Need recommendation 48V 3-4KW inverter/charger - no solar - just a big UPS.

[IslandBill]

I need to UPS a smart bakery oven (120v @ 14A) and related machinery (motors & computer control). I can make due with somewhere between 3kw - 4kw demand. I can size the battery storage as needed; that's not a problem. I can't find an appropriate inverter/charger.

I'd like an inverter/charger that charges via 240V but the output (inverter) is all 120V @ 60Hz, meaning the inverter is 100% carrying the load all the time.

Charging via 120V gets into circuit breaker issues at this load because when the grid power comes back on, the oven and other equipment is still running AND the batteries need charging resulting in more than 4kw demand at the load center after a power outage. High amperage circuit breakers for 240V are more available than what a load center can handle at 120V.

I want full sine wave because the machinery is all computer controlled.

 

[Brucey]

If you go with Victron you can configure the max AC draw from the grid in Amps, so you don't trip a breaker. A multiplus 2 5kVa 120V for example. But not sure what the max input you can provide is, as you say there may not be much leftover for charging if it's powering the load as well.

 

[IslandBill]

Brucey: Thanks for the reply.
The power outages are infrequent, so I can afford to charge at a slow rate. My actual max load is 3.4kw of already running motors, so no motor start surge. Turning off equipment ruins whole batches of whatever is in a large commercial oven and is what I'm trying to prevent.

I wouldn't mind purchasing solar equipment that can perform the function of an inverter / charger now (no solar) since I plan on having completely off grid solar in future. I'll check out Victron to see if their gear can do what I need now and add the solar later. The guy at Off-Grid Garage loves their stuff so that's also a recommendation.

 

[Brucey]

Sounds like a multiplus 2 or Quattro would work well as they are strictly inverter/chargers, no built in SCC. And have a proven reputation to be rock solid. They also have very good surge capabilities if you need them, as long as your battery is robust enough.

 

[IslandBill]

Thanks for the lead.

 

[Hedges]

Sunny Island. Available discounted on eBay.

For charging from 240V, put a transformer between the grid and it.

You can turn it into an off grid system with solar in the future.
Either DC coupled SCC, or move the transformer to its output to get 120/240V and AC couple to old Sunny Boy grid-tied inverters.

 

[IslandBill]

Thank you for the suggestion.

 

[webbbn]

Why not just use a 240V split-phase inverter and put the oven on one phase, and the rest on the other phase?

I may not be fully understanding the problem, since you also mention that the inverter will carry 100% of the load all the time, but that could somehow overload the charging circuit. Some inverters can augment inverter power with grid power, and visa versa, but that doesn't sound like what you're looking for.

Another option, if you really mean that you will not use grid augmentation, is charging the battery with a chargeverter and using a 120V inverter to power the load.

 

[IslandBill]

If I could get an inverter charger that inputs 240 and outputs 120 only on one phase, that would be the one I'd purchase. Split phase is second best. Motor startup draws a lot of current and I know these units can take over current for a short time, but I don't like relying on it.

Most of the time the motors are already running but the large oven cycles its motors as it sees fit. In a split phase set up, it's the startup current that may trip an inverter given other loads running at the time. The chances of this happening are small, but an oven load is worth a few hundred dollars worth of ruined product.

I'll take whatever I can get, but I'm aiming for the best solution and willing to settle for less. I thought about separate units but that's such an odd situation I didn't know if that was even possible, having these units connected output to input with the batteries as a large capacitor equivalent between them.

 

[webbbn]

Low-frequency inverters handle surges much better than high-frequency, so look for, and expect to get a big heavy box.

I would also spend a bit more on a higher-power inverter to ensure it could handle the surge and to provide a buffer, and I suggest getting a clamp meter with an inrush function to measure what you will need.

This advertises 18kW of surge capability, and it's not very expensive. I remember seeing some issues with the 10000T, so you might want to research it more, but there are many similar inverters.

Having a separate charger and inverter is not much different from an integrated unit as far as the battery is concerned. The main disadvantage is that you can't do grid passthrough. Low frequency inverters tend to be very inefficient, so you will use more overall power running off of the inverter all the time, but the advantage is that there's no risk of backfeed if that's a concern.

 

[IslandBill]

I'll read up on that unit. If it can run as an inverter charger for the time being plus allow for solar later, then it's a winner. Assuming each leg gets about 2.5kW steady, that would be perfect.

Thanks for the lead.

 

[Hedges]

Charging via 120V gets into circuit breaker issues at this load because when the grid power comes back on, the oven and other equipment is still running AND the batteries need charging resulting in more than 4kw demand at the load center after a power outage. High amperage circuit breakers for 240V are more available than what a load center can handle at 120V.

