| Author | Message | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 79 Registered: 11-2006 Posted From: 69.232.64.102  Rating: N/A |
I know someone here can help me with this. I have decided to do away with the orginal air conditioning compressor near the engine. Too maney problems with the system when I had it working. I want to use a alternater instead to run two 13,500 roof airs from the inverter while driving only. I bought a 24 volt, 225 amp alternater. It has four terminals on the back, two of which are for the battery hookup. One marked B+ and one marked B-. I assume I need to hookup those to the batteries. My batteries are in the middle, right side bay on my 40ft MCI, about 20 ft from the alternater location, old compressor location.------ What size battery cables do I need? ------- Also where do I hookup to the batteries? Do I hook up to the positive terminal on one of the four house batteries at one end of the bank and to the negative terminal on the other end of the battery bank? | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 798 Registered: 1-2003 Posted From: 67.142.130.19 Rating: N/A |
Roger, Unless someone's ripped it out, your MCI already has a massive, oil-cooled 270-amp alternator, which is capable of running your air conditioners while driving. All you would need to add is a bridge solenoid to connect your house system to the chassis system while driving. If you do decide to install the additional alternator, it will require more than ten horsepower from the engine to run it at full capacity (and, to run two 13.5's, it will definitely be at full capacity). You'll need a very serious belt to run that kind of power. Regarding the correct hookup sequence, I'd need to know the make and model of alternator, and whether it is internally or externally regulated. If the latter, I'd need to know what model regulator you will use. To carry the 225 amps 20 feet you should use a minimum of 00, 000 is better, and 0000 is better still. You should run both a positive and a negative cable. Always connect to parallel battery strings "on the diagonal" -- positive to one end of the string, and negative to the other. -Sean http://OurOdyssey.BlogSpot.com | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 80 Registered: 11-2006 Posted From: 69.232.64.102 Rating: N/A |
Sean, I read somewhere that someone used their 270 amp alternator for this purpose and latter had to replace that alternator. This one only cost me about $200.00. That is my only concern about using the 270 amp one. Roger | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 756 Registered: 8-2006 Posted From: 64.55.111.6 Rating: N/A |
Roger, How about if I play the devil's advocate for a minute? 1. Why do you think the bus alt will fail while running rwo roof airs, and the new alt you propose to purchase won't? 2. The present system uses a 1 hp condenser fan, and a 1 hp evaporator blower. This electric load is slightly more than the load of one roof air. 3. Any chance the failed alt had 10 years and two million miles on it? Now that we have this in perspective, lets think a little further. At 10 EER, two 13.5 roof airs will draw 2700 Watts. That is at 85 degrees outdoor temp. Above 85, the Amp draw will increase somewhat, to a little above 3000 at a hundred outdoor. 3000 Watts at 120 Volts is 25 Amps, so you see why two roof airs USUALLY will run on a 30 amp park service. 25 Amps at 120 Volts, is 125 Amps at 24 Volts, if inverters were perfect, which they aren't. Since a 24 Volt system runs at about 28 Volts, which will make an inverter happy, actual amp draw will be just a little over a hundred. Sean is right about "serious belt," 225 Amps at 28 Volts would require 8 1/2 hp. Somebody is going to say "Two 13.5 roof airs would only need 3.61 horsepower," without thinking of the probability of starting up with low house batts, and the air on.. Tell us what the alt model is, and we'll tell you how to wire the reg, and switch the field circuit... Regards, George | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 81 Registered: 11-2006 Posted From: 75.3.205.82 Rating: N/A |
OK George, you have convienced me. That is the knid of responce I was looking for after what Sean said. What I need is the bridge solenoid and how to hook it up. Do you know where I can get one? Thanks, Roger | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 757 Registered: 8-2006 Posted From: 64.55.111.6 Rating: N/A |
