Home » Public Forums » GMCnet » [GMCnet] Onan For Sale
| [GMCnet] Onan For Sale [message #150887] |
Mon, 28 November 2011 18:56  |
bdub
Messages: 1578
Registered: February 2004
Location: Central Texas
Karma: 5
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FYI
Onan Generator from 1973 23' GMC motorhome for sale. It was operational
when replaced with a new Honda generator, but needs a rebuild on the engine.
It is great for parts. $600.
Bud Worthington
Longview, Texas
bworthington@ccfww.com
903-445-4725
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bdub
'76 Palm Beach/Central Texas
www.bdub.net
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| Re: [GMCnet] Onan For Sale [message #150892 is a reply to message #150887] |
Mon, 28 November 2011 19:19  |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
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| bdub wrote on Mon, 28 November 2011 16:56 |
Onan Generator from 1973 23' GMC motorhome for sale. It was operational
when replaced with a new Honda generator...
|
Bud,
What type of Honda Generator did you use in the 23 foot GMC and what did you need to do to get it to fit?
Due to size restrictions on the 23, many have been looking for an alternative to the 4000 watt Onan power drawer.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Onan For Sale [message #150914 is a reply to message #150892] |
Mon, 28 November 2011 21:08 |
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On behalf of Bud Worthington [BWorthington@ccfww.com]
I used an EV4000. It is discontinued but still a few around. Small enough
to fit with minor modifications. I had East Texas Power Solutions in
Whitehouse, TX do the install.
Bud Worthington
Coghlan Crowson LLP
-----Original Message-----
From:] On Behalf Of Mike Miller
bdub wrote on Mon, 28 November 2011 16:56
> Onan Generator from 1973 23' GMC motorhome for sale. It was operational
> when replaced with a new Honda generator...
Bud,
What type of Honda Generator did you use in the 23 foot GMC and what did you
need to do to get it to fit?
Due to size restrictions on the 23, many have been looking for an
alternative to the 4000 watt Onan power drawer.
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bdub
bdub.net
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| Re: [GMCnet] Onan For Sale [message #150941 is a reply to message #150914] |
Tue, 29 November 2011 06:39 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
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The 3600 Generac makes a smooth installation in the 23'. I am not crazy about it for ther reasons, the install is clean.
--johnny
________________________________
From: Billy Massey <bdub@wtconnect.com>
To: gmclist@temp.gmcnet.org
Sent: Monday, November 28, 2011 10:08 PM
Subject: Re: [GMCnet] Onan For Sale
On behalf of Bud Worthington [BWorthington@ccfww.com]
I used an EV4000. It is discontinued but still a few around. Small enough
to fit with minor modifications. I had East Texas Power Solutions in
Whitehouse, TX do the install.
Bud Worthington
Coghlan Crowson LLP
-----Original Message-----
From:] On Behalf Of Mike Miller
bdub wrote on Mon, 28 November 2011 16:56
> Onan Generator from 1973 23' GMC motorhome for sale. It was operational
> when replaced with a new Honda generator...
Bud,
What type of Honda Generator did you use in the 23 foot GMC and what did you
need to do to get it to fit?
Due to size restrictions on the 23, many have been looking for an
alternative to the 4000 watt Onan power drawer.
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Onan For Sale [message #150945 is a reply to message #150941] |
Tue, 29 November 2011 07:09 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Rick Denney has used the Generac in his 23', but the inverter board failed and it is no longer supported by Generac. I don't remember what he has installed now, if anything. Ken Henderson has modified a Troy built generator and managed to get it in his 23', with minor fuel delievery problems.
Ken had also tried the discontinued Generac, which failed.
The 23' generator compartment seems to make it difficult to find a generator that will fit, and has 4k of power. I would think that the Honda 3k inverter quiet design, taken down to it's basic components might work. But this might be a budget busting experiment. The Honda 3k may not start the A/C's on the coach. I know that my Kipor copy, 3.5K will not start my old Dometic A/C. I have not tried it on my new A/C.
The Honda's do show up on Craig's List, but you have to keep looking. I managed to get 2 ev6010's, and still look for additional ones for parts. The ev6010 fits very nicely in the generator compartment of the 26', but is too long for the 23'.
