SQ pumps on mod sine wave [RE-wrenches]

[Kirk Herander]

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?

thanks
Kirk

Vermont Solar Engineering - a Xantrex / Trace Certified Dealer
Kirk Herander
PO Box 697
Burlington, VT. 05402
www.vermontsolar.com
www.backeastsolar.com
800.286.1252 - 802.863.1202
fax 802.863.7908

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