On 1/13/22 17:56, Aaron C. de Bruyn via NANOG wrote:
I bought one of those power monitors and tossed it on the circuit that
goes into my house. At *night* when everything is off, I might get
down as far as ~800 watts.
During the day it's more like 2,000-3,500.
Almost the same here... down to about 700W between 11PM - 4:30AM, and
mostly 1,500W - 2,000W during the day, unless the Mrs. wants to grill
some chicken or do some baking in the oven that day.
Fair point, it's a family of 4 + 1, so...
If I get the hat-trick (water heater, central air, and well pump)
running at the same time, I can get up to ~24,000 watts.
Ouch!
For our traditional water heater, we're using a system that can power
the tank elements either via its own independent PV array or via the
grid (where the grid is either the main house's PV array or the utility):
https://www.geyserworx.co.za/
I, then, added tankless, on-demand gas heaters into the mix, and piped
that into the house:
https://gasgeysers.co.za/qr/20lt-room-sealed-fan-forced-gas-geyser/
I use a solenoid valve attached to a little IoT thingie to switch
between the tankless gas heater and the traditional tank, depending on
time-of-day. Tankless heater on at 8PM - 10:30AM, and traditional tank
on at 10:31AM - 7:59PM (unless we had poor solar yield that day and it
didn't heat up enough).
In all, we haven't had to use the utility to heat water since we went
this route. Saved tons of cash, and guarantees a hot shower any day, any
weather.
I definitely notice it when the power goes out. The sound of UPS
relays and alarms is enough to wake the dead.
For my setup, even if we generally can transfer from utility grid to
battery backup between 0ms - 20ms, I attached UPS's to all sensitive
appliances in the house as an additional backup anyway (small ones, 1kVA
- 2kVA, type-thing). The reason for that is if we have an outage while
the battery inverter is forming its grid from the utility, there are
instances where the power outage is not a clean one (like a brownout, or
slow low voltage event), and this would trip the battery as the inverter
tries to quickly re-form the grid from the battery (230V/50Hz).
In such cases, the battery would protect itself from a possible short
circuit, and shutdown for about 50ms, but that's long enough to power
down the inverter, and it would take 60 seconds for it to restart.
During that time, the UPS's will keep appliances running (Internet, TV,
computers, consoles, a/v, e.t.c.).
Of course, if a utility outage occurred when the inverter was forming
its grid from the battery, then we won't notice anything.
I've added voltage sensors to the grid supply to cut the power before
the voltage gets too low, too quickly (cut at 219V), but that only
improved the situation slightly. There are other inverters that have
their own internal voltage sensors that could handle this far better,
but I preferred the model I went with for its data management capabilities.
Mark.