I'll post physical size data, once I get out to the coach, and look at the Honda documentation.
It would be interesting for the photos of the ev4010 install to be posted.
Tom Phipps, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: [GMCnet] Onan For Sale [message #150962 is a reply to message #150945] |
Tue, 29 November 2011 11:19 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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I have to do some more research, my Generac manual says the machine swaps windings to allow variable engine spoeed and efficiency. It's speced at "55-65" hz. And a cursory look doesn't show anything with devices big enough to switch 4KW. So I got to wonder, is it a true inverter, or something Generac cooked up? More research is required.
Complaints (mine) revlove around the thing is nearly impossible to get at anything on it. The oil pressur esender is unreliable, so when the A/C kicks on and the RPM sags a bit, it shuts the thing off. Cure - unplug the wire to it... it doesn't appear to be accessible without major surgery. Generac offers a replacement, their 'cure' was, substitute a 10-PSI with a 5PSI. And, it regularly removed the 'run' wire from itys push on terminal. Out goes the run light and off goes the booster fan and the set stops. And it takes an hour to get the tin off enough to put the wire back and then replace everything.
I'm not sold on it.
--johnny
'76 23' Trandmode Norris - with a Generac
'76 Palm Beach - with a working Onan 6K
________________________________
From: Thomas Phipps <tph1pp5@yahoo.com>
To: gmclist@temp.gmcnet.org
Sent: Tuesday, November 29, 2011 8:09 AM
Subject: Re: [GMCnet] Onan For Sale
Rick Denney has used the Generac in his 23', but the inverter board failed and it is no longer supported by Generac. I don't remember what he has installed now, if anything. Ken Henderson has modified a Troy built generator and managed to get it in his 23', with minor fuel delievery problems.
Ken had also tried the discontinued Generac, which failed.
The 23' generator compartment seems to make it difficult to find a generator that will fit, and has 4k of power. I would think that the Honda 3k inverter quiet design, taken down to it's basic components might work. But this might be a budget busting experiment. The Honda 3k may not start the A/C's on the coach. I know that my Kipor copy, 3.5K will not start my old Dometic A/C. I have not tried it on my new A/C.
The Honda's do show up on Craig's List, but you have to keep looking. I managed to get 2 ev6010's, and still look for additional ones for parts. The ev6010 fits very nicely in the generator compartment of the 26', but is too long for the 23'.
I'll post physical size data, once I get out to the coach, and look at the Honda documentation.
It would be interesting for the photos of the ev4010 install to be posted.
Tom Phipps, MS II
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Onan For Sale [message #150988 is a reply to message #150962] |
Tue, 29 November 2011 16:19 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Compartment minimum dimensions:
EV4010 : 26.2" (width) x 14.6" (height) x 20.0"(depth
EV6010 : 28.1" (width) x 15.2" (height) x 21.5" (depth)
This includes an air flow allowance. The ev6010 easily fits the 26' compartment. I don't know about the ev4010, or the size of the 23' compartment. Weights are; ev4010 - 203 lb, ev6010 - 214 lb.
They share a common Honda engine, with the generator/inverter being the difference.
Tom Phipps,
MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: [GMCnet] Onan For Sale [message #151498 is a reply to message #150887] |
Sat, 03 December 2011 22:28 |
zhagrieb
Messages: 676
Registered: August 2009
Location: Portland Oregon
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Ken Frey put an Onan Microlite 2800 in my 26' for a PO and I like it a lot. It will run the AC and my microwave at the same time. I think it will fit a 23'.
Glenn
Glenn Giere, Portland OR, K7GAG
'73 "Moby the Motorhome" 26'
[Updated on: Sat, 03 December 2011 22:30] Report message to a moderator |
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| Re: [GMCnet] Onan For Sale [message #151546 is a reply to message #150887] |
Sun, 04 December 2011 11:42 |
pickle4k
Messages: 129
Registered: January 2011
Location: San Leandro
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Glenn,
My PO installed a 2.8 Microlite in my 23'. It fits, BUT I have to choose between running the A/C or running the rest of the coach house items. It will not support the roof A/C and the water heater, so I have to remember to switch over at night in order to have hot water for the shower in the morning. I am looking to install a larger unit with Miguel in So Cal.