Roger, A "Bridge Solenoid" bridges the gap between the chassis electrical system and the house system. If your house batteries are already set up for 24 Volt, (Neg to Pos between each of the four, or series connected) how, or are they, being charged by the engine alt now? Sean is figuring you aren't OTR charging, I guess, anyhow the solenoid would be a 200 Amp CONTINUOUS DUTY, with a 24 Volt coil. Big terminals with his cable size recommenations, connect between the positive terminal of the chassis batt, and the positive of the house batts. The small (coil) terminal wires to the switched side of the master, so it is only energized when the master is on. If the solenoid has two small terminals, ground the other one. I would put a 5 amp fuse in the coil circuit, close to the master switch, cheap fire protection! NAPA, or an RV supply. Tell us how you are charging your house batts now please, and how your house batts are connected. Regards, George | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 800 Registered: 1-2003 Posted From: 67.142.130.21 Rating: N/A |
Roger, To add/modify George's comments: You can buy the solenoid at Grainger, among other places. Several from which to choose; as George says, get one with at least a 200-amp continuous-duty rating. Where I differ from him is in how to connect the coil terminals. I favor connecting the coil either to the relay off the alternator's "R" terminal (so the connection is made only when the alternator is putting out charge) or to the oil pressure switch (so that the connection is made only when the engine is running. On my system, I even added a delay timer between the alternator signal and the bridge solenoid, to let the engine and alternator come fully up to speed and the chassis batteries to settle before the house system connects. I found that, before adding the delay, the bridge would connect before the starter had even finished cranking. There is little doubt that you will put more wear and tear on the 50DN by running these airs on it, and that may mean having it rebuilt sooner. But I would still guess that to be less expensive than fitting a whole extra alternator, even if it was only $200 to buy, and I will almost guarantee that the oil-cooled Delco will give you longer service at those loads than the belt-driven aftermarket job. BTW, George's 8.5 HP figure would assume the alternator itself is 100% efficient in converting mechanical energy to electrical, which it is not (the inefficiency shows up as heat given off in the alternator itself). This is why you need to figure on at least 10 HP for the belt drive calculations. FWIW. -Sean http://OurOdyssey.BlogSpot.com | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 82 Registered: 11-2006 Posted From: 69.232.64.102 Rating: N/A |
Sean and George: All I know right now on the charging of the house batteries is that the inverter control panel has a switch that turns the battery charging on and off. I have a small alternator mounted over and between the radiater fan blowers over the engine. Whether it is charging the house batteries or not I do not know. I will try to find out as soon as I can. | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 83 Registered: 11-2006 Posted From: 69.232.64.102 Rating: N/A |
I went online to Granger electrical supplies and found one as follows: DC Power Solenoid, Coil Voltage DC 24 , Amps 200, Coil Type Isolated From SPNO, Coil Terminal 5/16-24 Thread, Contact Material Silver Alloy, Duty Cycle Continuous, Mounting Base Std, Bracket, Series 586, Enclosure Water Resistant. I an assuming this is the right one. I believe my 4 house batteries are set up in parrall as 12 volt system. And the 2 engine start batteries are in series for a 24 volt use. Also, Sean what kind of Relay timer do I need? I also have a question about my inverter. Is it OK for this use. From the manual it is a FREEDOM 20 INVERTER/BATTERY CHARGER. Heart Interface. In one paragraph it reads, There is a low battery cutout circuit and consideable momentary surge power is available for starting electric motors. Automatic transfer switch between inverter power and incoming AC power. Three stage automatic battery charging plus manual battery equalizing. AC to DC power converter. The inverter provides 2000 watts of voltage and frequency reglated AC power from a deep-cycle battery bank. The Output is a modified sine wave and is compatable with virtually all consumer appliances . The idle circuit reduses battery power consumption when the inverter is unloaded. The freedom 20 battery charger is electronically controled and rated at 100 amps DC (50 Amps DC for 24 Volts). There is a lot more, but I hope this will give you what you need to know to give me a good answer. Thanks for all of your help Roger | ||
