The usual way to manage critical loads is to isolate them in a subpanel so that during an outage or other similar event you can power just that panel. That works more or less OK when you’re doing new construction, or you can easily access the wiring coming into your main panel. But if your panel is flush mounted and your wiring runs through the wall (as most home wiring does) then the job is messy at best. A critical loads panel also assumes you can anticipate future needs with perfect accuracy. For example, in my case the most critical load is going to be a pump in my pool equipment room. There’s no way I would have anticipated that, and it’s almost impossible now to manage that through a critical loads panel. It’s in what is essentially a separate house, with its own load panel, that is powered by a separate main breaker at the service entrance.
The method I’ve come up with might be useful to other people who need the option of powering only selected loads who don’t want to rewire their entire house to do it. Or for that matter in any situation where needs change unexpectedly–which is pretty much the definition of an emergency, or just life.
Load shedding is a common practice for powering critical loads–simply turning off loads that aren’t critical, either by switching off the load, or opening breakers. But it’s generally manual. Which means you have to be present to use it. Given the capabilities of smart devices and a system to control them it’s possible to shed loads without being present, either by remote control or triggered automation.
So here’s short version of what I’m up to–I’ll shed all the non-essential loads using Home Automation and just power the critical loads. Basically the high-tech version of going around your house during an outage and shutting off all the non-critical stuff. No re-wiring necessary, no additional panels, just a home automation system that will also make your home more pleasant, more energy efficient, and more secure. And you can change the loads dynamically, as the situation requires.
This approach continues and extends my underlying concept for the wildfire mitigation project I’m working on: I’m trying to make certain that all the major elements of the project provide other benefits beyond wildfire mitigation. I think installing single use systems that only deal with emergencies that may never happen has a strong likelihood of not being maintained after the immediate threat fades–and therefore might not be ready for use if the emergency occurs. I’ve seen this play out in numerous ways–from first aid kits that wind up will nothing useful in them to emergency generators full of old gasoline that’s turned to varnish in the carburetors. Solutions that provide other benefits and see frequent use will be maintained and improved if the benefits are worthwhile. For example:
- A solar power source with battery backup will see use every day, offsetting electric bills and supplying critical loads during outages.
- The Home Automation system I’m implementing to shed loads during a fire emergency or an outage also saves energy by managing the timing of larger loads better, and makes our home more enjoyable, more secure, and more efficient.
- Firewise landscape management around our home is actually easier to maintain than our typical overgrown landscape. The landscaping changes we’ve made increased air flow reducing our mosquito problem instantly, opened dark areas to light, improved the view and will probably help our citrus trees bear more fruit. I think we’ve increased the value of our home while making it safer from wildfires. Keeping vegetationfurther away from our house, pruning trees to raise the canopies, and thinning out overgrown areas with an eye toward reducing leaf litter and ladder fuels made our landscaping easier to maintain and makes the land more usable.
Here’s the detail of what I’ve been up to.
I’m working on a wildfire mitigation system at my home in Maui. I plan to have a water deluge system–basically an emergency sprinkler system using large agricultural sprinklers to hose down the house and grounds if a wildfire occurs. The system needs uninterruptible power and a source of water than won’t be cut off. The uninterruptible power will be provided by an EG4 12KPV inverter and an all-weather wall mount battery, the water source is a lap pool at my home.
The pool equipment room is part of a separate structure that includes a guest bedroom and caretaker apartment. It’s across the lap pool from the main house. It’s fed power from a separate 100 amp breaker that feeds a load panel in the caretaker apartment.
The main house has a 150 amp feed to a load panel in the garage.
In theory we could just feed the 100 amp service with uninterruptible power, but power outages are not unusual on the north shore of Maui, and we have two refrigerators that we’d like to supply, as well as general LED lighting. My wife is diabetic, so refrigerating her insulin is critical, and two refrigerators full of spoiled food is not a good outcome under any circumstance.
We need a solution that satisfies three scenarios:
Normal grid power: We have a legacy solar system using 32 ground mounted panels with enphase microinverters. We want to maintain the battery at close to full capacity, feed any excess to the grid during the day (we’re grandfather into a net metering agreement with 15 years remaining in the contract), and power all loads at night with the grid, reserving most of the battery for fire emergencies or outages.
The system we’re installed to power all the loads is
Grid Outage: We want to supply the main house with power for the refrigerator and LED lighting. We can shed all the other loads, the major loads being two water heaters (one conventional electric, one heat pump) and the pool recirculating pump. We don’t have AC or heat. We don’t need it where we live. We want to keep the battery above 50% power in case the outage turns into a wildfire emergency. I’ve constructed an outage scene in home assistant that is automatically triggered by loss of power on the grid. The outage scene shuts off the pool pumps, both water heaters, and cuts off all loads in the caretaker apartment and the two guest rooms. The only remaining loads are lighting, our two refrigerators, the electronics associated with the home automation system, and the garage door openers. I can restore any load remotely from my phone.
Wildfire emergency: I’ve created a wildfire scene has two modes: Grid powered and grid outage. In the event og a grid outage the system sheds all loads other than lighting, home automation system power, and the deluge system which includes a pump, control system, and valve actuators. Our lighting is all LED so the power demand is tiny–generally less than 100 watts, the entire home automation system and deluge control system is about 200 watts. Essentially all the emergency power is available to run the 750 watt pump that supplies the sprinklers using our lap pool as the water source. The level in the lap pool is automatically made up with municipal water. The system can run for a long time with no external power and no sun.
