sine waves are giving me a headache!

Here's a blurb from APC's Q&A page. http://www.apc.com/solutions/display.cfm?id=0D72DB57-8963-47DA-9ADC4EB3FD07511D

APC's Back-UPS®, Back-UPS Office®, Back-UPS Pro®, and PowerCell® all output a "stepped-approximated" sine wave when the unit is On Battery. While this kind of waveform is ideal for computers and computer-related equipment, it may not be compatible for other types of loads like motor loads. If you are using non-computer loads with one of the above-mentioned UPSs, consult the manufacturer's specifications to determine if the equipment can run off of a "stepped wave". If it can't, then it will require a UPS that outputs a pure sine wave when On Battery. APC UPS models that do output a Pure Sine Wave include: Smart-UPS®, Matrix-UPS®, and the Symmetra® Power Array®.

hossthehermit said:

jbmaine said:

Hi all, I posted a few days ago about getting a UPS to run with my P68 to correct power flickers and for when I use my portable generator ( not a honda) to power my stove during power outages. I got several recommendations for units around the $70-100 range. I was also told my harman needed a pure sine wave. I've done some research and this is what I've found. APC brand has a stepped approximation to a sine wave. Cyberpower brand has a simulated sine wave. Tripplite has sine wave on AC power and pwm sine wave on battery power. I don't know the difference in these different sine waves, if any, and am starting to wonder if I'm making a mountain out of a mole hill. If a UPS doesn't damage a computer how can it damage a pellet stove? Has anyone actually damaged their pellet stove using a UPS? Is there something obvious that I'm missing? Any thoughts or opinions would be greatly appreciated.
Thanks
JB

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All yer missin' on the computer / pellet stove comparison is the fact that your computer doesn't have any electric motors. A "modified" or "simulated" or "stepped approximation" is simply turning "on" and "off" all the electric motors (circ fan, comb fan, auger) about 30 times per second. Electronics don't mind. Electrics do. BUT, that's just MY opinion.

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Computers have fan motors and servos. both have small electric motors.

My US Stove 6039 doesn't like anything but pure sine wave power....with a stepped wave the motors may run, but they sure sound labored. At lower speeds, the motors shut down on ups power. I came across a junked ups from work that is supposedly pure sine on battery-tested motors at all speeds for a short time a couple of weeks ago, so far so good. I think it's supposed to clean up incoming ac power also, a small cheap generator may be in my future if it's true.

smwilliamson said:

hossthehermit said:

jbmaine said:

Hi all, I posted a few days ago about getting a UPS to run with my P68 to correct power flickers and for when I use my portable generator ( not a honda) to power my stove during power outages. I got several recommendations for units around the $70-100 range. I was also told my harman needed a pure sine wave. I've done some research and this is what I've found. APC brand has a stepped approximation to a sine wave. Cyberpower brand has a simulated sine wave. Tripplite has sine wave on AC power and pwm sine wave on battery power. I don't know the difference in these different sine waves, if any, and am starting to wonder if I'm making a mountain out of a mole hill. If a UPS doesn't damage a computer how can it damage a pellet stove? Has anyone actually damaged their pellet stove using a UPS? Is there something obvious that I'm missing? Any thoughts or opinions would be greatly appreciated.
Thanks
JB

Click to expand...

All yer missin' on the computer / pellet stove comparison is the fact that your computer doesn't have any electric motors. A "modified" or "simulated" or "stepped approximation" is simply turning "on" and "off" all the electric motors (circ fan, comb fan, auger) about 30 times per second. Electronics don't mind. Electrics do. BUT, that's just MY opinion.

Click to expand...

Computers have fan motors and servos. both have small electric motors.

Click to expand...

Those fans, motors, and servos are all DC parts.

A "good" AC generator should run with no issues. For a UPS - I tried them all and returned them all - modified sine, similar to sine, etc. You need a PURE SINE WAVE output. Without it, your fans will run like crap and the control board will not respond properly. I went with the Sentry, since the charger is part of the unit and got 2 Golf Cart batteries.

http://www.secamerica.com/ss_sentry.html

This will be my 3rd season with it. It keeps the stove on in minor power outages and fluctuations, which I get very frequentely and in one big outage, I let it run till the power came on to see how long it would go

Unbelivable 14 hours on level #3 and it was still going strong. If you find another brand, they all even out to the same $$$ with a charger. A generators fine, but if your heating primarily
with the stove and are away for a time, this will do it. Plus with my Enviro, I don't have to set the reset button after an outage. Power goes out at night, I go back to sleep!

Boy I'm confused. I thought that the way the computer sized ups worked was the AC in got converted to DC went thru the inverter and then out to what ever was connected. That way if the AC fails the battery supplied the inverter. That was the magic of "uninterrupted " in UPS. That means to me that anything plugged into the UPS gets whatever sine wave the UPS puts out all the time not just when the AC fails. Does anybody else understand it differently?

Hi DBCooper-

How the typical UPS works is to pass thru the line AC voltage and condition it.
Some models do not provide the line conditioning (surge suppression etc.). Look at the unit specs.
When power is lost my unit picks up in 16.5 ms (1 cycle typ.) and the inverter does its job outputing the AC (PWM format)
As I indicated previously the APS 1250 with its PWM output has worked for my needs quite well on a P-68.
I have run it over 20 hours continously with no issues.
The stove ran just like it does when it is on utility supplied power.

Hope this helps you -