: 92 Registered: 10-2005 Posted From: 63.229.7.19 Rating: N/A |
I find it odd that there is not a simple guide to the use of this inverter in bus applications, there seem to be a lot of people using them. I too am concerned that if I use 2/0 cable from the alternator to the battery bank and drive for 6 hours with both AC units running that the bank will run low and the inverter will then want to draw enough juice to run the AC's and recharge the bank all through a 2/0 cable... | ||
| Jerome Dusenberry (Jerry32)
Registered Member Username: Jerry32 Post Number: 33 Registered: 1-2007 Posted From: 148.78.243.51 Rating: N/A |
It does sound iffy with no backup plan to use. The alternator should carry the load though but the voltage may gt on the low side and still operate. The A/c units should continue to operate down to 105 volts but the invertrer may drop out if gets too low. then you would have to reset it. Jerry | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 671 Registered: 10-2003 Posted From: 71.58.117.21 Rating: N/A |
Unless the price has suddenly dropped, those Hydro caps, although the cat's meow, are pretty expensive to install when you have more than one battery-6 per battery at something like 5.95 or more each? They are supposed to be replaced periodically. | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 672 Registered: 10-2003 Posted From: 71.58.117.21 Rating: N/A |
I believe that the some of the city busses use a 360 or 450 amp oil cooled direct drive alternator, which would probably fit the same location. | ||
| JR Lynch (Njt5047)
Registered Member Username: Njt5047 Post Number: 172 Registered: 7-2006 Posted From: 69.132.237.9 Rating: N/A |
Interesting discussion. Wouldn't the cost of operating an engine driven alternator (in fuel consumption) be similar to the cost of running an appropriately sized diesel genset? And a decent quality diesel genset would be much less problematic. I would expect that the huge constant load on the bus alternator will do it no good. Operating an old bus alternator at max output for extended periods will likely open your wallet...and PO your spousal component when it fails. Most folk cannot travel in a coach without AC during hot weather. I doubt that the bus alt can maintain the output required to power two ACs unless operated at highway speeds. A 50dn alternator failure on the road could set you back a couple thousand bucks...depending on how creative a mechanic you may be. FWIW, I agree with the genset approach to power the AC. Especially if you need both ACs to operate at the same time. Or, fix the bus OTR air...which is a bad idea really. You'll need a genset anyway whenever the bus is idled for long...even in traffic..or the engine is shut off. Or, horror of horrors, the bus engine shuts down unexpectedly. You are taking out vital redundency using the bus alternator to supply all electrical power for all systems. The house batts offer some buffering capacity, but every amp used must be returned. Good Luck, JR | ||
| Kevin Black (Kblackav8or)
Registered Member Username: Kblackav8or Post Number: 67 Registered: 8-2005 Posted From: 24.152.174.198 Rating: N/A |
My vote is for the genset also. More versatile and in the long run I think more reliable and probably ultimately cheaper and simpler. On edit. I just spoted this on Ebay. Not enough for 2 AC's but might be adaptable to charge up batteries or something. Cheap enough to experiement. http://cgi.ebay.com/Generac-Auxillary-Power-Unit-APU-4-5DC-NEW-3-Phase_W0QQitemZ170130341981QQihZ007QQcategoryZ106437QQrdZ1QQssPageNameZWD1VQQcmdZViewItem (Message edited by kblackav8or on July 26, 2007) | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 613 Registered: 1-2003 Posted From: 67.142.130.11 Rating: N/A |
Wow, lots to answer here. "1) The tie line between the chassis system and the house system being sized lower (200A) than the current the chassis system could possibly provide (270A). ... The nearly dead house batteries would want to draw current from the chassis system to charge, but the 4024 would also be wanting currnet, the chassis system would try to provide the full 270A it can, and you'd blow the fuse..." This has to be a "managed" connection. You only want to allow it to connect when the draw will be 200A or less. There are devices to do this, or you can just monitor it and not turn AC loads on until the charge current has dropped. We have a shunt on our intertie, and it might spike a tad above 200A when it first connects, but always drops below that number within four or five seconds. A slow-blow fuse could handle this. Remember that the much-vaunted 270-amp rating of the 50DN is an absolute maximum -- under most circumstances, it puts out less than that. On top of which, you will have up to 30 or 40 amps of "chassis" loads that will come out of that number before there is any left to transfer to the house side. This includes charging the chassis batteries. "...I am guessing the numbers we see for wire ratings are continuous. If we could dig a bit deeper, you could probably find ratings for wire under surge of a given duration..." The NEC does not allow ratings this way, except for motors with time-delay protection. You can not assume that the SW4024 itself will act as a current-limiting device, and so the cables and fuses