Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

is it better to run the generator once a month or can it be stored until it is needed.I read it should be run monthly under load so the generator head stays magnetized.Is this true?

Good question. 

I've left my home emergency  generator unfired for a good 18 months.  I fired it up this fall and it was fine. 

I've got a diesel generator at my camp that I leave in storage for six months every year for close to 30 years now.  It always fires up and pumps out juice every spring.  

Maybe there are certain types of generators that have exciters that needs a regular electrical charge.  I don't know.  I'm sure there are people here who probably know.

A modern generator is okay to be stored for an extended time. There's really nothing in the mechanical or electrical parts that requires exercise to keep it ready. Keep it dry and out of the weather and it can sit for quite a long time.

The same is not true for fuel. Be sure to drain out all the gasoline (or run it dry) if you don't expect to use it for 30 days or more. Today's gasoline breaks down much faster and debris can quickly form in the fuel system, often clogging up the carburetor and making the generator impossible to start, or run smoothly. To keep fuel handy, store it in a gas can, and recycle it by dumping old fuel (> 45 day old) into your car's fuel tank. Refill the gas can with fresh fuel.

If you have an electric start generator, connect a trickle charger to the battery to keep it ready to go.

Caveat: I work for Honda, but the preceding was my opinion alone.

I have a Coleman/Powermate generator I bought in 1985, I always store it dry (tank and carb.), never had a problem.  This past October with the blizzard and 3 1/2 days with no power it fired right up and got me through. The last time I had used it probably was 7 to 8 years ago, stored dry , covered in my garage. I did switch over to a synthetic oil half way through the last power outage. Since my last usage I have read alot about having to "excite" some units, I guess I must have been lucky during all these years. 

the key to not losing the magnetizem is to disconnect the load on the generator before shutting it down.   Shutting it down with a load connected is a no no

carlb wrote:
That makes sense not just for the generator but also whatever might be on at the time of shutdown, such as electronics etc. 

I have a 60 amp main breaker that I always throw before shutting down the power plant.  In all of my years, I've yet to have a problem.

yes electronics and even electric motors wont like it when the engine spools down and the voltage and frequency starts to drop

  Quite often during my long term outages my generator just runs out of gas......I just go out and fill-er-up again, starts right up and generates. Could running out of gas cause a problem? Sounds like I may be luckier than I think.......

That is, after it runs out of gas I disconnect it first, fill-er-up, start it up, then reconnect to my system. This is a wonderful site...... 

letting it run out of gas under a load is not good for the gen head or the loads that it is powering.   If you are running out of gas I suggest you go out to the generator when you have at least 1/2hour left of run time, disconnect the loads and shut it down to re-fill.  Some might refill it with the engine running but you are taking a big chance if you spill gas on the muffler or exhaust.  

The other option is installing a larger fuel tank.

Roger the good suggestions carib, I will do a better job of filling before running out. All this good info/input is well advised. Just never knew or heard that a shut down because of  gas shortage could be a problem. I will heed this word to the wise............thank you for the tip...... 

One explanation that I heard for why to shut down "manually" (shut off and disconnect the loads, then kill the engine), vs running out of gas, was:

- The more obvious, the voltage change and frequency change will likely not be good for electronics/motors. Maybe not a problem if you're running a simple light bulb, or basic heater ("dumb" resistive loads). But sounds like they could be rough on other devices.
- The aspect I'd never considered was that there is a voltage regulator in most modern generators. It's some sort of magic (to me, at least ) electrical device that basically amplifies the generator head's output voltage if it's below, say, 110V, or regulates it down if it's too high. Under normal operation, the regulator's job isn't too bad. But during an out-of-gas type shutdown, under a load, the generator head's output voltage drops as the engine slows. As the source voltage drops, the regulator tries to keep sending 110V to the outlet, so it cranks up its amplifier, can overheat, etc. Over time, you can damage the regulator when shutting down like this.

I have no idea how quickly real damage to the generator could happen. But I've been sure to avoid running the generator out of gas, on the occasions I've had to use it.

Plus, if you're going to shut it down "permanently" (not just filling the tank quickly), you want to disconnect the loads, then let it run for a few minutes under no load, so the engine's internal temperatures have a chance to drop, and equalize. Otherwise it's hot from running under a load, then when you abruptly shut it down, the airflow stops, and it stays quite hot, with localized hot spots. Again, just what I've read. Maybe a few minutes with no load is not really essential. But for the rare times I use it, trying to treat it "gently" is not a big deal, and is cheap insurance.

