| Author |
Message |
Wayne Buttress (Flyingb) (66.52.189.99)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, October 17, 2001 - 10:57 pm: | |
Hi Guys,
Have Eagle 20 that comes with a 24 volt alt that runs the blowers for the A/C unit that I,m removing. Is it feasable to keep the 24 volt alt. and step it down to 12 volts to run the house systems or just purchase a 200 amp. 12 volt alt.
Thanks, Wayne |
FAST FRED (63.208.87.55)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 18, 2001 - 5:29 am: | |
The wiring for 24 V is half the size of the wiring for 12V due to the amperage .
Simplest is to keep the coach 24V and install a 12V alt to run all the house stuff.
The 12V alt should have an external regulator , if your going to have a house set of deep cycle batts.
You also could recharge the house deep cycles with a good {$$$$} 3 stage charger.
FAST FRED |
CoryDane N/E IL (4.17.253.30)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 18, 2001 - 12:27 pm: | |
The 24v alternator puts a large current out allowing your 24v input inverters (if you so choose) to supply power to the air cons or system power supply(ac cb panel). It will do this at much less input current to the inverter making the wiring, as fred says, smaller in size.
Lemme see if I can compute this, say you have two air cons at 15 amps each or a total of 30 amps current(this is not considering the startup currents, just running load.
A 12 volt alternator will have to supply 12v current at (if I did the numbers right) 300 amps while a 24volt alternator will supply 24v current at 150amps to inverter which supplies the air cons.
You would benefit by smaller cable size from the alternator to the batteries and from the batteries to the inverters. My gosh for a 12 volt system the cables will be huge.
If I am not on the money, I should be close so you should have a good idea of what you are asking. cd |
CoryDane N/E IL (4.17.253.30)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 18, 2001 - 12:33 pm: | |
Oh my, I read the rest of your post, sorry for the second message.
You can access 12v dc from a 24v battery bank by tapping on the center tap for 12v. this does lend some interesting charging problems as you are draining only half the battery bank.
The other alternative would be to buy a dc converter, it converts 24v to 12v for the 12v systems on board. My converter supplies 75amp from the 24v battery supply. Hope this addendum also clears things up. cd |
Greg Roberts (172.164.126.136)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 18, 2001 - 10:43 pm: | |
Wayne,
Are you aware that your bus has a 300 AMP 12VDC alternator hard mounted on the rear of your 6V92 that powers the 12VDC bus system? The bus battery system is therefore also 12VDC. |
Steve Fessenden (63.27.88.13)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 18, 2001 - 11:54 pm: | |
You can keep the 24 volt alternator and buy an Equailizer that will keep the two batteries at the same charge level so you can center tap the system for 12 volts. Don't try a center tap without an equalizer. I've had that nightmare. It kills batteries. An equalizer only has to exceed your average 12 volt loads. An equalizer is more efficient than a 24 volt to 12 volt DC to DC converter. The battery can put out occassional high amp outputs and the equalizer will catch up.
Steve Fessenden |
John Biundo (Jbiundo) (209.239.204.240)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 19, 2001 - 1:22 am: | |
Steve,
Sorry, but could you please explain a little more about the "center tap" (I haven't heard this term before) and the equalizer? I was thinking about staying at 24 volts and using a 24 volt to 12 volt DC converter, but your post seems to make the case for a more efficient approach. Also, any reference to product vendors/model names that can be used to implement this approach would help. Thanks in advance,
John |
R Johnstone (Chilebrew) (164.64.174.66)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 19, 2001 - 11:36 am: | |
WHOA! Eagle 20's are 12 volt. 12v lights, 12v batteries, 12v starter, HUGE 12v alternator.
Engine driven a/c compressor also drives 24v alternator; output solely for a/c blowers, no charging of any batteries.
Wayne, why remove the bus a/c? You can't replace it with anything nearly as powerful. Refrigerant is R-22, any home or Thermo-King dealer can service it. Present unit is up, out of the way. Why fill a bay or mess up your roof?
Depending on your shore power available, tee in a 120 or 240 compressor, have the best of both worlds. |
rmontbrand (129.238.237.95)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 19, 2001 - 1:59 pm: | |
I agree with R Johnstone, Might want to keep the coach A/C its somewhere around 10 tons of R-22 charged A/C. Bob is right it is up and out of the way. Sure keeps the coach cool in 100+ temps down the road. Roof units are about 1 ton each and must be used with shore power or your generator down the road. I am working out an electric compressor which will allow my unit to run on shore and generator when parked. The unit is Thermo King current stuff. That compressor is $2500 to replace.
Ron |
Steve Fessenden (63.27.88.114)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 19, 2001 - 6:14 pm: | |
It has been done, but it took 220 volt motor and a separate compressor.
