| Author |
Message |
james dean boggs (Jd_boggs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 24, 2004 - 12:09 am: | |
Have installed 2 portable generators in my bus. But I only want one AC circuit inside. I may not want to run them both if they are not needed. But when I need to power both air conditioners then I need more power. How do I connect them? Can I just connect them in parallel? Nuetral to nuetral, load to load and ground to ground... Or do I need a special switch?
thanks.
PS.
Merry Christmas all ! |
Gary Stadler (Boogiethecat)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 24, 2004 - 1:22 am: | |
Could be easy and could be messy. There's a remote possibility that simply hooking the two generators together once they're running will cause them to sync up together and act as one bigger generator, but I would venture to guess that's a VERY remote possibility. Much more likely one or both would go poof, let the smoke out, and be dead generators from that point on.
If I were you, I'd probably just find a single larger generator, unless that's absolutely not an option. It would keep the system clean and foolproof.
Otherwise, the best way to do it in my mind would be to make one generator your "primary" generator and hook it to your bus's mains. Call it Gene #1 and run everything off of it, including one of your A/C's.
Hook neutral and ground of generator #2 in parallel with generator #1 but NOT the hot wire.
Then use a single pole double throw switch on your second A/C that either hooks it's power lead to the main systems' hot or generator #2s' hot.
So here's how it would all work-
You'd start gene #1 and you could run your #1 AC and all your bus stuff with it. If you wanted, you could turn A/C #1 off, flip the double pole switch so that gene #1 would hook it's power to A/C #2, and operate A/C #2. But obviously you couldn't run both A/C's at once.
If you need to run both AC/s at once, you'd fire up Gene #2 and flip the double throw switch so that gene #2 is now powering A/C #2, and then it'd be OK to turn on AC#1 (which is permanently hooked to Gene #1)
The double throw switch could be replaced with a relay that did the swap automatically whenever Gene #2 was turned on... you'd hook the contacts up the same way as the switch would have been and hook the relay's coil so that it's energized by Gene #2... that way it's a lot more brainless but either way you look at it, it's probably going to be a hasslesome system.... and if nothing else, the vibration from two generators has gotta be horrible.... |
Craig Smith (Craigs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 24, 2004 - 8:28 am: | |
I think I'd hook one genset to one side of my breaker panel and the second to the other side. That would keep the hots separate. Don't hook the outputs of the two gensets together. I'd then balance my load in the breaker panel, one A/C on each side plus the other loads.
Craig S |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 24, 2004 - 8:33 am: | |
James-
How about the simple way, and do it like the commercial RVs
do for the shoreline hookup?
One AC and the rest of the electrical system is on one circuit,
and the other AC is on it's own circuit. A "reversing" switch
to swap inputs to either output, will allow you to run either the
front or rear AC with either of the gensets.
Or, if you really want to get fancy, the addition of an alternating
switch that allows the power to automatically transfer from one
AC unit to the other (designed for use with 30amp setups), will
accomplish want you want also. About $200
-------------
Description
Run both your air conditioners on only 20/30 amps of park power or a
4 KW generator. Cycle both your RV air conditioners alternately,
keeping both living and bedroom areas cool. Also cycles your heat
strips on and off. Pulse-AirŪ eliminates your worries about power
drops, burned-out compressors or accidental circuit breaker
tripping. Saves gas. Control box is 6 1/2" L x 4 1/2" W x 3 1/2" D.
Draws 5 watts max.
http://www.campingworld.com/browse/skus/index.cfm?deptID=3&skunum=9320&src=FPC
------------- |
Gary McFarland (Gearheadgary)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 24, 2004 - 9:19 am: | |
I think he wants to combine the supply, and as he stated, he doesn't want to split the circuits.
I think matching the phase is the issue, I don't know the rest, but I bet Richard does.
Gary |
Johnny
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 24, 2004 - 9:42 am: | |
Replace them with Honda Eu2000's, which are designed to do this with a simple connection cable. |
Steve Gibbs
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 24, 2004 - 10:16 am: | |
Although I don't know how it is done, I do know that at the hospital I worked at we had two big generators feeding the entire facility sharing the loads.
If on failed, then some equipment would start load shedding some of the less esential systems.
Contact your local Cat power systems dealer for some more informaiton.
FWIW
Steve
MC9 |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 24, 2004 - 10:34 am: | |
It is impossible to synchronize two gensets like this. It takes special governors that can talk to each other to maintain proper RPM and special voltage regulators that permit the units to share connected load.Perhaps I should not say impossible. With enough money, anything can be done!
If I were doing it I would wire it similiar to how a 50 amp 240/120 volt system power system is wired with split busses that can be paralleled if only one 120 volt source is available and operated independently if two 120 volt sources are available.
