| Author | Message | ||
| chuckMC8 (68.211.10.67)
Rating: |
Like everything else on the bus conversion project, Theres many things that go into the planning of each "System" on the rig-I guess that's what makes it challenging. Just assembling and installing the proper collected items isn't a big deal (Usually), It's figuring out what you need to do what you want,make sure they are compatable,and to make those items work together properly, And THEN, acquire the necessary parts and pieces on your budget. I do not have the time,energy,or money for "Do-Overs" at this point. After busting it for nearly two years, I've finally gotten the bus drivable, and am looking forward to "Using" it. Sorry for the rambling on........Heres the question. I had posted a question regarding house batteries. Thanks for the replies. I've bought 6 Trojan T-105 Golf Cart Batteries ($59)each. I also posted on the flea market section that I need an inverter. Thanks for the prompt, helpful and kind responses. There are quite a few to choose from. In looking at all the options available, It wasn't my original plan, but I feel that I should also consider the prospect of running my front roof air off an inverter. I'm kind of perplexed as to the equipent needed to make that happen. I have a Duo-therm 13,5 Btu model. I need to know how many amps it "Draws" on start up. I havent had any luck with the mfg on this info. (although that being said. I just tried to call and the only way to access the techs is thru e-mail question, and of course, I just wanted to speak to someone). So, I was able to contact an inverter Mfg tech.I spoke to a sweet California girl who answered the phone, told her what I wanted and next thing I'm talking to a jerky guy with a heavy middle eastern accent (isnt that always the way now?) Outsource that Job! Anyway, I want to know how big of an inverter that I need to run the A/C, And I know I didnt have the information that he needed, (Start up amps)but he could have been nice, none the less) And the third variable is the alternator that I plan to add to the engine for the house batt bank-I had thought of just buying a 12v delco one wire and letting her fly.....But, Seems like the alternator needs to be sized to the inverter, (if its running a a/c) If its output is less that the inverter is drawing to power the a/c, Well, that couldnt work out in the long run. I had read where Fast Fred had reccomended using 3 stage external regulator thats made for house batt banks that properly charges the system. All this has got to live together......Thoughts? What have you guys put together thats doing what I'm thinking about (thats scary)and its proved satisfactory? THanks for the help. Chuck | ||
| TWO DOGS (63.185.80.155) Rating: N/A |
guess lots of people are going to try to prove me wrong....an air cond. uses LOTS of elec......myself....will use a/c only while plugged in to power pole...and if I win the lottery ,will buy a generator... | ||
| Geoff (Geoff) (66.238.120.27)
Rating: N/A |
You didn't say whether you are going with 12v or a 24v house system. If you go with 12v you should get at least a 160 amp alternator, although a 200 amp would be better. The A/C unit is going to draw around 12 amps at 120v, which is 120 amps at 12v. Surge is probably 18-20 amps. Alternators, even big truck ones, get hot and don't put out the advertised amperage so it is always better to go bigger. And these truck alternators get very pricey once you go over the standard 130 amps. If you are going with 24v, your bus alternator would power a 24v inverter and run a roof air with no problem, but then you would need equalizers to get your house batteries down to 12v for conversion use. Which inverter to buy?-- I highly recomend the Trace SW series, they cost a little more, but the added features are well worth the extra money. | ||
| John the newbie (199.232.244.28) Rating: N/A |
Divide the watts by the voltage and you will arrive at the amps. 120 (volts) into 2040 (watts) will be 17 (amps) Likewise, multiply the amps times the volts and you'll get the watts. 17 (amps) times 120 (volts) equals 2040 (watts). The DuoTherm 13.5 specs are: Amps 11.0 cooling, 12.7 Heating w/optional heat strip (http://www.pplmotorhomes.com/parts/rv-air-conditioners/duo-therm-rv-air-conditioner.htm) That's quite a load on 12v batteries! This link will provide you with some more info: (http://www.batterystuff.com/battery/solar-tutorial.htm) 12 volt inverters require approximately ten (10) amps DC input for each 100 watts output power used to operate an AC load. 24 volt inverters require approximately five (5) amps DC input for each 100 watts output power used to operate an AC load. Do the windows open? | ||
