Can you help with a solar dump into an emersion ?? Ask questions and find answers to many subjects relating to electrics and electrical work

[collectors]

Hi, cant quite get my head around solar dumping. It sounds like a good idea but i cant find the right info. I have 2 x 6kw inverters & a 2x15kw battery banks =30kw, batterys are linked in parelel.linked & the 2 inverters share the whole bank. Now, when the batterys are full any spare solar i would llike to dump into making hot water. Is this done direct from the panels or cam i missing somthing, as i would not of thought a 2 or 3kw emersion would harm the panels.

[Mr White]

It does not work like you think. You need a "solar diverter" (Many brands available)

[collectors]

It does not work like you think. You need a "solar diverter" (Many brands available)

Ah! I have been reading a bit more & looks like if you have battery's use them. But also noticed it would take a wile to get your money back on a diverter.

[ericmark]

I found with my solar, the iboost+ unit was really a waste of money, a simple time switch would have been better. So let me explain.

In the system I have, 6.4 kWh of battery, and 6 kW of solar panels, and 5 kW inverter. So in winter, December is the worst month, there is not enough solar for my needs, so I have an EV off-peak supply (no EV just use that tariff) so 00:30 to 05:30 cost 8.5p/kWh, and I fully charge the battery, in summer by 9 am, I am getting solar, but battery is not empty, so by 12:00 battery full and exporting, but I am exporting at 15p/kWh so if I divert the solar to heat DHW that is costing 15p/kWh in lost revenue, where if I heated it overnight it would cost 8.5p/kWh so the iboost+ is pointless, not worth getting rid of it, but a simple time switch would have been better.

Some of the solar diverters have extra outputs, and can also work underfloor heating, but would not want that in summer, and unlikely to have spare solar in winter, it seems the Eddi has more options to the iboost+ the iboost+ will work two immersion heaters, so heat top of tank first, then it starts heating bottom of tank.

I use around 12 kWh per week to heat the water.

The unit turns the 230 volt supply into pulsed DC, so it can heat with around 150 watt to 3 kW it just uses the excess, and a battery powered CT coil tells the unit when you are exporting, think mine set to start diverting when the export exceeds 150 watt.

In the beginning, solar was paid for based on the size of your array, it was not metered, it was assumed half would be exported, so the more you used, the more you got. Today you're forced to have a smart meter to be paid for export, and you have a second MPAN number, so you could export to a different company to who you import from, not a good idea as the rates are rubbish. But now export is metered the iboost+ no longer makes sense.

There are some at the moment illegal solar panels in the UK, but legal in Germany which simply plug in, if using these then the iboost+ would work. But once you have the MPAN number for export, who would know if you add extra panels?

Note kW and kWh are not the same, my battery can charge at 4 kW, and discharge limited by my inverter at 5 kW but they store 6.4 kWh of energy,

[collectors]

I found with my solar, the iboost+ unit was really a waste of money, a simple time switch would have been better. So let me explain.

In the system I have, 6.4 kWh of battery, and 6 kW of solar panels, and 5 kW inverter. So in winter, December is the worst month, there is not enough solar for my needs, so I have an EV off-peak supply (no EV just use that tariff) so 00:30 to 05:30 cost 8.5p/kWh, and I fully charge the battery, in summer by 9 am, I am getting solar, but battery is not empty, so by 12:00 battery full and exporting, but I am exporting at 15p/kWh so if I divert the solar to heat DHW that is costing 15p/kWh in lost revenue, where if I heated it overnight it would cost 8.5p/kWh so the iboost+ is pointless, not worth getting rid of it, but a simple time switch would have been better.

Some of the solar diverters have extra outputs, and can also work underfloor heating, but would not want that in summer, and unlikely to have spare solar in winter, it seems the Eddi has more options to the iboost+ the iboost+ will work two immersion heaters, so heat top of tank first, then it starts heating bottom of tank.

I use around 12 kWh per week to heat the water.

The unit turns the 230 volt supply into pulsed DC, so it can heat with around 150 watt to 3 kW it just uses the excess, and a battery powered CT coil tells the unit when you are exporting, think mine set to start diverting when the export exceeds 150 watt.

In the beginning, solar was paid for based on the size of your array, it was not metered, it was assumed half would be exported, so the more you used, the more you got. Today you're forced to have a smart meter to be paid for export, and you have a second MPAN number, so you could export to a different company to who you import from, not a good idea as the rates are rubbish. But now export is metered the iboost+ no longer makes sense.

There are some at the moment illegal solar panels in the UK, but legal in Germany which simply plug in, if using these then the iboost+ would work. But once you have the MPAN number for export, who would know if you add extra panels?

Note kW and kWh are not the same, my battery can charge at 4 kW, and discharge limited by my inverter at 5 kW but they store 6.4 kWh of energy,

Thanks ericmark, great explanation. I am not fully up & working, but should be in a month or two. I'm using 2 x 6kw growatt inverters & 2 x 15kw lifepo4 banks of battery's. The batterys are 2 x 15kw linked in parellel & the 2 inverters are linked to the batterys but the inverters are not linked. I am with eon & will look to change my tariff to their EV at 6.5 off peak for 6 hours. I think i got the wrong idea on things like the iBoost & was thinking the power came direct from the panel as i couldnt cwork out how it was seperated & i was hopping that once the batterys were charged the emersion was being fead some other way. "Wrong". So i will look to make a unit that mesures my batterys voltage linked to an adjustable photo-cell with a 2 pole contactor to & see if i can just feed the emersion when the sun is out. But need to think on this one.

