I am aware of certain normal maximums. I guess I'm looking for somebody to tell me that I'm pushing things too far, or not. I want to hook up a portable air conditioner (Sunpentown WA-1220E) which is rated at 950 watts (and, mysteriously, at 9.0 amps) along with an HP 4Si printer, which is rated at 1100 watts (9.4 amps, per the documentation) with a 12 amp maximum for 20 milliseconds.

I certainly understand that if both units were operating continuously, the wattage (950 + 1100) = 2050 exceeds the recommended maximums of 80% of capacity (20 amps * 120 volts = 2,400 * 80% = 1,920).

But the printer doesn't operate continuously. Most of the time it is in standby mode. In standby mode it uses about 240 watts (120 if in powersave mode).

Clearly, as long as I don't print (!), I don't have a problem.

I guess my question is: assuming the air conditioner is running, and assuming I start the printer printing, after how long should I shut off the air conditioner (or stop the printer, give it a rest, and if so, for how long, and then start it back up again)?

Thanks

George

tkrussell

The 80% derating factor is only for loads that run continuously , which is considered to be 3 hours or more. Otherwise a circuit can be loaded 100%.

Check the AC documentation. It should tell you how long to leave the AC off before turning back on. If you turn off an AC unit, and try to turn it back on right away, the compressor is still in a locked rotor condition, and may trip the breaker by itself.

According the the manufacturers website, your unit is rated at 950 Watts for AC only, and the 9 Amps is if it had the optional heat mode.

Since the printer is only on for a short time, you should have no problems running the AC and the printer together.

NoCalHomeowner2

Thanks for your quick and helpful response.

George