| Author |
Message |
dougthebonifiedbusnut (136.217.0.198)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 18, 2003 - 3:23 am: | |
To all the electrical guru's,
I will be putting 3 electric fans on my crown. The total amps will bew around 42 amps.Im think Ill need to switch them on one at a time as not to slam the alternator which will be dedicated to only powering thoise fans.Need advice as to what types of switching mechanisms I will need. DO I even Need toi switch them on one at a time? |
FAST FRED (67.75.113.122)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 18, 2003 - 5:25 am: | |
42 A is a lot to run thru a LONG wire to a big switch and back to the fans.
The RV stores have relays that are usually used to join the chasis & house batts rated at 75A for about $15.
That would be my choice.
FAST FRED |
Richard Bowyer (Drivingmisslazy) (24.196.191.70)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 18, 2003 - 7:47 am: | |
Might be easier to just switch the excitation to the alternator on and off. Only a few amps of current. I do not think "slamming the alternator" with a large load will hurt it any.
Richard |
Gary Stadler (Boogiethecat) (68.7.217.217)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 18, 2003 - 8:48 am: | |
One of these relays per fan will work nicely, easily and cheap.
You other busnuts might find these neat as well. 12 volt relay, SPDT, 30 amps on the N.C. contact and 40 amps on the N.O. contact, 2 bucks each:
http://www.allelectronics.com/cgi-bin/category.cgi?category=500700&item=RLY-631&type=store
Not to be cynical Doug, but now that I'm done with my Crown and have been driving it a lot, I'd say yes, you oughta switch your fans individually, so you'll have a choice of overheating, overheating a lot, or overheating seriously.... keep the belt driven fan....
Cheers
gary |
Scott Whitney (66.82.9.13)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 18, 2003 - 9:32 am: | |
How do you have an alternator dedicated to the fans? Are they run off a dedicated battery (bank)?
Scott |
Henry R. Bergman, Jr. (Henryofcj) (63.164.175.14)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 18, 2003 - 4:00 pm: | |
Let me show my ignorance by assuming these fans are for interior ventilation and NOT an attempt to cool the main engine radiator.
If in fact they are for interior ventilation, then wiring each individually makes some sense. The DC wiring will need to be sized for...
...ideally no more than a 2 and one half percent voltage drop, including a fudge factor for less than perfect crimped and heat shrink wrapped...
...connections including just a plain DC fuse or a fancy circuit breaker do hickie thing. How big is the Crown alternator? Forty extra amps draw...
...may affect other DC engine driven systems, such as the headlights and stuff. Just wondering at what point a shunt type amp gage may help. CROWNS FOREVER |
R.C.Bishop (128.123.221.135)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 18, 2003 - 7:38 pm: | |
Henry, my coach has four roof ventilators, 4 heater motors in the coach and two in the driver area. Never a problem....far as I know.
Not sure the size of the alternator.
RCB |
Richard Bowyer (Drivingmisslazy) (24.196.191.70)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 18, 2003 - 9:30 pm: | |
I would guess they are radiator fans based on the current consumption. My 16 inch fans draw about 12 amps each.
Richard |
dougthebonifiedbusnut (136.217.0.198)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 19, 2003 - 6:20 am: | |
Thanks guys,
I have bee thinking about this alot and this is what ive come up with. When Crown desighned the cooling system they placed the radiator where it is because on the average the deflected wind of the front of the bus would return the side of the bus at approx that location at speeds of generally less than 55 mph . The faster the bus travels the farther back the air would travel before returning to the side of the bus. As soon as I get back home Im going to test my theory by taping pieces of string to the side of the bus and go down the highway and see if in fact i have the right idea, much the same way laminar flow is determined on an aircraft . If i find Im right than what Im going to is move the radiator back as far as I can (about 16" I think )Then hook upo the two 2800 cfm fans giving me 5400cfm of air thatis being pulled directly throgh teh radiator instead of being pulled threw the radiator turned 90 degrees and than pulled another 3' by thatbig noisey fan. I think I am right but if i have to than Ill Have a new radiator built the same distance as the added length of the inlet for the origanal radsiator put a third fan dr4iven by a dedecated alternator . Thats why I need to know about switchinfg the fans on one at a time. Tats the hypothesis Now on to proving or disproving it As always all input greatfully appreciated. the extra cooling capacity and one more fan will give 8400cfm. got to be plenty.If anyone has any #'s with regard to the cfm of that inefficiant fan system thats o the bus now Id sure like to see them |
Richard Bowyer (Drivingmisslazy) (24.196.191.70)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 19, 2003 - 7:54 am: | |
For the extra alternator to work properly, I think you are going to have to a battery connected to it. Probably would not have to be a big battery, but something to stabilize the alternator output and a source of excitation voltage when first starting.
If I were installing a system like this, I think I would use two electrical thermostats, installed in the return hot water or on the radiator, and control relays. The first thermostat would close at 190 degrees and turn on the first fan. The second thermostat would close at 200 degrees and turn on the remaining fan(s).
