Inverter that blends grid power

[rhinehart22]

Hello all, I am new to solar and am looking to build my first system. My project will consist of two stages: powering a large RV and then powering a mid-large house. I am hoping to find something expandable that will work for both.

I've been looking a lot into Growatt 5000 es and MPP lv6548/6048 as they can be wired in parallel. One of my biggest questions is if these inverters can blend grid power with PV/batteries to power large loads that exceed the maximum output of the inverter, meaning that if the inverter is outputting at 100% but the load is 250% of the inverter the grid will power the remaining 150%. Do either of these units do that? Are there any all in one inverter that operate this way? Recommendations would be extremely helpful as I have been searching for over a week and have not been able to find any answers.

 

[Lt.Dan]

I'm not sure if any other inverters will, but I own 2x LV6548s and they do not do what you are asking. You cannot exceed the output of the inverter in any way.

But, I have 13kw of available power, and thats pretty hard to exceed, I've only done it once and its because I exceeded just one inberter due to an imbalance in loads, so if I balance my loads more, it will handle it with ease.

There are people who buy 12kw Growatts for theyre whole house (Ian from Watts247 has one for his house) and he says its damn near impossible to overload that thing lol

 

[rhinehart22]

One thing that has brought up this concern is my recent learning that electric tankless water heaters require an insane amount of power, 27kW for some I have found. When there are large loads like that I would love to still use renewable energy as much as possible. I have heard that Outback and DEYE has inverters that can operate this way but the literature is a little confusing.

 

[mrzed001]

I'm not sure if any other inverters will, but I own 2x LV6548s and they do not do what you are asking. You cannot exceed the output of the inverter in any way.

But, I have 13kw of available power, and thats pretty hard to exceed, I've only done it once and its because I exceeded just one inberter due to an imbalance in loads, so if I balance my loads more, it will handle it with ease.

There are people who buy 12kw Growatts for theyre whole house (Ian from Watts247 has one for his house) and he says its damn near impossible to overload that thing lol

Hmmm If I remember correctly if they got a bigger load than they can handle they go into BYPASS mode (if there is AC power coming in).
Got it, menu 23: Overload bypass: When enabled, the unit will transfer to line mode if overload occurs in battery mode.

 

[Lt.Dan]

Hmmm If I remember correctly if they got a bigger load than they can handle they go into BYPASS mode (if there is AC power coming in).
Got it, menu 23: Overload bypass: When enabled, the unit will transfer to line mode if overload occurs in battery mode.

Yes but bypass is limited to 40a, which is LESS than the inverter will output. You CAN blend PV with Grid, but you still cannot exceed the 6500 watts (54.1a) that the inverter is rated at.

 

[Lt.Dan]

One thing that has brought up this concern is my recent learning that electric tankless water heaters require an insane amount of power, 27kW for some I have found. When there are large loads like that I would love to still use renewable energy as much as possible. I have heard that Outback and DEYE has inverters that can operate this way but the literature is a little confusing.

Is that 27kw continuously? Or in surge? The Growatt 12kw with surge up to 36kw for several seconds pretty easily from what I've heard.

Thinking about it, if its a water heater, it most likely won't surge, but holy sh*t 27kw are you trying to boil thousands of gallons an hour? My water heater is 12-1400watts and I almost never run out of hot water

 

[mrzed001]

Yes but bypass is limited to 40a, which is LESS than the inverter will output. You CAN blend PV with Grid, but you still cannot exceed the 6500 watts (54.1a) that the inverter is rated at.

I see this in the manual:
Max AC Input Current 60A

 

[rhinehart22]

Yes but bypass is limited to 40a, which is LESS than the inverter will output. You CAN blend PV with Grid, but you still cannot exceed the 6500 watts (54.1a) that the inverter is rated at.

This can't be a new idea; something like a hybrid bypass/pass-through that joins the grid input and inverter output together.

Maybe I am asking the wrong question. What kind of inverter (preferably an all in one unit) would I need to power a whole house, even with peak loads in excess of 27kW? If I am understanding you correctly, if I had two lv6548, I would still never be able to have loads greater than 13kW even with grid input?

 

[rhinehart22]

Is that 27kw continuously? Or in surge? The Growatt 12kw with surge up to 36kw for several seconds pretty easily from what I've heard.

Thinking about it, if its a water heater, it most likely won't surge, but holy sh*t 27kw are you trying to boil thousands of gallons an hour? My water heater is 12-1400watts and I almost never run out of hot water

My thoughts exactly when I learned that. I believe it is not a surge, but for up to a minute or two depending on how much water is needed.

