"David" wrote in message
.196...
We have a gas boiler heating system with three zones. 1st zone is for
the downstairs, 2nd zone is for the upstairs and the 3rd zone is for
heating the hot water.

We are currently having problems with the 2nd zone in that it is keeping
the upstairs at 76 degrees. I have recently replaced the thermostat
upstairs and set it at 45 degrees. But the temperature still remains at
76.

But then for a week or so it seemed like when we turned the downstairs
heat off, the upstairs would turn off also. But yesterday and today we
turned the heat all the way down downstairs and the upstairs pipes
remained hot.

One thing of note, is that prior to replacing the mercury thermostat
with a digital thermostat, I did move the thermostats control up and
down (with the cover off) and did not see any sparks when the merury
made contact with the wires to start the heating process.

Hopefully someone out there can help us out. We don't want to be frying
in the middle of summer and having the ac compete with the heater.

Heat rises. Any heat from the first floor winds up on the 2nd floor.
The 2nd floor thermostat will always be satisfied and the 1st floor will
alway be calling for heat.

Test the theory by nailing (?) a blanket across the top of the stairs to cut
off the air flow. Or use a candle to find the drafts. There will be cold
air flowing down along the stairs to replace the hot air going up along the
ceiling.