I saw a beautiful Executive Coach Corporation Prevost XL with an electric motor driven compressor to run bus air. They could not do it on 110 volt, so it is a 220 system, which means it is only good on shore power in some parks. I believe they had a separate compressor also and used valves to accept the compressor that was running.
Steve Fessenden |
Steve Fessenden (63.27.88.114)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 19, 2001 - 6:34 pm: | |
Center tap draws 12 volts from the first battery in a 24 volt system. (This does not apply to 12 volt systems like an Eagle.)
A Vanner, or other equalizer will continuously monitor the voltage of the two batteries in series and deliver power from the 24 volt battery terminal to the 12 volt terminal to keep the voltage of the 12 volt battery at exactly half of the 24 volt battery. Power is not drawn through the equalizer, so you can exceed the equalizer rating without hurting it. As long as the high amp 12 volt loads are short term the equalizer will work continually to catch up.
Power for 12 volt sources goes THROUGH a Converter which will only supply the rated output. A converter supplies exact voltage, which is its big plus but you usually don't need that kind of precision. Converters have a higher standby current drain than equalizers and do nothing to prolong battery life.
With a center tap and an equalizer the voltage varies battery charge and alternator output and load just like any automotive, boat, RV or aircraft system. 12 volt equipment is designed for this.
Steve Fessenden |
Tom Caffrey (Pvcces) (12.146.33.247)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, October 19, 2001 - 10:50 pm: | |
Hey, fellas, there is one thing that using an equalizer overlooks. Batteries discharge at one voltage and recharge at another.
What this means is the only way you won't run into battery problems is if the 12 volt loads aren't significant. If there is any serious unbalance in the state of charge, the low battery will never have a chance to catch up.
A battery discharges at 12 to 12.5 volts, but requires 14 to 15 volts to fully recharge. If an equalizer were to attempt to make both batteries the same voltage, the high one would overcharge and the low one would not catch up.
The only way out of this predicament is if the equalizer has a way of figuring out which battery was low and then it would have to turn up the recharge voltage until the low one caught up.
I know there are smart chargers out there, but they work without center tapping any of the cells.
You could use two 12 volt charging systems hooked up in series. That way the system could deal with unbalanced loads and still give you 24 volts. One one the two charging systems would require a full floating ground.
A floating ground would also mean that any loads hooked to that part of the system would have to be isolated from ground (the chassis) at all times.
If you don't really need 24 volts, then an all 12 volt system should be a lot simpler and cheaper to set up, even if it would take larger cables than 24 volts.
Tom Caffrey PD4106-2576 |
CoryDane N/E IL (4.17.253.79)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 20, 2001 - 12:33 pm: | |
Keeping the original coach air is possible, but consider it was intended to cool a bus in the middle of a heat wave with 50+ people aboard on the hot pavement. Also consider all the posts I have read about using the original air brings in yearly maintenance costs to the tune of about $600 every year.
=
Roof top units cost about that each and will faithfully run for many years. Even then if one stops operating, you could replace it with new and still be money ahead of the original unit.
-
A thought that has passed by the boards.-cd |
Scott Whitney (63.151.68.130)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 20, 2001 - 1:27 pm: | |
I saw a Prevo in Laughlin that used an auxillary motor to run bus air while camped. But if I remember correctly it did require 50A service to run it. It was probably a 220v motor. Pretty cool though. Pun intended.
Scott |
Wayne Buttress (Flyingb) (66.52.189.59)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 20, 2001 - 9:14 pm: | |
Wow!!!
Ask a question and get a lesson. I need all the input I can get as I only want to do this once.
Can I place a device between the 24v alt and 12v batts. that I will use for running the "house" systems or should I purchase a 12v alt.
Would like to use the existing 24v unit if possible. I figure 2 alts. are better than one. |
Steve Fessenden (63.27.89.242)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 20, 2001 - 11:20 pm: | |
Tom:
I have dealt with the suggested system of two 12 volt chargers for a 24 volt system. It doesn't work well enough. Neither does having a separate 12 volt alternator charge the lower battery. I had both and they are not nearly satisfactory.
I moved my reply to another heading, since this was originally an Eagle (12 Volt)question.
Steve Fessenden |
ronmont (24.253.45.3)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, October 21, 2001 - 11:49 pm: | |
Wayne,
Ont he NJ eagle 20's you have a 24 volt alt. and a 12 volt 300 amp alt on the back of the engine to run the coach stuff. The 24 volt is for the A/C fan motors. It is a special unit only on the NJ eagles as far as I have seen. As far as the coach A/C units they are charged with R-22 not much of a cost to maintain.
cheers,
Ron |