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Author Topic: pressure switch  (Read 1999 times)
luvrbus
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« Reply #15 on: December 15, 2013, 09:34:38 AM »

You are 100% about the load required to open and close a relay but that nothing to do with the amps a relay or solenoid will carry
« Last Edit: December 15, 2013, 10:31:45 AM by luvrbus » Logged

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Melbo
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« Reply #16 on: December 15, 2013, 11:20:49 AM »

I have the dash switch method with a 400 amp solenoid. I have three dash switches I turn on in the process of starting the bus.

1 to charge house batts
2 to power the 12 converter
3 to provide 12 volts for the 12 volt guages I have

Of course there is a special order to turning on the switches --- Just like the order of checking and starting the bus up.

HTH

Melbo
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RJ
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« Reply #17 on: December 15, 2013, 11:37:48 AM »

I think you should also include a small LED warning light on the dash, or an illuminated switch that indicates the circuit is "on."

If you could figure out a way, have it flash when you turn off the ignition switch as a reminder the batteries are still interconnected.

FWIW & HTH. . .

  Wink
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RJ Long
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Skykingrob
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« Reply #18 on: December 15, 2013, 12:15:41 PM »

Well, I think I have found the relay to use to control the charge current to the house batteries. Here is the link, see if you agree (may have to cut and paste into a browser window if the link doesn't start on it's own):
 
http://www.texasindustrialelectric.com/Relays_24824_01.asp

What I have not settled on or found yet is a switch to control the relay. It could be air, oil or just a toggle switch. Advantages and disadvantages to each of them. I will need to study the manual on the DN50 Jon, to see if it has a relay on it that will work.

If I have the relay right, let me know.

Rob
91 XL 40
Missouri
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bevans6
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« Reply #19 on: December 15, 2013, 01:06:24 PM »

All 50DN alternators have the R terminal, the bus wiring would have a relay that might be connected to it.  It's a tap onto the center of one of the three diode pairs, so it puts out a ripply half voltage signal.  If yours is a 24v alt, it will put out a 12v signal.  All it does is tell something, usually a relay (because a half voltage signal full of ripple isn't good for much other than turning on a relay) that the alternator is operating.   So if you plan to use this, it's not only exactly what the R terminal is supposed to be used for but you need to look for a relay of appropriate current capacity but it has to have the correct voltage for the control coil.  As with all things, there are caveats and things to know...  On many buses the R-terminal is already connected to a relay and that relay works (among other things) the Alternator tell-tale light on the dash.  With many buses (my MCI for example) the 50DN will start to flicker the No Gen light if there is little load on and the batteries are fully charged.  If that should happen with your bus and you are using the R-terminal to control the relay, the relay will be toggling open and closed with every flicker.  That is something to be aware of.  There is a reason an awful lot of people decide to use a manually controlled switch - or just combine the start and house banks permanently, the idea being that the generator (with a separate start battery) can be the back up if things get drawn down too far to start the bus.

Edit - I think the relay is fine.  For me, the number to look at is the surge rating, which in this case is 600 amps, for boost starting the engine.  If you do the R-terminal deal discussed above, then you would use that relay, driven from the output of the R-terminal relay.  The 50DN would not switch that big relay directly from the R-terminal.

Brian
« Last Edit: December 15, 2013, 01:17:24 PM by bevans6 » Logged

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gus
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« Reply #20 on: December 16, 2013, 10:03:31 AM »

I agree with Brian, that relay should work fine. Or you probably can find one at your local auto supply store, depends on the prices. Just make sure it is a full time. It will look like a generic start solenoid/relay on older cars except it is rated full-time (Constant current).

The only time it will be carrying many amps is if you ever have to use it as a start booster, a rare thing normally. I've maybe done it three times in seven years.

It still won't take anything more than a simple toggle switch, holding current is small even for a high capacity relay. Simple is better!!
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wagwar
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« Reply #21 on: December 16, 2013, 11:31:30 AM »

On my MCI there is a relay in the rear junction box that is activated only when the air pressure is up, the engine is running and the alternator is operating. It is on the OEM A/C wiring circuit. It originally prevented the A/C blower to come on before the engine was running and the alternator was operating.  If memory serves me correctly, that relay can provide a signal to your battery solenoid. You can route that signal through a toggle switch and also use an empty telltale socket for an 'on' light. I also added a small timer circuit in between the relay signal and the toggle so that there is a 30 second delay after I flip the switch between the alternator coming on (Gen Light goes out) and the solenoid is fed the signal. If you use a toggle switch that has an On Off MOM positions, you can manually bridge the house batts to the starter batts for emergency starting situations. Use the On for your full time connection and the MOM for the emergency bridge. That MOM has really come in handy a few times when the start batts got run down. If you have a sufficiently large inverter, you can run some heavy loads from it while running down the road with your house and start batts bridged to the 50DN (280 Amps!)   
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Jon
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« Reply #22 on: December 16, 2013, 01:36:17 PM »

Rob, That switch looks like it will do the job. As an alternative you can use an isolator such as have been used on our store bought conversions. They are a little pricey and they take a little more room.

I have had both types that I mentioned on my coaches and in 15 years I replaced two solenoids, so far no isolators have failed in about 10 years of experience with them. http://www.allbatterysalesandservice.com/browse.cfm/4,6120.html
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Jon

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Knoxville, TN
luvrbus
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« Reply #23 on: December 16, 2013, 01:49:24 PM »

Isolators take more cable than a relay to hook up but they work good,the battery separator gizmo is getting popular but I have no idea how they work   
« Last Edit: December 16, 2013, 01:52:56 PM by luvrbus » Logged

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Skykingrob
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« Reply #24 on: December 16, 2013, 06:54:21 PM »

Thanks to everyone for input. Still studying the pros and cons of the switch. The reason I was looking at the air or oil switch was to make it as automatic as possible so if I forgot, then drained batteries was not the consequence but as you all have pointed out, there are other consequences to air and oil switches that I had not anticipated. So, still thinking that decision through.
Thanks again. If more ideas, let me know.

Rob
91 XL 40
Missouri
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wagwar
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« Reply #25 on: December 17, 2013, 10:52:57 AM »

Just my $.02 - battery isolators produce heat and as such are less efficient than a solenoid. If you want one, contact me off the board as I have a nearly new one available.
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