Hello ladies and Gents.

I have the option of setting up my inverter AC output voltage to either 230 or 240, Volts, what will be the best setting in order to protect house appliances.

Thanks in advance.

42 minutes ago, Antonio de Sa said:

Hello ladies and Gents.

I have the option of setting up my inverter AC output voltage to either 230 or 240, Volts, what will be the best setting in order to protect house appliances.

Thanks in advance.

My guess will be SA standard voltage of 230V. Most items are designed and tested at this level. Those areas running at 240+ tend to do it to reduce under voltage due to drops in their network. Some areas in Jhb go to 250V at times. 

When we test PCBs we test at 230V and adjust PSUs at this level. 

Edited December 16, 20232 yr by Scorp007

Yes 230volt is the standard for South Africa

230v would be the norm in SA but it is not always possible to strictly fix it at 230v due to no load voltage vs full load voltage being the volt drop at the supply transformer terminals and the supply cables, no load to rated load. The voltage between phases is 400 V~415V which falls to 380 V under load conditions. An exception is Cape Town where the voltage between phases is about 420 V.

@TaliaB @Clint @Scorp007 My fault, I did not explain my question properly. Let me start again. 

I know the standard voltage is 230, in actual fact it should be 240 as most of our minisubs distribution transformers are DYN11 rated 11 KV/ 420 V and I can see on my monitoring system that the grid voltage is +_ 230 V.

• If i have my system running on SUB mode, the output voltage is the same as the grid voltage.
• If running on SBU or island mode I have a choice of setting the output voltage to either 230 V or 240 V AC see dashboard.
• So, my question is what the best voltage during Island mode to protect my appliances.

As you can see in the dashboard as a test, I changed the output voltage to 240 V and had the system running for a while.

The spikes you see is when I switch the inverters off.

• 

 

6 minutes ago, Antonio de Sa said:

@TaliaB @Clint @Scorp007 My fault, I did not explain my question properly. Let me start again. 

I know the standard voltage is 230, in actual fact it should be 240 as most of our minisubs distribution transformers are DYN11 rated 11 KV/ 420 V and I can see on my monitoring system that the grid voltage is +_ 230 V.

• If i have my system running on SUB mode, the output voltage is the same as the grid voltage.
• If running on SBU or island mode I have a choice of setting the output voltage to either 230 V or 240 V AC see dashboard.
• So, my question is what the best voltage during Island mode to protect my appliances.

As you can see in the dashboard as a test, I changed the output voltage to 240 V and had the system running for a while.

The spikes you see is when I switch the inverters off.

• 

 

I stand by my reply. Set your voltage in SBU mode to 230V. The fact that the rating of transformers went up from the old 380 then to 400 and lately 420V does not make a difference to equipment designed for 230V. I feel it's just the supply authorities that requested a 420V secondary to allow voltage drop in order to try and supply 230V to the end consumer. Taps on the transformers will still be changed to a lower or higher value where they are installed and based on the loads supplied. 

Some authorities are just better at meeting the 230V level than others. 

AFAIK even if transformers are rated 420V the SANS standard voltage is still 230/400V.

@TaliaB correct me if I'm wrong on any statement. 

20 minutes ago, Antonio de Sa said:

I know the standard voltage is 230, in actual fact it should be 240 as most of our minisubs distribution transformers are DYN11 rated 11 KV/ 420 V and I can see on my monitoring system that the grid voltage is +_ 230 V.

• If i have my system running on SUB mode, the output voltage is the same as the grid voltage.
• If running on SBU or island mode I have a choice of setting the output voltage to either 230 V or 240 V AC see dashboard.
• So, my question is what the best voltage during Island mode to protect my appliances.

I don't think this is a big deal. I live in an area such as @Scorp007 describes, where voltage is forced up so as it doesn't sag so low under stress.

My inverter runs at 240ish V when there's grid, 231 when there isn't. This is doing no harm save that some LED lights flicker as the voltage changes.

I asked a neighbour who is an engineer. He said that exactly 230 seldom happens in real life and so 10% either way is fine. 

10 minutes ago, Bobster. said:

I don't think this is a big deal. I live in an area such as @Scorp007 describes, where voltage is forced up so as it doesn't sag so low under stress.

My inverter runs at 240ish V when there's grid, 231 when there isn't. This is doing no harm save that some LED lights flicker as the voltage changes.

