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Honeywell/Aprilaire humidity sensor failure pietu 03-04-2007
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Posted by pietu on March 4, 2007, 4:12 pm
I have an Aprilaire 600 whole house humidifier controlled by Honeywell
PC8900 thermostat. For a while now the PC8900 has been showing
"Humid--%", which according to the Owners Manual means that I have a
humidity sensor failure.

Is this a sensor inside of the PC8900? If so, is it something that can
be replaced or do I just need to order a new thermostat?

Could any indirect reason (i.e. solenoid valve failure) cause this error
message.

Appreciate any input

Posted by Bubba on March 4, 2007, 9:14 pm
On Sun, 04 Mar 2007 15:12:42 -0600, pietu <pietu1_at_juno_dot_com>
wrote:

>I have an Aprilaire 600 whole house humidifier controlled by Honeywell
>PC8900 thermostat. For a while now the PC8900 has been showing
>"Humid--%", which according to the Owners Manual means that I have a
>humidity sensor failure.
>
>Is this a sensor inside of the PC8900? If so, is it something that can
>be replaced or do I just need to order a new thermostat?
>
>Could any indirect reason (i.e. solenoid valve failure) cause this error
>message.
>
>Appreciate any input

We all know its your thermostat. Get a new one. You might want to get
an extra one as a spare. They fail quite frequently.
Bubba

Posted by pietu on March 5, 2007, 1:02 am
Bubba wrote:
> On Sun, 04 Mar 2007 15:12:42 -0600, pietu <pietu1_at_juno_dot_com>
> wrote:
>
>> I have an Aprilaire 600 whole house humidifier controlled by Honeywell
>> PC8900 thermostat. For a while now the PC8900 has been showing
>> "Humid--%", which according to the Owners Manual means that I have a
>> humidity sensor failure.
>>
>> Is this a sensor inside of the PC8900? If so, is it something that can
>> be replaced or do I just need to order a new thermostat?
>>
>> Could any indirect reason (i.e. solenoid valve failure) cause this error
>> message.
>
> We all know its your thermostat. Get a new one. You might want to get
> an extra one as a spare. They fail quite frequently.
> Bubba

Thought so. Unfortunately it seems Honeywell no longer makes PC8900 or
any other model with a humidifier control built in. It looks like White
Rodgers model 1F97-391 would have it, for a hefty price though. Is it
safe to assume that all these are compatible as long as I can get the
wiring right?

Posted by Bubba on March 5, 2007, 7:31 am
On Mon, 05 Mar 2007 00:02:49 -0600, pietu <pietu1_at_juno_dot_com>
wrote:

>Bubba wrote:
>> On Sun, 04 Mar 2007 15:12:42 -0600, pietu <pietu1_at_juno_dot_com>
>> wrote:
>>
>>> I have an Aprilaire 600 whole house humidifier controlled by Honeywell
>>> PC8900 thermostat. For a while now the PC8900 has been showing
>>> "Humid--%", which according to the Owners Manual means that I have a
>>> humidity sensor failure.
>>>
>>> Is this a sensor inside of the PC8900? If so, is it something that can
>>> be replaced or do I just need to order a new thermostat?
>>>
>>> Could any indirect reason (i.e. solenoid valve failure) cause this error
>>> message.
>>
>> We all know its your thermostat. Get a new one. You might want to get
>> an extra one as a spare. They fail quite frequently.
>> Bubba
>
>Thought so. Unfortunately it seems Honeywell no longer makes PC8900 or
>any other model with a humidifier control built in. It looks like White
>Rodgers model 1F97-391 would have it, for a hefty price though. Is it
>safe to assume that all these are compatible as long as I can get the
>wiring right?

Just replace the low voltage wiring from the humidifier to the new
stat and you should be good to go. The stat needs to match the new
wiring for correct operation.
Bubba

Posted by Noon-Air on March 5, 2007, 8:18 am

"pietu" <pietu1_at_juno_dot_com> wrote in message
> Bubba wrote:
>> On Sun, 04 Mar 2007 15:12:42 -0600, pietu <pietu1_at_juno_dot_com>
>> wrote:
>>
>>> I have an Aprilaire 600 whole house humidifier controlled by Honeywell
>>> PC8900 thermostat. For a while now the PC8900 has been showing
>>> "Humid--%", which according to the Owners Manual means that I have a
>>> humidity sensor failure.
>>>
>>> Is this a sensor inside of the PC8900? If so, is it something that can
>>> be replaced or do I just need to order a new thermostat?
>>>
>>> Could any indirect reason (i.e. solenoid valve failure) cause this error
>>> message.
>>
>> We all know its your thermostat. Get a new one. You might want to get
>> an extra one as a spare. They fail quite frequently.
>> Bubba
>
> Thought so. Unfortunately it seems Honeywell no longer makes PC8900 or any
> other model with a humidifier control built in. It looks like White
> Rodgers model 1F97-391 would have it, for a hefty price though. Is it
> safe to assume that all these are compatible as long as I can get the
> wiring right?

Use a Honeywell Model Number:TH9421



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