Hi,
I was going over the manual for Honeywell Vision Pro 8000 and noticed
it can run on 24V system control power with battery as back up during
power failure, if wire is run to connect C terminals
between furnace control board and thermostat. I queried about this
to Honeywell tech support to confirm it. If you did not know about this,
check your manual, other non Vision Pro 8000 series thermostats may be same.

On Sunday, June 8, 2014 11:15:35 PM UTC-4, Tony Hwang wrote:
Hi,

I was going over the manual for Honeywell Vision Pro 8000 and noticed

it can run on 24V system control power with battery as back up during

power failure, if wire is run to connect C terminals

between furnace control board and thermostat. I queried about this

to Honeywell tech support to confirm it. If you did not know about this,

check your manual, other non Vision Pro 8000 series thermostats may be same.

Nice they answered your question. My experience with VisionPro was that
if you ask anything other than how to use it as a consumer, Honewywell tells you
to get lost and they won't answer the question because you're not an authorized pro. In my case, I wanted to change one programmable setting on the "installer
menu" and they insisted that I had to call one of those cigar smoking guys
with his butt crack showing that charges $100. Fortunately all I couldn't remember was how to put it into installer mode so I could change the setting
and I eventually figured it out.

BTW, one advantage to powering it is that the backlight is then on low
all the time. With battery only, it only lights up when you touch it.

trader_4 wrote:
On Sunday, June 8, 2014 11:15:35 PM UTC-4, Tony Hwang wrote:
Hi,

I was going over the manual for Honeywell Vision Pro 8000 and noticed

it can run on 24V system control power with battery as back up during

power failure, if wire is run to connect C terminals

between furnace control board and thermostat. I queried about this

to Honeywell tech support to confirm it. If you did not know about this,

check your manual, other non Vision Pro 8000 series thermostats may be same.

Nice they answered your question. My experience with VisionPro was that
if you ask anything other than how to use it as a consumer, Honewywell tells you
to get lost and they won't answer the question because you're not an authorized pro. In my case, I wanted to change one programmable setting on the "installer
menu" and they insisted that I had to call one of those cigar smoking guys
with his butt crack showing that charges $100. Fortunately all I couldn't remember was how to put it into installer mode so I could change the setting
and I eventually figured it out.

BTW, one advantage to powering it is that the backlight is then on low
all the time. With battery only, it only lights up when you touch it.

Heh?
Maybe it has some thing to do with I being ex-Honeyweller? 3 AAA
batteries don't last long in this particular 'stat.