Hi There,

Can someone please explain the use of Setting No.38? 

Thanks

2 hours ago, paulw said:

Can someone please explain the use of Setting No.38?

You can buy a box, or make your own, that connects the AC-out neutral to earth when the inverter is operating in battery mode only. I believe that it changes the function of the "dry contact" relay when you do this, and does the standard behaviour when this setting is disabled.

If you always ground the AC-out neutral, then when the inverter is in bypass mode, it will connect AC-in neutral to AC-out neutral, so you will have two connections from neutral to earth. This can cause havoc with Residual Current Devices.

Note that some models connect AC-out neutral to earth internally when in battery mode. I believe it's the ones that come with firmware 73.00.

6 hours ago, Coulomb said:

Note that some models connect AC-out neutral to earth internally when in battery mode. I believe it's the ones that come with firmware 73.00.

@Coulomb which Axpert is this? VM, MKS or King? 

 

4 hours ago, fvanz said:

which Axpert is this? VM, MKS or King? 

73.00 only comes with MKS models. I don't know if other models have this feature.

The way to tell would be if there is connectivity between AC-in neutral and AC-out neutral with power off and all AC isolated. That would presumably be through the normally closed contact of a relay.

So if I undetstand correct I dont need to use it. Switch it of if it has it. If it doesnt still bridge the neutral and earth on the AC out of the inverter. Split the neutral bars between the Main ac(eskom) and the inverter ac out. And take neutral and live between of each supply through the change over switch to the main house db?

8 minutes ago, paulw said:

If it doesnt still bridge the neutral and earth on the AC out of the inverter. 

I assume that "it" above refers to inverter-charger models that conditionally connect AC-out neutral to earth. The problem with your plan is that the inverter will still connect AC-in neutral and AC-out neutral when in line mode (they all do that, regardless of whether they conditionally connect AC-out neutral to earth). So you'll end up with two connections from neutral to earth, so the neutral current won't always equal active current, and that will cause problem with residual current devices. You will want one of those between the inverter and any general purpose outlets, and in Australia at least, also to any lighting loads.

12 hours ago, Coulomb said:

73.00 only comes with MKS models. I don't know if other models have this feature.

@Coulomb Thank you!. Can you please tell me what the cooling fans behavior is with firmware 73.00? I spoke to the importer of my Invermax VMIII  (which is presumably identical to the RCT VMIII of some other user that mentioned the same fan behavior with the exact firmware version 41.3 that I have) and they say that this is normal, and that there is no other firmware that will change that. Normal maybe, but very annoying and I don't see the point. If the batteries are charged and you are using the utility grid (in bypass mode) there is no need for the fans to run on and off, as the inverter is not doing any work. 

If the fan behavior of the MKS is less annoying (only on when charging and when load is demanded from the inverter when batteries are delivering the power) I will try get hold of an MKS in stead of the VMIII I have now. In the mean time have I installed a change over switch to totally isolate the inverter from my DB, and I can connect it when the need arises (load shedding form our utility). Kind of defeats the object of having an Inverter setup as a UPS, but I cannot live with the fan noise the whole time, and I do not have another suitable place to install it and the batteries. I just make sure the batteries are fully charged, Isolate the inverter and draw my "standby bus" in the DB from utility (actually from the CB that feeds the inverter).

Can all MKS 5KV units be loaded with firmware 73.00? 

 

@Coulomb

My inverters don't have the earthing function. I had a debate with a lot of people on the issue of connecting earth to neutral for the AC out on the inverters. Everyone has there own meaning regarding it. I even spoke to a Electrician who said I have to connect all neutral to a common bus (which I don't agree with). 

When running on utility(Eskom) point of supply is the transformer neutral which is earthed. All faults will find it way back to the supply. According to my understanding, the inverter is the new source, thus the neutral and earth must be bridged.

Attached is what I have in mind off how it should be connected to my main DB. Any comments please..

Inverter Lives wired to single pole MCB's, and a change-over switch (Solar and Bypass)

Thanks

Edited March 17, 20205 yr by paulw