On Thu, 12 Apr 2018 11:18:35 -0700, jrwalliker wrote:

On Wednesday, 11 April 2018 21:56:37 UTC+1, Johnny B Good wrote:

The genset may be able to handle such a surge loading without the
backup
of the SmartUPS in any case.

I tested the overload behaviour of my 1kVA inverter generator. For
modest overloads, it drops the output from 230V to 210V for about 3s.
If the overload is sustained then it cuts out. This means that motor
loads such as my small angle grinder can be started.

It is happy driving computers and other capacitive loads as expected.

Thanks John,

The user guide for the Parkside PGI 1200 B2 claims a 5 second overload
sustain of 1.2KVA with a maximum continuous load rating of 1KVA. I
estimated a fivefold startup load from the freezer for its 70 watt steady
running state, about 350W peak. That's only an educated guess but I think
it's in the 'Ball Park'.

Assuming I time a freezer switch on for no or very little load, I'd have
to have underestimated the peak by a factor of three to be in trouble.
I'll know for certain when I've finished commissioning the UPS in
readiness for the genset's first run (no point starting it up until I
have the UPS back in commission).

At the moment I've got the UPS sat on my workbench connected to a 48v
battery pack of 7A SLAs (a brand new set of alarm batteries) after
opening the inverter case to access VR4 (the float charge voltage setting
pot)[1] which I've now got set to 54.2v with the battery disconnected
(UPS disabled - it drops to 53.9/54.0 v when enabled). I'm allowing it
some 'warming up time' to let it settle before I close everything up and
return it to its basement location.

I obviously need to increase the voltage slightly to account for the
small discrepancy between enabled and disabled charging operation. I'm
aiming for a float charge voltage of 54.1/54.2 volts (13.525/13.55 volts
per SLA battery). My big mistake with the other battery packs had been to
try and set it to 55.2v (13.8v per SLA battery) without disconnecting the
battery, relying on the batteries having reached full charge after
several days of charging and therefore at their limiting voltage. Months
later, that limiting voltage had crept up to 55.5 volts. Naively, I
didn't think the extra 0.3v was of any significance back then so left it
alone. I've since come to realise that that was a big mistake. :-(

Float charging at a constant 13.8v per 6 cell pack 24/7 365 days a year
is bad enough without pushing it even higher to almost 13.9v! I'm not
going to make *that* mistake again so I'm setting the enabled float
charge voltage to 54.2v. I'd rather sacrifice a few percent of new
battery autonomy for an extra two or three years of *useful* service life
thank you very much, APC! ("Consumables" my arse!).

Getting back on topic, it looks like I'm going to be paying my local
MachineMart a visit tomorrow to pick up the Hippo Pump that Terry Casey
recommended. Despite all our valiant efforts in clearing our blocked
drain, I'm still seeing water ingress into the basement. It's been a dry
day today so it's a bit of a puzzle as to the true nature of our elevated
water table and I'm beginning to wonder whether there's a leaking water
main nearby.

I shut off our stopcock about an hour ago to test for the unlikely event
that we have a sneaky leak somewhere. I turned the bathroom basin cold
tap on half an hour later to test and, worryingly, only got a short
trickle. The groundfloor cold taps produced the expected flow, suggesting
there may be a leak in the first floor plumbing but if there is, it's a
damned quiet leak considering its effect on the local water table.

I'll give it another hour or so before I take another look at our pond
in the coal hole to see whether shutting the water off has had any
positive effect on the situation. TBH, I'll be totally flabbergasted if
it has.

[1] The circuit diagram sheets for this ancient UPS are dated "7/7/93"
making the design, if not its manufacture, almost a quarter of a century
old! Although it's microprocessor controlled, I can't recall seeing any
options in its command set regarding float charging voltage settings
which I believe much later models have. In any case, the settings in this
model seem to have been locked against any changes being made. It's just
as well that there is a "VR4 Pot" for adjusting the float charging
voltage or else I'd be 'stuffed' with regard to improving the life of my
"Consumables".



--
Johnny B Good