Rinnai convector FC824N keeps heating even after reaching set temp.

rcmitch99

Hi, I could use some help with my Rinnai convector FC824N unvented gas heater. It keeps heating even after reaching set temp.
Its summer time, its 75 in the room, the rinnai display "room temp" says 72. set temp is 60. it just runs and runs. any suggestions would be appreciated.

Big Ed_4

Is the fan running ? Does the unit feel warm ? Fan should be set to auto . Off season shut it off and open window .

rcmitch99

Thanks for the reply. The fan runs perfect. I only ran it in the summer to test it, to see if it's working. The unit runs great in timer mode. But I left it on thermostat control a few times during the winter and it got up to 80+ degrees in the house. Just need to know if its the motherboard that needs replacing.

109A_5

Hello @rcmitch99,

Odd set of symptoms;
It does not accurately sense room temperature.
If set to 60 yet comes on at 70, are you somehow overriding the thermostat mode ?
Have you tried a power reset, remove power from the unit for 30 Seconds or more?

Seem like more than the thermistor that is used to measure room temperature is out of tolerance.

User manual https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Rinnai-FC824N-User-Guide.pdf

mattmia2

Does it tell you what temp it thinks the room is?

mattmia2

From the manual:
AUTO OFF:
When AUTO OFF is selected, the indicator light will
glow. The unit will now be under full thermostat
control. The heater will operate to reach the
selected room temperature and then turn OFF. Press
AUTO OFF again to disable this funcƟon.
NOTE
When AUTO OFF indicator light is not glowing , the
unit will conƟnue to produce heat in at least a low fire
capacity unƟl the unit is manually powered down.

rcmitch99

ok thanks for the comments. After doing some reading, it seems like I need to move my thermostat higher. (a common problem it seems.) Currently, its in the back at the very bottom. Thanks for your help everyone.

bburd

Not the best location for a thermostat for sure, since cold drafts tend to move along the floor.

I have seen the same overheating behavior in hotel style PTAC units with the thermostat sensing bulb located in the return airstream near the floor. Many such units installed in cold climates are controlled from a wall thermostat for this reason.

Big Ed_4

A typical space heater ...