Inverters in parallel to power a house

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T1 Terry
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Inverters in parallel to power a house

Post by T1 Terry »

First, some background to the problem.
I installed 2 x PIP4024MS inverters in parallel some where around July last yr. The system has been running well until just before Christmas when the younger members of the family (who have no idea about power conservation or maximum limits) travelled up to this holiday house and proceeded to turn just about every appliance they could find on at the same time.
The inverter running in slave mode went into a code 51 (overload) shutdown, yet the master inverter continued to run until it was finally overloaded and shut down as well. The master inverter reset and continues to function as normal, the slave inverter will reset, but throws another code 51 after 20 mins operation.
MPP Solar asked what load type the inverter was running when it failed, I'm assuming they mean resistive or inductive, being a full house it would be a mix of both types.

The question that has come to my mind, is there a way to stop an inductive surge overload from possibly damaging an inverter already under high load stress?
Could this have caused the failure in one inverter but not the other?
Could there be a problem with load sharing between the 2 inverters that may have caused this problem?
Is there a way to protect any single inverter in a parallel group from suffering induction load overload damage?

I have replaced the faulty inverter with one we had in stock so I'd like to feel confident the "kids" won't kill that one. Could the fix be to add yet another inverter to make the system a bit more "kid" proof, that would be easier than trying to re-educate the "kids"

T1 Terry
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paulvk
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Re: Inverters in parallel to power a house

Post by paulvk »

I installed 2 x PIP4024MS inverters in parallel
At 8000 watts that is an boat load of amps at 24V close to 400 amps what batteries have you for this.
Could the fix be to add yet another inverter
That would be 600amps

T1 Terry
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Re: Inverters in parallel to power a house

Post by T1 Terry »

This particular set up has 6 x 200Ah Winston LYP cells in parallel x 8 in series to build a 1200Ah @ 24v battery. The 3 inverters at full load would only be around 240 amps because the load would not be enough to pull the voltage below 50vdc, at peak overload only 480 amps and the 0.5CA capacity rating for these cells would be 600 amps from the 1200Ah pack, so effortless as far as the battery pack is concerned.
The charging is via a 10kW solar array and a back up 10.5kva genset that is as noisy as a Mack truck without a muffler, so they certainly know it if they over reach on the capacity :lol:
Powerpack RH view 2.jpg
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Powerpack LH view.jpg
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T1 Terry

EDIT: This one is a 24v set up, best I use 24v for the calculations eh :oops: 26v under load is 300 amps and a peak of 600 amps for the 2 inverters and 460 amps for the 3 inverters in series, still under the 0.5CA of 600 amps, if they tried to put all 3 inverters under peak overload the RCD's would trip
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paulvk
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Re: Inverters in parallel to power a house

Post by paulvk »

Forgot about those batteries must be the smoke was like fog yesterday.
How about having the BMS shut down the inverters at a preset current

T1 Terry
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Re: Inverters in parallel to power a house

Post by T1 Terry »

paulvk wrote:
Mon, 13 Jan 2020, 12:16
Forgot about those batteries must be the smoke was like fog yesterday.
How about having the BMS shut down the inverters at a preset current
That would work for a long term load, it's the induction motor start up current that I think might be causing the problems. That load isn't constant so an over current one either the DC or AC side won't necessarily trip because the overload is so short term, but plenty long enough to fry electronic components.

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Rusdy
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Re: Inverters in parallel to power a house

Post by Rusdy »

Nice setup! :geek:

I must say, that is far more compact than I expected. At 30kWh, that is just a tad more compared to 2 x Powerwall-2 in parallel for roughly the same size (considering the gateway requirement as well).

Do you mind revealing how much your system cost (just the one in the photo)? I wonder whether that comes cheaper compared to 2-off PW-2 (which is roughly AUD26k)

T1 Terry
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Re: Inverters in parallel to power a house

Post by T1 Terry »

Rusdy wrote:
Thu, 16 Jan 2020, 09:46
Nice setup! :geek:

I must say, that is far more compact than I expected. At 30kWh, that is just a tad more compared to 2 x Powerwall-2 in parallel for roughly the same size (considering the gateway requirement as well).

