italie |
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MAME owes italie many thank yous, hah
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Any HVAC guys in the house?
#241947 - 12/26/10 05:32 PM
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I have a Carrier Gas furnace, PAV58. Just put in the new thermostat, had to run a new common wire as the previous owners were not running one.
Seeing issues with the thermostat now where 24V is dropping out just before the heat cycle completes. It loses 24V for about 5 seconds, comes back right after. This is causing issues with temperature settings, as the thermostat doesn't have a battery backup.
I'm wondering if something energizing on the new thermostat (Fast TS21) that is causing the dropout, or it's the furnace and this behavior is what killed the last thermostat. I'm betting on the latter...
Any common issues on the control board to check?
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| italie |
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MAME owes italie many thank yous, hah
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scratch that.
[Re: italie]
#241957 - 12/26/10 07:57 PM
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> I have a Carrier Gas furnace, PAV58. Just put in the new thermostat, had to run a new
> common wire as the previous owners were not running one.
>
> Seeing issues with the thermostat now where 24V is dropping out just before the heat
> cycle completes. It loses 24V for about 5 seconds, comes back right after. This is
> causing issues with temperature settings, as the thermostat doesn't have a battery
> backup.
>
> I'm wondering if something energizing on the new thermostat (Fast TS21) that is
> causing the dropout, or it's the furnace and this behavior is what killed the last
> thermostat. I'm betting on the latter...
>
> Any common issues on the control board to check?
Code 33 thrown on the furnace, looks like I've got an airflow issue that is throwing the furnace into failsafe.
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Re: scratch that.
[Re: italie]
#241958 - 12/26/10 08:00 PM
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Maybe it's time setting up blog like the one from Dad Hacker. 
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Re: Any HVAC guys in the house?
[Re: italie]
#241959 - 12/26/10 08:02 PM
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I understand HVAC to mean High Voltage Alternating Current.
24 Volts is hardly High Voltage and the post indicates 24V DC that is being dragged down.
However it sounds like there is a ballast/pull-up resistor in place that is preventing a short-circuit and tracks/wires burning out. Lucky for you.
Also sounds like the 24V comes back when this "load" is switched off again.
Check what is being activated when you lose the 24V and look down that line for the fault.
Regards
Mark
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| Gor |
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Giver of truth.
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Re: Any HVAC guys in the house?
[Re: bodger319]
#241960 - 12/26/10 08:59 PM
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Heating, Ventilating, and Air Conditioning
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Oh for Pete's sake.
loser.com
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| redk9258 |
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Regular
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> Code 33 thrown on the furnace, looks like I've got an airflow issue that is throwing
> the furnace into failsafe.
If it started acting up when you changed thermostats, I'd put the original back on the wall and see if it clears itself up.
I have a Carrier furnace that had a problem with the fan would power back up for about one second at the end of a cycle. I took the PCB out and replaced about 5 capacitors on it. It's been fine every since [knocks on wood!].
[ATTACHED IMAGE]
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