5 ms·

I keep seeing these "grid synchronizing" inverters that don't require transfer switches and can generate to offset the energy pulled from the grid - in the even

I keep seeing these "grid synchronizing" inverters that don't require transfer switches and can generate to offset the energy pulled from the grid - in the event of a full grid outage, you can always manually hit the disconnect and run the home - provided the load doesn't surpass the generation capacity (or storage capacity if running with batteries). It seems like this hasn't really made it's way into North America, which is unfortunate as it would lower the barrier of entry for home solar considerably vs traditional grid-tie/net metering which requires a ton of permits, electricians, meter changes, disconnects (or transfer switches) and generally lots of delays and cost. I would be very curious how the "migrogrids" interconnect in PR - it seems there is some kind of synchronization and neighborhood-level disconnects to isolate from the shared grid.

rtkwe 1y ago
Grid synchronizing is not the same as being able to operate in island mode. The only reason you can run those inverters without an automatic transfer switch is because they don't function when there's no grid to follow so they shut off when power goes out meaning they don't backfeed the grid outside the home. A lot of inverters are just grid following and you need some other source creating the 60-hz signal for the solar inverters to follow. Generally this is either a battery or generator because solar has a really hard fall off in the power provided the instant you try to draw too much so instantaneous spike loads like motors starting (compressors/fans/etc) will often collapse off grid solar only installs.
- bob1029 1y ago
  > motors starting This is a big problem when working with single stage HVAC condensers. These motors can have a LRA rating of well over 100 amps.
  - tgtweak 1y ago
    There are solutions like Microair easy start - these are pretty common on generator setups too as these peak starting amps can snuff a generator too.
  - briHass 1y ago
    The bang-on, bang-off compressors are a dying breed, however. The efficiency and output modulation of the inverter units means even the conventional split systems have been switching over. Likewise, the 'minisplit' (originator of these efficient compressors) definition has expanded to include ducted models, even ducted models with conventional high-cfm blower wheels.
    - bob1029 1y ago
      Putting semiconductors in front of a 3+ ton heat pump when you live in a rural area is guaranteed bad times. Not only can you not find many people who have parts or knowledge on hand, but you also have to deal with the fragility of the system. A single stage compressor is very robust to electrical transients. These units can take direct lightning strikes and continue to function normally. Worst case, you replace a contactor, capacitor and some wire. Every hvac tech on earth has these things in their truck right now. Efficiency and gently ramping loads are nice, but these things don't matter so much if the system is going to have maintenance issues.
      - eldaisfish 1y ago
        the factors that kill semiconductor switches are heat and voltage switching transients. This is why the 800 V electronic components in some EVs fail - the voltage. The voltage in a heat pump is 240 V. The power is typically a couple of kilowatts. Reliability of silicon switches at that voltage is excellent. This is just not a widespread problem.

rtkwe 1y ago

Grid synchronizing is not the same as being able to operate in island mode. The only reason you can run those inverters without an automatic transfer switch is because they don't function when there's no grid to follow so they shut off when power goes out meaning they don't backfeed the grid outside the home. A lot of inverters are just grid following and you need some other source creating the 60-hz signal for the solar inverters to follow. Generally this is either a battery or generator because solar has a really hard fall off in the power provided the instant you try to draw too much so instantaneous spike loads like motors starting (compressors/fans/etc) will often collapse off grid solar only installs.

bob1029 1y ago
> motors starting This is a big problem when working with single stage HVAC condensers. These motors can have a LRA rating of well over 100 amps.
- tgtweak 1y ago
  There are solutions like Microair easy start - these are pretty common on generator setups too as these peak starting amps can snuff a generator too.
- briHass 1y ago
  The bang-on, bang-off compressors are a dying breed, however. The efficiency and output modulation of the inverter units means even the conventional split systems have been switching over. Likewise, the 'minisplit' (originator of these efficient compressors) definition has expanded to include ducted models, even ducted models with conventional high-cfm blower wheels.
  - bob1029 1y ago
    Putting semiconductors in front of a 3+ ton heat pump when you live in a rural area is guaranteed bad times. Not only can you not find many people who have parts or knowledge on hand, but you also have to deal with the fragility of the system. A single stage compressor is very robust to electrical transients. These units can take direct lightning strikes and continue to function normally. Worst case, you replace a contactor, capacitor and some wire. Every hvac tech on earth has these things in their truck right now. Efficiency and gently ramping loads are nice, but these things don't matter so much if the system is going to have maintenance issues.
    - eldaisfish 1y ago
      the factors that kill semiconductor switches are heat and voltage switching transients. This is why the 800 V electronic components in some EVs fail - the voltage. The voltage in a heat pump is 240 V. The power is typically a couple of kilowatts. Reliability of silicon switches at that voltage is excellent. This is just not a widespread problem.