Of course, also disconnect any loads before starting it. Then connect them on one by one, once the engine is warmed up. Having a few motors (fridge, furnace, etc) all trying to start at the same time will put a really big load on the generator.

Back to the original question, I don't run mine monthly, the way the manual instructs. But I have not had a problem when starting it back up after maybe 6 months. I do plan to start shutting off the fuel flow, and running the carb dry, before storing it. Until now, I'd been shutting it down, *then* closing the fuel valve. That leaves gas in the carb, which can gum it up. For an engine that I do not run often, but is really required when I need it, I want to reduce the chances of a problem. Use fuel stabilizer if you plan to keep the gas in there for a while. Better yet, don't keep any gas in the carb or tank. As was suggested, keep it in cans, and put that gas into the car periodically, to keep fresh gas around. Sorry for the long post.

Real generators may lose their field strength over time. Self-exciting alternators do not have such problems. You may want to check you owners manual to see what you have....check to see if it refers to "flashing the field" or such. As far as cooling a generator/ alternator.. There should be no "hot spots" in the unit. Even a 240 v generator only running on one phase at full load should be able cool itself or disperse heat evenly, copper being the secound most wildly used thermal conductive metal after silver... My 2 cents Friiy

I'm thinking about converting my EU2000i's to a tri fuel option.

As far as running a generator with no load for a few minutes after use, that is something I have heard of all OPE or engines in general.

As far as a "Cool down Period".(no-load for X min after use)...  What is going to happen?  Is the engine going to get HOTTER than running under load?  Does anyone have a "cool-down period" for their car?

Just food for thought...

Friiy

friiy wrote:
Actually the engine will get hotter for a period of time after shutdown when running under a load.  When the engine is running air is being moved across the engine in large amounts to pull heat away from the engine.  In a water cooled engine the water is being circulated and cooled in the radiator to remove the heat.  When shut off both engines will heat soak.

The engine will cool down idling under a no load condition.  With an air cooled engine letting it run for a few minutes with no load will help it from heat soaking and possibly cooking the oil some.   A hard run water cooled engine should also be allowed to run at an idle for a bit before shutdown. 

Your car is not normally driven anywhere near its max load but a generator is.  If you take a car and run it hard under a load and shut it off I am certain it will puke water all over the place.  

I used to race both cars and motorcycles and we always allowed a idle cool down period after a hard run.  Drag race cars normally don't need an idle cool down because they normally don't get too hot in one pass, but  if you put a few passes on it in a row it will get quite hot and need to be cooled down by idling and blowing cold air, water, nitrogen  or nitrous through the radiator to help cool it down.


Carl

I disagree with the statement , not the proceedure. The engine will not get "physically hotter" if you shut it down, oil will not "bake". The worst condition that the engine or oil is under is full load, it gets no hotter. Anything that can't handle full operating temp. probly isn't worth having. I believe in a cool down period in my own person equipment. Not for the engine's (block) sake, but ease of putting the damn thing away or fueling it. Not trying to pick a fight I just think the idea is flawed as stated. We can all state "novelty engines" or special requirements, but as blanket statement I believe it's false. Especially in regards to OPE. Friiy

You're both right ... or you're both wrong, take your pick   It's a whole lot simpler if you just trace the heat path I'm not saying anything here you don't already know, just stating it differently.

In an air cooled engine the moving air extracts heat from the fins, which extract heat from the block [I'm including the more "solid", unfinned, parts such as the cylinder housing with the term block here]. The fins will be cooler than the block under normal conditions.
This is where the engineer who designed this engine has to know his stuff, and most of them do. Anyone who has had a mouse build a nest under the cooling fins and seen what happened to the engine can tell you that.  Sizing the fins and the fan (flywheel fins) and designing the tins is critical, but we don't have to worry about it since the engineer already did.
When the engine is shut off, there's no moving air and less heat will be absorbed by still air. If the fins are still cooler than the block, they'll continue to absorb heat while giving up less, so  their temp will climb until some sort of balance is reached with the block. (this can include the actual engine block absorbing heat from the heads or jugs depending on the configuration) The block can only cool down as:
(1) It is giving up heat to the air around it and to the fins.
(2) No new heat is being produced.

In a water cooled engine the radiator (appropriately named, isn't it!) gives off heat to the air; the same principle applies except for the extra step of transferring the heat to and from the water that connects (heat path, not physically) the radiator to the block. That has a fan also. Shut that fan off and the radiator/water temps climb for the same reason - the water is absorbing heat from the block but the radiator is no longer absorbing as much heat from the water as it did because it is no longer ... radiating. So the water can get hotter and start spitting out the pressure relief on the cap.