Nick R. NorCal
76-23'Transmode-Norris
Rear Bath and
75-26' Avion
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| Re: [GMCnet] Onan For Sale [message #151617 is a reply to message #151458] |
Sun, 04 December 2011 20:04 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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| Richard Denney wrote on Sat, 03 December 2011 16:36 |
On Tue, Nov 29, 2011 at 8:09 AM, Thomas Phipps <tph1pp5@yahoo.com> wrote:
>
>
> Rick Denney has used the Generac in his 23', but the inverter board failed
> and it is no longer supported by Generac.
>
No, it was Ken that had trouble with the inverter circuitry.
The problem I had was the shaft rotation sensor that was used for engine
RPM sensing. When I replaced it, my Generac worked fine and it's still
working. When will the next thing break? Who knows?
Rick "who also replaced the ignition module because it was much easier and
might have been the problem" Denney
--
'73 230 "Jaws"
Northern Virginia
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The problem with invertor generators is that they will not tolerate an overload or a high starting load. They will immediately kick off while a convetional generator can load down and recover.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Onan For Sale [message #151912 is a reply to message #151617] |
Tue, 06 December 2011 13:46 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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On Sun, Dec 4, 2011 at 9:04 PM, Bob de Kruyff <NEXT2POOL@aol.com> wrote:
>
> The problem with invertor generators is that they will not tolerate an
> overload or a high starting load. They will immediately kick off while a
> convetional generator can load down and recover.
>
>
It's true with my 3.6 KW Generac, but it still depends on the generator.
The Onan uses mechanical inertia to absorb sudden loads. That takes that
monster flywheel and all the beefier engine parts to hold the engine
together with that much rotational inertia, which is one reason the Onan
weighs so much.
It's easy enough to put a soft-start kit on the AC, which uses a large
capacitor to store a starting boost for the compressor. In home AC units,
they call them hard-start kits, but they are the same thing. That will
reduce the startup surge quite significantly. My roof AC is relatively new
(maybe 15 years old) and it has a soft-start kit in it, near as I can tell.
The Generac speeds up when the AC compressor comes on, but it doesn't bog
down. There is no startup surge with the other devices we use.
But I try not to load the Generac close to its rated load except for those
surges. If I run the AC and the microwave, that's maybe 2500 watts total.
If the water heater is on, too, then it's up to the rated load. I've
certainly run the AC and the water heater, and the microwave and the AC,
and the microwave and the water heater, but never all three at once. That
leaves 800-1100 watts in reserve for other miscellaneous load and for the
startup surge of the AC. If I was running two AC units, I'd find a way to
put in a bigger generator, but in the factory spot of a 230, a bigger
generator is no mean feat.
I was ready to replace the Generac out of hand when the speed sensor died
and the generator came to a stop with a bang. When I dug into the options,
though, I ended up pulling the bed apart to get into the compartment from
the top, and then worked my way down the top of the Generac until I got to
the part. A chunk of work but what are you gonna do?
Rick "whose Onan could have been used to oil dirt roads" Denney
--
'73 230 "Jaws"
Northern Virginia
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| Re: [GMCnet] Onan For Sale [message #151958 is a reply to message #151912] |
Tue, 06 December 2011 19:40 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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I got a 3.6 Generac too. But it doesn't look like a proper inverter, and the shop manual mentions multiple windings and gives the very loose frequency spec. Most inverters will run dead nuts on 60Hz. So I can't figure what this toy is doing as it changes speed. I can't get at the top of it without removing the vainty and sink in the bathroom, and the cabinet under them.
According to the book,
"Stator output is between 336 and 540Hz. This corresponds to engine speeds of 2520 to 4050 RPM. A frequency cionverter changes the high frequency to a useful frequency i.e. one that is compatible with the load requirement."
"The SYSTEM CONTROLLER selects the correct number of generator pulses which are combined to form each 60Hz half cycle" It is neither a rectified DC drive to an inverter or a traditional volts-per-hertz synchronous setup.
