5500 onan gen.

[tedskeet]

I am new here with a not so big problem.i have a vista 33T 2007 when I have the shore power cord pluged into an ac post and start the 5500 onan gen.in about 10 min it shuts off but if I plug the power cord into the gen.it runs great.i like to run it about once a week just to keep it oiled and once a month with a load on it.anyone know why it would shut off.

[worleybyrd]

Welcome sorry I can't help but someone will chime in soon

[edgray]

Originally Posted by tedskeet

I am new here with a not so big problem.i have a vista 33T 2007 when I have the shore power cord pluged into an ac post and start the 5500 onan gen.in about 10 min it shuts off but if I plug the power cord into the gen.it runs great.i like to run it about once a week just to keep it oiled and once a month with a load on it.anyone know why it would shut off.

Welcome to the forum.com.

I'm not sure I fully understand your problem / question, but generally speaking it is NOT a good idea to start your generator while already plugged into shore power. MOST coaches have a transfer switch which defaults to use the genset power and "disconnects" you from the shore power. I've never heard of a coach that is wired to use 120V AC power from two independent sources simultaneously, hence the transfer switch.

Please elaborate on why you think this is necessary, and please explain what you meant by "but if I plug the power cord into the gen.it runs great"

[winnie32v]

"but if I plug the power cord into the gen.it runs great"

Same question I had.
Need to clarify this..............

Also, even though I have a transfer switch, I NEVER start the Onan with the shore line plugged in.
I know what is SUPPOSED to work but I don't like surprises.

Advise please ......

[ct78barnes]

You must not have a transfer switch if you have to plug it into the gen set .When you are at a campground with power just plug it in . Then if you need to use the gen set you have to go out and plug it into the gen set plug and it will use the gen set for power.Our 2003 Sightseer was this way

[94-Newmar]

edgray: Many smaller Class A and C units do not have transfer switches. Instead there is a 30amp outlet wired to the generator right inside the shore power compartment. Want to run on genset? Just plug your shore cord into the genset's own 30amp outlet.

tedskeet, winnie32v: The generator is most likely shutting off with an error code of "overspeed". The generator is probably running too fast (RPM) when there is no load on and it's producing power over 65HZ in frequency (which will cause it to shut down after a few minutes).

When you have the coach plugged into the genset's 30amp outlet there is enough "load" on it to slow it down under 65HZ. If you're comfortable adjusting this yourself let me know and I can explain.. you'll need a volt/ohm meter that reads Hertz (HZ). Otherwise you need to take it to a tech whom can adjust it for you properly.

[John Hilley]

I believe the problem is that the generator doesn't like to run without a load.

[edgray]

Originally Posted by 94-Newmar

edgray: Many smaller Class A and C units do not have transfer switches. Instead there is a 30amp outlet wired to the generator right inside the shore power compartment. Want to run on genset? Just plug your shore cord into the genset's own 30amp outlet.

tedskeet, winnie32v: The generator is most likely shutting off with an error code of "overspeed". The generator is probably running too fast (RPM) when there is no load on and it's producing power over 65HZ in frequency (which will cause it to shut down after a few minutes).

When you have the coach plugged into the genset's 30amp outlet there is enough "load" on it to slow it down under 65HZ. If you're comfortable adjusting this yourself let me know and I can explain.. you'll need a volt/ohm meter that reads Hertz (HZ). Otherwise you need to take it to a tech whom can adjust it for you properly.

94-NEWMAR: Thank you, EXCELLENT post.

I never considered the fact a 2007 coach may not have a TS.

If that is true, I guess no harm can come from starting the Genset while plugged into shore power, except that the genset is making power with no place to send it, hence the shutdown after a few minutes without a load.

I hope you will agree that it isn't a good idea to "test" a TS by running the genny with the shore power still connected.

[Doggy Daddy]

Always run your genset under a load [a/c, toaster, microwave, hair dryer, portable heater, etc.]. If you don't, the valves will carbon up.

[Clay L]

I have to plug mine into a receptacle in the service bay also. Since we are in high desert for the summer with very low humidity and don't have to worry about needing to dry out the coils any more than just from the heat build up from the engine, once a month I usually run it for a hour or so while plugged into shore power to use up the fuel in the carb and have the slip ring brushes work on the slip rings some.
Mine runs until I shut it off.

[jerichorick]

When I worked for a living I did a lot of generator routine starts. Onan told us that we had to run them under load. The engine needs the load to run correctly and the generator end of the genset needs a load in order to stabilize the regulator (120VAC).

You can use adapters to go down from the 30A plug to a 20A plug. I would invest in a inline fuse holder and make an adapter fused at 15A to plug a flat iron or heater into. Use this as your 'loadbox'. If the generator quits in a short time with the arrangement you definitely have a problem. But, as stated by others, it is not a good practice to frequently run your genset without a load. You can get the Onan operators and service manual for this from Cummins.

[94-Newmar]

Agreed that the genset should be run with at least 1/2 load during exercise periods.. but we're not referring to exercise periods here therefore it must still run with zero load as well.

