Offgrid - Use Low and High frequency inverter?

solardad

Solar Addict
Joined
Apr 13, 2020
Messages
398
Hi -

I can't remember where I saw the post on using a low and high frequency inverter for an offgrid setup but it seems like an unique approach to build a system.
Does anyone use this setup successfully?

Based on expected demands of an offgrid cabin I was thinking the following as an example:

Growatt SPF 6000T DVM-MPV 120/240 (low frequency 6kw/18kw surge) + a Growatt 5000ES (high frequency 5kw 240v)

6000T would have 2.5kw - 3kw of PV connected (250v mppt limit)
5000ES would have 6kw of PV (450v mppt limit)

The 6000T is connected to the load panel (120/240) and the 5000ES would be connected to the AC IN of the 6000T and both are connected to the same battery bank (15-20kw).

The 6000T is set for Utility 1st (then solar/battery usage), which means the 5000es is powering the 6000T
Per manual the 6000T can pass up to 60A UTL AC, which should cover 90-95% of the demands.

The 5000ES is set for SOL (solar/battery/utility) and I was thinking I could have the 5000ES connected to a generator and leverage the dry contact switch for a two wire start if the batteries dropped to a certain level the generator would kick on and provide backup battery charge.

Some thoughts / questions on the setup...
1. Is there an overall improved efficiency gained with the 5000ES passing power to the 6000T?
2. If house demand exceeds 5000ES limits would the 6000T make up the difference, blend in power?
3. No need for a seperate transformer, 5000ES is always leveraging the 6000T built in transformer
4. Setup has expansion options since the the AC IN limit is greater than what a single 5000ES can supply
5. Per the manual when the 6000T is doing AC passthrough the MPPT controller and battery charging are still taking place so I assume no impact or loss?

Am I missing something..? Does this setup work as I am envisioning it or is there a gotcha that would make this a crappy idea....?

Thanks!
 

upnorthandpersonal

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I'm doing something like that. When I have the power and need it, I use my MUST EP3000 low frequenct 6kW inverter. It's got about 50W or thereabouts self consumption, but it's great to drive wood processing equipment and other stuff. When I don't need the power, I use a Victron Phoenix 48/1200 which only has a 6W idle draw. They're bot connected to a transfer switch, so I can pick which one I need easily.

I don't use all-in-one units: I prefer my charge controllers to be separate devices in part because of this set-up. It gives me the flexibility to swap out inverters when I need it - for example if I decide the Phoenix isn't what I need anymore.
 

timselectric

If I can do it, you can do it.
Joined
Feb 5, 2022
Messages
4,759
Hi -

I can't remember where I saw the post on using a low and high frequency inverter for an offgrid setup but it seems like an unique approach to build a system.
Does anyone use this setup successfully?

Based on expected demands of an offgrid cabin I was thinking the following as an example:

Growatt SPF 6000T DVM-MPV 120/240 (low frequency 6kw/18kw surge) + a Growatt 5000ES (high frequency 5kw 240v)

6000T would have 2.5kw - 3kw of PV connected (250v mppt limit)
5000ES would have 6kw of PV (450v mppt limit)

The 6000T is connected to the load panel (120/240) and the 5000ES would be connected to the AC IN of the 6000T and both are connected to the same battery bank (15-20kw).

The 6000T is set for Utility 1st (then solar/battery usage), which means the 5000es is powering the 6000T
Per manual the 6000T can pass up to 60A UTL AC, which should cover 90-95% of the demands.

The 5000ES is set for SOL (solar/battery/utility) and I was thinking I could have the 5000ES connected to a generator and leverage the dry contact switch for a two wire start if the batteries dropped to a certain level the generator would kick on and provide backup battery charge.

Some thoughts / questions on the setup...
1. Is there an overall improved efficiency gained with the 5000ES passing power to the 6000T?
2. If house demand exceeds 5000ES limits would the 6000T make up the difference, blend in power?
3. No need for a seperate transformer, 5000ES is always leveraging the 6000T built in transformer
4. Setup has expansion options since the the AC IN limit is greater than what a single 5000ES can supply
5. Per the manual when the 6000T is doing AC passthrough the MPPT controller and battery charging are still taking place so I assume no impact or loss?

Am I missing something..? Does this setup work as I am envisioning it or is there a gotcha that would make this a crappy idea....?

Thanks!
I would actually go the other way around.
6000T feeding the 5000ES .
The 5000ES can share solar with AC input. (SUB)
This way, you get all of the available solar powering the loads. And charging the batteries.
 

solardad

Solar Addict
Joined
Apr 13, 2020
Messages
398
I'm doing something like that. When I have the power and need it, I use my MUST EP3000 low frequenct 6kW inverter. It's got about 50W or thereabouts self consumption, but it's great to drive wood processing equipment and other stuff. When I don't need the power, I use a Victron Phoenix 48/1200 which only has a 6W idle draw. They're bot connected to a transfer switch, so I can pick which one I need easily.

I don't use all-in-one units: I prefer my charge controllers to be separate devices in part because of this set-up. It gives me the flexibility to swap out inverters when I need it - for example if I decide the Phoenix isn't what I need anymore.

The end users who will be using the system needs more of a set it and forget it scenario. We put in a very basic MPP 24v inverter AIO about 3 years ago and it has been trouble free outside of a cleaning that was needed about a year ago, insect nests. So they basically want to upsize with that style of AIO inverter. Switching back and forth would not be in the cards for them.
 

solardad

Solar Addict
Joined
Apr 13, 2020
Messages
398
I would actually go the other way around.
6000T feeding the 5000ES .
The 5000ES can share solar with AC input. (SUB)
This way, you get all of the available solar powering the loads. And charging the batteries.
@timselectric Ahh ok so the 6000T can not blend the incoming 5000ES AC with it's solar...? That would be a bummer if so..

(Edit) looks like the MPP LVX6048 supports SUB, solar and utility power blend unlike the growatt low frequency versions

https://watts247.com/manuals/mpp/PIP-LVX/LVX6048 split phase manual-20210312.pdf?x49702#page12
 
Last edited:

RoySalisbury

Solar Enthusiast
Joined
Apr 24, 2022
Messages
104
I was looking over high and low frequency inverters today to find the right setup for my needs. I have a wood and metal show with various machines and tools (table saws, laths, mills, welders, ect). From what I can see I would probably want to go with a Low frequency inverter. But it would not need to be that big.. perhaps a 5kw or 6kw inverter. for everything else I could get away with a high frequency inverter (appliances, tvs, computers, ect).

What I was thinking of doing was taking two HF inverters in parallel (say 2 Growwatt 6K's) and put them as the main system. These would be connected to the solar arrays, batteries and household power. Then take a single LF inverter (say the LVX6048) and use it just for the shop. It would not share AC with the other inverters and would be on a seperate circuit. However, it would be connected to the battery bank for power. no solar hookup here (but I could add some if needed).

I'm looking at cost here mainly. 2 HF inverters is about the cost of a single LF inverter. And on the reliability front I don't have any surge issues on the HF systems.

Thoughts? Am I over thinking this? Right now on my Outback inverter (VFX3548) I can get small brownouts (surges) when a circular saw is turned on when the inverter is under high loads. I'd like to solve that.

Roy
 
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