One of the agravating things about our english system of measurement is that it's a PITA to figure out pilot drill sizes for tapping holes.

Here's the easy way. You have a 3/8-16 bolt and need to know the drill size. Take the 16 threads per inch and invert it... 1/16. now take 3/8 minus 1/16. that's 6/16 - 1/16 = 5/16... there's your drill size.

Let's do that again.... 1/4-20 .... in that is 0.25 - (1/20th) = .20" . The correct answer is actually 0.2050 but it's close enough.

Backfeeding your house from a generator or solar inverter. You can either create a subpanel with your critical loads on it and feed that from the generator or solar, or you can install a generator interlock on your main panel. Just use the top left or top right breaker to feed in and this interlock "gate" will prevent you from having the main breaker and your generator on at the same time. I use this method to feed my entire house from my 12kw worth of inverters. In my case, I have enough batteries and inverters to run everything, but most people won't.

My advice is to mark all the breakers with a sharpie that need to be on when running on emergency power. Be sure to find all the breakers for the fridge and freezer as well as other comfort items like ceiling fans and room lights.

There are many types of generator lockouts available. And these are much cheaper than a 200amp transfer switch.

Note on the water heater: it is advisable to swap the heater elements out with 1500w 240v heater elements if you are running them off inverter power. That way you still have 10.5kw remaining for other loads in the house.

Additional note... You may find that some inverters don't have enough surge capacity to start a heat pump. Solark might not, and the transformerless inverters like growatt and EG4 probably won't either. Inverters with transformers that weigh 150lbs like Schneider or Sunny Island will absolutely start a heat pump.

https://youtu.be/-Ez4cbuy7IQ

These inverters are rated for 6.8kw each. This guy ran two in parallel at 17kw and still started a 5hp air compressor.

And two of them pull 37watts at idle.

Seriously worth considering if you want to run your whole house.

Quick reference chart.

When you work on batteries be damned sure to tape your wrenches. Wrap wrenches in electric tape and the shank of your screwdriver too.

My neighbor and I are working on a way to interface the Victron Smart Shunt to our SMA inverters. Smart Shunt is extremely accurate and can be used to keep track of SoC by directly measuring amps in/out. This is good if you have a mix match of BMS units that don't talk to each other. So our goal is to read the serial data from smart shunt once a second (contains voltage, temperature and SoC among other values) and pass that SoC along to the SMA inverter on CANBUS. The processor that does this communication bridging is an $7 ESP32.

So far we've done a proof of concept and gotten numbers from smart shunt and we've sent "canned" messages to the SMA inverters to make them happy. Eventually, we'll include features like forwarding all smart shunt data and all SMA data such as AC power in/out to a database via MQTT and then make a remote display for my kitchen.

CANBUS is pretty interesting... it's like a party line where any device can hear or speak to all other devices. The data structure is pretty rigid. In a system a variable such as voltage is assigned a number. Amps or temperature are assigned numbers as well. So we agree that a packet containing 100 will be voltage, and 101 will be amps, etc. The packet also has a place to store the value being communicated. So we might have a packet off 100=12.8 or 101=10 or 102=72 . That's 12.8v, 10amps and 72F.

the voltage on the CAN-L and CAN-H signals are usually the same. This is the "non active" state of the bus. When a device wants to send a 1 it does nothing and the termination resistors at each end of the line "float" the two lines to the same voltage. But when it wants to send a 0 it "yanks" the CAN-H to 5v and the CAN-L to 0v. Believe it or not this is a part of how the collision control works.

Imagine a room where 2 people stand up and speak at the same time. When one guy hears another speaking he stops talking.

Consider that two devices try to transmit at the same time. Each waits a few milliseconds after the last traffic on the network and each starts to transmit at the same exact moment. Each one sends a 1 or a 0 and looks at the voltage on the line. If one of them is sending a 1 (meaning they aren't actually asserting anything on the line. So as each device starts to send a 1 and it realizes another device is actively asserting a 0 (can L and H are 0 and 5v), that device will actually stop trying to transmit. This means that even if 10 devices tried to transmit, each would drop off as soon as it tried to send a 1 and saw someone else was sending a 0.

By the time a device as transmitted the ID number's last digit, it will be the only device that still "has the floor". It transmits the value such as voltage or temperature.

Continued.

The device also transmits a checksum and leaves a pause at the end of it's still on-going transmission. In this gap, all other listeners will quickly add up the check sum for what they've received and assert a "0" on the line if all is correct. Consider this to be a little applause after a speaker makes a statement. If no one fills that gap with "applause" the device will either think that it is alone or the packet got garbled and send it again.

The transmitter will then conclude the packet with a few 1's and 0's. Think of this as "shave and a haircut", and after a short intermission, each of the devices that yielded to the previous packet will start. Once again, the one with the lowest number packet will prevail.

So for each packet send, all devices play a game of "last man standing". It really is pretty slick. In my ham radio days we'd send an entire packet hoping for the best and often had desctrive collisions. With this method, order comes out of chaos due to the "last man standing" concept. SLICK.

And if all of that glaze ya'll over.... my wife said the rooster in one of our coops bristled up at her yesterday and attacked her leg. She hit it with a piece of PVC pipe and he retreated but bristled at her thru the coop fence. I told her you gotta beat him repeatedly to establish dominace. Like my dad used to say "beat your kids until they stop crying".

SO there.. ha.... one extreme to the other... goats, rabbit chickens, canbus and solar power. All under one roof. A one stop shop! 😁