10 kva hybrid solar inverter trips during switchovers

[DRSWAPNIL]

Hi, I am an eye doctor from india and have landed myself in a soup. Need some help.
We recently got a 3 phase hybrid solar system installed. The inverter is a solar hybrid Zeta 3 phase model by UTL, 18 solar panels of 540 watts each and 10 lead acid batteries for power backup. The system works great most of the times with good generation and good backup but there is a scenario which is causing us grief.
We have 3 1.5 tons split ACs (air conditioners) installed on this system. At any point of time a max 2 ACs run and during power outage we try to limit to 1.
The system can support 2 ACs without any problem when the state power (board power) is not working. The ACs start normally and run well. Each AC draws something like 6-6.5 amps of current.
When board power is also there, there is no issue.

We are having issue when the board power turns of due to any reason. For a split second when the state power gets cut off, the current draw of the AC increases from 6-6.5 to something like 30 amps. This triggers the inverter to a fault and it cuts the power off.
We have tried to install voltage stabilisers for 1.5 or 2 ton AC inbetween the AC and the solar hybrid inverter but to no avail.

https://www.upsinverter.com/product/zeta-hybrid-solar-pcu-10kva-120v/

this is the inverter and its running in Smart hybrid mode.

The installation person is not able to help at all. The manufacturer of the inverter is also not helping at all.

I dont mind the AC remaining off for say 1-2 mins once the state board power is off. All I need is for the hybrid inverter to not go into fault mode. All of my ACs are single phase ones.

I have attached a small video showing whats happening. Hope it helps. Any help would mean a world to me. Thanks

 

[BentleyJ]

Large start up surge currents with inductive loads like A/C or heat pump compressors, well pumps or shop equipment like air compressors or saws really test the limits of an inverter. Most of us who run Air Conditioning with an inverter use soft starters such as Micro-Air, HyperEngineering or Schneider.

Hyper Engineering HVAC Soft Starters

Hyper Engineering designs, manufactures, and exports single phase and three phase electronic software-driven soft starters for residential HVAC systems.

invertersrus.com

Also, really helps if 2 A/C units do not try and start up at the exactly same time. They should be set up each with a different delay timers. Most common built delay is 5 min usually built into the thermostat or PCB on the compressor unit.

 

[mciholas]

Adding soft start to the HVAC units is my first thought which has benefits all around. They probably sense grid drop and then restart the compressors at much lower current. You may need to find the "right" on to do this, I don't have specific suggestions.

Another thought is if somehow the inverter is trying to back feed the grid and that overloads it. How is this wired, exactly? Maybe this is a setup problem of some sort.

But ultimately, what you want to do is drop the compressor load as soon as the grid goes away.

I can see two ways to do this.

First, there can be a contactor/relay that is operated by grid power that drops immediately upon grid power failure. Then this contactor is closed again after 2 minutes on backup power. You can stage the units so that delay is not the same for each unit, say 2, 2.5, and 3 minutes.

Second, the units already have a contactor/relay in them. If you can modify them to interrupt that contactor control, which will be a low volts signal, when grid power goes down, and then restore that signal after some delay, you will get the same effect without having a big new contactor for the AC lines. Often, for split units, the contactor control is part of the control wiring between the air handler and the outdoor unit.

Does the inverter drop ONLY occur if an HVAC unit is running? If that is not the case, then the HVAC units are not the actual problem.

Mike C.

 

[automatikdonn]

Large start up surge currents with inductive loads like A/C or heat pump compressors, well pumps or shop equipment like air compressors or saws really test the limits of an inverter. Most of us who run Air Conditioning with an inverter use soft starters such as Micro-Air, HyperEngineering or Schneider.

Hyper Engineering HVAC Soft Starters

Hyper Engineering designs, manufactures, and exports single phase and three phase electronic software-driven soft starters for residential HVAC systems.

invertersrus.com

Also, really helps if 2 A/C units do not try and start up at the exactly same time. They should be set up each with a different delay timers. Most common built delay is 5 min usually built into the thermostat or PCB on the compressor unit.

+1 for soft start - they are worth every penny.