Something new ever day in this GMC world.
I happened to have the Onan Guru out today doing annual service on a couple of my sets and asked him about the thing "Junkerac is wierd" was his comment.
My coach is set with a choice - AC or water heater, toggle switch selected. And another to choose shore power or genset.
--johnny
'76 23' transmode Norris with a strange AC electric system and stranger generator
'76 Palm Beach
________________________________
From: Richard Denney <rwdenney@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Tuesday, December 6, 2011 2:46 PM
Subject: Re: [GMCnet] Onan For Sale
On Sun, Dec 4, 2011 at 9:04 PM, Bob de Kruyff <NEXT2POOL@aol.com> wrote:
>
> The problem with invertor generators is that they will not tolerate an
> overload or a high starting load. They will immediately kick off while a
> convetional generator can load down and recover.
>
>
It's true with my 3.6 KW Generac, but it still depends on the generator.
The Onan uses mechanical inertia to absorb sudden loads. That takes that
monster flywheel and all the beefier engine parts to hold the engine
together with that much rotational inertia, which is one reason the Onan
weighs so much.
It's easy enough to put a soft-start kit on the AC, which uses a large
capacitor to store a starting boost for the compressor. In home AC units,
they call them hard-start kits, but they are the same thing. That will
reduce the startup surge quite significantly. My roof AC is relatively new
(maybe 15 years old) and it has a soft-start kit in it, near as I can tell.
The Generac speeds up when the AC compressor comes on, but it doesn't bog
down. There is no startup surge with the other devices we use.
But I try not to load the Generac close to its rated load except for those
surges. If I run the AC and the microwave, that's maybe 2500 watts total.
If the water heater is on, too, then it's up to the rated load. I've
certainly run the AC and the water heater, and the microwave and the AC,
and the microwave and the water heater, but never all three at once. That
leaves 800-1100 watts in reserve for other miscellaneous load and for the
startup surge of the AC. If I was running two AC units, I'd find a way to
put in a bigger generator, but in the factory spot of a 230, a bigger
generator is no mean feat.
I was ready to replace the Generac out of hand when the speed sensor died
and the generator came to a stop with a bang. When I dug into the options,
though, I ended up pulling the bed apart to get into the compartment from
the top, and then worked my way down the top of the Generac until I got to
the part. A chunk of work but what are you gonna do?
Rick "whose Onan could have been used to oil dirt roads" Denney
--
'73 230 "Jaws"
Northern Virginia
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Onan For Sale [message #151968 is a reply to message #151912] |
Tue, 06 December 2011 20:29 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Well, a capactor isn't going to store energy for an AC motor. So it's doing something else if a bigger one makes thye A/C start better.
I went back to the Generac manual - the 3.6 and 4.0 had a lot of thought put into the design, and it's passing fair strange. First of all, don't be running an electric clock or an older phono or tape machine - it really does vary the frequency over abut a ten hertz range. And I'm gonna haul out my scope and lookit the waveform, it is gong to be knida funky as well. The thing has two sets of windings run in quadrature, so it develpos a bunch of AC pulses. It runs each one through a couple of triacs, and switches them on or off as required to make a wave between 55 and 65 Hz. With a kinda lumpy top and bottom, but a clean zero cross. Voltage is directly proportional to engine speed - it's a permanent magnet rotor - so the controller jacks the speed to keep it between 115 and 120 volts, and then switches windings in and out based on the speed to get something approximating 60Hz. Power triacs are relatively cheap, no need for filtering and
such, and no commutator in the thing,.
They can build it for about 75 cents on Honda's - or any inverter's - dollar, and it retains the 'inertia headroom' of a volts per hertz unit like the Onan while also gaining the efficiency of a variable speed engine. Somebody in Waukesha got a bonus for this design. I'm impressed.
--johnny
3.6 Generac with a 23' Transmode warpped around it
6.0 Onan surrounded by a Palm Beach
________________________________
From: Richard Denney <rwdenney@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Tuesday, December 6, 2011 2:46 PM
Subject: Re: [GMCnet] Onan For Sale
On Sun, Dec 4, 2011 at 9:04 PM, Bob de Kruyff <NEXT2POOL@aol.com> wrote:
>
> The problem with invertor generators is that they will not tolerate an
> overload or a high starting load. They will immediately kick off while a
> convetional generator can load down and recover.
