I recently bought a house with really nice hardwood floors, but the builder didn't put any thought into installing a humidifier system. I'm now looking into my options and steam humidifiers seem to be the highest output solution, albeit overkill. Unfortunately, the only power source I have available in the furnace room is on a 15A breaker shared with two bathrooms, but my tinkering instincts won't accept defeat so quickly.
I'm thinking that I could use a UPS with sufficient output power to support the 7A steam humidifier. The trick is that I would use a current switch to sense when the humidifier is on and subsequently turn off the power source to the UPS (with a relay) and when the humidifier is off the UPS will reconnect and start charging. My theory is that the no load charging current of a UPS is always lower than the maximum load current. Someone correct me if I'm wrong.
The question is: How do I determine a UPS's charging current spec? If this is low enough to put on the 15A circuit then I'm good to go. If it's still too high then I have to accept defeat... unless someone has another clever solution. Given the construction of the building I cannot run a new 20A drop to this room.
Assumptions: Yes, I know, this isn't what a UPS is meant for.. but that isn't a part of the question. Also, I'll probably go through a set of batteries in a year and I'm OK with that.