There were a couple of things about the PIP-4048MS that I didn't realise until David Chaplin and I actually tested it on site, with a generator.
It became obvious, first to David Chaplin, and then to me, that I'd been thinking the wrong way about parameter 01, the AC output source priority. This parameter supposedly determines which of three sources, solar, battery or "utility" (i.e. AC input, either grid or generator) are used, when more than one is available.
One of the three options displayed is "SbU" which stands for Solar then Battery then Utility. The mixture of upper and lower case is because it's only a seven-segment display. So you might think there would be six options, SbU, bUS, USb, UbS, bSU, SUb.
But you can't feed solar energy to the loads if the battery is not available (is low voltage), so "S" and "b" aren't really independent. In effect, whenever you have both S and b, S will feed the loads before b, so you really have a fixed priority pair (Sb). So then you'd think there would only be two options, (Sb)U and U(Sb).
Well there are those two, but they are called SbU and UtI (utility first), and for some dumb reason I had it in my head that when the utility isn't normally present (off-grid) you'd want to give solar/battery the priority and so set it to SbU, but as David Chaplin soon made me realise, it's the other way 'round. When you're off-grid you want to give the "utility" priority, because if someone goes to the trouble of starting the generator, the system had damn well better make full use of it. So UtI mode is what you want when you're off grid.
Whereas, when you're on the grid, and "utility" is always present, you want to give solar and battery the priority, so you only use the grid when the battery gets low. So SbU mode is what you want when you're on grid.
Probably seems obvious, right? My confusion must have been because I was short on sleep. Yeah, that's it.
But what still isn't obvious is what the hell the third
option is about. It's called "SOL" (solar first). As far as I can tell it behaves exactly the same as SbU mode except in the case where you have no solar input but you have both utility and battery. In that case it will use utility where SbU would use battery.
So SOL is SUb priority, right? Well, not really. Because that would imply that if the battery was low and the choice was between solar and utility, it would use solar. But it doesn't. It uses utility. So "SOL" mode can't be described as a priority ordering of the three sources at all!
One can also say that SOL is the same as UtI except in the case where all three sources are available. SOL chooses solar instead of utility in that case, as you might expect from its name.
Avail. | Source, in mode:
U S b | UtI SOL SbU
0 0 1 | b b b
0 1 0 | S S S
1 0 0 | U U U
0 1 1 | S S S
1 1 0 | U U U
1 0 1 | U [U b]
1 1 1 | [U S] S
You really needed to know that, right? Well, it was driving me nuts that I didn't understand what SOL mode was. And you don't really understand something until you can explain it to someone else.
But I still don't know why you'd want to use SOL mode.
Now what about the other thing? That's a lot easier to describe. We set it to UtI mode and started the generator and, ... nothing happened. The PIP displayed the voltage and frequency of the generator, which were somewhat variable -- not surprising since it was completely unloaded -- but easily within the specified range for the PIP. But the PIP acted as though there was no generator there. It refused to feed it to the loads or charge the battery from it, but just kept running the inverter off the battery. I could only exchange stunned and mystified looks with David.
It was dark by this time and I couldn't think with the noise of the generator. So I walked around to the side of the house opposite the generator. Then I came back and stepped thru the PIP's parameters. Only one seemed like it could possibly have any bearing on the matter.
Parameter 03 is described as "AC input voltage range". The two options are APL (appliances, the default, 90-280 Vac) and UPS (uninterruptible power supply, 170-280 Vac).
I had set it to UPS, thinking I didn't want the PIP dragging the voltage of the poor generator down below 170 V if an underpowered generator was connected. But now I set it to APL, and it immediately switched the generator thru to the loads, and then it started ramping up the charge current. The generator stopped "hunting" and stabilised. Beautiful!
So apparently the UPS setting is not just about the allowed AC input voltage range, but also makes the PIP far more fussy about the frequency and voltage stability of the AC input.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).