UPS Battery Backup Problem

[Bad Wolf]

For what its worth, I bought a Xantrex PROwatt SW 600 watt (1200 watt surge) pure sine inverter for my TARM Excel 2000. I have two Grundfos 15-8's and five Taco 007's. (though only four would running during an outage.)
Everything starts fine and there is no humming at all. With two aging deep discharge batteries I'm able to go about 6 hours before the unit shuts down due to low voltage. According to the Kill-o-watt meter its usually drawing from 150 watts., fan and one circ, to 400 watts, fan and four out of six circs.

My thinking was this: power goes out at one a.m., stagger out of bed, get flashlight, go down stairs, unplug furnace from house power (this is already set up) plug into inverter, go back to bed.

Once I get up in the morning I can make a decision to start up the big generator, (7550 watts), or the little extended run generator (2000 watt inverter generator)

Its not automatic but I'm not really concerned about it going out when I'm not home.

Update: I just found that Xantex makes an inline transfer relay for $44. This looks like it would take care of the automatic function of a UPS. For 44 bucks I may get one after all.

http://www.xantrex.com/power-products/default/inline-transfer-relay.aspx

 

[ewdudley]

I think if you measure the output with a simple hand held meter with no other load a pure sine wave will read 120 volts. A modified sine wave or a square wave would measure 80 to 90 volts. Try it and see what you get for a reading.

One needs to be a little careful when interpreting what a DVM says. Most of them measure peak voltage and infer what the RMS voltage would be if the input AC voltage signal was a sine wave, which works fine for sine waves.

For a square wave RMS voltage is the same as peak voltage, for a sine wave RMS voltage is 0.70710678 times peak voltage. Try the arithmetic and see what you get for a reading.

 

[Fred61]

I don't have the materials to check my statement but I think you're right and I should have left "square wave" out of the sentence.