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Posted by Perry on January 17, 2009, 9:53 pm
Perry had written this in response to
http://www.thestuccocompany.com/hvac/Re-outside-temp-reading-jumpy-36511-.htm
:
-------------------------------------
Jeff D wrote:
> Here's another data point regarding the outside temp sensor. It is only
> erratic when the auxiliary heating is on, not sure what that
> interaction
> could be. What type of sensor is it anyway, thermocouple, rtd,
> thermistor,
> diode etc. Also it would be nice to get a print for the thermostat so
> I
> know what the maze of external wiring is connected to and their
> functions.
> The t-sat is a Lennox Signature Stat 81M28. I'm not a hvac tech, but
> was an
> industrial electrician for 30 years and worked on the wiring side of
> several
> hvac systems.
>> ok - well I'll make sure all the connections are clean and tight
>> and wait
>> for the t-stat to fail, probably on the coldest day of the winter,
>> maybe
>> today it's 11 below
>> message
>>> On Tue, 13 Jan 2009 12:39:54 -0500, "Jeff D"
>>> wrote:
>>>>I have a Lennox heat pump with the outdoor temp probe. It
>>>> sometimes
>>>>changes
>>>>5-10 degrees within a few minute period. I've replaced the
>>>> telephone
>>>>style
>>>>connectors with wire nuts and had the service man replace
>>>> the outdoor
>>>>sensor
>>>>while the unit was still warrantied.
>>>>Today I have a new problem, the thermostat goes blank
>>>> periodically for a
>>>>few
>>>>minutes then returns to normal. It's not just the display
>>>> going blank
>>>>because I hear an internal relay clicking when it dies and
>>>> comes back to
>>>>life. I went to all the wire connections and jiggled them
>>>> but couldn't
>>>>get
>>>>the the thermostat to crap out. Any ideas on a solution to
>>>> either or both
>>>>of
>>>>these problems. I'm out of ideas beside ringing out the
>>>> wiring for shorts
>>>>or
>>>>breaks and replacing all the telephone style crimp
>>>> connectors between the
>>>>furnace, heat pump and thermostat with screw terminals.
>>> After all..............
>>> its almost always the thermostat.
>>> Bubba
>>
The outdoor sensor tells the first stage heat to go off and the second
stage to come on, The outdoor sensor needs to be on a T-stat wire by
itself not tied in off the regular stat wire. Your tsat going off is
either a bad Tstat or its losing power from the furnace. Hope it helps
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> erratic when the auxiliary heating is on, not sure what that
> interaction
> could be. What type of sensor is it anyway, thermocouple, rtd,
> thermistor,
> diode etc. Also it would be nice to get a print for the thermostat so
> I
> know what the maze of external wiring is connected to and their
> functions.
> The t-sat is a Lennox Signature Stat 81M28. I'm not a hvac tech, but
> was an
> industrial electrician for 30 years and worked on the wiring side of
> several
> hvac systems.