Advice needed. Which genset for off grid?

frank8003

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Post #3 tells you how to save your life Cold is the absences of heat and can't stand low F°
If you got the wherewithall then also get a good commercial diesel machine.
Backups are necessary, Life is good, preserve it.
I refuse to even imagine being in temperatures below freezing, but to each His/Her own......
I already froze a few times and never again, I moved 1200 miles just to NOT put up with below body temp degrees.
 
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KTMGuy

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could be you need a DC charging generator to keep your batt bank up to level and continue using the inverter.
Hmm - right now we charge the RV through the shore line which is rated at 50A . We also have an adaptor and can flip a breaker switch from the inverter charger to a separate AC/DC charger just for the batteries, but you idea has merritt. Can you recommend a DC charging generator to look at?.

Vince
 

KTMGuy

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I think an AC generator is a must in case something happens to the invertor. I am assuming through all of this that you will be using wood for heat?
Wood and or coal for heat. We will also have a spare inverter charger just in case. I plan on lots of spares! Thats also why I want to keep the 802. Its been fine and the maintenance is easy and just plain works. Its looking like I just need another with the winter kit would be the best and simplest answer.

I do appreciate all the advice and comments! This place is awesome.

Vince
 

KTMGuy

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Post #3 tells you how to save your life Cold is the absences of heat and can't stand low F°
If you got the wherewithall then also get a good commercial diesel machine.
Backups are necessary, Life is good, preserve it.
I refuse to even imagine being in temperatures below freezing, but to each His/Her own......
I already froze a few times and never again, I moved 1200 miles just to NOT put up with below body temp degrees.
I know all about how good life can be. Ive been in war and lost friends saving my life or the lives of others. If I could go back in time to save them at the expense of my own life, I would do it in a heartbeat! So please dont tell me how to save my own life or give me simple science lessons.

Yes, its "my" choice to live in Alaska and my wifes choice also, so pardon me for saying it, but some people like the cold. Its also not year round either. Why, in Alaska the summer time temps hit 80 or even 90 degrees! I've been in lots of hot countries and a 6 month winter is just grand to me. Theres this thing called winter clothing and jackets and stuff. My truck has a really good heater if all else fails. (y)

Have a good day sir! I think I have all the advice I need now. Thank you all for your comments and advice.

Vince
 

Guyfang

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This is exactly what I was thinking in my first reply. I was a bit off on the generator dates because for some reason I keep mixing up my 002 with an 802. Old age, what can I tell you. But you have to remember that the military had access to an unlimited parts supply (absolutely incorrect. I spent 20 years in the Army, and endured many periods where this simply was not the case. In the early 70, we MADE, or fabrecated a repair of the bad parts, as there simply were not any parts to be had. Unlimited parts, is a civilian dream) AND they did not have to worry about paying for it, (once again, absolutely untrue. There is this thing called a budget. And the military has one and has to life with it. A commander only gets a certain amount of funds for the year, and that's it. The 70-80's were as tight as any time I ever saw. And company level, is USER level.) at least not at the user level. If they couldn't get parts they just replaced the genset, simple as that. (If you knew how easy it is to "Just replaced the gen set" you might re look that statement. Yes it can be done, but often it was not allowed. Money being the reason. Gen sets do not grow on trees. There is a document call MEL. Maintenance Expenditure Limits, that keep such practices as "just replacing a gen set", to a very limited option. You fixed it. Even if you needed several months.)You are not going to have that option plus, all those parts the military had are not as available (this is true) as they used to be AND, someone has to pay for them! (would not matter what type gen set it is. If you need the part, you have to pay for it.) and getting things to Alaska can be pricey. I like military stuff but I don't think I would put mine and my families life on the line depending on an older military genset. As was said, keep one as a backup but not a main source. If the civilian gen set were really so good, why do the military not buy them? There are ways to improve gen sets. Military or civilian. I would most certainly look into them. There are certain parts I would upgrade, for sure. And have running spares. A back up gen set.

A plan B is a must. But for long life, great dependability, I would always go for a military gen set.
 

Guyfang

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Hmm - right now we charge the RV through the shore line which is rated at 50A . We also have an adaptor and can flip a breaker switch from the inverter charger to a separate AC/DC charger just for the batteries, but you idea has merritt. Can you recommend a DC charging generator to look at?.

Vince
Sure. But 24 volt system.
 

KTMGuy

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Sure. But 24 volt system.
Well, boo. Thanks for trying. Hmmm, I just remembered something. Some of the guys used to preheat the intake on the generators? They would then start up in really cold weather. Is that correct? My diesel truck has a preheater smack dab in the middle of the intake and has always started even below 0*. No, I dont have a block heater on it either.

Vince
 
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rickf

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Ha! Forgive me for my poor choice of words. I watch too many episodes of the 3 Stooges.

Theres "needs" and "wants" in every aspect of life. Im old enough to want the heat, water, stove, fridge, tv, phones and entertainment. I have an awesome motorcycle that goes very fast and can spray dirt and rocks at people 100 ft away easily. I consider it a want and a need.

The sun angle is pretty near the horizon (21 degrees) in winter with an average of 3 hours of sunlight. The panels will only get an hour or 2 of sun if there are no obstructions in the way - like trees, of which there are many, so we will need a generator to charge the bank every 2-4 days depending. Solar panels have come a long way from even 5 years ago - very high efficiency, but they still need sun time. We're still debating on a ground mount or a tracking array on a pole.

We got 7 acres for $30k, so land is still cheap in places. The 20x24 modern log cabin will cost us $43k built and the solar power will be another $10k or so as we will install it ourselves. Im retired and have lots of time on my hands. Lots of people in Alaska and other parts of the world are "off grid" and do just fine in winter. If you want to see winter, then visit Norway - Alaska is the beach compared to that place. I've been to the sandbox several times and instantly thought how nice Alaska is in the winter.

