wrote:

I recently bought a home with a Honeywell Chromotherm III (T8600D)
model thermostat. My home has a natural gas burning furnace and an a/
c system, both operating off of a single transformer.

I am going to replace the thermostat myself and am considering either
the Honeywell RTH8500 or the TH8110. The RTH8500 is the "retail"
version of the thermostat and the TH8110 is the "professional
version".

The main differences I see between the two a

1. The retail version runs exclusively off of batteries. The pro
version also takes batteries but can optionally run off of the 24vac
"common" connection.

2. The pro version has a lot of installer options.

I read through all the different installer options for the pro and it
appears to me that given my setup I will be leaving them at the
factory default settings.

Also, I don't today have a wire coming from the common side of the
transformer into the existing thermostat, so I don't think I'll be
able to take advantage of
the 24vac option to power the TH8110.

So if I am going to rely on batteries either way, and if I have no
reason to change the factory defaults, is there any reason to get the
TH8110 instead of the RTH8500?

Do the "pro" versions of the thermostat have any other advantages over
the comparable retail model (like quality of construction or
anything)?

Thanks

Hi,
Pro version does not have wake, leaven, return, sleep mode. Instread
it's called occupied, not occupied something like that. If you want to
use 24V source for power then you can't do arm chair programming(I mean
off the wall). Either one will work fine, it's just your choice.
I used both of them and now I switched to wireless one to relocate the
'stat without messing with rerunning wires. One thing, make sure you
turn off power when you work on 'stats. Go to www.HVACmechanic.com
forum. There are many helpful techie folks.
Good luck,