You would need to take into consideration the wiring of the shore cord also, and it appears at first glance that it would be a fairly complicated wiring scheme. Definitely not FF's KISS system.
Richard |
jimmci9 #2
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 24, 2004 - 1:13 pm: | |
i second johnny's vote of the honda's.. they have a cord that enables 2 generators to be used as 1... i'm the local dd power systems mechanic that works on cat 2301 governors in scr rooms on diesel/electric drilling rigs and power generaion... |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 24, 2004 - 10:20 pm: | |
When we moved to Ketchikan in the mid 70s, there was very little automated equipment being used by the power company(a city operation).
The way the generators were synchronized was very simple. Neon lights were rigged between the loaded and unloaded generators. When they were nearly in step, the lights would get bright and go completely out and bright again.
The operator merely adjusted the speed until this was happening slowly enough that he had no trouble throwing the switch to tie them together when the lights were out.
Quite a few times, they got impatient or were too heavily overloaded and they just threw the switch. Then, lights all over town would get bright and dim for ten or fifteen seconds while the generators got in step.
I don't recall a single blackout occurring after one of these episodes, but the currents in those lines must have been fierce.
I have no idea how much they screwed up around this town doing that, but about fifteen years ago, they automated a lot of equipment and we no longer have these problems.
If you wanted to hook two generators together, I would think that it would probably work if you got them in step in the first place. Then, the loads on the faster running unit would tend to lock it in. You would need to limit the excitation to prevent serious overloading of the lead unit.
For example, if you had two like units with, say, 100 rpm droop between full and no load and you had a fairly fine governor adjustment, you would only need to get well within 100 rpm difference.
The fast one would take the most load, and the slow one would pick up what would be an overload for the fast one. Neon lights would let you get them in step.
I haven't tried this, but it has intrigued me for some time. Maybe I will, one of these days.
That's about as close to KISS as I can figure that one. I don't imagine many people would feel like fooling around with it, though.
For what it might be worth.
Tom Caffrey PD4106-2576
Suncatcher |
Jayrjay
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 24, 2004 - 10:53 pm: | |
Like the man said, when they build electrical equipment, they put the smoke in at the factory, and if you try to hook them up without very sophisticated controls, you will most surely let the smoke out, and they will quit working. Then by the time you buy two more to replace them, you could have purchased one large enough to begin with. And maybe a new coach to boot, if you burn it down in the process! Maybe smoke the old lady, or one of the kids too, huh? Ponder the possibilities! ...JJ |
Gary McFarland (Gearheadgary)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 24, 2004 - 11:07 pm: | |
Hey JJ, the smoke thing is top secret, you're not supposed to let on.
Gary |
Stan
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 25, 2004 - 9:49 am: | |
Listen to Richard. Both generators have to run at precicely the same speed and voltage. When two A/C sources are out of phase bad things happen. |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 25, 2004 - 10:29 am: | |
I suspect the sunchronizing lights were incadescent rather than neon.
Oroginally all gensets were synchronized by connection an incadescent (clear) lamp between phase 1 of genset 1 and phase 1 of genset two. By slowly adjusting the speed of the slave unit, you could get the light to slowly blink on and off and you could see the dimness and brigtness very clearly due to the clear bulb. Since a neon bulb does not fire until the voltage gets to about 60 volts, I do not think it would be a good synchronizing indicator.
Anyway, the trick was to have the slave unit running just slightly faster than the master. This could be told by watching the blinks. Once the light then went to zero, the main switch would be thrown and the gensets paralleled.
At that time a load would be placed on the slave, since it was going sligtly faster than the master, part of the load would be placed on the slave and it would naturally slow down a bit and the two units would be operating nearly in synchronnism. It was then a relatively easy manner to adjust the voltage output of the slave unit until both units were carrying a balanced load. Takes a lot longer to explain than to do it. Three things have to be matched, frequency, KW and KVA. Now it is all done completely automatic.
Richard |
Marc Bourget
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 25, 2004 - 12:18 pm: | |
What guaranteed that the units remained in sync?
Would it be correct that a large genset copul, er coupling would experience less variation than a small pair?
Richard, all the "good guys" on this BB are with you in spirit!
Onward and Upward |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 25, 2004 - 12:35 pm: | |
Good hydraulic governors for one thing. Also, if one started slowing down it would put a load on the other unit whose load would increase and the current would start going up, which would then slow it down. A lot depended on the type of governor, they type of voltage regulator, and the power room operator himself.
Yes, the larger the units, the easier they are to parallel and to keep sharing the load, since the load changes are generally a smaller proportion of the load.
