"Sam Takoy" wrote in message
...
Hi,

I have recently purchased a Honeywell wireless thermostat (YTH6320R1015).
Manual is here, page 4 is key:
http://www.pexuniverse.com/docs/pdf/...-guide-efs.pdf


I have split setup: A gas boiler in the basement (2-conductor thermostat
wire). My relatively modern Bryant AC unit is in the attic. I therefore
have two transformers. (For what it's worth, I've made sure they have the
same phase.)

I would like to control both systems with my thermostat. Honeywell tech
reps all agree that this must be possible, but give me contradictory
instructions. After several exchanges they seem to come to an agreement
that I might need a third transformer just to power the unit independently
from the transformers in my systems.

Does that make sense or could there be an easier solution!

Many many thanks in advance!

Sam

I don't see an issue. The "EIM" needs power (24 volt). It could be powered
by either transformer. Choose one. If you locate the EIM in the attic, power
the R and RC and C, from the air handler. Remove the existing jumper, which
is between R-RH-RC, from RH, which will be powered from the heating system.
The two wires go to RH and W O/B. If you want to install the EIM in the
basement, you can power the device from that transformer by removing the RC
from the jumper.