| Gary Pasternak (Cessna5354)
Registered Member Username: Cessna5354 Post Number: 61 Registered: 2-2007 Posted From: 72.75.143.101 Rating: N/A |
Roger, If you have done away with your OTR air conditioning, you have two 200A 24VDC continous duty relays in your bus. They are the contactors utilized for the evap & blower motors in the MCI. I pulled mine from the forward bay ceiling, drivers side (5C). I used mine to isolate my inverter from the OTR charging system, when parked. This keeps the start batts. for starting only. Good Luck Gary | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 803 Registered: 1-2003 Posted From: 67.142.130.46 Rating: |
OK, hold everything. My recommendation to use the stock alternator and install a bridge solenoid was based on my understanding that you had a 24-volt house system. I got that understanding from you, because you told us that you had purchased a 24-volt alternator in your original post. If you have a 12-volt house system on your 24-volt bus, you can not simply bridge the two systems with a solenoid as I had originally recommended. However, neither can you use the 225-amp, 24-volt alternator you told us about initially. Before you do anything else, you need to determine conclusively what voltage your house system is using. FWIW, it will require over 300 amps to run your two A/C's on a 12-volt system, changing my earlier wire recommendations, and requiring a much larger alternator. It will also require a larger inverter. The Freedom Combi 20 inverter/charger is a 24-volt model. The Freedom Marine 20 is a 12-volt model. It is also not capable of running two air conditioners. The Freedom-20 is a 2,000-watt continuous unit; to run two air conditioners, you need at least a 3,500-watt unit. So you need to sort this out before proceeding further. -Sean http://OurOdyssey.BlogSpot.com (Message edited by Sean on March 24, 2009) | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 84 Registered: 11-2006 Posted From: 69.232.64.102 Rating: N/A |
Sean That is why I would like someone to look at my setup who knows all of this stuff. I have tryed to find someone around here but I have not had much success. Thanks, Roger | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 759 Registered: 8-2006 Posted From: 64.55.111.6 Rating: N/A |
Roger, Sean has my vote above. The solenoid you mention is correct, however, as Sean says, the system won't work. As I posted way above, and Sean says right above, two roof airs will draw 3000 Watts running, (continuous.) This will require an inverter rated at LEAST 3500 Watts CONTINUOUS. It sounds like you have a seperate 12 Volt alternator to charge your house batteries, which are connected in series-parallel, which is quite common. That's the bad news. The good news is that you CAN run a 24 Volt inverter off of the chassis side of the system, and power it thru the condenser fan solenoid, which prevents OTR A/C operation if the engine alternator isn't charging. ("R" terminal as posted above, I just didn't want to get that involved at the time.) Second piece of good news, maybe, is that I have a one-day commercial wiring job to do next week in Santa Ana, and my Lady likes to go to Pala. So, e me off bd, and lets see if we can work out a meet? George | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 805 Registered: 1-2003 Posted From: 67.142.130.14 Rating: N/A |
Roger, We're on our way to the desert east of you. At Morongo Casino tonight in Cabazon, and tomorrow we'll either be in Whitewater Canyon (N. of Palm Springs) or Box Canyon (E. of Mecca). Either way a couple of hours or so from you. We should be there (one place or the other) for a week or so. If you wanted to bring your coach out for a day, I'd be happy to look at it with you, if you don't connect with George. Keep an eye on the blog to see where we end up. -Sean http://OurOdyssey.BlogSpot.com | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 85 Registered: 11-2006 Posted From: 75.3.205.82 Rating: N/A |
George sience you will be the closest to me I will be very happy to meet you at PALA. Or if you like you can come to my place in Valley Center. We are near all of the casino's in this area. Harris about 20 minuts away and Valley View is about 10 minuets away. And if you like you can stay the night. I have 50 amp servise, and water. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 760 Registered: 8-2006 Posted From: 64.55.111.6 Rating: N/A |
