Drawing power directly form the generator or Alternator

[goodnews]

I am trying to determine if it is possible to draw power directly from my generator or alternator to provide 110 volt AC without going through the batteries by using an inverter on an isolated circuit.

I want to operate coach air conditioning and other 110 volt appliances without drawing from the batteries and I have been told that this is possible. If anyone is doing this and is willing to share how you are doing it I would appreciate hearing from you.

I have PD 4104-5030 which is a 1960 model.[ GM. I have removed the factory air conditioning and am experimenting with ways to replace it with on the road Air Conditioning. Either my roof air or another type of built in system.

What would be the minimum size inverter needed to do this job? How should it be wired in?

Thanks,

Clifford Neal

[Zeroclearance]

You will need to have some sort of battery bank..   

If you run the Delco 50 DN @ 27.5 volts you can get 7400 watts out of it..   

Do your calcs based off the 7400 watts.   The road A/C motors will eat alot of the wattage.

I run the 450 amp Niehoff with a custom Balmar regulator.

[buswarrior]

goodnews, from your question, I think you've got this a little confused.

The batteries are in the circuit all the time, you hook your inverter up and carry on. The regulator for the alternator takes care of everything, the batteries won't be harmed in a properly sized system.

For your loading considerations, in rough terms, using a good quality pure sine wave inverter, running two roof airs via the proposed system is pretty much equal to the electrical load that the original coach HVAC fans put on the alternator.

So the alternator won't know the difference.

happy coaching!
buswarrior

[goodnews]

Are you saying that I do not need to add a larger battery bank? That is what I am attempting to eliminate. I do not need to have a large reservoir for use when the bus is not running. I can use either shore power or my generator when the bus engine is not running. I understand what you are saying but had gotten the idea that in slow, start and stop traffic, I would draw from the batteries and pull them down dangerously with the standard two battery bank that is in my bus. Someone told me that I could isolate a circuit directly from the alternator and bypass the batteries altogether. Is this not the case?

[buswarrior]

As noted, there will be no difference to the coach stock electrical system if you use an inverter and a couple of roof airs or the coach stock HVAC.

Same loads, same conditions as the manufacturer built it to.

How big/small are the two batteries you are using for the system now?

happy coaching!
buswarrior

[Sam 4106]

Some of you are assuming that a 4104 has a 24 volt electrical system. Unless the bus has been substantially altered to 24 volts, it is 12 volts.

Before you can know if you can run an A/C with your bus charging system you need to determine if you still have the 12 VDC original generator which was positive ground. It's unlikely you can find a positive ground inverter. If your bus has been switched to negative ground you will have a chance to run 1 A/C if you have a large enough battery bank, an adequate inverter, and large enough cables from batteries to inverter if you have a 225 amp alternator. A 120 VAC A/C that draws 15 running amps will require at least 180 12 VDC amps to run. Maybe higher, depending on the efficiency of the inverter. So forget running 2 A/Cs. tell us what alternator you have, the size of your batteries, the size of the inverter, and the running amps of your A/C and we can give you some better answers.

Good Luck, Sam

[goodnews]

You are correct that my 4104 is 12 volts with positive ground. My 110 volt Ac circuits have been isolated to negative ground however. I will have to check to see the battery sizing tomorrow and get back to you. I honestly do not know if the bus has an alternator or a generator. I do not know how to distinguish between the two. I also do not know exactly what the output of the power supply is from the alternator/generator. Do I have to use a voltage and amperage meter to determine this or is there another way to do it?

The bus has always used two 8D batteries till recently. I changed to smaller size because of the weight of the 8D's. Actually, I think the smaller batteries I have provide higher amps than the 8D's did but I will check that tomorrow and get back to you guys.

I do appreciate your help.

Clifford Neal

[Len Silva]

If you bus is still positive ground, it most likely has the generator and carbon pile regulator, both can be problematic and hard to find.

In addition, even with a big 50DN alternator at twelve volts, you will not have enough charging at idle speeds to maintain the air conditioner load with substantial batteries.  That is not the case with a 24 volt bus.  Two 8-D's should be OK and be sure to raise the idle speed (with the hand throttle) if you are going to be stopped for any length of time.

[boogiethecat]

If you have the engine space to bolt in an Auragen system, it's a no brainer from there.

There's a complete one on ebay right now  http://tinyurl.com/bjkqb9r

These things are basically a gigantic alternator-kind-of-thing with a built in inverter that puts out 120 volts AC (sine wave) up to 5KW.