Do you mind revealing how much your system cost (just the one in the photo)? I wonder whether that comes cheaper compared to 2-off PW-2 (which is roughly AUD26k)
The one in the photo is 32kWh, 10kW continuous, 15kW for 20mins (depends on temperature and type of load) and a peak of 20kW. That makes it about 2.4 Powerwall units. The specs on the Powerwall 2 unit are some what confusing as well
https://www.tesla.com/sites/default/fil ... _en_AU.pdf
The footnotes don't appear to support the specs in the main section, total energy 14kWh and useable energy 13.5kWh with footnote 1, but foot note one says at 25*C and actual charge/discharge power is 3.3kW.
The system in the photo can handle over 12kW of solar and 5kW of battery charging from the mains/generator while switching the AC through to the loads as well, so maybe another 10kW plus on the AC side and all can run simultaneously if you had a big enough generator. The operating temp isn't really comparable either, the Tesla is a max of 50*C internal temperature where the pictured set up can handle 70*C and lives in the cool under the house ..... very important is South Australia at the moment ;)
Without the solar (because the owner organised someone else to do that cause I wasn't real keen on being 3 stories up on a hot tin roof :lol:) was some where around the $32,000 mark including labour.
A smalls solar array and battery pack job, 15.6kWh @ 48v nom. but still the same 10kW continuous was around the $21,000 mark including labour. That one was a retro fit rather than an original equipment install that the first system was and being 48v rather than 24v the MPPT controllers in the inverters could handle the solar without the extra MPPT controllers the photo'd set up has.
There were a lot of RCD's and circuit breakers for both the solar and AC and additional cabling as well as an auto start for the back up generator involved in the pictured set up as well.

T1 Terry
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Rusdy
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Re: Inverters in parallel to power a house

Post by Rusdy »

T1 Terry wrote:
Thu, 16 Jan 2020, 11:31
...
The one in the photo is 32kWh, 10kW continuous, 15kW for 20mins (depends on temperature and type of load) and a peak of 20kW.
...
Wow! That makes me even more curious, what did the 'kid' do to overload it? The system got loaded for more than 10kW for more than 20 minutes? That 'kid' must be mining bitcoin somewhere in the house!! :lol:

At 32k is very cost effective indeed, considering with bells and whistles! Thanks for sharing!

Did I mention I really like the setup? Especially the wheeled cart :geek:

T1 Terry
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Re: Inverters in parallel to power a house

Post by T1 Terry »

Rusdy wrote:
Thu, 16 Jan 2020, 12:07
T1 Terry wrote:
Thu, 16 Jan 2020, 11:31
...
The one in the photo is 32kWh, 10kW continuous, 15kW for 20mins (depends on temperature and type of load) and a peak of 20kW.
...
Wow! That makes me even more curious, what did the 'kid' do to overload it? The system got loaded for more than 10kW for more than 20 minutes? That 'kid' must be mining bitcoin somewhere in the house!! :lol:

At 32k is very cost effective indeed, considering with bells and whistles! Thanks for sharing!

Did I mention I really like the setup? Especially the wheeled cart :geek:
Rooftop swampy on full power, water pump pulsing on/off to lift the water to the roof 3 stories up, all the lights and entertainment system, an array of Christmas items that all do something, sort of like Grace Bros once did in their display window, a kettle, toaster, assorted kitchen appliances, then the girl friend decided to turn the deep fryer on as well ..... I'm guessing the pump surge on start up as it is an induction motor and the swampy on the roof that is also a big induction motor might have been the killers that produced a load to fast for the overload protection to shut the inverter down.

This is the job we did just before Christmas
Woodchester off grid 1.jpg
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Before
Woodchester off grid 2.jpg
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Finished
Woodchester off grid 3.jpg
Woodchester off grid 3.jpg (54.84 KiB) Viewed 182 times
Battery pack with balancers.
Next job on that one is to replace the 20 plus yr old panels that were "professionally wired" with twisted together 2.5mm cable to end up with a 2S12P solar array of what appears to be 170w panels and a Vmp of 60vdc @ 25*C (not a common event in South Australia) to charge lead acid batteries that required 66v to equalise :roll:

All the systems are all set up to Bluetooth to a Smart phone using a Victron 712BMV, all the battery details and a warning if battery voltages or SOC drop below a preset point and if the battery voltage goes above a preset point.
The clear lid box with the 2 LCD displays is a combination secondary charge controller referencing cell voltages rather than combined battery voltage and a battery isolator if the SOC, battery voltage or any individual cell voltages drop below minimum specs. We try to hold 5% capacity in the battery so if the system does shut down the owner can over ride the isolation so they can see what they are doing and stop the wife from screaming at them while they fire up an alternate charging method. That only happens if things went real pearshaped and the generator either wouldn't auto start or was out of fuel.
The kid at the other install managed to meet all the required parameters on a previous unsupervised house stay including no fuel in the generator .... he had syphoned it to use in the ski boat rather than driving to the servo with the jerry cans .......

T1 Terry
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