Gene Rochester from South Carolina (by the way, anybody know what happened to him, he hasn’t posted for months) conducted a similar experiment on his Eagle by taping some colored streamers in the area of his radiator. While going down the road at speed, the streamers were standing straight out from the bus, as I recall. This would leave one to believe that the radiator is actually in a low pressure area and would seriously affect the supply of cooling air to the radiator. Almost as if the fan should be blowing out instead of sucking in. The problem, as I see it would be that you would be sucking air from the engine compartment which would be hot air trying to cool the radiator.
He also proved (at least to me) that the lower front of the bus is a low pressure area. The front of his bus was open to the outside when he brought it home, and papers lying on the floor were sucked out the front of the bus while driving down the highway.
I saw a bus in the northwest where the owner has installed a drivers A/C system and the condenser was installed in the spare tire compartment with two fans blowing thru the radiator toward the front of the bus. This would seem to be backward as the fans would be fighting the natural flow of air generated by the forward speed of the bus. I do not remember why he actually installed it this way, but he indicated that the A/C system worked fine.
Richard |
RJ Long (Rjlong) (24.127.74.29)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 19, 2003 - 10:12 am: | |
Doug -
Just a simple question before I throw in my two cents worth. . .
Are you currently experiencing overheating problems with your Crown?
Reason I ask is that I've driven 10-wheeler, mid-ship Crowns, fully loaded, at 70 mph on the freeway here in the HOT Central Valley of CA and up over the 6% Grapevine hill on I-5, with outside air temps in the 100s, and NEVER had one overheat on me with the factory cooling system.
So I'm curious about why you want to "fix something that ain't broke". . .
RJ
PD4106-2784
Fresno CA |
Henry R. Bergman, Jr. (Henryofcj) (63.224.197.10)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 19, 2003 - 1:54 pm: | |
I also have decided to leave the factory stock cooling system alone on my '74 Crown 10-wheeler.
The system holds about 102 quarts of coolant and is powered by a large plastic 6 bladed fan...
..run off of 2 large belts from the Cummins crankshaft end. At 2100 rpm, I bet it has to...
...take at least 20 hp to turn that big fan. The belts are huge. Never had any problems overheating.
However, the belts can break. This happened to me way back in 1970 or soossss with another...
...another old '63 Crown 10-wheeler with the older 743 220 Cummins. I raised all the side...
...windows and drove it back to the barn. Never got above 190 F. At speed the aerodynamics...
...apparently sucked enough air thru the radiator to keep the mill cool. The mechanic showed me...
...that mudflap do-hickie thing than runs across the bottom of the bus in front of the mill...
...and just behind the side radiator. He told me it creates a low pressure area under the coach...
...at speed to help suck air thru the radiator. I do not know if electric fans could move...
...enough air to do the same thing as that huge factory fan turned by two large belts. CROWNS FOREVER and good luck. Henry of CJ. |
RJ Long (Rjlong) (24.127.74.29)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 19, 2003 - 2:21 pm: | |
Oh, Doug, another thought:
Have you looked at where GMC and MCI placed the Air Conditioning condensors on their coaches? (Up to the 45-foot DL series for MCI's at least.)
Remember, these are highway models, running at freeway speeds. . . with up to 12 tons of A/C capacity. . .
Where are they?
In exactly the same place Crown put their radiator for the mid-ship powerplant.
Hmmmmm. . .
RJ
PD4106-2784
Fresno CA |
dougthebonifiedbusnut (136.217.0.198)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, July 20, 2003 - 8:05 am: | |
Hi RJ,
Good questions RJ (by the way I love your coach) The truth is I have never noticed were they place the a/c rads but here is why im doing what im doing. When I rteplaced thew old 220 with the 1986 855 the old fan drive would not fit on the new engine so i tried to find a pulley that i could use .None to be found so started my quest for another system. So to make a long story short I have been racking my brain to solve this particular problem.I hate the noise that the fan makes i could go the route that Gary went but the cost of having someone else doing the machine work makes me shy away from doing that and still having a nmoisey fan. oh ya one more thing the fam i have is the origanal it used to be a veriable pitch that i had to make a fixed pitch. not to mention the room i would get by doing what i propose.I have no cooling problems at all so i dont think its going to be a big deal to cool it with the fans im thinking about using As for Henry's response (oh by the way thank you Henry) I will be putting a flap in front off the radiator.Also thank you Richard I think that may be a good solution.One more think I forgot , the fan pulley is a single belt that isa very large pulley which takes a very large belt, the engine shive is a regular size as a lastr resort i may have to have a new pulley made with the same large belt shive. The good advice that I get from all you guys might push me in that direction. Thanks all and keep your thoughts coming. |
Richard Bowyer (Drivingmisslazy) (24.196.191.70)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, July 20, 2003 - 11:40 am: | |
I really doubt if you will ever be able to keep it cool without the engine driven fan, especially in extreme temperature conditions. Might contact Dave at Southern Oregon Diese. He has a source for all types of fans.
Richard |