need to be sized for the maximum current, not the usual continuous current. In other words, you need to assume the maximum possible current will be carried continuously -- to do otherwise is to invite overheating. "...Also I think it is important that you run your cables in 'free air'." Umm, if it's enclosed in a bus, by definition, it is NOT in "free air." Free air means just that -- nothing but air on ALL sides of the cable for a meaningful distance (in this case, several inches). The minute you strap that cable to a wall, put another cable (or more) right next to it, or enclose it in a wall, chase, etc., it is not considered free air, and you need to de-rate accordingly. Again: NO use in a motor coach would be considered "free air" and so the "free air" rating is NOT the appropriate rating to use. (The number is published for engineering purposes only.) "...No corrosive vapors in the battery area. ..." HydroCaps(TM) and their competition explicitly disclaim this -- they will not guarantee that no dangerous hydrogen gas will be emitted. Putting anything that makes sparks (and that includes any inverter) above flooded batteries is a recipe for disaster -- don't do it. "... I find it odd that there is not a simple guide to the use of this inverter in bus applications, there seem to be a lot of people using them. ..." Outside of the professional converters such as Marathon and Vantare (who have already got it figured out), the number of SW-series inverters put into on-road vehicles is a drop in the bucket. Perhaps dozens sold per year, compared with thousands of other models installed in coaches. On top of this, Xantrex *knows* that the SW-series in vehicle applications is a HUGE liability, since there are several design defects. (This product would not meet today's standards for RV equipment.) They don't want to assume additional liability by publishing bulletins or in any way encouraging use of this product. Which is why you may get the feeling you are "on your own." "... The A/c units should continue to operate down to 105 volts but the invertrer may drop out if gets too low ..." The SW-series has fully settable limits. I run mine with a low-voltage cut-out of 96 volts. I generally try not to run the A/C's below 100. "... I believe that the some of the city busses use a 360 or 450 amp oil cooled direct drive alternator, ..." The Delco 50DN alternator we have been discussing IS a direct-drive, oil-cooled unit, and is the largest Delco makes. Remember, this is 270 amps at *24* volts, or 6,480 watts. I think you might be thinking of the 12-volt model, which typically comes in a 350-amp rating, but, at only 12 volts, that's just 4,200 watts. "... Wouldn't the cost of operating an engine driven alternator (in fuel consumption) be similar to the cost of running an appropriately sized diesel genset? ..." Not even close. My genny, which is admittedly too large, runs about 1.1 GPH at average load. Even a set sized more appropriately will run around .6 to .8 GPH. By contrast, the delta on fuel consumption on my 8V92TA between "chassis-only" alternator load and "full interties capability" (around 200 amps) is between .1 and .2 GPH. The difference in operating cost gets MUCH bigger if you factor in everything else (genny oil and filter changes vs. the incremental load on the big diesel). We use our generator when we are parked. If we are running down the road, the 50DN provides all the juice we need at a mere fraction of the cost of running the genny. -Sean http://OurOdyssey.BlogSpot.com | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 614 Registered: 1-2003 Posted From: 67.142.130.11 Rating: N/A |
Kevin, (1) Could you please re-edit your message with a shorter link? That monster is making the whole thread difficult to read (the line length is now bigger than my, and most, screens, requiring scrolling back and forth). (2) The link you posted is either for a three-phase generator, or a 96VDC generator (the rating plate is confusing on this matter). In either case, not particularly useful in most bus conversions without a complete re-wire of the head -- beyond many people's wherewithal. (3) It is also a LPG/CNG unit, again not particularly useful for the bus crowd (although I know some folks are using LP units). Diesel is a much more efficient and certainly much safer alternative. (4) It's a Generac. For a lot of people on this list, one need say no more. FWIW. -Sean http://OurOdyssey.BlogSpot.com (Message edited by sean on July 27, 2007) | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1957 Registered: 1-2001 Posted From: 75.108.73.6 Rating: N/A |
Thanks for the tip Sean. I was wondering why all of a sudden the posts were not wrapping properly to read. Richard | ||
| Christopher Goodwin (Cgoodwin)
Registered Member Username: Cgoodwin Post Number: 93 Registered: 10-2005 Posted From: 71.212.72.228 Rating: N/A |