>
>
It's true with my 3.6 KW Generac, but it still depends on the generator.
The Onan uses mechanical inertia to absorb sudden loads. That takes that
monster flywheel and all the beefier engine parts to hold the engine
together with that much rotational inertia, which is one reason the Onan
weighs so much.
It's easy enough to put a soft-start kit on the AC, which uses a large
capacitor to store a starting boost for the compressor. In home AC units,
they call them hard-start kits, but they are the same thing. That will
reduce the startup surge quite significantly. My roof AC is relatively new
(maybe 15 years old) and it has a soft-start kit in it, near as I can tell.
The Generac speeds up when the AC compressor comes on, but it doesn't bog
down. There is no startup surge with the other devices we use.
But I try not to load the Generac close to its rated load except for those
surges. If I run the AC and the microwave, that's maybe 2500 watts total.
If the water heater is on, too, then it's up to the rated load. I've
certainly run the AC and the water heater, and the microwave and the AC,
and the microwave and the water heater, but never all three at once. That
leaves 800-1100 watts in reserve for other miscellaneous load and for the
startup surge of the AC. If I was running two AC units, I'd find a way to
put in a bigger generator, but in the factory spot of a 230, a bigger
generator is no mean feat.
I was ready to replace the Generac out of hand when the speed sensor died
and the generator came to a stop with a bang. When I dug into the options,
though, I ended up pulling the bed apart to get into the compartment from
the top, and then worked my way down the top of the Generac until I got to
the part. A chunk of work but what are you gonna do?
Rick "whose Onan could have been used to oil dirt roads" Denney
--
'73 230 "Jaws"
Northern Virginia
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
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| Re: [GMCnet] Onan For Sale [message #151969 is a reply to message #151958] |
Tue, 06 December 2011 20:29 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Y'All might as well go ahead and go Kludge:
http://www.gmcmhphotos.com/photos/showgallery.php?cat=5330
Now that I've figured out the fuel feed problem, it's very reliable.
Probably as noisy as the Onan was, but not objectionable to me inside. At
about $750 total, it's a real bargain for 5500 Watts. It surprises me how
easily it assumes and drops loads -- barely quivers when the A/C comes on.
Its biggest shortcomings are 1. It's not approved for the use so the
Forest Service might not like it. 2. I haven't found a way to monitor oil
level -- the little B&S engine is not pressurized.
Lowes no longer carries this battery start model & I don't know if TroyBilt
even makes it now. Other brands would probably work as well if you can
find one that will fit the hole.
Ken H.
On Tue, Dec 6, 2011 at 8:40 PM, Johnny Bridges wrote:
> ... "Junkerac is wierd" was his comment.
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Onan For Sale [message #152051 is a reply to message #151968] |
Wed, 07 December 2011 11:36 |
Richard Denney
Messages: 920
Registered: April 2010
Karma: 9
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Senior Member |
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On Tue, Dec 6, 2011 at 9:29 PM, Johnny Bridges <jhbridges@ymail.com> wrote:
> Well, a capactor isn't going to store energy for an AC motor. So it's
> doing something else if a bigger one makes thye A/C start better.
>
This confuses me. Capacitors are used all the time as starters for AC
motors. I see one or two of them mounted to the side of many large motors.
>
> I went back to the Generac manual - the 3.6 and 4.0 had a lot of thought
> put into the design, and it's passing fair strange. First of all, don't be
> running an electric clock or an older phono or tape machine - it really
> does vary the frequency over abut a ten hertz range.
It depends on which model. Ken and I both had the Impact 36G Plus, which
uses a separate dedicated inverter. The two stator winding outputs are
rectified to a DC output with that model, which is then wired as the input
to the inverter. The inverter changes it back to 60-Hz AC. Mine maintains
pretty decent frequency control--certainly as good as or better than the
Onan, whose frequency is derived from engine speed which is mechanically
regulated and which varies by load. I keep a line monitor permanently
plugged into a receptacle in the coach that I can see from the open door,
and it reports voltage and frequency.