| John da newbie (199.232.244.28) Rating: N/A |
Oh, and this link might be of some help also: http://www.all-battery.com/index.asp?PageAction=Custom&ID=40 Take note to their comment: "When operating the inverter with a deep cycle battery, start the engine every 30 to 60 minutes and let it run for 10 minutes to recharge the battery" | ||
| TWO DOGS (63.185.81.70) Rating: N/A |
plus...how many times can you run the battery down and recharge it....every 60 minutes... | ||
| John da noooobie (199.232.244.28) Rating: N/A |
They said it best at that link: "500 Watt and larger Inverters: We recommend you use deep cycle (marine) batteries which will give you several hundred complete charge/discharge cycles. If you use the normal vehicle starting batteries they will wear out after about a dozen charge/discharge cycles. If you do not have a deep cycle battery, we recommend that you run the engine of your vehicle when operating the inverter." Yeow. $$$$$ | ||
| TWO DOGS (63.185.64.166) Rating: N/A |
that's about 3.00 an hour...lets see...72.00 a day for a/c | ||
| Jon the newbie (199.232.244.28) Rating: N/A |
It's going to make you feel cooler without all that insulation from that cash in your wallet! | ||
| TWO DOGS (65.177.144.211) Rating: N/A |
if you use a/c 12 hours a day...that's only $11,000.00 a year for a/c | ||
| James Maxwell (Jmaxwell) (66.81.33.183)
Rating: N/A |
If u are going to use the roof A/C down the road from the inverter, I would agree w/ Geoff and his recommendation of the Trace SW Series or for a little less money, the PS Series (does not have the grid sharing capabilities of the SW Series). Modified Sine Wave type inverters are not satisfactory for inductive loads such as an A/C compressor and they will cause about 20-25% loss of efficiency with the AC unit. My PS 2500, 24v, was $1800 w/ remote digital meter and control abt. a yr. ago. With an equalizer for your 12v load, I consider this the preferable system, since I can use the Delco high capacity alternator that came with the bus, but my bus came with a set of equalizers, so I didn't have to buy one, which can be pricey if u don't shop around. | ||
| Don KS/TX (66.82.9.29)
Rating: N/A |
I am not so sure about the 20-25% loss of efficiency James, where do you get that figure? I had a Heart 2500 and ran the Coleman AC from the inverter powered by the regular 24v bus alternator, and I could never tell any difference between that and shore power, neither could others. | ||
| Sean Welsh (Sean) (64.81.73.194)
Rating: N/A |
Don, How would you know if it was being less efficient (meaning: using more energy and getting hotter internally to achieve the same set-point) unless you had a true, load-factoring power meter on the circuit? Not sure where James is getting his specific numbers, but that sounds about right for a "modified" wave powering inductive (motor) loads. -Sean | ||
| Chuck Lott (Chuckmc8) (68.211.10.67)
Rating: N/A |
I have a Onan 7kw that I can use whenever I wish to run the A/C's. Sorry I didnt make that clear in the original post. I would'nt try to run the a/c's from the inverter without the bus engine running. I also have engine A/C for the road. I'm just weighing my options regarding the inverter. Thats intriguing about the 24v option, I hadnt considered that. Thanks for the input...Chuck | ||
| Don KS/TX (66.82.9.49)
Rating: N/A |
Well Sean, that is why I asked the question. I hear that a lot, but as I said, they seemed to get just as cold and run just as well off the inverter (which was not a sine wave job of course). I and others have found the AC will run for hours on end, cooling just as well in our opinion. I would have to assume that a 25% reduction would be something you could notice pretty easily, right? | ||
| Richard Bowyer (Drivingmisslazy) (66.168.168.57)
Rating: N/A |
