Mmm.. fried inverter

[chilly2]

The breaker panel in my house is a lug load center, with no main breaker of it's own, so to de-energize it I have to go outside and flip a 100A breaker by the meter.

When the grid was down, I *had* a WZRELB split phase inverter ready to run the house, just a breaker flip away. There was a big notice on the procedure. Grid down - Go outside, turn off the 100A. Come back, turn on the breaker to the inverter. Grid up - turn off the inverter breaker, turn on the 100A outside.

You can see the obvious risk of human error, and despite years of diligently following the routine, this weekend I hadn't had my coffee (as the power was out) and forgot to turn off the inverter's breaker before restoring the grid power.

It was rather underwhelming actually. As I flipped the outdoor breaker I was like 'oh.... crap'. Walked inside, and there it was, just off, with a fried electronics smell.

A postmortem revealed nothing obvious. It looked pristine in fact. Alas that was as far as it went as I didn't know what else to check, so the inverter is toast. I thought I trusted myself enough, but still made the mistake, so I'm going to pay an electrician to run the 100A into a manual transfer switch, and put the replacement inverter there.

Oh well. A lesson learned!

 

[SparkyJJO]

Oops

 

[ricardocello]

Sorry to hear about that, never a good feeling to lose good equipment.
Thanks for sharing, so others who think they don’t need a manual transfer switch or breaker interlock can see what happens for themselves.
Even the most experienced and diligent people can make mistakes.

 

[HarryN]

The breaker panel in my house is a lug load center, with no main breaker of it's own, so to de-energize it I have to go outside and flip a 100A breaker by the meter.

When the grid was down, I *had* a WZRELB split phase inverter ready to run the house, just a breaker flip away. There was a big notice on the procedure. Grid down - Go outside, turn off the 100A. Come back, turn on the breaker to the inverter. Grid up - turn off the inverter breaker, turn on the 100A outside.

You can see the obvious risk of human error, and despite years of diligently following the routine, this weekend I hadn't had my coffee (as the power was out) and forgot to turn off the inverter's breaker before restoring the grid power.

It was rather underwhelming actually. As I flipped the outdoor breaker I was like 'oh.... crap'. Walked inside, and there it was, just off, with a fried electronics smell.

A postmortem revealed nothing obvious. It looked pristine in fact. Alas that was as far as it went as I didn't know what else to check, so the inverter is toast. I thought I trusted myself enough, but still made the mistake, so I'm going to pay an electrician to run the 100A into a manual transfer switch, and put the replacement inverter there.

Oh well. A lesson learned!

Welcome to the real world of electricity. It is so easy to make a small mistake, especially when tired. You are aren't the first and won't be the last. Now you are 'experienced".

 

[chilly2]

Sorry to hear about that, never a good feeling to lose good equipment.
Thanks for sharing, so others who think they don’t need a manual transfer switch or breaker interlock can see what happens for themselves.
Even the most experienced and diligent people can make mistakes.

Thanks! I do have some rough schematics for a new setup in the works. Might post them here in a bit if you're curious. I think they're fail-safe but other eyes on them would help.

 

[chilly2]

Welcome to the real world of electricity. It is so easy to make a small mistake, especially when tired. You are aren't the first and won't be the last. Now you are 'experienced".

I might update my title on here. Amateur fry cook.

 

[chilly2]

I've included...

- the current setup (that led to the death of the inverter)
- adding a manual transfer switch.
- replacing the grid tie inverters and the off grid with a nice new hybrid.

Adding the transfer switch gives me the same functionality as I have today without the ability to blow up the off grid inverter, at the cost of a new inverter plus electrician to add the transfer switch.

Then there's the second more expensive option...

As you can see from the initial diagram, the HVAC is invisible to my system as it's not part of the main panel. There's no space for the sense or inverter CTs, so I can't back feed, and even if there were, I would want a way to decide if I wanted the solar to power the HVAC at all or not.

In the Hybrid diagram I will have an AIO that can back-feed it's grid ac in port and monitor with CTs, while also supplying via load 1 or load 2 ports. Also, unlike the old grid tie inverters, there are dedicated CTs for each leg, so output will match house load far more accurately. It also can handle 10kw, so far more capable.

So the flows are...

When grid is up:
meter > 100a > junction > manual transfer (grid position) > panel > house.
meter > 100a > junction > hybrid grid terminal (in) (to charge batteries over night off peak)
hybrid grid terminal (back-feed) > junction > manual transfer (grid position) > panel > house. Zero export with CTs.

When grid is down:
hybrid load terminal > manual transfer (load position) > panel > house.

A circuit will be run from the panel out to an HVAC transfer switch along the same path as the 100A in.
The switch can be moved between the old invisible direct path and having the inverter and Sense monitor see it.

Finally, a Microair soft start will be put on the HVAC.

Not perfect, but a lot better.

Thoughts welcome. With the weather lately things are vulnerable to another grid outage while I deliberate over the above solutions.

 

[ricardocello]

In the Hybrid diagram I will have an AIO that can back-feed it's grid ac in port and monitor with CTs, while also supplying via load 1 or load 2 ports. Also, unlike the old grid tie inverters, there are dedicated CTs for each leg, so output will match house load far more accurately. It also can handle 10kw, so far more capable.

So you are also eliminating the old grid-tie inverters when you get the hybrid?
You already have an interconnect agreement with the utility company, so you probably don’t care if the Hybrid exports some power, right?
Remember, zero export isn’t zero.

A circuit will be run from the panel out to an HVAC transfer switch along the same path as the 100A in.
The switch can be moved between the old invisible direct path and having the inverter and Sense monitor see it.

Finally, a Microair soft start will be put on the HVAC.

That will let you power the HVAC in real time, which is one of my favorite things about my ESS (hybrid) setup.
I can completely offset the summer air conditioners with solar most of the day,

Not perfect, but a lot better.

A lot of this comes down to how hard it is to install new runs and transfer switches, and if you have the room.

 

[Brett V]

Lesson learned. I’m glad you are putting in a proper transfer switch, it will be safer for both your gear and people.