[collectors]

I found with my solar, the iboost+ unit was really a waste of money, a simple time switch would have been better. So let me explain.

In the system I have, 6.4 kWh of battery, and 6 kW of solar panels, and 5 kW inverter. So in winter, December is the worst month, there is not enough solar for my needs, so I have an EV off-peak supply (no EV just use that tariff) so 00:30 to 05:30 cost 8.5p/kWh, and I fully charge the battery, in summer by 9 am, I am getting solar, but battery is not empty, so by 12:00 battery full and exporting, but I am exporting at 15p/kWh so if I divert the solar to heat DHW that is costing 15p/kWh in lost revenue, where if I heated it overnight it would cost 8.5p/kWh so the iboost+ is pointless, not worth getting rid of it, but a simple time switch would have been better.

Some of the solar diverters have extra outputs, and can also work underfloor heating, but would not want that in summer, and unlikely to have spare solar in winter, it seems the Eddi has more options to the iboost+ the iboost+ will work two immersion heaters, so heat top of tank first, then it starts heating bottom of tank.

I use around 12 kWh per week to heat the water.

The unit turns the 230 volt supply into pulsed DC, so it can heat with around 150 watt to 3 kW it just uses the excess, and a battery powered CT coil tells the unit when you are exporting, think mine set to start diverting when the export exceeds 150 watt.

In the beginning, solar was paid for based on the size of your array, it was not metered, it was assumed half would be exported, so the more you used, the more you got. Today you're forced to have a smart meter to be paid for export, and you have a second MPAN number, so you could export to a different company to who you import from, not a good idea as the rates are rubbish. But now export is metered the iboost+ no longer makes sense.

There are some at the moment illegal solar panels in the UK, but legal in Germany which simply plug in, if using these then the iboost+ would work. But once you have the MPAN number for export, who would know if you add extra panels?

Note kW and kWh are not the same, my battery can charge at 4 kW, and discharge limited by my inverter at 5 kW but they store 6.4 kWh of energy,

Thanks ericmark, great explanation. I am not fully up & working, but should be in a month or two. I'm using 2 x 6kw growatt inverters & 2 x 15kw lifepo4 banks of battery's. The batterys are 2 x 15kw 48v linked in parellel & the 2 inverters are linked to the batterys but the inverters are not linked. I am with eon & will look to change my tariff to their EV at 6.5 off peak for 6 hours. I think i got the wrong idea on things like the iBoost & was thinking the power came direct from the panel as i couldnt cwork out how it was seperated & i was hopping that once the batterys were charged the emersion was being fead some other way. "Wrong". So i will look to make a unit that mesures my batterys voltage linked to an adjustable photo-cell with a 2 pole contactor to & see if i can just feed the emersion when the sun is out. But need to think on this one.

[Mr White]

All a photo cell and contactor would do is switch the immersion heater on as soon as it is bright enough, regardless of the battery condition, if you use a solar diverter it measures current supply and draw and only when the batteries are charged then it will turn on the immersion.

[ericmark]

kW and kWh are not the same, I assume 15 kWh not kW for the batteries, That would run my house for 2 days with no off-peak or solar. I use around 12 kWh per day, some homes use half of that. But with EV charging and heat pumps it could be well over that amount.

The way my system works, is the off-peak charges the batteries, in the morning I use 5.5% of the battery per hour, but as the day goes on the use increases, but until 9 am I don't use much, and by 9 am, I am starting to get solar, and by 11 am the battery fully charged again. And it has only dropped to 85%, so my battery did not really need fully charging, if charged to 35% would have done. Which would have allowed me to use more of the solar, however on a poor solar day last Wednesday for example I only exported 0.3 kWh, so since the off-peak rate is more than the export rate, it does not matter.

But once you take into account losses, the 8.5p to 15p differential is not enough to make money with, so my 6.4 kWh is enough to mean it is rare I use any peak power, and batteries do have a limited life.

If however I went to the flux tariff, then the export rate 4 pm to 7 pm is very good, but the off-peak rate not as good, so one needs to sit down and do the maths, and until you have done the first year you have not got the figures to work it out with.

My panels are South - West so I get more in the evening, which works well, but when I look at worst month December, I run out of battery before 7 pm on quite a few days, so I didn't go for Flux as the peak rate is rather high.

12 kW and 30 kWh seems quite a lot, what you have not said is how much you use, I would assume you have a heat pump or an EV and these will make a diffrence.

[collectors]

Hi, sorry, yes kwh. Here is a couple of photos of the project.

[ericmark]

[quote="Mr White" post_id=135638 time=1757696186 user_id=92685]
All a photo cell and contactor would do is switch the immersion heater on as soon as it is bright enough, regardless of the battery condition, if you use a solar diverter it measures current supply and draw and only when the batteries are charged then it will turn on the immersion.
[/quote]
Very true, but also iboost+ does not "Switch" on/off, it controls how much goes into the immersion heater, which is often less than 3 kW.

You will need either a G98 or G99 form needs completing and submitting, I think G99 in your case as over 3.68 kW, and then you get the MPAN export number. You must not mix up kW and kWh on the forms.