Roger, The bus is apart for the repower, so we will be in a pickup truck, which will make it easy to come to you. It looks like Sat or Sun right now, but I won't know for sure until about Friday morning. As soon as I get back from work, I'll post, and we can get set up. Looking forward to meeting you, George | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 86 Registered: 11-2006 Posted From: 69.232.64.102 Rating: N/A |
George, Thats sounds great. I am really looking forward to seeing you. Thanks, Roger | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 809 Registered: 1-2003 Posted From: 67.142.130.24 Rating: N/A |
Roger, I've tried to answer your pm but your ISP is trapping my emails. You need to add me to your whitelist. Check your spam folder. -Sean | ||
| Tom Christman (Tchristman)
Registered Member Username: Tchristman Post Number: 72 Registered: 1-2006 Posted From: 66.218.33.156 Rating: N/A |
Personally believe that if you want to run one roof A/C from the inverter-great! If you want to run two or three-then just run the generator. Remember-this power doesn't magically come from nowhere. Whether you're taping off the main engine, or running the generator, you'll be burning close to the same amount of fuel to cool the bus. I would rather have all the power available at the big engine and just run the generator, then all these problems with the inverter, extra batteries, what cable size, etc will be a moot point. Good Luck, TomC | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 810 Registered: 1-2003 Posted From: 67.142.130.25 Rating: N/A |
Tom, You are right, it costs money (fuel) to run the air conditioning from the main engine or the generator. However, the cost is vastly different. The ~10hp that the alternator will rob on level ground or going up hill will cost you about .1-.2 gph. Even with an efficient 0.5gph genset, this is only 20-40% of that amount. Also, drawing this power from the alternator does not change the main engine maintenance intervals, so the oil and filter component of generator cost-of-operation goes away, and it will probably have a much smaller effect on engine life expectancy than for the dedicated generator power plant. All told, perhaps only a quarter of the cost per unit of energy than running the generator. Remember also that all the power coming off the alternator is 100% free when going downgrade, so the numbers are actually better than this in "average" driving. In our case, it costs $2.60 an hour to run the generator (at today's diesel price of $1.99 per gallon), whereas it only costs us about $0.40 per hour to run two air conditioners from the main engine while driving. Since we have a dash switch "over-ride" for our bridge solenoid, we can switch it off when, for example, climbing steep grades, to give that 10hp back to the engine. We just let the air conditioning continue to run from the batteries, then flip the bridge back on when on the downgrade. Over the course of a driving day, that's a savings of $10 or more per day by using the main engine vs. the generator at today's fuel prices; a few months ago, the savings was double that. We have a pretty inefficient (because it's huge) 1.1 GPH generator; for folks with more reasonable 0.5 GPH units, the savings would be roughly half that. But still significant. FWIW. -Sean http://OurOdyssey.BlogSpot.com | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 87 Registered: 11-2006 Posted From: 69.232.64.102 Rating: N/A |
George, I have entered a 2nd e-mail on my profile for my home computer, Thanks, Roger | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 764 Registered: 8-2006 Posted From: 64.55.111.6 Rating: N/A |
Roger, I sent an e to the home comp about 8am. Could I be caught in your spam filter? (It didn't come back, so I think I got it right?) Will be out of touch 'til morning, G | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 88 Registered: 11-2006 Posted From: 69.232.64.102 Rating: N/A |
George I received you e-mail and sent you a reply, Roger | ||
| Clint Hunter (Truthhunter)
Registered Member Username: Truthhunter Post Number: 97 Registered: 1-2009 Posted From: 24.129.235.190  Rating: N/A |
/// and with that extra ten bucks I could buy me & the dogs a round of Mcburgers when we bunk down for the night at the next Walmarked,,, ,,,this said and accepted as a possibility, I do "more than less agree" with SW. beside the measurable extra safety risk of having a second engine (location dependent)active while cruising. | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 89 Registered: 11-2006 Posted From: 75.3.205.82 Rating: N/A |
