Need advice for auto-start generator

alter · September 2017

Hello,

I purchased several years ago a "Xantrex XW4024" and the "Xantrex Auto Generator Start module", and it has been installed and working along with a bank of batteries for a while now, and I'd like to add a generator that turns on automatically every time the batteries get too low. I have on site a large propane tank, and I would like to get a generator that runs on propane, that would be compatible with my system. I've seen some Generac models that appear to fit the bill. I would just like to solicit feedback on them and see if anyone has any advice. Also the system is currently small, would it make sense to get a 22kw generator, or would it not provide any real benefit over the 11kw and just burn propane faster? There are only a few hundred amp hours of batteries and the electricity usage is very minimal (refrigerator runs off propane, and no air conditioners or high draw devices)

Also does anyone have a ballpark estimate on what I could expect to pay for a pro to install the generator and hook it up to the auto start module, propane, etc?

Thanks in advance!

Estragon · September 2017

A 22kw generator is huge for your requirements. I run a 4kw diesel to charge, and although 6kw or so would be better to handle some loads as well, the 4kw works fine to charge ~350ah@48v bank.

To charge "a few hundred amp hours" at 24v shouldn't need anything like a 22kw generator. Most likely, yes, you'll just be burning extra propane. Depending on the engine, it may also not be good for it to spend most of its life essentially idling. It may not get up to proper operating temps, move oil around properly, etc.

alter · September 2017

Estragon said:

A 22kw generator is huge for your requirements. I run a 4kw diesel to charge, and although 6kw or so would be better to handle some loads as well, the 4kw works fine to charge ~350ah@48v bank.

To charge "a few hundred amp hours" at 24v shouldn't need anything like a 22kw generator. Most likely, yes, you'll just be burning extra propane. Depending on the engine, it may also not be good for it to spend most of its life essentially idling. It may not get up to proper operating temps, move oil around properly, etc.

OK Yes I thought it was a bit much, I just want it to be able to handle future demands, larger devices, more batteries, panels, etc.

But it sounds like based on your experience, the 22kw would be overkill. I will mostly just be using it to charge batteries, although once in a while a higher draw device like a large power tool or something might be used. So I will focus more around the 11kw model. Any idea on how much I should expect to pay for the install? I suspect a small concrete slab needs to be poured, then connect a line into the propane tank, then it needs to be connected to the generator auto-start device, and the system to be programmed to use it. The generator comes with its own weatherproof outdoor enclosure.

Can anyone confirm whether the generac models work with the xantrex generator auto-start?

Thanks

Aguarancher · September 2017

If you are off grid, I think I remember reading about Generac not wanting to warranty their generators. Might want to check that out prior to purchasing.

alter · September 2017

Aguarancher said:

If you are off grid, I think I remember reading about Generac not wanting to warranty their generators. Might want to check that out prior to purchasing.

OK They do have one now called the "Ecogen" that is specifically designed for off-grid applications though. I'm having a guy from Generac come out on site, since I found that option on their website.

jonr · September 2017

That's an interesting generator. The specs say "it electronically manipulates alternator output to achieve 60 Hz electrical power" and "electronically controlled 3 windings instead of two". I interpret this to mean that it doesn't use an inverter. But if not, I'm not sure how it produces 60Hz as engine speed varies (2700 - 3600 rpm). Maybe it runs only runs at those exact speeds?

mike95490 · September 2017

Find out what your battery charger Power Factor is. That is important to generator sizing, along with PF for other large appliances like air conditioning or well pumps. Most generators need to be oversized to allow for lousy power factor of some loads, all depends on what your loads are going to be, I have a 3Kw diesel, which I run about 3 hours daily (in 2, 90 min shifts) to keep batteries going in foul weather. It handles all my loads, and I can still charge a bit from it too.

alter · September 2017

mike95490 said:

Find out what your battery charger Power Factor is. That is important to generator sizing, along with PF for other large appliances like air conditioning or well pumps. Most generators need to be oversized to allow for lousy power factor of some loads, all depends on what your loads are going to be, I have a 3Kw diesel, which I run about 3 hours daily (in 2, 90 min shifts) to keep batteries going in foul weather. It handles all my loads, and I can still charge a bit from it too.

OK thanks to all for the feedback. The generator is actually a 15kw one so it should definitely be powerful enough for future expansion. I will update the thread if and when I get it installed, in case anyone else wants to know how it went.

Need advice for auto-start generator

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