But you gotta have three things- engine space, bucks, and a little bit o' crazy (which we already have if we own busses..!)

[robertglines1]

Your going to spend Big money to get it done and even more to maintain. History proven by time here.  My question is why not just spend it once on a good used gen set?  The end total cost and more flexible and economical use would be worth it.  Many --Including myself-- have been where you are in your thought process..Just look at my off wall bus building--don't guess I will never learn. 1  ea 15000 roof top is going to take a min 18 amps @ 120v clean to start and 14 amp @ no less than 110V 60h to run: or basically you risk destroying unit.  Then your out-- All your supply work plus AC unit. I fried 2ea AC units in past.   FWIW  In the final big picture----We are busnuts That's why we do it our way anyway.   Best of luck.   Bob

[robertglines1]

Wanted to add I know of couple that have been succesful(sp) here but have extensive batt banks and or inverter AC systems. Big bucks compared to simple 7.5 KW gen set. Just wanted to acknowledge it is being done and do respect those who are doing it. It is not cost effective for my lifestyle.   Bob

[TomC]

Running a 12v inverter, about a 2,800 watt is the largest made. 24v can get 4,000 watt or higher and can stack them. I would run at least a 270amp alternator (at 14.1 volts that makes 3800 watts). Then you should run through a bank of batteries-like at least 2 8D deep cycles to buffer the idle and full speed to the inverter. Without a deep cycle battery there would be too much voltage drop and peaks that would take out the inverter in a very short time.

I have a 2,500 MSW inverter, but just use it for short term, or low watt usage. Like TV, Stereo, microwave, toaster oven, bathroom heater, primary electric water heater, etc. If I use any of my three roof tops, they are not wired through the inverter. Hence, either the power pole or generator. Good Luck, TomC

[buswarrior]

Oops.

Absolutely correct, I did not consider the coach was a 4104.

The 4104 air conditioning compressor was powered by a separate engine all together, however, the coach electrical system still had to run the big fans, so that part is quite strong. But, the positive ground makes some more trouble for off the shelf inverters.

In your case, running a separate generator for the air conditioning going down the road would be an easy choice to make.

There would be no need for a big battery bank if contemplating using a big inverter to run some AC going down the road. The chassis batteries would be just fine. That's all the coach had in revenue service?

happy coaching!
buswarrior

[Sam 4106]

Hi Clifford,

I emailed Dave Shiney at Northern Arizona Wind and Sun to see if there is a positive ground inverter available. Neither Magnum nor Outback has one and I suspect no other company does either. You could change your bus to negative ground and install a 50DN alternator. But, with that cost and the cost of an inverter, battery cables, fuse and holder and other associated expenses, I think you will be better off using a diesel generator to power your A/C, as buswarrior suggested. I know that's not what you wanted to hear, but that's the best advise I can give. Sorry!

Good luck, Sam

[goodnews]

Thanks again guys. I am not sure I am understanding all the information I am getting here however.  Buswarrior seems to be telling me that I can run the roof air, ( I only use one unit going down the road in the front half of the bus. The rear of my bus is closed off by a door) in the way I thought possible but the use of terms seems to confuse me and others who are writing as well.

Let me see if I can be very clear in what I am talking about. Forget that I have a genset in the bus. I am trying to set up not to use it. I want to use the power created by the alternator on the 671 diesel power plant. The fact that the bus has positive ground should be overcome by simply reversing the wires when connecting to the inverter and insulating the inverter from the chassis of the bus. This creates an isolated circuit to be used with the air conditioner and whatever else I might want to connect to it. I have already accomplished the with small wattage inverters for running microwave, refrigerator, Television and computers. They work fine and have for several years with no difficulty whatsoever. So this is what gave me the idea to do the same with the roof air by using a larger inverter. My concern was whether I would need to have a larger capacity battery bank.

If I understand Buswarrior, this is not a concern as the coach is already set up to produce more power than I need after removing the large 12 volt fan that ran the factory air, which has been removed.

I hope this makes it very clear what I am proposing. If this works, I find it hard to believe that there are not many 4104 owners already doing this.

Does this change the advice anyone is providing? Not being an electrician, I may be completely off base and I hope someone can clearly tell me that it will or will not work without me going to the trouble and expense to try it.

Thanks,

Clifford Neal