SQ pumps on mod sine wave [RE-wrenches]

[Kirk Herander]

Hi Allan,

More info: I specified the pump and the well driller installed it and set up
the tank. Originally this problem would happen once every few days, and I
discovered that the tank precharge was set incorrectly - actually set too
high, so I adjusted it to 28 psi (cut-in 30 psi) and it seemed to help. The
pressure switch is not a low-pressure cut-off type (no lever to manually
reset).
Kirk

----- Original Message -----
From: "Allan Sindelar" <allan at positiveenergysolar.com>
To: <RE-wrenches at topica.com>
Sent: Monday, April 22, 2002 2:03 PM
Subject: Re: SQ pumps on mod sine wave [RE-wrenches]


> Kirk,
> We haven't worked with the SQ pump, but I would check the pressure tank
> first. Your tank precharge pressure should be set at 1-2 psi below the
> cut-in setting on the pressure switch. If it is set too low, the tank
> pressure will drop quickly before the pump re-establishes pressure, which
> seems to fit your description.
>
> To check precharge, you must bring system pressure to zero or thereabouts,
> then use an accurate tire gauge on the pressure tank's Schraeder valve.
> Bring an air compressor or tire inflator.
>
> Also, some pressure switches have an optional low-pressure cutoff built
into
> the switch, to provide dry run protection. If cut-in pressure is reached
but
> the pump doesn't recharge and pressure continues to drop, the low-pressure
> cutoff will be reached. This requires a manual reset.
>
> Allan at Positive E
>
> ----- Original Message -----
> From: "Kirk Herander" <kirk at vtsolar.com>
>
> > Group,
> > I have a customer running a 1/2 HP Grundfos SQ series (soft start) pump
on
> > an old Trace U 2024 mod sine inverter. Occasionally, like once every two
> > weeks, the pump won't fill the pressure tank when cut-in pressure(30
psi)
> is
> > reached. The pump turns on, but the pressure hovers around 10-15 psi.
> There
> > is also a dc pump plumbed to the tank from a spring. Once we switch over
> and
> > allow the DC pump to pressurize the tank, then switch back to the
> Grundfos,
> > it will work fine for a couple of weeks until this happens again. Any
> ideas?
> > Battery voltage is not low when this occurs.
> >
> > Also when cut-in is reached, the pressure will drop from 30 to 0 psi for
a
> > second, then rise normally as the pump pressurizes the tank. Is this
> sudden
> > pressure drop to be expected from a soft-start pump?
>
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