On 07/19/2016 11:08 AM, Paul Koning wrote: > The expense of a new service for 3 phase is one issue; it may not be > available at all. A lot of US rural areas have a single wire > running along the street. The only way you could get 3 phase service > is for the utility to replace that by 3 wires, for however many miles > it takes to get to the spot where their 3 phase service ends.
Depends upon your "rural area" and the local utility. Ours is a rural co-op and service is very good. The neighborhood is wired on a buried 12KV three-phase setup with a large disconnect box at each driveway. This allows the utility folks to perform "load balancing" on an individual basis. >From discussions with the utility personnel, I did have (but didn't know about) the option of having an extra wire buried along the driveway to the transformer pad by the house for 3-phase service, had I requested it. Now, of course, it would cost real money. Some of the farms out here have large high-draw electrical gear, such as hay dryers--which do take 3-phase power. Many of my neighbors have single-phase 400A installations. Compared to the service that folks in town get from their municipal utility board (higher rates and lousy service), I consider myself to be fortunate. I recently replaced my home's heat pump (the old one had 24 years on it and used R22 refrigerant) and was a bit surprised to see how the business of motors has changed in that time. Compared to the original blower and fan motors, the new ones look almost tiny. They're BLDC or VFD models and apparently develop more (and better controlled) power. The controllers are, as one might expect, PCBs full of SMT--I think I spotted a couple of ST MCUs there. The thermostat has a color touch-screen display and monitors not only temperature but humidity and uses only 2 wires to communicate with the rest of the system. It's like looking under the hood of my wife's Prius. --Chuck