The largest system that I was ever responsible for was while I was working as a civilian in DaNang, Vietnam. I had responsibility for about 50 gensets scattered thruout the DaNang area providing all AC power for the US Military in the area. What fun. They were all paralled together for the whole area.
At the Jet Propulsion Laboratory I had four 500KW gensets for emergency power. Anytime they were running, I had an operator at the control panel. Any three of the units could carry the connected load so that if one unit failed, we never dropped the critical load. The Woodyard governors and Basler regulators really did an excellent job of keeping the load shared equally.
A point of interest. These were diesel fired units (Fairbanks Morse) that after coming up to operating temperature switched over to natural gas for operation. I was Facilities Manager at the Space Flight Operations Facility at the time.
Richard |
jimmci9 #2
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 25, 2004 - 1:09 pm: | |
the drilling rigs i work on are mostly diesel electric.... caterpillar diesels with kato or cat generators... the governors on the bigger engines, 398's, 399's, 3512's, and 3516's have either a cat 2301 governor or wodward electonic governor... and use actuators on the engines themselves...frequently i have 3 or 4 gensets paralleled ... creating a 4000kw package... the scr-controls make the process easy... just have to watch the load sharing.... on smaller engines, the 3300 and 3400 series cat engine, some use electronic governors with actuators and some use hydraulic 3% dashpot governors... its interesting work.... |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 25, 2004 - 2:18 pm: | |
Yep. I really miss it Jim.
Richard |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, December 25, 2004 - 10:52 pm: | |
Good point about the lamps, Richard. I didn't think about the 60 plus volts that it took to fire the neon lamps.
Thanks.
Tom Caffrey PD4106-2576
Suncatcher |
jimmci9 #2
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, December 26, 2004 - 8:11 am: | |
another trick..... got a photo tach and a florescent light??? plug it it...and hold the photo tach to the florescent tube... you'll read 7200 if you're on 60 cycles (hertz)....easier than putting a piece of reflective tape on a moving part of the engine... |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, December 26, 2004 - 11:23 am: | |
Jimmy, thats a new one for me. Never too late for an old dog to learn new tricks. Please explain, and what is a photo tach? What is the 7200 in reference to? is that on 1800 rpm engines or 1200 rpm?
Thanks for any help. I still like to learn, even if I will never use it.
Richard |
jimmc9 #2
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, December 26, 2004 - 11:53 am: | |
the photo tach is a hand-help tachomoter that uses reflective tape... put a piece of reflective tape on a pulley....then start the engine....the reflective tape is read by tach....and gives you rpms...on the other hand, the florescent lights beat at 7200.... 3600 from each end..so you get a reading of 7200 from the phototach..... |
jimmci9 #2
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, December 26, 2004 - 12:20 pm: | |
need to add.... the 7200 that shows up as rpms readout on the tach... signifies that it is 60 cycle.... slower than 7200 is less than 60 cycle... etc... does'nt matter if its single or 3 phase,... 2 or 4 pole generators,,... 1200 1800 or 3600rpm gensets...all its' doing is counting cycles... |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, December 26, 2004 - 1:11 pm: | |
Well, how about that? four pole generator operates at 1800 rpm. 1800 times four equals 7200. Two pole generator operates at 3600 rpm. 3600 times two equals 7200. Pretty clever.
Richard |
jimmci9 #2
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, December 26, 2004 - 3:07 pm: | |
it has more to do with the pulses that is necessary to make a florescent lamp work... than the number of poles in the generator...i know that this same discussion was on here a while back...and it has to do with the way a florescent lamp operates... |
Marc Bourget
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, December 26, 2004 - 4:33 pm: | |
Correlation vs. Causation, what's the difference? They both add up to 7200! |
Geobus (4108gmc)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 27, 2004 - 2:58 pm: | |
Like the Honda EU1000 and 2000's, which I think are inverters and allow one to connect them in parallel, can he somehow take the 120v from each gen set convert it to 12V to run or charge batteries and then come out of the batteries with a heavy duty inverter back to 120v. It may not be efficient but I think the new inverter technology is pretty forgiving.
Just and idea but maybe someone knows how to make it work.
Have a great day. |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 27, 2004 - 3:45 pm: | |
The inverters are great for changing DC to AC for operating AC appliances, or for changing AC to DC for battery charging, but they will not do both actions simultaneously.
It seems to me that your idea would take four inverters. Two for changing the AC to DC (one for each genset)and two for changing the DC back to AC. Probably would need two battery banks also.
Richard |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 27, 2004 - 3:48 pm: | |
Didn't this guy just want to run two ACs off one small genset? |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 27, 2004 - 3:58 pm: | |
I dont't think so. I think he wanted to use a second generator when he needed two A/C units. Been so much extranious BS since then, maybe a new thread is needed. LOL
Richard |