Update after reading this: Remember that the various parts of a running engine will be at different temperatures. Once that engine is turned off, the parts that are bolted together will tend to stabilize. Parts that were cooler become hotter, and other parts will cool down. Most likely the combustion chamber will be the hottest and the tips of the fins the coolest.

When I was tuning/testing my twin cylinder air cooled two stroke Yamaha motorcycles, I'd use an infrared thermometer to check the heat on each cylinder/head/exhaust pipe etc. to see if the readings on each side of the engine were reasonably close.  While the engine was running, the heat remained consistently higher than shortly after shutting it down. 

I've never seen an occasion when any part of the engine actually returned a higher temperature reading after shutting it down.   Finned parts of the engine cooled more rapidly than say, crankcase areas.  Exhaust pipes cooled the quickest due to having the highest temperatures vs. ambient temperatures. 

That makes sense. Totally finned jugs with no tins so you'd have direct convection. I'm sure you noticed that stopped at a light on a hot day! I know I did. Something like an Onan twin, even some B&S single cylinders, would surround those fins with tins that trap heat when there is no air being forced through them.

I stand by my assessment that it is best to idle down an engine that has been working hard for a few minutes before shutting it down. Exhaust valves and seats get very hot when the engine is run hard under a large load and if when you shut down the engine the exhaust valve is closed a lot of heat is trapped in the valve and seat. Idling down for a few minutes allows the exhaust valve and seat to cool a fair amount before stopping the engine.

carlb wrote:
I have no problem with the idea of allowing the engine to idle for a bit after a long hard run.  It's something I normally do with a riding mower for instance.  After cutting, I'll disengage the mower blades, lower engine rpm and casually ride the machine back to the storage shed.  If nothing else, the lower engine speed will continue to circulate oil which may allow the cooling of hot spots on cranks, bearings, cylinders and valves for instance.  Don't think it would hurt any with a generator.  Particularly if the generator had been operating near maximum output.  Leaving it spinning with no load would also likely assist in cooling the power head which would be beneficial for bearings and electronic/electrical components.

I do not agree however, that an engine will continue to "produce" heat once it's shut down.  When combustion and movement stops, so does the production of heat.

Agreed that the engine won't continue to "produce" heat after shutdown. That is, the hottest point in the engine (wherever that may be) will only get cooler. However, things near it may warm up.

I had an interesting example of the getting-hotter-after-removing-the-heat-source phenomenon a few years ago. We were injection molding some solid round b a l l s. Maybe 1.5" in diameter. The plastic material is injected at about 450-500F. The mold is cooled with roughly 80F water. A typical injection molded part is quite thin, relative to its surface area. These, however, were extremely thick, much more so than would be typical.

The plastic would be injected, and the parts would sit in the mold to cool, for quite some time (say a minute), so the outside would become firm enough that they could be ejected from the mold. During that time, the surface of the part is exposed to metal being cooled by 80F water. The center, however, is still very hot from the 450-500F plastic that you'd put in.

The interesting thing was that, when the parts were initially ejected from the mold, you could easily hold them in your hand. The outsides were warm, but OK. But wait 20-30 seconds, and you had to put them down, or you'd burn your hand. You'd removed them from the steel, which was drawing all the heat away. So as the remaining heat from the center (still at, say, 300F, to pick a number) continued to conduct outwards, the outer surface of the parts heated up a *lot*. This is in contrast to a typical-geometry injection molded part, which, to the touch, only gets cooler once it comes out of the mold.

Different context, but same phenomenon. No longer introducing any additional heat source (engine shut down), but remove some of the active cooling (airflow from flywheel), and the temperatures of some of the cooler areas will climb as things equalize.

Guys we could go round and round with this,    Say-we run a engine at full load for a few minutes, then to be nice guys, we remove the load to allow full airflow over our hot engine.....

Has anyone heard of the effects of "shock cooling".....  I have seen a lot of Franklin, Continental, Pratt and  Lycoming jugs replaced due to cracking from shock cooling...

More food for thought...

Friiy

I've hear aircraft guys around here refer to it as "super cooling" the engine.  Shock cooling is probably the same thing.  

Not particularly familiar with the phenomenon.  What's the cause and effect of shock cooling?   I assume it has something to do with shutting the engine down too soon after landing.


RedOct:

A similar but much simpler example of what you're talking about is taking a boiled egg out of the cooling water too soon.  Seems fine at first but is soon too hot to hold.  Simple matter of heat dissipation. 

Shock cooling refers to cooling the outside quicker than the inside,   the outside shinks and splits/cracks over the larger inside..

Friiy