I asked a neighbour who is an engineer. He said that exactly 230 seldom happens in real life and so 10% either way is fine. 

@Bobster. you are 100% correct the grid voltage in my area varies +_ 10% see dashboard.

Much more stable when running on Island mode.

My reason for asking is if I increase the voltage to 240 I will reduce the current supplied by the inverter.

Edited December 17, 20232 yr by Antonio de Sa

1 hour ago, Scorp007 said:

I stand by my reply. Set your voltage in SBU mode to 230V. The fact that the rating of transformers went up from the old 380 then to 400 and lately 420V does not make a difference to equipment designed for 230V. I feel it's just the supply authorities that requested a 420V secondary to allow voltage drop in order to try and supply 230V to the end consumer. Taps on the transformers will still be changed to a lower or higher value where they are installed and based on the loads supplied. 

Some authorities are just better at meeting the 230V level than others. 

AFAIK even if transformers are rated 420V the SANS standard voltage is still 230/400V.

@TaliaB correct me if I'm wrong on any statement. 

Yes you are correct in your above statements. @Antonio de Sa It would not affect your appliances running at 240v normally on all electronics the smps allow for voltage variations so you will be good on that front appliances like kettles, washing machines couldn't care less. Running the inverter at 240v would decrease current flow according to ohm's law. The real danger in all of this discussion is when the star point of the transformer should be lost or neutral cable be stolen or damaged then it all ends up in smoke totally out of our control.

21 minutes ago, TaliaB said:

Yes you are correct in your above statements. @Antonio de Sa It would not affect your appliances running at 240v normally on all electronics the smps allow for voltage variations so you will be good on that front appliances like kettles, washing machines couldn't care less. Running the inverter at 240v would decrease current flow according to ohm's law. The real danger in all of this discussion is when the star point of the transformer should be lost or neutral cable be stolen or damaged then it all ends up in smoke totally out of our control.

@TaliaB I've installed and commissioned lots of transformers, oil immersed and dry type, the dry type mostly in data centers in basements where the sumps are not needed or not viable to install. (my last project was at Teraco data center)  I know that all our dist. trafos the vector group are DYN11 or 5, The damage will happen regardless of the output voltage been 220 or 240 V if the star point on the transformer fails due to loss of neutral or cable theft.

Edited December 17, 20232 yr by Antonio de Sa

29 minutes ago, Antonio de Sa said:

@TaliaB I've installed and commissioned lots of transformers, oil immersed and dry type, the dry type mostly in data centers in basements where the sumps are not needed or not viable to install. (my last project was at Teraco data center)  I know that all our dist. trafos the vector group are DYN11 or 5, The damage will happen regardless of the output voltage been 220 or 240 V if the star point on the transformer fails due to loss of neutral or cable theft.

Yeah exactly my sentiment ending up with phase voltage on all single phase appliances. I did a assesment for an insurance company where 35 dwellings lost 90% of appliances where the neutral was lost on a 1Mva 11/0.415,KV transformer in the Van Eck substation near Brakpan.

53 minutes ago, Antonio de Sa said:

I've installed and commissioned lots of transformers, oil immersed and dry type

In the good old days i worked for Bonar Long for a while where we manufactured these transformers and FS-6 breakers. I see they where liquidated last year.

26 minutes ago, TaliaB said:

In the good old days i worked for Bonar Long for a while where we manufactured these transformers and FS-6 breakers. I see they where liquidated last year.

The biggest project I was involved was Cookhouse wind farm 66 x 2 MVA dry types + 4 spare transformers. 

• The wind farm comprises 66 Suzlon S88 (2.1MW) wind turbine generators (WTGs) and has an installed capacity of 138.6 MW.
• Construction of the wind farm commenced in February 2013.
• The wind farm first supplied electricity to the grid in March 2014 and Commercial Operation Date was achieved on 19 November 2014.
• It supplies approximately 341 000MWh/year of clean, renewable energy to the national grid, addressing the ongoing and increasing need for electricity in South Africa.

1 hour ago, TaliaB said:

Yeah exactly my sentiment ending up with phase voltage on all single phase appliances. I did a assesment for an insurance company where 35 dwellings lost 90% of appliances where the neutral was lost on a 1Mva 11/0.415,KV transformer in the Van Eck substation near Brakpan.

