With an off-grid inverter, there’d be no need for diversion. He wants to avoid backfeeding the grid, so if the inverter isn’t grid tied…
Right?
Another OM hi-hi I was 4 in 1968 
73’s G6ZKC
Those countries don’t offer FiT tariffs.
As I said, that’s not a concern, in the UK anyway. Meters indicate reverse energy flow, but that’s normal with a solar installation, not an error.
Grid-connected inverters won’t let you electrocute anyone even if you’re not qualified. They turn off the solar power when the mains goes off for that very reason. You would need a system capable of islanding to do anything different.
Diverters are useful (I have one of Robin’s) but they aren’t designed to stop export. They only do that as a side-effect of their real purpose and only for as long as you have something you want to divert energy into. So in midsummer they typically allow quite a lot of export.
Which brings me back to my original questions. What are you trying to do?
Actually, I suggested a diverter.
I’m curious what the point of a dump load is with a PV system. With a solar thermal yes but why with a PV system? Why not just turn down the output if export is discouraged?
Again, that depends on location. The vast majority of electrical energy suppliers in the US offer
compensation in one form or another for energy exported to the grid. Some will actually pay the
customer. Some credit the export against the customer’s import. Some will trade kWh
for kWh. There are probably other “methods” as well, but those are three that I’m aware of.
Indeed you did. I was referring to Brian’s mention of a PV diverter. (yes, I know. same device)
Because aircon compressors don’t run continuously and I didn’t yet have a net meter installed.
Robin’s PV diverter enabled the dump load to “eat” the excess energy, yet “step out of the way”
transparently and almost instantly when the aircon systems needed it.
(I have two aircon systems. A 2-ton unit and a 3-ton unit)
If not for the dump load, the excess energy would’ve caused my meter reading to increase which meant I’d be paying for the energy I was generating.
Once a net meter was installed, I didn’t need the diverter. But it kept me from paying for exported
energy for about 9 months. It took that long to get a net meter installed because the local electrical
utility “didn’t know anything about solar” when I went to them and asked for a net meter.
Justafiably so, they were worried about islanding.
Many farmers in Oklahoma will backfeed their grid connection with a generator during a power outage caused by severe weather, without disconnecting their local connection from the grid. They were worried my PV system would present the same hazard. Once I showed them the relevant
whitepapers from Enphase, they understood that would not be the case and installed a net meter.
There’s no way to do it with the Enphase Envoy I have. The Envoy-S Metered and the IQ Envoy
have the ability, but they weren’t developed until after I installed my system.
In the US, exporting to the grid isn’t discouraged, but without a net meter, one ends up paying for the energy they generate vice getting paid for it.
Hi Guys,
I’ve had a look around and it appears that zero feed in is a bigger thing than I thought. Quite a few inverters do have output control, here are some examples I’ve come across:-
https://www.victronenergy.com/live/ac_coupling:fronius
I seem to remember a user from Spain who noted that there, customers who exported energy were penalized.
I remember that too. Hence my statetment of "in the US" in the post you mention, and
that depends on location in a couple of other posts in this thread.
I thought you might have been alluding to that.
I had a similar thought. I installed my own panels and last summer had a surfeit of electricity. I built my own diverter and the tank gets hot. But I still generate excess electricity during the day (in the summer), give it away for free and then import from the grid during the night. So time for step 2 I thought.
I’ve been experimenting with a solar charge controller to charge batteries off a portion of the power availalble during the day with the plan to feed back into the mains using a micro grid tied inverter during the evening.
To control the power of the inverter off batteries I feed it from the batteries through a current limited DC-DC converer. I got a module off ebay that is supposedly 300W that cost a few quid. It’s got 2 pots, voltage and current. I set the voltage to somewhere in the inverter MPPT range and the current limit to that power I require using P = V * I.
It seems to work OKish (DC-DC coverter efficiency about 80%), although at the moment I have it connected up to an ancient off-grid square wave inverter I had knocking about, I haven’t tried with an MPPT grid tied one yet. Thats the next step, if this off grid inverter survives a few months. The step after that I might consider controlling the power output using an electronically variable resistor in place of the current potentiometer on the board, but given the size of my battery bank its probably easier for me just to generate base load through the night and that way at least each kWh of night time solar power is a kWh less from the grid. There is a minimum power draw required to ensure combination of the DC-DC converter and inverter are at reasonable efficiency.
Google on “grid tie inverter with limiter”. In a blue box. Have installed several of these 1000w GTIL2 inverters. The limiting function works and it is built in. You use their supplied clamp sensor. For usa split phase you solder two clamps in parrellel, one for L1 and one for L2. The 1000w version auto senses 110v vs 220v and works on either. I have personally only used the 1000w on 110v and the 2000w version on 220v…
Thanks Doug, That sounds interesting - I’ll have a Google.
Welcome to the forum !
Hi Doug,
Welcome aboard!
I searched for grid tie inverter with limiter and found the “blue box,” but none of the ones I found were
capable of auto 120/240 operation. Could you post a link to the one you’re speaking of?
Thanks!