 

[time2roll]

One thing that has brought up this concern is my recent learning that electric tankless water heaters require an insane amount of power, 27kW for some I have found. When there are large loads like that I would love to still use renewable energy as much as possible. I have heard that Outback and DEYE has inverters that can operate this way but the literature is a little confusing.

I would sooner install a compressor water heater with a tank. Should get 2x the BTU per kWh vs resistance heating. The heat is extracted from the house or garage to potentially reduce summer cooling loads.

 

[mrzed001]

This can't be a new idea; something like a hybrid bypass/pass-through that joins the grid input and inverter output together.

Maybe I am asking the wrong question. What kind of inverter (preferably an all in one unit) would I need to power a whole house, even with peak loads in excess of 27kW? If I am understanding you correctly, if I had two lv6548, I would still never be able to have loads greater than 13kW even with grid input?

You could, but why don't you buy a decent water heater that has a tank?
It would much more cost effective.
And still have a solar system that can run your whole house on a blackout, mix solar to grid power when sun shines ...

 

[Lt.Dan]

I see this in the manual:
Max AC Input Current 60A

Yes, and AC Input current is different from AC Bypass Current.

This can't be a new idea; something like a hybrid bypass/pass-through that joins the grid input and inverter output together.

Maybe I am asking the wrong question. What kind of inverter (preferably an all in one unit) would I need to power a whole house, even with peak loads in excess of 27kW? If I am understanding you correctly, if I had two lv6548, I would still never be able to have loads greater than 13kW even with grid input?

Its not a new idea, I believe Victron can do it, but you gotta think, even if it could bypass 2x the inverters limit, the LV6548 is still limited to 6AWG wire, which is limited to 55 amps. You cannot exceed your wiring rating. The only way to do this is with more inverters.

4x LV6548s would output 26KW if you want to go through the struggle.

 

[time2roll]

Easy enough to add a sub panel to power just the critical and needed items from solar/battery. The A/C, EV charging, W/H, electric dryer, electric oven or range can be utility power only fed from the existing panel. Your choice on what you move to avoid overload.

In time you could add a second inverter and subpanel to power the A/C or something else.

 

[rhinehart22]

I appreciate all the input and have learned a lot more. I guess I have one more beginner question which I thought I knew but am confused on now. With any inverter with grid input, you are never going to be able to use more power than the inverter is rated for even if using grid power? Are there some kind of external ATS that can make this happen. I ask this because even with a regular water heater, I would still have very high continuous energy usage and expect high surges.

 

[Lt.Dan]

A quick search shows the average tankless water heater draws 120a which is 28.8kw at 240v.

Time to start looking at a tank water heater lol

 

[mrzed001]

I appreciate all the input and have learned a lot more. I guess I have one more beginner question which I thought I knew but am confused on now. With any inverter with grid input, you are never going to be able to use more power than the inverter is rated for even if using grid power? Are there some kind of external ATS that can make this happen. I ask this because even with a regular water heater, I would still have very high continuous energy usage and expect high surges.

There are solution for that too with a relay/PLC
But a regular water heater does not have a big W need. Max 2-3000W.

 

[12VoltInstalls]

Plus, a water heater is an energy storage device. The on-demand just uses power: the tank water heater basically uses excess power and feasibly you can kill its input at sundown with the right relay setup.

 

[Sirtate]

The Tankless water heaters need serious energy. They're adding 120deg to flowing water at 10-15GPM... (50C at 50LPM)...
Water is a great heat sink, so BTUs/Watts are significant... Which is why most tankless use Propane/Nat.Gas for heat...

As mentioned, a 60Gal tank that can absorb heat at a slower rate, capable of being provided by solar is a better bet.
(the heat pump-heat sink idea for the A/C is a great plan, You're paying for that energy transfer anyways)

 

[summit]

have been running (now obsoleted) GeoSpring HeatPump water since 2013 set to HeatPump only. It draws at most 500-w. I would like to disconnect the resistive elements but I think the self-test would complain. I would imagine the current day HP water heater has similar draw. Am planning to operate it from an mpp5048-GMX

 

[wattmatters]

One of my biggest questions is if these inverters can blend grid power with PV/batteries to power large loads that exceed the maximum output of the inverter, meaning that if the inverter is outputting at 100% but the load is 250% of the inverter the grid will power the remaining 150%. Do either of these units do that? Are there any all in one inverter that operate this way?

The sort of inverters you are looking at operate in series with a grid connection. As such available output is limited to the output capacity of the inverter(s) no matter whether the source of power is from the solar PV array, a battery or the grid supply or any combination of these.

There are however grid-tied inverters (e.g. Fronius, SMA, Sungrow, Solaredge, Enphase, Huawei, etc etc) which operate in parallel with the grid supply. IOW these inverters supply what power they can to household loads and the grid supplies whatever balance is required.