I fully agree. Normally no matter how large an installation is the removal of a Neutral due to its consequences is a test that is not performed. 

During Easter 2022 a Neutral was lost in Pretoria and about 15 pieces of equipment went up in smoke. Cable theft. Even if some were not switched on like a AC powered Fluke multimeter with dual screen for dual comparative measurements. This unit was priced over R5000 way back in the late 1970's. Various switched mode PSUs. A major loss and initially the insurance did not want to honour the claim but did pay out. 

49 minutes ago, Scorp007 said:

Very pleased with our voltage. It is as steady as one could expect. 

One could think I get supplied from another utility/country.

 

@Scorp007 lucky you check mine, Ok I have to admit that I poll every 5 seconds, you scanning mode may be like every 5 minutes.

Just now, Antonio de Sa said:

@Scorp007 lucky you check mine, Ok I have to admit that I poll every 5 seconds, you scanning mode may be like every 5 minutes.

Yes it is based on your graph that I placed mine. Yes polled during the day only at 5min.

I have been testing out lower than normal voltage for over 6 months now and I don’t see any negative effects. In fact, according to my research, most of the appliances should be better and last longer at lower voltage. I set my SunSynk at 200V output in island mode. No problems with any appliances so far and the geyser runs at about 2.6kW with the 3kW element, which give me more room for extra load during loadshedding without overloading the inverter. 

Edited December 17, 20232 yr by PowerUser

29 minutes ago, PowerUser said:

I have been testing out lower than normal voltage for over 6 months now and I don’t see any negative effects. In fact, according to my research, most of the appliances should be better and last longer at lower voltage. I set my SunSynk at 200V output in island mode. No problems with any appliances so far and the geyser runs at about 2.6kW with the 3kW element, which give me more room for extra load during loadshedding without overloading the inverter. 

A lot of failures you only pick up may be after years. Should your fridge compressor konk in you will not even think it must be the years it drew a lot more current with each start. 

To do the same work the compressor will draw more current due to lower voltage. 

For the element no problem. It just takes longer. 

Edited December 17, 20232 yr by Scorp007

25 minutes ago, Scorp007 said:

A lot of failures you only pick up may be after years. Should your fridge compressor konk in you will not even think it must be the years it drew a lot more current with each start. 

To do the same work the compressor will draw more current due to lower voltage. 

For the element no problem. It just takes longer. 

Agree with you, it makes sense to increase the voltage, thus reducing the current, more current = more heat.

3 hours ago, Antonio de Sa said:

Agree with you, it makes sense to increase the voltage, thus reducing the current, more current = more heat.

And those of our age will remember how all motors in the factories had a current heat generated thermal overload. Boy was the old Allan West unit a masterpiece to adjust the time delay in the oil pot and plunger. The years when many live part were open inviting you to touch them. 

I cannot agree with your proposals. I think you are mixing parameters.

Question #1: What voltage to protect the appliances? None of them will notice any difference at 230 or 240 as they are designed to work at both voltages.

Question #2: At what voltage will they use less power? It depends on the type of appliance. A resistive load will use less power at 230V than at 240V as stated by Ohm’s law.

Every inverter/rectifiying/electronic controlled type load will use exactly the same power as they transform mains power into dc power directly. The product voltage x current will usually remain the same. 240V = less current. In any case, it is only 4% difference.

14 hours ago, Mauritius B said:

I cannot agree with your proposals. I think you are mixing parameters.

Question #1: What voltage to protect the appliances? None of them will notice any difference at 230 or 240 as they are designed to work at both voltages.

Question #2: At what voltage will they use less power? It depends on the type of appliance. A resistive load will use less power at 230V than at 240V as stated by Ohm’s law.

Every inverter/rectifiying/electronic controlled type load will use exactly the same power as they transform mains power into dc power directly. The product voltage x current will usually remain the same. 240V = less current. In any case, it is only 4% difference.

I fully agree with you but a lot of guys are still using normal induction motors on fridges. Water pumps are perhaps 99% induction. Most fans if not all are split phase. Older aircons as well as a number of new heat pumps. This one can see due to the number of questions around getting them started from inverters. Lawnmowers if you buy your own. These can trip a 20A MCB easier if running on 240V vs 230 or 220V. Here you will see a difference. 

We are only dotting our i's due to the OP asking.