Inverex Nitrox F35 — No AC Grid (No Utility)
What it means: The inverter cannot see a usable mains supply on its grid input, so it has stopped importing and exporting and has switched the house over to solar and battery. Inverex's hybrid fault table gives the description "No AC grid" and the plain cause "No Utility", and its first instruction is simply to confirm whether the grid is lost or not. In Pakistan this is usually a correct report of a real condition outside the inverter — load shedding — rather than a fault inside it. The same number means "No AC grid" on the three-phase Nitrox string inverters too.
Why does Inverex show F35?
- Mains genuinely absent — load shedding or a feeder outage
- The AC isolator or changeover between the inverter and the grid is switched off
- A tripped MCB on the inverter's grid-input circuit
- A loose or burnt grid-side terminal, so the inverter sees no supply even though the house does
- A manual changeover left in the generator position after a power cut
The Pakistan factor
On most Pakistani connections F35 is the normal, correct response to load shedding and will appear and clear several times a day without anything being wrong. Treat it as a fault only when it stays up while the neighbours have light. The one local trap worth checking first is the manual changeover switch — a great many houses feed the inverter through one, and it is routinely left in the generator position after an outage, which starves the inverter of mains and produces a permanent-looking F35 that has nothing to do with the inverter or the grid.
How to fix it (safe to try yourself)
- Check whether the rest of the street has light, and whether house circuits that are NOT on the inverter are live. If mains is genuinely off, F35 is correct, nothing is broken, and the inverter reconnects on its own when supply returns.
- Read the grid voltage on the inverter display and confirm it shows zero or near zero.
- Confirm the AC input breaker and any manual changeover feeding the inverter are in the ON or mains position. Switching a breaker back on at the board is fine; if it trips again immediately, leave it off and call an electrician.
- If mains is present everywhere else in the house and the breakers are on but the inverter still reports F35, stop here. Do not open the inverter's AC input compartment or the distribution board — a loose or burnt grid terminal is the common cause at this point and it is live work.
- Call your installer, or an Inverex service centre for a unit still in warranty. The manual's own escalation is to contact the dealer with the inverter serial number, the install date and a description of the fault screen.