Anyone know where i can find a 24 volt 4000 to 5000 watt inverter? Thanks, Roger | ||
| Pete/RTS Daytona (Pete_rtsdaytona)
Registered Member Username: Pete_rtsdaytona Post Number: 547 Registered: 1-2005 Posted From: 97.104.19.180 Rating: N/A |
if you don't need a built in "CONVERTER / SMART CHARGER FEATURE" an MODIFIED SINE WAVE is ok then see-> http://www.invertersrus.com/5000w24.html | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 812 Registered: 1-2003 Posted From: 72.171.0.139  Rating: N/A |
Pete, He wants to run air conditioners, for which an MSW is probably not OK. MSW inverters will have another 10%-20% performance penalty running induction motors, and the motors themselves will heat up. Also, the motor performance will suffer. All of which adds up to shorter A/C life, less cooling, and the possibility that a 4kW MSW won't even start a second air conditioner. For this application, you definitely want to go with true sine wave. Roger, give Jim at Infinity Coach a call, (253) 891-0879. He's got refurbished SW4024s in stock, and I know he has or can get other models as well. I sent you a PM this morning, BTW. -Sean | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1529 Registered: 12-2000 Posted From: 76.69.143.72  Rating: N/A |
I have a Trace 4024 and love it. It can run a pair of mid 80's Dometic roof airs. I bought mine, so I wouldn't have to upgrade later, and really glad I made that choice. happy coaching! buswarrior | ||
| Roger Baughman (Roger)
Registered Member Username: Roger Post Number: 90 Registered: 11-2006 Posted From: 75.3.205.82 Rating: N/A |
In addition to the two roof air's I want to istall a auto/truck type air conditioner for the driver's area. Sean say's that the auto size compresser powered by the engine is too far from the condensor, 40 feet. What about running the compresser with a AC electric motor near the condenser in the existing condenser compartment of my MCI9? Any and all idea's will be very welcome. Roger | ||
| Peter E (Sdibaja)
Registered Member Username: Sdibaja Post Number: 281 Registered: 5-2002 Posted From: 201.130.137.133  Rating: N/A |
sure sounds like a lot of power loss making and using electricity when a direct hookup of the pump is so easy... and it works too. junkyard ac compressors are almost free, and you can use the electric clutch too. PS: those junkyard ac compressors make excellent air pumps too. | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 815 Registered: 1-2003 Posted From: 67.142.130.18 Rating: N/A |
Pete, Power is lost when converting mechanical energy to electrical and back again, it is true. However, power is also lost when pumping fluid through 85'-90' of lines. Also, in the latter case, efficiency of the system is further lost to heat picked up by the refrigerant in the lines; effectively, you are cooling the underside of the bus. Clearly, when the engine is right next to the condenser and evaporator, and the length of the plumbing is minimal, such as with a truck or car system, it is more efficient to use mechanical drive. Equally clearly, over some distance, the greater efficiency of electrical transmission (over fluid transmission) makes an electrical system more power-efficient. The question then becomes just what that distance is. Clearly, for example, the distance from the power plant to your house qualifies. I don't have the HVAC skills to do this math, but I am guessing that at 45 or 50 feet one-way distance, you are starting to come close to a draw. BTW, I question your assertion that a "direct hookup of [a] pump is so easy." There are many other factors besides hooking up the compressor, including properly sizing the compressor, choosing and acquiring the right condenser and fan for the application (the bus condenser and fan is no longer correct here), sizing and replacing the refrigerant lines, choosing the right expansion valve, ensuring the compressor gets enough lubricating oil, and determining the proper refrigerant charge. Complete kits, pre-engineered with all these items already properly sized, are, of course, available, and work well. But that's not what was asked. As I said in the other thread, this can be done, but it requires the skills of someone competent with refrigeration systems. FWIW. -Sean http://OurOdyssey.BlogSpot.com |
