I just installed a Reliance furnace transfer switch model TF151W to my main circuit panel. I tried to test it by running an extension cord from another outlet to the transfer switch. I put the P3 International P4460 Kill A Watt EZ Electricity Usage Monitor in the line to test the watt consumption of my hot air furnace.
After switching from Line to Generator and cranking up the heat, I noted the wattage was only 3.7 watts? Is this because the common neutral is not switched? If I was to connect the Honda EU2000I 2000 Watt inverter generator would I have any problems?
Best Answer
Well, from the tests you ran (see comments above), your setup is correct.
The Kill A Watt EZ should show a reasonable reading, BUT it appears that that kind of device requires balanced current.
So, because the furnace neutral current is not flowing through the Kill A Watt, it does not compute a valid power based on the current and voltage it does see. (Note that the meter is seeing a "ground fault" from its perspective.)
EG:
This is an apparent limitation of this model of meter; your setup is correct.
To determine the furnace's power draw, if you don't trust the label plate :), and, since you've access to the wiring at the furnace, measure the current and voltage there with standard AC meters.
Multiply the voltage and current to get KVA. The KVA will be slightly more than the actual power used (thanks to power factor), but your generator needs to be able to supply about twice that KVA anyway (allows for motor start).
Since your furnace has a 1/3 HP blower (max 250 watts, steady state), your Honda 2000 Watt generator should be just fine to power your furnace.