I have a Rheem Heat and air unit. Model # RGAC-080AW Serial # CM3D104 F4782 4794 and need to find out where the filter for the unit is located.

The burner cover plate for your Rheem RRNL-B030JK08E unit can be obtained from an authorized Rheem dealer or distributor. You can visit the Rheem website to locate a dealer or distributor in your area. Alternatively, you can contact Rheem customer service for assistance in obtaining the burner cover plate. Be sure to have the model and serial number of your unit available when contacting Rheem customer service.

I can't find any information on that MODEL you listed in your question. It's sort of like the Rheem Air Handler models but notthing comes back. In any case you will NEED the SERIAL number, as that will tell you all you need to know about it. If you can't decipher SN, call RHEEM and they can give you the info on that unit. Sorry I could not be of more help.

Call Rheem tech support www.Rheem.com

Sounds like a relay inside the air handler is stuck 'closed'...

Question posted under Rheem tankless water heater:

Call Rheem at 800 432 8373
They will need serial number located on label on side of unit.
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Usually I recommend that people tear out their tankless water heater and sell it on ebay, and then install tank-type heater from different manufacturer:
http://waterheatertimer.org/How-to-install-gas-water-heater.html

I would be very reluctant to connect used gas appliance without a product manual, and service manual.
http://waterheatertimer.org/images/Exploded-house3.jpg

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

According to the 2012 manual, 'the LED display only shows F.'
Bottom page 65. Yet the F temperatures are also shown as C in the manual.
http://waterheatertimer.org/pdf/How-to-set-Rheem-tankless-temperature.pdf
You probably have different model, or older model?.?
Older manual (page 15) shows same temperature range with both F and C, but typical of Rheem, the manual is totally vague about settings and say that qualified tech needed to adjust temps beyond factory default range (with no mention of display showing C) ... which is safeguard since the damg product cannot always heat water fast enough to reach higher set points above 120F.
http://waterheatertimer.org/pdf/TanklessOutdoor_95_84_64X_UC_AP15318.pdf

Call Rheem 800-432-8373 and give your product serial number and model number located on side of unit, and ask them.

Don't forget to keep the product maintained to avoid common error codes.
http://waterheatertimer.org/pdf/Rheem-CondensingTankless-maintenance-2012.pdf

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

1) Never, ever install tankless water heater, unless your wallet is 2" thick and you enjoy nuisance problems and recommended continual maintenance.
2) Add in-line air vent.
http://waterheatertimer.org/images/Air-vent-added-to-return-22.jpg
3) Look for check valve along the line. Look for mixing valve, pressure regulating valve, etc.
4) If you have recirculation system, remove cross-over check valve and see if problem is located there.
5) Contact Rheem. 800-432-8373 They will want model number, serial number, and name of installer. And might recommend contacting installer or plumber.
6) Increase water flow. Check water flow requirement of tankless (.5 gallons per minute activation) with actual flow at faucet.
7) Clean water filter at tankless unit.
http://waterheatertimer.org/pdf/Tankless-maintenance.pdf
8) Crossover at single-handled faucet.
http://waterheatertimer.org/Crossover.html
9) Fix all leaking faucets indoor and outdoor so no air is being sucked in.
10) Bad TP valve on water heater sucking in air each time water pressure pulls on the valve?

Additional resources: No information about air-in-line
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Could be a restricted inlet pipe just as you suspected.
http://waterheatertimer.org/pdf/ErrorcodeTroubleshooting.pdf
error 15 is 'Boiling safety device'
"Check for closed water heater inlet valve or restrictions in cold water inlet pipe (must be fully open).
Check for clogged heat exchanger (scale buildup).
On commercial water heater, lower setpoint temperature below 180F at high altitude."

Open following links for Rheem tankless resources including Rheem chat and phone support:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html
http://www.rheem.com/products/tankless_water_heaters/customer_support/

Before calling service technician, best way to approach this problem is to contact Rheem with your specific model and serial number.
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

Error codes are starting place for troubleshooting.
C2 11 is gas and ignition related.
The same symptoms on your tankless unit can have different cause and solution than another tankless unit.

The burner might need to be cleaned.
Undersized gas meter, or low gas pressure should be checked.
Air in gas line.
Short circuit in gas solenoid.
Bad igniter.
Igniter wiring harness.
Tankless is not grounded.
Vent exceeds allowable height or length limit

All gas water heaters require periodic maintenance.
The manual is a good place to start for advisories and troubleshooting and required maintenance.
Tankless water filter should be cleaned monthly, and heat exchanger de-limed yearly.

Upvote the help.
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

I had the same problem and called the manufacturer. The error code C-8 was followed by the number 76. They told me to disconnect the thermostat/digital display from the main unit. This was fairly simple to do by removing the front panel. The unit works steady now without shutting down after a few minutes. The help desk told me that the main circuit board needs to be replaced for the unit to work with the display and that they would mail me one asap. At least we have hot water again.

Oakville, Ontario