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PW Inverter shut off issues...
- Thread starter Dom_t
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- powerwall 2
Ok, so I did simulate a blackout via shutting of mains. Heres what happened:
Around 11 am (Cloudy) Generating 1.5-2kw of power between the 2 inverters.
Killed mains, Battery went into backup mode, with partial backup loads still working (As predicted)
1 inverter completely shut down, as expected being on the other phase, whilst the other kept running producing around 1kw. However, the battery being at 20% charge did not alter the frequency, staying at 49hz, along with everything else. Worked as expected. But I will test again once the solar is making more than 5kw to see whether the same thing happens, or the inverters shut down.
Ideally, in that situation, I'd like for the solar to power the house (We almost never pull more than 5kw during the day) whilst charging the battery, working together to support the draw of the house throughout the day. Since discovering that each inverter is routed on each phase and that one shuts down after an outage, This may help me in alleviating the trouble of producing more than what the battery can handle, because each inverter is rated at a max output of 5kw.
This may also be an issue when I hope to move my house to single phase 100amps, being that both inverters would possibly still stay online during a blackout, thus having the Powerwall to alter frequency to slow down production of solar. I hope to move the house to a single phase because currently my hot water system is not connected to the battery or solar, which is a shame. We're only really paying for the connection fee and the hot water in electricity costs from our grid.
Do you guys think it's a reasonable move? or should I keep the house on 2 phase with the hot water system? Also if anyone knows some good controllers for hot water let me know, as I'd love the ability to choose when the hot water system turns on/off.
Cheers.
Around 11 am (Cloudy) Generating 1.5-2kw of power between the 2 inverters.
Killed mains, Battery went into backup mode, with partial backup loads still working (As predicted)
1 inverter completely shut down, as expected being on the other phase, whilst the other kept running producing around 1kw. However, the battery being at 20% charge did not alter the frequency, staying at 49hz, along with everything else. Worked as expected. But I will test again once the solar is making more than 5kw to see whether the same thing happens, or the inverters shut down.
Ideally, in that situation, I'd like for the solar to power the house (We almost never pull more than 5kw during the day) whilst charging the battery, working together to support the draw of the house throughout the day. Since discovering that each inverter is routed on each phase and that one shuts down after an outage, This may help me in alleviating the trouble of producing more than what the battery can handle, because each inverter is rated at a max output of 5kw.
This may also be an issue when I hope to move my house to single phase 100amps, being that both inverters would possibly still stay online during a blackout, thus having the Powerwall to alter frequency to slow down production of solar. I hope to move the house to a single phase because currently my hot water system is not connected to the battery or solar, which is a shame. We're only really paying for the connection fee and the hot water in electricity costs from our grid.
Do you guys think it's a reasonable move? or should I keep the house on 2 phase with the hot water system? Also if anyone knows some good controllers for hot water let me know, as I'd love the ability to choose when the hot water system turns on/off.
Cheers.
Even if you consolidate to single phase, you should keep one solar inverter outside the backup gateway. Today, my understanding is that one Powerwall really can't handle 10kW of solar during backup operation. In theory, they could improve the firmware to handle that case well (batteries low, but solar output exceeding Powerwall inverter power handling), but the solar inverters would have to have working proportional curtailment.
I don't know what kind of hot water system you have, but I assume it's a large storage tank that is designed to heat during off-peak and just coast through the rest of the day. Personally, I feel the best hot water solution when you have a large solar system and battery for self-consumption is a hybrid heat pump water heater. However, I don't know if they are commonly sold in Australia.
I don't know what kind of hot water system you have, but I assume it's a large storage tank that is designed to heat during off-peak and just coast through the rest of the day. Personally, I feel the best hot water solution when you have a large solar system and battery for self-consumption is a hybrid heat pump water heater. However, I don't know if they are commonly sold in Australia.