Sean- you say that when running down the road your alt provides all the power you need. So if you are running and have your AC units on, they are being powered by your batt bank. When the bank drops to 50% or 60% your inverter charger must kick in to recharge the batteries from someplace. Soes it start the genset? or does it simply cut AC power until the alt has brought the voltage in the bank back up? You have 6 8d cells if memory serves me, do you think this sufficient for running two AC units while driving? I finished playing with my Honda ES6500 genset converted to propane - I already need propane for my Jenn Aire grill in the kitchen so it seemed to make sense to convert to propane rather than carry yet another fuel on board. I am installing it today in the rear most bay and have run the AC wiring there already so it is almost test time.... I understand that Xantrex is not interested but there are all these busnuts who spend hours a day typing, you would think one would simplify the installation and write it up. I know you Have Sean but it is quite a system. Have you thought about writing a guide to the SW4024 installation in coaches with simple and complex systems? | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 616 Registered: 1-2003 Posted From: 66.82.9.53 Rating: N/A |
Chris, When we are underway, the house batteries are really only providing current to start the AC compressors. Once they are running, the draw is only around 150-160 amps (@ 24VDC). That's with two units running, one roof unit upstairs, and our funky home-brew dash unit downstairs, which uses a bit more current. Our intertie is capable of 200 amps -- we have a 200-amp continuous-duty solenoid, and 200-amp shunt with bi-directional meter on it to monitor the flow. And 200 amps is just about what's left on the alternator after chassis loads are met (we *always* run with all our lights on, for example). So after the 160 amps or so of A/C, there is still around 40 left over for house battery charging. In practice, because the intertie cables are long (~20'), the voltage drop is enough to ensure that the house battery charging will happen at a lower rate (than if those batteries were closer to the alternator), so, after a minute or two of running, the batteries can seldom take even this much charge anyway (although, when they are waaay down, we've seen over 100 amps flowing to them through the intertie). We actually have eight 8D AGM batteries, 220AH each. Not only is that enough to provide a good buffer while driving, it's enough to run one air conditioner for six to eight hours while we are parked, and we have done so on many occasions. For example, where we are now (in Zion National Park), generators are only allowed four hours a day: 8-10am, and 6-8pm. Having the ability to run the A/C from the batteries during the hottest (=94°) part of the day has been very handy. As for writing a guide, well, sometimes it seems like I've done enough typing on these boards to have written a guide several times over. But the reality is that every installation is different, and I wouldn't know where to start. Besides, the guides already written by George Myers, Dave Galey, and others already provide many of the basics, and, of course, the archives here provide a wealth of information (although it seems few people check them before asking questions that have been asked and answered many times). -Sean http://OurOdyssey.BlogSpot.com | ||
| Christopher Goodwin (Cgoodwin)
Registered Member Username: Cgoodwin Post Number: 94 Registered: 10-2005 Posted From: 71.212.49.21 Rating: N/A |
I will take that as a "No" then. I checked the archives several tiems, read arguements and discussions, one about using a manual plug to make or break the ground another about running AC untis off house batteries and everyone told the guy he was nuus, etc. WHat does not exist is even a basic guide specific to the SW4024 whihc covers these issues without wading through page after page of seemingly contradictory information or jumping back and forth between manuals for different models. I have several texts on Marine wiring, living on 12 volts, the Galey books, about 4 texts on solar systems and I am no fool, if this seems difficult and contradictory to me then I can assure you, others have difficluty with it as well. I have to ask, why the bi-directional meter? | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 621 Registered: 1-2003 Posted From: 67.142.130.30 Rating: N/A |
Chris, Good point about the contradictory information in the archives. What I learned early on in my BBS history is that any board, whether it's about buses or basket-weaving, has some number of people who know whereof they speak, and dispense good advice, and there are some who just think they know whereof they speak, and dispense advice anyway. And then there are always some who have to comment on every thread, whether they know anything about it or not. So, in combing the archives for good information, it helps to first develop a sense of who the relevant contributors are, and who the know-it-alls are, and view the advice through that filter. FWIW. And, rather than say "no", I will reiterate that I would be happy to contribute to your effort -- but I don't want to spearhead it. You could probably go back through the archive on this board and the MAK board (which, unfortunately, did not start archiving until after my 500th or so post over there) and collect everything that I've said about the SW series, and maybe everything Jerry Liebler has said, and there are probably one or two other folks with good experience on the SW series whose names are not popping in to my head right now, and have a good starting point. And I'd be happy to help and