Error Code 28 - 10 Minute Average Grid Voltage Fault

[d.garaffo@gmail.com]

Hi Guys, after getting the "error code 28" my inverter (Model : H1-6.0-E) remains in the "waiting" state for several hours (4-8hrs) even if the voltage is well within the tolerance range. During this time the system draws power only from the grid and not from the battery or photovoltaic. Does this seem correct to you? Is there a way to change the waiting time and restart the inverter immediately after? Even if I turn the inverter off and on again, nothing changes. For more than a month, my system has been unusable on sunny days!

[Dave Foster]

Your grid voltage is too high for the limit set in the 10 minute alarm setting - if you are in the UK you should be able to call your DNO and they will measure it and address it if necessary.

You can adjust the alarm limit, look at the max grid voltage your inverter is reporting and set this limit to be a few volts higher - see this post viewtopic.php?p=668#p668

[Robgshanahan]

Very useful thread.

My supplier attended and took a volt reading at 2100, it was 251. He explained that because I am close to the sub and further down the line there is a school the transformer is tapped fairly high to cater for the demand of the school that it can pull. This is why during non peak periods the voltage is running high and this my inverter is going into error 28.

I have upped my voltage on the inverter to 255. Earlier my Pv was running about 1.3kwh and the voltage was around 254.6 so still close!

My question is: what is the highest I can safely run my 10 minute average at and what are the potential implications of running it at a higher number. Say 257 for example.

I have a H1-5.0-E

Thanks in advance

[Dave Foster]

Very useful thread.

My supplier attended and took a volt reading at 2100, it was 251. He explained that because I am close to the sub and further down the line there is a school the transformer is tapped fairly high to cater for the demand of the school that it can pull. This is why during non peak periods the voltage is running high and this my inverter is going into error 28.

I have upped my voltage on the inverter to 255. Earlier my Pv was running about 1.3kwh and the voltage was around 254.6 so still close!

My question is: what is the highest I can safely run my 10 minute average at and what are the potential implications of running it at a higher number. Say 257 for example.

I have a H1-5.0-E

Thanks in advance

Don't forget it's a 10 minute average so your peak has to be sustained for it to generate the alarm, I usually advise to set it 1 volt higher than your highest reading which should cater for all conditions.
This is becoming more and more of a problem as renewables power the grid, it was never designed for distributed systems putting so much power back into the system (which obviously isn't a bad thing) but it messes with what the DNO has previously set local transformers to. The DNO engineers I have spoken to suggest they are looking for the tolerances to be relaxed and accept that the local grid running at a slightly elevated level is better than running at a lower level.

Back to safety limits, if the inverter is measuring 257V when you are exporting, the grid will be lower when measured outside where the grid incomer terminates on the smart meter - possible up to 7V depending on your internal cable distribution, but more likely 3V lower so 257V is actually 254V at the incomer and only just over the allowable tolerance; if it only happens for a short while the DNO would accept it and likely change nothing.

I really wouldn't recommend going any higher than 260V without taking DNO advice and getting long term logger measurements from your incoming grid, they will do that if you are seeing such high voltages.

[Robgshanahan]

Thanks David.

read an Australian thread, I think they have a lot of the same issue.

One person suggested upping the cable size between the inverter and the mcb that ties you into the grid. I currently have a 6mm2 cable as per the manual with 40amp breaker.

If cable size is greater then ohms law would mean less resistance and therefore a lower volt reading at the inverter.

Although given this cable run is no greater that 10 meters I’m not sure on how much difference it would make?