The former 36G (without the "Plus") had direct AC output that was regulated
rather strangely. I did manage to find an installation manual that refers
to that model and that may be what you are looking at--at one time that one
was easy to find on the Internet. I have a service manual and an owner's
manual (with installation manual included) for the later model.
On the later model, the two phases of AC output from the stators are
rectified. The rectifier has an output to the control board (which is under
the sheet metal on the generator housing). That control board controls a
stepper motor for the throttle and other outputs for engine control
functions. It also has a 9-wire interface with the inverter, which I assume
is used to provide data to a processor in teh inverter which returns
control functions based on the load, frequency, and so on. The inverter
also gets the direct DC output of the rectifiers, and also a power-supply
input from one of the stators, which is, I'm sure, rectified and regulated
to operate the processor in the inverter. There is also a speed sensor and
a battery charger hanging off the stator.
The generator head is a permanent-magnet rotor that spins around the stator
windings. I can tell you how strong those magnets are. Fortunately, my
fingers let go before being sucked into a place where they would not fit.
I've never scoped the Generac waveform, and I suspect it's sloppy like many
of the inverter-style generators. It certainly sprays RF like there's no
tomorrow. You should have heard the widespread complaining the last time I
cranked it up during a radio-club operation.
Rick "who has, unfortunately, needed that manual" Denney
--
'73 230 "Jaws"
Northern Virginia
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| Re: [GMCnet] Onan For Sale [message #152077 is a reply to message #152051] |
Wed, 07 December 2011 17:00 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
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Senior Member |
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I believe capacitor start motors have a separate "out of phase"
winding in the motor to which the capacitor is connected. The
capacitor shifts the phase by a bit less than 90 degrees and
"kicks" the motor's armature in the correct (desired) direction.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~ ~ ~ ex-Palm Beach, 76 ~ ~ ~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
> Date: Wed, 7 Dec 2011 12:36:31 -0500
> From: rwdenney@gmail.com
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] Onan For Sale
>
> On Tue, Dec 6, 2011 at 9:29 PM, Johnny Bridges <jhbridges@ymail.com> wrote:
>
> > Well, a capactor isn't going to store energy for an AC motor. So it's
> > doing something else if a bigger one makes thye A/C start better.
> >
>
> This confuses me. Capacitors are used all the time as starters for AC
> motors. I see one or two of them mounted to the side of many large motors.
>
>
> Rick "who has, unfortunately, needed that manual" Denney
>
> --
> '73 230 "Jaws"
> Northern Virginia
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| Re: [GMCnet] Onan For Sale [message #152092 is a reply to message #152051] |
Wed, 07 December 2011 18:31 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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The capacitor generates a pahse shift to a second winding on the motor which is sufficient to make the rotor begin turning. It is normally then switched out via a centrifugal switch because once the motor is up to run speed, it is not only not needed, it bucks the main winding and reduces torque. Three phase motors don't require one because the relationship of the three phases pulls the rotor along from standstill.
In re the G and G+, the G+ was developed because the G didn't work very well. I spent the day with my genset mechanic doing PMIs on a couple of systems, he has had very poor luck with the G. Its positives are, it was cheaper to build, and it had the advantage of the stored inertia of the engine and alternator spinning to supply 'surge' loads like motors or compressors starting. An inverter system has no reserve beyond the capabilities of the DC supply and the limits of the switching devices. The inverters >can< be made to produce to good sine wave and a dead - nuts 60Hz if you're willing to pay for it. I've a 35KW three phase inverter in a closet up here which produces a lower harmonic content in its waveform that Georgia Power, whom it backs. It wasn't >even< inexpensive.
The problem with the G seems to be, the iteration of a fairly good idea was a bit too close to the edge, probably for cost reasons, to be reliable. Normal component value drift is lijkely ebnough to create trouble in it. Also, the + or one of its kin can be had with the inverter remotely located from the engine which produces some benefit in both packaging and in keeping the electronics cool.