I have never seen anything in writing from a test lab or other verifiable, knowledgable source that would indicate that an ac motor performs less efficiently on a modified square wave. The motor is a large inductor and an inductor is utilized in ac circuits as a filter and to shape the wave shape. As an example, ac motors work very satisfactorily on a Pulse width modualted signal which consists of 2500 or more pulses per second, and varying in width to simulate an ac signal. If you look at the PWM signal on a scope, all the pulses are of the same amplitude and the pulses are really dc pulses being varied in width. A large majority of motors in industrial applications are being operated on PWM in order to obtain accurate speed regulation. Until someone furnishes test data performed by a certified lab that would indicate otherwise, I personally think that it is just an old wives tale (and FF) that there is a large reduction in efficiency. Some people who do not understand electrical power will look at the amps being consumed and think that an increase in amps indicates an increase in power and nothing could be further from the truth. What is really happening is that the power factor may be changing and increases the amps, but that is not actual power. It is apparent power. Unless you have a true power meter that measures both kva (apparent power) and KW (real power) you can not determine the efficiency of the motor. Richard | ||
| Sean Welsh (Sean) (64.81.73.194)
Rating: N/A |
Don, A loss of efficiency will not necessarily manifest itself as a reduction in output, which was my point. Output temperature (at any given set of inside and outside ambient temperatures and humidities) is governed strictly by the physics of the refrigeration process, and has nothing at all to do with how efficiently the motor converts electrical energy into mechanical energy. The assertion here is that the motor uses more electrical energy to do exactly the same amount of work (and thus, unnoticable at the output) when supplied by a square-wave source than a sine-wave source. Where does this excess energy go? Into inductive heating of the motor itself. (The motor's own heat is such a small part of the cooling process that this additional heat would not be noticeable from inside the vehicle). If you measured the case temperature of the motor itself, you would find it to be higher (under the same circumstances) when running on your inverter than on shore power. This has two implications. (1) You draw more energy from your battery bank when running an A/C through a MSW inverter than you would running it through a true-SW inverter. And (2) the extra inductive heating in the motor contributes to shortening the life of the motor. -Sean | ||
| Sean Welsh (Sean) (64.81.73.194)
Rating: N/A |
Richard, Here's something in writing from a test lab: http://ece.clemson.edu/power/pqia/pdfs/acpart1.pdf As with most of the research in this area, this one specifically applies to three-phase motors, so the results are not necessarily applicable. I don't know enough about roof air motors and their associated circuitry to know what the exact effects will be of non-sinusoidal waveforms. I was simply pointing out that, as you say, one needs a true power meter to know -- one can't tell simply from casual observation of the cooling performance of the unit. Personally, I would not subject motors to MSW waveforms. The upcharge for a true-SW from a quality MSW unit is minimal, compared to the investment I have in air conditioners and 120-volt pumps. -Sean | ||
| Richard Bowyer (Drivingmisslazy) (66.168.168.57)
Rating: N/A |
For some reason my computer will not open that file. However I can well understand your personal preference to to not utilize MSW inverters. That is what the world is about. Personal preferences. My personal preference is the same but that does not mean the MSW inverters would harm anything in my bus. If fact I operated for about 15 years with a MSW inverter and never noticed any harmful effects to any of the electrical or electronic devices I had installed. Richard | ||
| Don KS/TX (66.82.9.66)
Rating: N/A |
Well, in all my years with MSW I did find one problem Richard, my X10 remote light control system just would not work on it. With the keyring remote, I could tell I was on inverter power when I drove in at night and could not light up the bus from the entrance to the park. Then again, that was not really a problem, it alerted me to the fact that the power was off in the park, or someone had pulled a prank and unplugged my unit. The X10 signal was the ONLY thing I found bad about the MSW, computer, printer, everything else worked like it should. The AC units motors have a thermal cut off if they get hotter than designed to operate, they never did upset the thermal switch. Another factor most people ignore, the roof units are made to be MOVING down the road for cooling, and that of course is the only time you use the inverter/bus alternator, so maybe, just maybe, they run cooler with the inverter than sitting in a park on shore power, reckon? | ||
| Buswarrior (Buswarrior) (64.229.209.54)
Rating: N/A |