Thanks for all of your help. Yes, we currently have a big 315L, which runs on off peak. Looking at a heat pump system in the future as it’s way more efficient!
We have A geothermal heat pump that is used for heating and cooling our home and for hot domestic water. Radiant heating uses a heat exchanger inside our domestic water tanks. Very efficient and in the summer, heat from air conditioning the house goes into the domestic water so to some extent one or the other is free.
On the other hand, the nice thing about resistance heating water in large tank is that you can dump excess power to it when it is available, not when the hot water is needed. It does not care if the power is intermittent. When we lived on a sailboat with a single 15 amp 117V breaker, running the AC water heater was always a problem as if we were cooking, drying hair, ironing or using a space heater, the combination of hot water and anything else would blow the breaker and one would need to go out into the cold and rain and reset it. I designed and built a demand controller that would measure the instantaneous AC current being used by the boat at any given time, and modulated the current going to the water heater, using a triac, so that the total would be just below 15 amps. There was also an alarm if any combination of uses started to exceed the limit. To keep the lights from flickering and minimize RF interference, I used a zero crossing detector to either let a whole 60 Hz cycle through or not. Worked great and we had hot water from then on. I don't know if such a commercial device exists, but there are probably several situation where it would be handy. i don't see why your water heater needs both legs to work. Could you not heat twice as long with half the power?
On the other hand, the nice thing about resistance heating water in large tank is that you can dump excess power to it when it is available, not when the hot water is needed. It does not care if the power is intermittent. When we lived on a sailboat with a single 15 amp 117V breaker, running the AC water heater was always a problem as if we were cooking, drying hair, ironing or using a space heater, the combination of hot water and anything else would blow the breaker and one would need to go out into the cold and rain and reset it. I designed and built a demand controller that would measure the instantaneous AC current being used by the boat at any given time, and modulated the current going to the water heater, using a triac, so that the total would be just below 15 amps. There was also an alarm if any combination of uses started to exceed the limit. To keep the lights from flickering and minimize RF interference, I used a zero crossing detector to either let a whole 60 Hz cycle through or not. Worked great and we had hot water from then on. I don't know if such a commercial device exists, but there are probably several situation where it would be handy. i don't see why your water heater needs both legs to work. Could you not heat twice as long with half the power?
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Yes, thanks for the help.
We will be upgrading it soon to a Bosch heat pump model, which links to our Fronius inverters to run during the day with the excess solar.
Not too sure how that would work with the battery, as we'd want the hot water to be the last thing on the priority list 2nd to the battery being charged. I'll have to do more research into it!
I went Sanden heatpump, ditched the controlled load circuit, and programmed the Sanden to come on at 11am, drawing directly from the panels as part of the house load - and backed up by the battery as well. It runs for 2 to 3 hours, pulling 1 kW - Almost exactly one quarter the kWh the old electric element water tank used. Its more expensive than a new old-style HWS, but even accounting for the cost of power as foregone FIT @ 11.1 c/kWh, it still pays for the difference after around 4 years.
Nice!
I've looked into the Sanden units also. Are they easy to program? We'd like to get rid of the controlled load also (Free a bit of space in our meter box, since we have a separate "Smart" meter for the extra load)
Dead easy to program - the controller allows you to set a 'blackout' period, a 'start hour' and a 'finish hour', for when you DONT want it to come on. For normal non-solar houses, this is to enable you to prevent it coming on during peak and shoulder cost periods - effectively do what the controlled load circuit is trying to do, but adjustable by you. For our solar home, I set it to NOT come on from 5pm through to 11am - so after we have showers etc at night and then the morning, by 11am the thermostat is telling the unit it really needs to kick in and heat up, so it does until thermostat says stop a few hours later. As a bonus, because it is heating during daytime rather than during night, it has warmer air to work with, so runs for a shorter time.
I’m just now looking at getting a Sanco2 unit and I’m curious what you think about yours now, 4 years later? Any issues or regrets?
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