--johnny
'76 23' transmode norris
'76 palm beach
________________________________
From: Richard Denney <rwdenney@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Wednesday, December 7, 2011 12:36 PM
Subject: Re: [GMCnet] Onan For Sale
On Tue, Dec 6, 2011 at 9:29 PM, Johnny Bridges <jhbridges@ymail.com> wrote:
> Well, a capactor isn't going to store energy for an AC motor. So it's
> doing something else if a bigger one makes thye A/C start better.
>
This confuses me. Capacitors are used all the time as starters for AC
motors. I see one or two of them mounted to the side of many large motors.
>
> I went back to the Generac manual - the 3.6 and 4.0 had a lot of thought
> put into the design, and it's passing fair strange. First of all, don't be
> running an electric clock or an older phono or tape machine - it really
> does vary the frequency over abut a ten hertz range.
It depends on which model. Ken and I both had the Impact 36G Plus, which
uses a separate dedicated inverter. The two stator winding outputs are
rectified to a DC output with that model, which is then wired as the input
to the inverter. The inverter changes it back to 60-Hz AC. Mine maintains
pretty decent frequency control--certainly as good as or better than the
Onan, whose frequency is derived from engine speed which is mechanically
regulated and which varies by load. I keep a line monitor permanently
plugged into a receptacle in the coach that I can see from the open door,
and it reports voltage and frequency.
The former 36G (without the "Plus") had direct AC output that was regulated
rather strangely. I did manage to find an installation manual that refers
to that model and that may be what you are looking at--at one time that one
was easy to find on the Internet. I have a service manual and an owner's
manual (with installation manual included) for the later model.
On the later model, the two phases of AC output from the stators are
rectified. The rectifier has an output to the control board (which is under
the sheet metal on the generator housing). That control board controls a
stepper motor for the throttle and other outputs for engine control
functions. It also has a 9-wire interface with the inverter, which I assume
is used to provide data to a processor in teh inverter which returns
control functions based on the load, frequency, and so on. The inverter
also gets the direct DC output of the rectifiers, and also a power-supply
input from one of the stators, which is, I'm sure, rectified and regulated
to operate the processor in the inverter. There is also a speed sensor and
a battery charger hanging off the stator.
The generator head is a permanent-magnet rotor that spins around the stator
windings. I can tell you how strong those magnets are. Fortunately, my
fingers let go before being sucked into a place where they would not fit.
I've never scoped the Generac waveform, and I suspect it's sloppy like many
of the inverter-style generators. It certainly sprays RF like there's no
tomorrow. You should have heard the widespread complaining the last time I
cranked it up during a radio-club operation.
Rick "who has, unfortunately, needed that manual" Denney
--
'73 230 "Jaws"
Northern Virginia
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GMCnet mailing list
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http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
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| Re: [GMCnet] Onan For Sale [message #152094 is a reply to message #152091] |
Wed, 07 December 2011 18:44 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
Alls it will do is shift the phase of the start winding farther than the originally fitted one. Capacitors do >not< store alternating current. DC only as a storage medium.
--johnny
'76 23' Transmode Norris '76 Palm Beach
________________________________
From: Richard Denney <rwdenney@gmail.com>
To: gmclist@temp.gmcnet.org
Sent: Wednesday, December 7, 2011 7:25 PM
Subject: Re: [GMCnet] Onan For Sale
On Wed, Dec 7, 2011 at 6:00 PM, D C *Mac* Macdonald <k2gkk@hotmail.com>wrote:
>
> I believe capacitor start motors have a separate "out of phase"
> winding in the motor to which the capacitor is connected. The
> capacitor shifts the phase by a bit less than 90 degrees and
> "kicks" the motor's armature in the correct (desired) direction.
>
All AC compressors use a "run" capacitor, maybe wired as you describe. A
hard-start kit wires in parallel (switched in with a relay) to that
capacitor to increase overall capacitance and charge storage.
Here's the data sheet for one:
http://www.coburns.com/Images/PDFs/NORDYNE-%20HARDSTART.PDF
It will definitely reduce the startup surge on a marginal power source.
Rick "noting the schematic on the last page" Denney
--
'73 230 "Jaws"
Northern Virginia
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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