19 Jul
2016
19 Jul
'16
12:08 p.m.
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