All the major (and most minor) loads communicate with our smarthome system (Home Assistant) and can therefore be managed to meet any scenario with automated tasks. Given my forgetful nature it’s very useful.
For example, both water heaters can be turned on and off and have their temperature set and maintained by Home Assistant. We have no freezing risk (near sea level in Maui) so there is no good reason to keep the water heaters energized. There is a separate water heater for the primary guest room and the caretaker apartment. When no one is staying in those rooms the water heater is automatically turned off completely. When someone is scheduled to stay with us, the water heater is turned up to 110 degrees F the day before they arrive–and then is turned up to 120 for the hours that hot water is generally used.
The hot water for the main house is provided by a heat pump water heater. When we are present it’s set automatically to 120F except for hours when we are sleeping, when it drops to 110F. The house is geofenced to recognize our smartphones, so when were are present it automatically goes to 120F during waking hours. Our dishwasher has a heat booster so there is no need for higher temperatures.
That’s just the tip of the iceberg–I can manage almost anything in my home with this system.
All the functions of the pool equipment are likewise managed. So we will have all three scenarios directly managed to shed their loads appropriately with the results displayed on dedicated dashboards. No separate load panels necessary. And of course we can monitor all the aspects of the solar power system directly in Home Assistant.
We also have a load monitoring system in each of the panels that reports all major loads. In the event some load isn’t correctly managed we’ll know about it and can take action.
The deluge sprinklers will be directly managed in Home Assistant through OpenSprinkler. We also have cameras to monitor the home and grounds. We can focus the deluge where it will do the most good, and do it all from a smartphone, without being present. Of course if the internet goes down we won’t have control or monitoring remotely. I’m considering alternatives to eliminate or mitigate this vulnerability. Starlink mini with a roam plan looks like a viable candidate since the limited system offers more than enough capability for this system, and the service can be turned on and off so I’ll only be charged for it when I need it.
The PV system is a ground mount, installed 12 years ago by a company that is long ago out of business. All the local solar companies refuse to work on it because the hill it’s on is steep as a cow’s face. I don’t really expect or need much from the PV system, but since I’m using a hybrid inverter for this project which has two unused MPPT controllers capable of supporting an additional 12KW of panels the rational way to boost input if I need it would be either a solar carport or an added ground mount further up the slope with some hefty bi-facials panels on it. I might do that to charge our two EVs, but for the general system demands and to cover outages it’s not necessary.
Adding more ground-mounted panels might require trenching which would be a real mess since the yard section it would run through is fire resistant artificial grass. Alternately I could upgrade the existing 12-year-old panels and add higher wattage microinverters, but that’s unattractive as an option. In reality, for the scope of this project where the primary aim is providing power throughout an all-too likely power outage, the current arrangement will do nicely.
Using home automation I can shed loads to reduce the total daily draw to about 3.6KW peak with a base 24 hr load of 1.7KW–so about 40KWh. With a 16KWh battery and about 48kwh of power from the panels the system can run for long as the sun shines. I will probably do more–if only because I can. But I need to work out a practical approach, and today’s modest setup is adequate.
Putting panels on the roof is a completely out of the question. Anyone wanting to understand why could take a look at my video on RSD (https://youtu.be/bhmedZxtdU0) or see the related blog post: https://expertamateur.com/whats-with-rsd-how-can-it-even-work/, but then also realize that my gorgeous blue tile roof is: Stupidly valuable, extremely hard to repair, and a bit fragile.
When we paint our house we don’t allow the painters on the roof–not even with wood decks on mattresses. The roof peak trim gets painted by a guy in a bucket lift. That may sound OCD but we’ve had to replace cracked and broken roof tiles before from a painter using wood decks on a mattress. The replacement was incredibly difficult, and cost many times more than what a bucket lift rents for. We bought this place 25 years ago when it was affordable, since then we’ve both retired and we neither could nor would be able to buy it today. Anything that would cover or damage the roof is a complete non-starter.
Despite it’s size and appearance our home uses very little power and what it does use is managed directly through Home Assistant. The biggest installed load is the pool circulation pump with a variable 2.5 HP pump. Second largest is two water heaters, one for the building across the pool which is electric resistance but which operates on a schedule when it runs at all, providing hot water for guests during the hours they’d likely need it–but if there is no guest the water heater is in vacation mode. The second is a heat pump water heater which uses a shockingly tiny amount of power and cools the only room in the house that ever gets too hot for comfort–the garage/shop. There’s no heat or AC other than a little portable in the garage (which is now rarely necessary).
We’ve never needed heat or AC, thanks to a well-designed home with great natural cooling from tradewinds and the narrow temperature extremes of the tropics.
In an outage the Home Automation system automatically sheds all the loads except lighting, refrigerator (vital because diabetic wife and who wants a refrigerator full of rotted food) the electronics to run the HA system, and the wildfire deluge sprinkler pump.
Using Home Automation to shed loads turns out to be incredibly effective since virtually anything we buy these days is “smart”. Even the Jandy pool control system is directly controllable through Aqualink, which our very sharp pool guy installed two years ago to get rid of the expensive and unhandy remotes.
I think for the average solar enthusiast who isn’t as concerned as I am with wildfires the most valuable thing in this series will be understanding how the EG4 inverter/battery system works, and how to use home automation to both manage and reduce normal loads, and to shed loads during outages without the expense and inconvenience of critical load panels. You can literally change what is or isn’t a critical load and control about everything in your home from your smartphone–regardless of where you are in the world.
It’s pretty cool.