Vince
I have been to Alaska a couple times in the summer, this goes back to before the AlCan highway was paved! I drove a truck up there and I never had so many flat tires in my life and on that road you change your own. That was when I found out about Alaska's state bird, The huge freakin mosquitoes!!!! One distracts you by flying in front of you and his buddy comes up behind and grabs you and you better be hanging on to something or he will take you away!!!
It sounds like you have this thing pretty much figured out. I have just seen so many people try this over the many years I was involved with the outdoors and at least half of them failed due to underestimating nature. And advice given. Didn't want to see another.
 

Guyfang

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120v @60A should be 7.2kW
Exactly. And running a 5 KW for any longer period, at 7.5 KW is asking a bit much. Everyone wants to load these sets to the max. Do you run your car at max RPM in 1st gear? Not long. If you plan a 5 KW load, and it spikes every now and then. No problem. Or 1-2 KW for short times, no problem.

You need to do a max possible load plan. Worst case plan. Then add about 4-5%. Then you can decide what you need. But right off hand, I would be leaning towards a 10 KW. But the plan is a must. Too little gen set, you are load managing. Do-able, but you can't sleep at the wheel. You have to MANAGE. When we were in the field, everyone and his dog hooked up "Just a coffee pot", "or just a TV". Well, before you know it, the set would kick off for over load. Reset, kick off. My cure was side cutters. I simply walked around cutting off plugs.

Too little load, waste fuel and wet stacking. Too little gen set, management.
 

Coug

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Coug, I'm tired so hope I get my words right...ya can't examine kw load for fuel usage comparisons. Since we're comparing a nearly identical 2-cylinder to a 4-cylinder...at idle 2 vs 4 of the same size pistons will use the proportionate amount of fuel, same holds true for at rpm...1800 rpm is 1800 rpm so the CFM the engines displace is exactly double, given the average fuel use since the pistons and injectors are approx the same. The only fluctuation would be a surge draw or constant high load draw.

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That isn't exactly how it works.
The 4 cylinder engine isn't going to be using the same amount of fuel in each cylinder as the 2 cylinder engine for identical overall power output with everything else being equal. The 4 cylinders are producing half the power output each of the 2 cylinders.

The general rule of thumb (at least for propane generators) is that it takes 16k btus of fuel to produce 1kw of electricity. There is still some minor fuel used just to keep an engine running even with no load, but you aren't talking a half a gallon per hour for those 2 extra cylinders.


To borrow real world numbers from another thread:
https://www.steelsoldiers.com/threads/mep-802a-fuel-usage-report.172820/
Post number 6 in this thread lists these results from one member's testing

Results for 802A

.25 gph at 600 watts
.28 gph at 1000 watts
.35 gph at 2000 watts
.45 gph at 3500 watts
.60 gph at 5000 watts

Results for 803A

.45 gph at 2000 watts
.50 gph at 3500 watts
.60 gph at 4500 watts
.90 gph at 9000 watts


So while the 802 is more fuel efficient (due to less rotating mass to keep spun up) the overall results aren't actually all that different when the 802 is under full load and the 803 is running half load (500 watts of power for the same fuel used, numbers underlined above).


Or if you want to look at this from another angle, I'll start with what you said. The 2 cylinder engine will use .5 gallons per hour for 5kw of load. The 4 cylinder has twice as many cylinders, so therefore it must burn twice as much fuel for the same 5kw of load because it is spinning at the same speed.
Then if the 4 cylinder engine is using 1 gallon of fuel to power 5 kw of load, but still only uses 1 gallon of fuel to make 10kw of load as stated in the manual, where is all that additional power coming from to power the extra 5kw of load you just added to it?
On the other hand, does that mean it will still use the same amount of fuel when there is no load applied to the engine? Will the 802 use the exact same amount of fuel at no load as it does at full load? (pretty sure looking at the numbers above that this isn't true)


The CFM of air entering the engine might be identical at 1800 rpms, proportional per number of cylinders, but that does not mean that the engine will be injecting an identical amount of fuel.
Diesel engines don't care much about the amount of air going into them as long as it is enough. Unlike a gasoline or other spark ignited engine, you don't have to achieve the correct ratio of fuel to air in order for a diesel to work. A diesel engine injects the amount of fuel it needs to maintain it's speed under load, and that is it. If you inject more fuel than it needs to maintain speed, even under varying load conditions, all you get is extra heat and soot.
 

Jeepadict

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I'm going to agree to disagree. My stuff obviously comes from a different place than your stuff. No sense in writing novels that won't change anything in the end. This was supposed to help a guy decide how to homestead off grid, not the finer points of debatable physics. I yield.

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Coug

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Exactly - the inverter can surge to 8000w. My plan as it is, is to have separate charging methods - charge from solar panels and a separate charge by genset as needed. I've learned to never rely on just one thing.

See my post above for the cabins power usage. I forgot to add the on demand instant hot water heater for the cabin - it'll be gas, not electricity.

Vince
The inverter output can surge up to 8kw, but what does it say about max input? If the generator is going to be a separate charger than the solar setup, you can size the charger according to the generator, as your battery bank should be more than big enough to handle any charge either the 802 or 803 would be able to produce.
At that point, the 803 will do a much faster bulk charge on the batteries, thus saving wear and tear on the generator. Then it's just a matter of whether you do a full topping/equalizing charge on the batteries which is going to be at a lower rate.
The 802 will be more efficient overall simply due to less rotting mass, and will run closer to ideal load during the entire charge cycle.

Overall, you will end up using more fuel with the 803. Minimum 10-20% more, maybe even more than that depending on how the charge controller is programmed.
 
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