best back-up LP generator in 4000-6000 W range?

Re: best back-up LP generator in 4000-6000 W range?

retrobolted wrote: »

1.4KW array, 870 AH Trojan Deep Cycle at 24V, a 4000W Magnum Energy Inverter/Charger and an Outback 80 controller.

That sounds a little small for the array... We recommend 5% to 13% range for solar (for proper battery charging), and 10%+ is pretty nice for a daily use/full time off grid system:

• 870 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 1,638 Watt array minimum
• 870 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 3,277 Watt array nominal
• 870 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 4,260 Watt array "cost effective maximum"

1,400 Watt array is less than 5%--For longer battery life and less generator use, you should be looking at a larger array.

We also used a Honda EU3000is during construction and, in the years since, as a back up generator. The system has worked brilliantly and I'm grateful for all the good advice I received.

I am hoping to get a little more advice at this point because my mom is getting on in years (she's 71) and running the back-up generator manually in winter is getting to be a bit too much for her. I also think it makes sense to switch to LP since she has tanks for heating and so wouldn't have to fuss with fuel cans, etc.

I wonder if setting up an electric/gravity feed fuel pumping system would work better... There is always the issue of running propane engines in cold weather and the possibly of freezing the tank as the generator runs... How cold does it get for her? How large is the propane tank? You may need a larger tank in order to keep it from getting so cold that it keeps the pressure up as the geneset+heater+stove+hot water etc. draws the tank down. Running a larger genset can make the problem worse.

Also--There is the issue of starting any engine in very cold weather... Gasoline is still the easiest.

One person here had very good luck running a Honda em4000sx (make sure it is the "sx") in cold weather. Has full electronic engine controller--including mixture/choke function. Can be modified to remote/auto start pretty easily.

- autostarts
- is LP
- runs 4000-6000 W ideally
- is *reliable* and *fuss free* for light use, say <150 hours a year

As I see it, the main options are:

1. Kit out the Honda EU 3000 with LP conversion, auto-choke and auto-start kit. This is cheap option but reliability really worries me, not of the Honda but of the system as a whole.

I have a friend that uses propane forklifts--Very good mechanic and older propane fork lifts are the bane of his existance--Always seem to barely run sort of OK. Problems with fuel system (vaporizers fail/leak, regulators that seem never to work right, hard starting). He is retired and getting well used lifts--But it has been less than fun for him.

I am not sure the eu3000i is worth the conversion... Look at the sm4000sx.

If you have fuel plumbed directly to the genset--Make sure the connections are made well and there is some sort of shutoff valve (electric/remote shut off that closes when engine is not running?). Also, is the generator (shed) away from the home and other "important" stuff... Fire always worries me, and autostart is just one more thing that can go wrong (one of the 9-11 buildings burned down because the diesel fuel from the basement was pumped up to the backup generators in the middle/upper floors--The broken fuel line's pump was powered by backup power and kept pumping fuel into the fire.

2. Cheap Generac-style back up generator. I think these are crap but if the usage is light, they could be replaced every few years if need be.

Maybe as the backup to the backup--Many of these "inexpensive" gensets seem to last ~100 hours and then fail. One series had some sort of plastic driver between engine and alternator that would fail in that time frame (maybe the newer ones are better).

For gasoline, the Champion brand seems to be rugged/reliable and available from Costco (in the US, I think it is this one) for something like $700... There is a similar unit available in Canada last I read here.

I am a bit believer in the Goldilocks generator (not too big, not too small, just the right size). Assuming that 10% to 20% rate of charge is "optimum" for your needs:

• 870 AH * 29 volts charging * 1/0.80 charger eff * 1/0.80 generator derating * 0.10 rate of charge = 3,942 VA rated minimum (87 amp DC charger)
• 870 AH * 29 volts charging * 1/0.80 charger eff * 1/0.80 generator derating * 0.10 rate of charge = 7,884 VA rated minimum (174 amp DC charger)

The 7 kWatt champion uses about 0.59 gallons per hour at 50% load (3.5 kWatt).

A 100 hours would be ~60 gallons of gasoline--Not too bad for deep winter in Ontario.

3. RV generator, e.g., a new Onan 4500 or 5500. I know the old ones have legendary reliability, but I assume that means with some sort of tinkering or fuss. I'm guessing a brand-new, out of the box Onan would be perfectly fine for 5-8 years with light use, regular maintenance, etc. These are all assumptions though so I'm hoping to hear more informed opinions.

Tony/Icarus has gotten some nice Onans out of RV Scrap yards for not too much money.

4. Something more serious, eg. a Lister-Petter or Winco 8000W (or larger) set up. Price worries me and I think it would waste fuel like mad given the size of the battery bank. Maybe fuel cost wouldn't be a big issue given the light use, but the initial cost is nonetheless daunting.

Diesel gensets--Need pre-heat and/or glow plugs for your cold weather? More complexity and electric power needed to get fired off... Again, do you have problems with diesel gelling in your climate? (note, I live near SF California--So my knowledge of cold weather is purely theoretical).

Also, with diesel you should run them (generally) at 40-60% minimum load. With the right size battery charger matched to the genset rating--You should be OK. Diesels are very good efficiency--Even at lower power levels (better than gasoline/propane for sure)--But that minimum load can be an issue. Wet stack, carbonizing, cylinder wall glazing can all be problems with running at low generator loads. The right battery charger and charging from 50% to ~80-90% battery capacity, then shutting down the genset is usually going to be your best/most fuel efficient cycling (and would keep a diesel happy too).

Does your mother have somebody nearby to help? I would still keep the Honda eu3000i serviced and ready to run--Having a backup genset for her that is still "relatively" easy to manual start/run is going to be critical for her (or nearby friend) to light off if needed.

Hopefully, some of our northern friends can help you here.

-Bill