I too, have one of the Honeywells. I can't seem to find the
model number on the unit, but I remember that it was something
like the previous poster's 3500 or 3600. It has the "electronic
anticipation" and has worked extremely well with my gas furnace.
I have also checked it with both termocouples and traditional
mercury thermometers and found it to be right on. Occationally,
and very occationally at that, I do get an anticipator failure.
By this I mean that the furnace fires up and then, before the
blower comes on, it shuts down. This seems to be related to the
temperature and temperature changes. As I said, it only happens
extremely rarely. BTW, one of those "smart" furnace guys came
into my house and said "the Honeywell is junk." He's junk.
This is why I do most of my own rebuilding/repair. BTW, I once
bought a digital thermostat that advertised a +/- 1/2 degree
accuracy. It had no anticipator. It, combined with the gas
furnace, overshot by 6 or 8 degrees. I returned it right away.
It had a bunch of big C batteries in it. BTW, the Honeywell
batteries (I think they're AAs) last for years. I don't know
when I last changed them and they are still going strong. Great
Product!

David Efflandt wrote:
On Thu, 20 Nov 2003, CBHvac wrote:

"Steve Stone" wrote in message
...

Don't most stats have a plus or minus 3 degrees or so in latitude in when
they turn off or on ?

They do.
There is a reason for this, and a good Honeywell mercury switch stat, can be
better than a Chronotherm model when it comes to comfort.
Its called a dead band, and since MOST people can not actually feel the 3F
difference in temps, you never know.


The RobertShaw thermostat that came with my house was +-1 (2 degree F
spread) at best, and usually overshot 1-2. It had no anticipator setting,
just gas/electric switch.

I changed to Honeywell CT3500 (should have gotten CT3600) with 1 degree
spread, and by comparing air and wall termperature learns to
electronically anticipate temperature rise to shut off before it reaches
setting if necessary (since steam radiators retain heat), and ramps up
from setback instead of all at once. It only rarely overshoots slightly
if the weather suddenly turns very mild. The only reason I would have
liked the CT3600 is because it logs total run time to tell most effective
setback.

I don't know if the original poster gave a model number or whether it was
wired or set properly for their hydronic system. But my Honeywell
electronic works great for single-pipe steam, although, I my old home has
plenty of thermal mass (drywall over plaster), so temperature changes are
never sudden.