Grid limited by inverter?

[jharber]

Hi there. I am asking more for my education than anything, as I am moving on from this house for (mostly) other reasons.

In the last few very cold weeks, putting more than a couple of heaters on has been tripping the 5kw inverter, despite being on grid power. The landlord and installer confirmed that the grid power is wired directly through the inverter, and insist that it’s totally standard to install this way. Effectively we are capped at 5kw at all times, by design.

Now I don’t know about standard, but it’s definitely not universal—I have been involved on the client side in the installation of several systems, all of which have some sort of automatic or manual changeover. And it seems bizarre, since an automatic changeover switch is all of R500. Is this arrangement in fact standard and indeed preferred, as the installer says?

He also said something about the grid load being capped at 38A before the inverter, and at 15A by <something hard to follow> so it’s not much difference. This doesn’t sound right to me. It’s an odd arrangement with a lousy old DB and a new one, and I think the stove, AC, and inverter are on the old one and everything else the new.

Have I got the wrong end of the stick here?

[TaliaB]

33 minutes ago, jharber said:

I have been involved on the client side in the installation of several systems, all of which have some sort of automatic or manual changeover.

Yes you are correct that each and every inverter installation should have a manual transfer switch for maintenance purposes on the inverter output size.

33 minutes ago, jharber said:

In the last few very cold weeks, putting more than a couple of heaters on has been tripping the 5kw inverter, despite being on grid power

The problem of running heaters on the essential side of as example 5kw Sunsynk inverter is the maximum pass through current( utility present) is 35A the capping the landlord mentioned. When connecting 2 heaters( average 4000w)on the essential side with other loads you can reach the maximum pass through current tripping the inverter.

33 minutes ago, jharber said:

It’s an odd arrangement with a lousy old DB and a new one, and I think the stove, AC, and inverter are on the old one and everything else the new

That sounds like non essential (old db) and essential( new db). My suggestion would be to use socket outlets( plugs) connected to the non essential ( old db) to run the heaters instead running all the load through the inverter.

It would be helpful to determine what exactly is connected to the essential side to be able to manage your load through the inverter.

Edited July 18 by TaliaB

[TaliaB]

That is the reason i label.all my socket outlets when i do an installation for the client to be able to differentiate between essential and non essential.  See picture attached.

 

[jharber]

Thanks, that’s clarifying. So that pass-through cap is exactly why one would use an automatic changover/bypass, no? So that the inverter doesn’t have to pass through grid power?

None of the plugs are on the essential side, just the geyser and stove. So it seems we have little choice but to freeze.

[TaliaB]

35 minutes ago, jharber said:

None of the plugs are on the essential side, just the geyser and stove.

You mean on the non essential side. 

In that case you need to manage your load when you run the heaters. For instance you are running 2 heaters at 3000w now you switch on the kettle(1500w) plus the tv, lights and refrigerator that is now the limit of the inverter. But before you switch the kettle on switch the one heater off etc ect ... you get the pattern. 

46 minutes ago, jharber said:

So it seems we have little choice but to freeze.

Gas heaters also an option.