Hello chuckmc8. I am approaching this same challange in a modular fashion... another way of saying, as I can afford the pieces!!! I have the Trace 4024, and will be sourcing the same T105 Trojans as you, only I'll assemble a 24 volt house system. Temporarily, I have been using an old pair of 8d starting batteries to keep a small refrigerator functional for a day at a time, and to get operational. Whether I can get away with 4 or have to get 8 of them, time and experience will tell. Same as you, I am keeping the coach air operational, so the original coach systems will continue in their stock configuration, powered by the stock 24 volt Delco alternator. In watching, reading and the advice of those smarter than I, I'm planning to add a second 24 volt alternator to take care of the house bank while underway, with the obligatory 3 stage regulator. Also gives back up to the big coach alternator, which gives little warning of failure. Solves the complications of mixing battery types and differing levels of charge as you pull out in the morning and try to charge the house bank which is down from the draws last evening and overnight, while the start bank only had to start the engine. I say this as one who will be on the move regularly, and recharging while underway will be the norm. At least for another decade and a half until I retire.....God and investments willing! The Trace and the existing stock coach alternator has no difficulty in running two roof airs while going down the road. The two roof airs make a fairly good substitute for the electrical demands of the stock coach air. Nice redundancy if the refrigerant goes south in the big coach system, or some other malady. Redundancy so that you are able to simply and effectively continue the journey is very important for those who are high miling it home for work on Monday morning. My design philosophy will change once I have control over my arrival times! From the rest of the posts, you can see you are on the right track! happy coaching! buswarrior | ||
| Tom Caffrey (Pvcces) (65.74.65.65)
Rating: N/A |
ChuchMC8, we have a 13,500 BTU air conditioner and a 2000 VA inverter from Heart. It's a Combi 358 and is designed for RV use. We have tried to start our air conditioner on the inverter quite a few times, but it only started once. We didn't realize that it was starting on the inverter when that happened. The generator was running, but I had forgotten to plug the shore power cord into the generator outlet when I stowed the cord. We were in Pheonix and it was about 95 degrees. After we got the air conditioner started, we made dinner and set down to eat it. Afterwards, I happened to glance at the Link and it was showing a 125 or 130 amp discharge. The air had been running for about 1 1/4 hours and was doing a fine job. I have seen reports that starting current might run as much as 6 times running current and I know that the inverter will put out around twice its continuous amps in surge. I have also seen reports that a 2500 MSW inverter will reliably start an air conditioner. From what I've seen, I don't think these inductive motors take quite 6 times to start, or if they do, the surge on the inverter is higher than the brags. I think the former case is more likely. We bought our inverter off of eBay. I don't know if you are comfortable doing that, but we got ours for about half of what Camping World wants for theirs. The transfer switch, temperature regulated 3 stage charging and cost made this unit the right choice for us. AM radios don't like the electrical noise, however, so we don't listen to the weaker AM stations, much. I hope you can make use of some of this. Tom Caffrey PD4106-2576 Suncatcher | ||
| Scott Whitney (69.35.62.177) Rating: N/A |
If running A/C going down the road, we have all the power we need from the bus alternator, so efficiency, as far as power usage, is not of concern to me in that circumstance. My only concern would be Sean's point about shortening the life of the motor. But are we talking about the compressor motor here? Aren't they liquid cooled anyway as the freon runs right thru the sealed motor case? So not sure if that would be a problem or not. I have my front A/C hooked to my Heart 3000 MSW inverter. It starts and sounds the same either way. I don't use it from inverter cause my big bus alternator is dead at the moment and I am using a bandaide truck alternator. But intend to swap out bus alternators and dedicate the big oil cooled alt for the house batts and leave the truck alt for the engine batteries. Will also install the 3-stage "in-Charge" regulator for the big bus alt. and house batts. That should keep the big alt at full tilt if needed to run A/C. Scott |