For instance, once the DC converter has successfully charged the battery(ies) and you are running the A/Cs in the summer when the A/C cycles off and suddenly there is no load on the genset anymore this unit will shut down. We certainly don't want it shutting down on an overspeed error between load cycles from the A/C. More than likely this is a simple governor adjustment. Once the OP can meter the HZ output from the genset unloaded and loaded we can help him adjust it.

[jerichorick]

I have not had experience with manual transfer switches in a real time situation. But it would seem that if the genset is plugged into service that there would be a constant load for most of the inverters I am familiar with are always charging or floating the batteries. This would be a load to the genset.

I have other questions about this type of system that are not for now. Without getting into extensive details, would it not be better for everything if the genset were started, run for a short time and then a switch was thrown to connect it to the coach and disconnect the line cord? I never feel comfortable inserting the power cord into a live outlet when the coach is demanding power. I like to apply power to the outlet after plugging in by operating the circuit breaker. Saves the plug and the equipment from unclean surges.

[John Hilley]

On most there is a 30 second delay after generator starts before switching.

[sswilson]

From what I have been told by a generator technician while he was replacing my voltage regulator--" the worst thing you can do is start and stop a generator while it is under load" They should be started no load, warmed a bit, and then add load. When you want to shut the Genny off, remove the load, let it stabilize, and then stop it. If you shut it off under load, the regulator is still searching for the power needed while the rpms drop. I was told that this will damage the regulator. I have a bill to somewhat prove it. Onan parts are not cheap. I used a jobber reg at about half the 500 bucks needed for Onan.

[KSCRUDE]

It hasn't been said yet, but propane also poses a high explosion and fire risk. We keep our rig in the garage and a propane leak in a enclosed area turns the building into a giant bomb. You don't have this risk with diesel. If we ever get another rig, it will be all electric diesel only powered. That's the only way I would ever give up the Norcold. Then we would have a residential fridge, and no propane tank on board at all.

[mel s]

Originally Posted by edgray

I hope you will agree that it isn't a good idea to "test" a TS by running the genny with the shore power still connected.

edgray

I don't see how starting the genset with the coach plugged into shore power could be a problem.

The function of a 'Transfer Switch' is to transfer the 120VAC power, from a running generator, to the coaches main electrical panel, (so the coach can use that power).
As far as I know that is the ONLY function of the transfer switch!

The Transfer Switch ALWAYS works if/when the genset is running...... (WHETHER OR NOT the coach is plugged to shore power).
If the transfer switch is not working the coach will not see generator power when the generator is running.

As far as I know that is the ONLY function of the transfer switch!

Is there another reason for a transfer switch?

[jerichorick]

Originally Posted by mel stuplich

edgray

I don't see how starting the genset with the coach plugged into shore power could be a problem.

The function of a 'Transfer Switch' is to transfer the 120VAC power, from a running generator, to the coaches main electrical panel, (so the coach can use that power).
As far as I know that is the ONLY function of the transfer switch!

The Transfer Switch ALWAYS works if/when the genset is running...... (WHETHER OR NOT the coach is plugged to shore power).
If the transfer switch is not working the coach will not see generator power when the generator is running.

As far as I know that is the ONLY function of the transfer switch!

Is there another reason for a transfer switch?

Transfer switches have many applications. Some are manual; put the shore cord plug into the genset receptacle or maybe flip a switch, and some are automatic. Some transfer small loads and others transfer building power or grid power. In our case we have small transfer switches, relatively speaking. The contacts in our ATS's are built to handle the current we draw at max with, I hope, a little head room. To slam one of these little devices into full load condition is not treating the little box with respect and WILL cause it premature failure. The inrush current to the AC unit that was on when you switched is very large. You may be running a heater or your inverter is pulling at its max. With relay bounce (inherent) arcing occurs and pits the contacts. Over time the resistance builds through the contacts and the switch gets to the point of not being satisfied with the voltage and starts to hunt.

As stated above about the regulator on the genset, it too has to be treated with respect. Applying a load after it has stabilized, (no load frequency and voltage are stable) about 30 seconds to a minute, will make the unit feel warm and fuzzy as it does what it is built to do.

I hope this helps you understand a little more of the complexity of our simple systems.

Happy trails,
Rick

[edgray]

Originally Posted by mel stuplich

edgray

I don't see how starting the genset with the coach plugged into shore power could be a problem.

MEL: As I understand them, TS are designed to automatically detect "when" 120V power starts coming from the Genset, and immediately switch off of the shore power it had been allowing to pass thru to the coach's electric panel. IOW, the TS is supposed to automatically "default" to genset power, and "disconnect" the panel from the shore power. But what if it doesn't???

My comment about "testing" the TS by deliberately starting the genset while connected to shore power was because I hate to think what may be damaged IF the TS "broke" and failed to accomplish its primary function. 50 AMPS of 120V unwanted current can do a lot of damage....... why take the chance?

[John Hilley]

The transfer switch actually defaults to shore power. When the generator starts, 120 vac is applied to the transfer switch coil, which pulls in the contacts and passes the generator power to the breaker panel.