Sunny Island, and probably an other similar inverters, you can set the maximum AC current draw from grid (it will invert from batteries as needed), also maximum battery charge rate from grid. It has a separate maximum battery charge rate including AC and DC coupled sources.

Low-frequency inverters handle surges much better than high-frequency, so look for, and expect to get a big heavy box.

Although there is an exception to "prove" the rule, from the pioneers of the industry.

Midnight Rosie is HF and has 15kVA (20kVA per some sources) 60 second surge.

Category Products - MidNite Solar's

MidNite Solar Category Products.

www.midnitesolar.com

 

[schmism]

I need to UPS a smart bakery oven (120v @ 14A) and related machinery (motors & computer control). I can make due with somewhere between 3kw - 4kw demand. I can size the battery storage as needed; that's not a problem. I can't find an appropriate inverter/charger.

I'd like an inverter/charger that charges via 240V but the output (inverter) is all 120V @ 60Hz, meaning the inverter is 100% carrying the load all the time.

Charging via 120V gets into circuit breaker issues at this load because when the grid power comes back on, the oven and other equipment is still running AND the batteries need charging resulting in more than 4kw demand at the load center after a power outage. High amperage circuit breakers for 240V are more available than what a load center can handle at 120V.

I want full sine wave because the machinery is all computer controlled.

120v@14a = 1680w. how did you get to 3-4kw? Its an oven = 100% resistive load aka no "startup" load.

standard growatt 3kw will cover this. can configure for grid charging and set charging current from the grid. Can configure for grid first priority to transition to batt if the grid goes down.

 

[Johneb]

Outback 4048/8048 ? Or Samlex EVO 4248?

 

[IslandBill]

Hedges : Thank You

schmism: I also have dough mixers, sheeters, dough dividers, blenders, and various other bakery equipment that may be running concurrent to an oven load. There's no telling when the local power utility on the island goes off line. Some of that equipment, when in use, can't take an outage without ruining whatever it's working on, like a dough mix of anywhere between 60 and 110 lbs of dough. It's only that equipment that needs protection.

The oven is fired by gas, but is computer controlled with a large motor that reverses cavity air flow (convection) every few minutes for even baking.

I only want to put my minimum load on a UPS setup. My entire current operation (Bakery / restaurant) runs on 200A and 100A load centers. If all the equipment were turned on simultaneously, such as after an extended outage, I estimate my draw would be over 20kW in my current location. I'm planning a move to a specifically built site and there I'd have solar running everything, large battery bank with a diesel generator as backup. I don't want to connect to the island grid at all since their electricity is US $0.45/kWh and A/C alone (24/7/365) costs a small fortune.

 

[IslandBill]

Outback 4048/8048 ? Or Samlex EVO 4248?

I bought a Samlex POS because I really liked their manual and specs. After I got it I had it out with their tech support and just threw the unit on a shelf. I won't go into detail but I consider it junk.

 

[Johneb]

I bought a Samlex POS because I really liked their manual and specs. After I got it I had it out with their tech support and just threw the unit on a shelf. I won't go into detail but I consider it junk.

Sorry to hear your problems with Samlex. However Outback is considered about bullet proof and will run for years without a hickup.

 

[schmism]

schmism: I also have dough mixers, sheeters, dough dividers, blenders, and various other bakery equipment that may be running concurrent to an oven load. There's no telling when the local power utility on the island goes off line. Some of that equipment, when in use, can't take an outage without ruining whatever it's working on, like a dough mix of anywhere between 60 and 110 lbs of dough. It's only that equipment that needs protection.

The units parallel up to 6x. my 2x units cover 3-4K great and have been running for like 2+ years now.

 

[IslandBill]

The units parallel up to 6x. my 2x units cover 3-4K great and have been running for like 2+ years now.

Parallel operation would be a plus.

Thanks

 

[ePowerBank]

@IslandBill
For a 10A sump pump backup (UPS) I did a Sungold Power LFP6048, split phase low frequency 48v 6kw hooked up to ED4LL48 server type 5kwh battery. From the subpanel that feeds the sump pump (automatically) I added a switch that can backfeed my main panel as back up power. The only way I can back feed my main is with mechanical interlock so I'm protected from dual power source.

What I liked about this inverter is: pure sine wave, low freq, split phase (120/240), and low cost (~$1200). Got the battery for about $1600 from Signature Solar which I think offers biggest bang for the buck. I went basic sub panel setup mounting everything on board. Inverter (100#) mounted on Z channel, battery (100#) mounted on L channel (old bed frame).

One sub panel is for inverter while other is for generator. One transfer switch is so that I back feed main panel with either generator backup or inverter backup. The 2nd transfer switch is so that inverter is fed by either Main (AC passing through to sump) or fed by generator so battery is recharged if power outage.