to review whatever you put together. As for the bi-di meter: It is possible for current to go either way on the intertie. For example, when the main engine is not running, but I want to put some charge on the chassis batteries (say we've been sitting parked for a month -- rare for us, but it does happen), I will activate the manual override on my bridge solenoid while the SW4024 is charging, and I can use this to monitor how much current is going to the chassis side. More importantly, if I get into a situation where the chassis batteries are so far down that they will no longer turn over the engine, I can use this bridge solenoid override to "jump start" the engine from the house batteries. Because my intertie is really only good for 200 amps continuous, I want to be able to see how much current the chassis system is pulling in from the house system during this emergency start procedure, to make sure I don't overload the intertie. -Sean http://OurOdyssey.BlogSpot.com | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 622 Registered: 1-2003 Posted From: 67.142.130.30 Rating: N/A |
Kevin Black: Could you *please* take that enormous eBay link out of your last post? It's really making it a PITA to continue to read this thread, and it affects the whole thread back to the beginning for everyone who visits here. There are much shorter ways to link to a specific item on eBay. For instance, this one will work fine for that item: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=170130341981 (And, for URLs that are not so easily shortened, there is always TinyUrl.com and its cousins.) Thanks! -Sean http://OurOdyssey.BlogSpot.com | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1958 Registered: 1-2001 Posted From: 75.108.73.6 Rating: N/A |
I@N,I@N,I@N,I@N,I@N,I@N,I@N, Can you please help Sean get rid of that link? Richard | ||
| Christopher Goodwin (Cgoodwin)
Registered Member Username: Cgoodwin Post Number: 96 Registered: 10-2005 Posted From: 71.212.48.143 Rating: N/A |
I believe your browser has a "wrapping" setting. Great Sean, I run a very active forum and know exactly where you are comming from, I have made a great many enemies by pointing out this behavior. I have several who will post volumes in reply to any question without understandign the intricacies of the system they are dispensing advice about. I correct them and some times I do it politely other times I tell them that their head is in thier backside and they are giving dangerous advice because they ahve no idea what they are talking about, at times I simply delete the post entirely. Some appreciate it others think me a Nazi. It's funny that a month after such an incident the same person is posting my corrected advice as though it is what they have been doing all along. Please do not take offense to this. I find your understanding of electrical systems admirable, but your convience of the information can be difficult to understand. I find this frequently with people you have a deep understanding of a particular system and assume that others do as well, a perfect example is a German technical manual, if you are not already a good mechanic with a background in German vehicles, they make no sense, if however, you are, they are simple, concise and to the point. Unless there is another Inverter which is better suited then I think a compilation needs to be made concerning the use of the SW4024 in this application, I bought mine based on your webpage and the comments of a few others. They are not inexpensive, they have a great number of features, and are very applicable. There is however no simple clear cut guide to thier use. Many points are beyone debate (IMHO) such as the neutral/ground bonding and breaking it & wire gauges for runs. These need to be put together in one place. One of my favorite sayings I learned from an old man when I was young enough to think him old was: "You have to know the rules before you bend them and when you know just how far they can be bent without breaking you can then push the envelope. If you know nothing, you better find someone who does" | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1046 Registered: 12-2000 Posted From: 70.53.130.135 Rating: N/A |
Hello. For those who are hesitant to use their big Delco... The stock HVAC in the coach had two big fans for the AC, condenser and evaporator, which were 1 or 1.5 HP each. In rough calculations done a long time ago, the SW4024 is pulling close by the same power that the big fans did, if it is running two roof airs. That's why I bought the 4024, and stopped thinking about it. Love this thread! happy coaching! buswarrior | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 235 Registered: 8-2006 Posted From: 207.231.81.129 Rating: N/A |
Sean, I agree wholeheartedly with your post of July 28. The first two paragraphs echo my sentiments exactly. In the interest of safety, I will extend an offer of help also. I imagine this will provoke a rash of comments about "who do they think they are," but if we keep one person from following bad advice and starting a fire, we will have done well. I also feel this should be limited to Electrical, and HVAC? It is also interesting that I mentioned in another article, the person you mentioned as being qualified. So, where does it go from here? George |
