inverter upgrade

jtdiesel65

Hi,

I currently have an older Xantrex 4024SW grid/off grid inverter.

Off Grid and looking at central air. It's a 1.5 ton unit (nominal=12a.LRA=48a). I need 240v. I also have a 240V well pump for which I have a transformer. So I'm thinking about changing inverters to get 240v. The choices seem to be limited to Schnieder Electric XW and SW models.

It doesn't look like a single 4000w inverter will drive an LRA=48a. Does anybody know if stacked inverters change the surge rating? A new offgrid 4024 SW is rated for 3500W continuous with 32a max surge. If I stack two of these, I get 7000w continuous. But, the manual says "AC transfer relay rating of 30-amps remains the same." in a stacked configuration. So it's not clear if the surge rating changes.

Any other ideas on inverter choices?

thx

Cariboocoot

Re: inverter upgrade

Instead of stacking two smaller inverters just go with a single XW6048. Self-consumption is low enough, you get 240, and the it can handle a surge to 12kW.

The other choice would be Outback's Radian, but that is probably overkill at 8kW and the XW will be more "familiar" to you for having a Xantrex unit already.

jtdiesel65

Re: inverter upgrade

Thanks. Due to battery, I think I'm kinda stuck at 24v.

Cariboocoot

Re: inverter upgrade

jtdiesel65 wrote: »

Thanks. Due to battery, I think I'm kinda stuck at 24v.

What exactly is your battery configuration? It may be possible to reconfigure them for 48 Volts; it would be the same amount of Watt hours available, just lower Amp hours at higher Voltage. Likewise the Classic controller can handle 48 Volts, and the twentty-four Suntech panels should be able to make 60+ Volts for charging with a bit of rewiring.

jtdiesel65

Re: inverter upgrade

It's a forklift battery with only 12 cells.

Cariboocoot

Re: inverter upgrade

jtdiesel65 wrote: »

It's a forklift battery with only 12 cells.

Well that's a bother because two of the XW 4024's will cost about $4,700 whereas one 6048 is $3,200. $1,500 is a lot of money by any standard.

Magnum makes a 4024 http://www.solar-electric.com/maenms4040wa1.html but it's about the same money as the XW 4024. The surge ratings aren't much different either.

If you do stack smaller inverters you do get higher surge capacity as well. The thing is you are looking at a really big demand with 48 Amps @ 240 Volts (if I read that right).

I'd still look at upping the system Voltage even if it was necessary to replace the batteries. How much battery can you buy for $1,500?

jtdiesel65

Re: inverter upgrade

yeah, it's the surge that is the problem. Plus there are other loads in the house.

I was looking at the SW ( http://www.solar-electric.com/schneider-electric-sw-conext-inverter-4024-120.html) which is a bit cheaper, but it's not clear if the surge capacity doubles when you stack these. The manual said that the slave inverter sits idle up until the master is putting out 60% of it's capacity and then the slave comes online. I wonder how long it takes for the slave to come online.

Cariboocoot

Re: inverter upgrade

Good question. It may be in the manual somewhere, probably as 'so many' cycles.

Also look and see if they can be stacked for continuous operation. It uses up more power (2X inverter draw all the time) but would guarantee full power available on demand. You can do this with Outback's FX series, but as they are 120 Volts and 3.5 kW (for the 3524) you'd end up having to buy four of them and a transformer - not at all a good solution!

animatt

Re: inverter upgrade

Is this ac equipment you already have, if not probably a good idea to look at alternatives. It is just the peak LRA that is making this expensive. Do you already have a generator? Obviously it depends on many factors and budgets, but I am not sure if you could use generator support with just a single inverter. Have the generator already started and then start the large load with inverter supplying say 15amp. I am not sure the response time for that. Then have the generator stop or not depending on SOC of batteries. It seems vastly easier to just pick a more friend piece of equipment to run your air conditioning. Just some thoughts. matthew wright

jtdiesel65

Re: inverter upgrade

No it's not something I already have. However, it is the smallest one the vendor makes.

I called schneider and was told:

"The Conext SW4024 has a surge rating of 7,000 for 5 seconds. If you place two in parallel that would be 14,000 watts. This output is only for inverting and not for passthrough where you are getting grid power going through the inverter. The Conext SW has a 30 amp relay transfer relay and that relay is fixed and does not increase with an additional inverter. So for inverting only, the surge output of two inverters would be 14kw, and in your case you have about 11,520 so it should work as long as the time and surge is below what it is rated for on the Conext SW."

by grid power I think they mean when the generator is driving the load. I think that is fixed at 30 amps.

mike95490

Re: inverter upgrade

jtdiesel65 wrote: »

....

by grid power I think they mean when the generator is driving the load. I think that is fixed at 30 amps.

That's what the Generator Support mode is for. I know it's on the XW inverter series, don't know about the SW. 30A pass thru [7Kw] (on the generator, and 14Kw from the inverter. ) 21Kw, Not too much that it can't start.