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Author Topic: keep 24 Volt? or go 12V  (Read 2439 times)
robertglines1
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« on: September 30, 2013, 04:28:39 AM »

On the 98 prevost rebuild :;I find I have not much need for any 24 volt at all.  A few gauges.  The ac motors are gone.  The starter is 12 volt. the truck alternator is 12 volt. I have 12 volt defroster fans,wiper motor.  The headlights are 12 volt. I'm replacing all the clearance lights with 12 volt. The DDEC IV is 12 volt .The level low has 12 volt coils. The fuel gauge is a problem I ask about on a separate post and I don't know about tach. All gauge sensor are from DDEC IV......  Can anyone think of a reason to keep a dual electrical system?     Bob
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
bevans6
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« Reply #1 on: September 30, 2013, 04:50:10 AM »

All I can think of is to run the inverter.  12V inverters need those big cables for decent power, and 3000 watts is about as big as a 12V inverter comes.  24V makes more sense if you need high power.  The battery requirement is the same.  You can stack 2000  or 3000 watt inverters to get more power if needed.  I don't think I would run a 24V system just for the inverter, to be honest.  The whole point of why a bus would have had a 24V system in the first place comes down to running the OTR AC fan motors, that is about it.  If it wasn't for that high power application buses would have 12V systems just like trucks do.  The inverter is our equivalent of the OTR AC load.

Brian
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luvrbus
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« Reply #2 on: September 30, 2013, 07:27:07 AM »

The DDEC doesn't care if it is 12v or 24v only the 1 and 11 DDEC  were volt sensitive 
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TomC
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« Reply #3 on: September 30, 2013, 08:04:19 AM »

Coming from my own experience with a 12v bus, go for it. Having all 12v is much easier. Virtually all over the road trucks are also 12v (no more 24v starters with a series/parallel switch). Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #4 on: September 30, 2013, 06:24:52 PM »

In years past people on this board would be jumping up and down telling you how great and more efficient a 24v system is in a bus.  I always took the other position-- 12v is the way to go for house and bus systems.  I only have the starter and and a few relays that are 24v, so I have a 160 amp 12v alternator and a 42 amp 24v alternator to contend with.  NO gear driven 300 amp 24v alternator to blow up and take the engine out.

--Geoff
« Last Edit: September 30, 2013, 06:31:04 PM by Geoff » Logged

Geoff
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« Reply #5 on: October 01, 2013, 03:50:09 AM »

If you replace the 24 volt bulbs with the same wattage 12 volt bulbs the amperage draw will double. Is the wiring size adequate?   

Ken
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robertglines1
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« Reply #6 on: October 01, 2013, 04:36:47 AM »

I will check clearance lights for voltage(only thing I haven't checked yet). Wires look to be at least 18ga maybe 16 ga-- might just go led.  good point!!  Feed harness is at lest 12 ga---I had to replace part of it due to the fire. All the other tail light etc are 12 volt in this coach already.   Always need help thinking things thru/check signals..  Thanks    Bob
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
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« Reply #7 on: October 01, 2013, 06:46:11 AM »

So not to hyjack the post but as I only have small 24 volt draw and the 24 volt heater motor for the bus heat that I hardly use . How much power does the 300 amp. dn 50 alt.  use and what about 1 @12 volt alt 140 amp , 1 @ 24 volt alt 85 - 120 amp looks like a better set up    thanks    dave
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« Reply #8 on: October 01, 2013, 07:52:53 AM »

Bob I would go LED lights and not worry about the 24V!
Grin  BK  Grin
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Len Silva
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« Reply #9 on: October 01, 2013, 07:55:36 AM »

Whether the alternator is 300 amp or 30 amp, it only uses the power you take out of it.
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robertglines1
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« Reply #10 on: October 01, 2013, 09:15:27 AM »

Everything but clearance has been changed over to 12 v led already. Just forgot about them till Ken jogged my gray matter.  Needs a little shake once and awhile.   Bob
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Bob@Judy  98 XLE prevost with 3 slides --Home done---last one! SW INdiana
bevans6
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« Reply #11 on: October 01, 2013, 09:52:39 AM »

How much power an alternator takes to drive is based on the wattage output, the drive type, the cooling fan (if any) and it's efficiency.  A 50DN takes very little to spin it if it's turned off, it's got good bearings.  It's probably in the 50% to 60% efficient range, so if one HP is 750 watts(ish) then you might get 400 watts out for every HP in.  If it's belt drive, figure 15% loss, if it's gear drive figure 30% loss, so 340 watts or 280 watts per hp.  If it has a cooling fan, figure another 15% for it.  You will probably get around 340 watts per hp for a belt driven oil cooled 50DN, 280 watts per HP for a gear drive oil cooled and around 250 watts per hp for an air cooled 50DN gear drive.  You get the picture.  Based on my instance, belt driven oil cooled, and pulling 2,000 watts to run my inverter powering my rooftop AC, I would figure a little under 6 HP.  That is around 72 amps at 28 volts continuous.  The thing is, any alternator is going to be very close to the same numbers for the same power output.  A modern brushless might be 60% to 70% efficient (Like the Delco in this thread) but it's belt drive, air cooled fan, and will pull the same rough power out of the engine to drive it.  Four drive belts is a little less efficient than two, depending on belt size and such.  The modern toothed drive belts can transfer a lot of power and are very efficient compared to the old heavy vee-belts.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
Geoff
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« Reply #12 on: October 01, 2013, 05:03:35 PM »

I easily run one 1500 BTU roof AC off my 160 amp, belt driven alternator.  According to my Trace inverter it is only pulling 8-9 AC amps at 120v.  I made a plate to cover up the hole in the flywheel housing where the gear-driven 24v 50DN was.  No more restless nights and days wondering if the 50DN would blow up and take out my gear train.

It's sitting on the floor of my shop with the regulator.  Any offers?
« Last Edit: October 01, 2013, 06:02:50 PM by Geoff » Logged

Geoff
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« Reply #13 on: October 02, 2013, 08:59:34 AM »

How often do the 50dn alt. granade and is there a warning to look for b 4 hand ?

thanks    dave
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« Reply #14 on: October 02, 2013, 09:14:40 AM »

Geoff opened a can of worms here lol you need to remove the 50D every 100,000 miles and check the alternator bearing and the gear alignment on the cam  it is not a easy task but it needs to be done they give no warning and when one goes it destroys a engine you save the block and crankshaft if you are lucky the rest is history  

The nut that holds the gear on is bad about coming loose if it hasn't been locked in someway I center punch the the shaft on the edge to prevent that from happening  fwiw

Some here say it never happens but it does I have rebuilt few engines because of a 50D I would not have one on my engine just like Geoff when you shut the engine down they backlash and it will take a toll in time JMO about a gear driven 50D YMMD

good luck
« Last Edit: October 02, 2013, 09:26:13 AM by luvrbus » Logged

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