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Code 12 is displayed on unit-- directing to a combustion air

Customer Question
Hi Pearl, JA: I'll do all...
Hi Pearl,
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: Code 12 is displayed on unit-- directing to a combustion air problemThe unit has been operating with out a problem at 8000ft for the past 7 years. Now on startup the code 12 is displayed after a good even blue flame startup. The unit is not a high altitude product but the air pressure here in the rural mountains mimics below 5000ft during the winter. I have cleaned the wall intake/exhaust tube, blower fan, inside filter, replaced the flame rod but the problem persists. There are not technicians close by with which to confer. Would like to get it running since winter has begun. Thank you for your assistance.
JA: Did you double-check the thermostat? And what about the unit's filters?
Customer: yes, there is no external stat with this unit.
JA: Do you plan on doing the work yourself?
Customer: I am a tech but dealt with simpler heating units
JA: Anything else we should know to help you best?
Customer: no'
Submitted: 1 year ago.Category: HVAC
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Answered in 8 minutes by:
10/13/2016
HVAC Technician: WCohn, Construction Worker replied 1 year ago
WCohn
WCohn, Construction Worker
Category: HVAC
Satisfied Customers: 1,200
Experience: Been in contruction 18+years
Verified

Hello my name is ***** ***** I look forward to helping you!

What exactly are we working on? Tankless water heater? What brand?

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Customer reply replied 1 year ago
Hello Wade,
Rinnai Energy Saver Wall Furnace
HVAC Technician: WCohn, Construction Worker replied 1 year ago

Well I know Rinnai water heaters inside out, but not their heaters. I'm going to request your question get moved from plumbing to hvac. Please wait for that.

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Customer reply replied 1 year ago
Thank you Wade
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago
Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8,824
Experience: Retired HVAC/ Electrical & Boiler contractor. Industrial
Verified

Hello, if you can give me the full model number of the wall furnace I can pull the manual on it in most cases and mark up a page or two with trouble shooting instructions.

So far I suspect a restricted vent, (wasps nest etc) or a problem with the pressure switch.

We can go from there.

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Customer reply replied 1 year ago
Hi Phil,
I apologize for I thought Wade had sent you all the information. Please find it following:
Code 12 is displayed on unit-- directing to a combustion air problem
Rinnai Energy Saver RHFE-263FA II-P Serial C8-00-000380
The unit has been operating with out a problem at 8000ft for the past 7 years. Now on startup the code 12 is displayed after a good even blue flame startup. The unit is not a high altitude product but the air pressure here in the rural mountains mimics below 5000ft during the winter. I have cleaned/disassembled the wall intake/exhaust tube, blower fan, inside filter, replaced the flame rod but the problem persists. There are no technicians close by with which to confer. Would like to get it running since winter has begun. Thank you for your assistance.
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Hello, locate the pressure switch (PS), then remove the pressure sensing tubes and using a paper clip wire clean out the orifices that tubes connect to. you can locate the pressure switch by following wires attached to terminal 1 and 3 click here

with the power disconnected, suck on the rubber tube lightly and see if you can hear the switch open and close (click sound)

I will be off to bed shortly if I miss you tonight I will pick up your response first thing in the morning.

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Customer reply replied 1 year ago
HI Phil.
I removed the pressure switch, cleaned both orifices and sucked on the connected black tube. No sound or click can be heard.
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Thanks, ***** ***** like a bad pressure switch, next use an ohm meter to check between various combinations of the 3 wire connections on the pressure switch as you suck lightly on the rubber tube connection... if the switch is working, you will see the switch open and close on the meter.

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Customer reply replied 1 year ago
HI Phil,
The readings I get sucking or not on either black hose or clear hose side of switch:
*Between White terminal-#3:Black terminal-#2 Closed Switch
*Between White terminal-#3:Red terminal-#1 Closed Switch
*Between Black terminal-#2: Red terminal-#1 Open Switch
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Thanks, ***** ***** readings do you get on the same terminals when the pressure switch is just sitting on the bench.

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Customer reply replied 1 year ago
Phil,
I got those readings with the switch removed. Was I not to remove the switch from the unit?
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

You did well. I am looking for different readings when the pressure switch is sitting on your bench.... if the readings are not different replace the pressure switch.

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HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

I am off to bed shortly, if I miss you tonight I will pick up your response in the morning.

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Customer reply replied 1 year ago
HI Phil,
Not sure how I would check the ohms with the unit attached to the furnace? I had to unplug the connector to get to the terminals. The pressure switch is on a bracket with no direct connection to the furnace. So the test would be no different than what I did with the unit removed from the furnace.
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

You would detach the wiring at the pressure switch and then check the ohms at the pressure switch. Unplugging the connector at the pressure switch would expose the terminals that you check the ohms on.

The ohms test on the bench would be of course with the wires disconnected and that is *perfect. (Ohms is resistance only) No wires need be or should be connected.

Send me a photo taken from about 6 feet away. with the service panel removed so that I can see the set up. then another photo taken from 4 feet away at a different angle.

Use the 'attach files' link to the left of your send button to send the photo's.

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HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Note: the purpose of the ohm tests is to see if the switch position changes when you suck on the pressure sensing tube lightly and when the pressure switch it just sitting there on the bench, no sucking on the tubes for that second test..... you can do the same tests with the pressure switch mounted in the furnace. (just disconnect the wiring to it)

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Customer reply replied 1 year ago
Hi Phil,
Maybe I used the incorrect wording, I apologize. I checked the switch both static and with some suction. The readings were the same.
Someone mentioned, could this furnace have a multiple amount of over heat sensors that may have failed triggering a code 12?
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Thanks, ***** ***** switch is bad.. replace it, that should solve the problem.

It is unlikely that there are multiple different failures at the same time... the error codes can also be bogus... lets change the pressure switch and see how it goes.

http://www.searspartsdirect.com/model-number/rh/fe1004fa/3088/1610460.html

scroll down their page to their 800# ***** should have the pressure switch... call them on the phone.

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HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Please don't forget to rate my work positively, that is the only way the company pays me for my time, lacking that I work at my own expense.To rate locate the 'finish and rate' link and click on it.

In exchange I will hold the question open on an unlimited time basis for any follow up might possibly need.

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Customer reply replied 1 year ago
Hi Phil.
Thank you, ***** ***** order the switch.
Erik
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Great, let me know how it works out.

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Customer reply replied 1 year ago
HI Phil,
I am having difficulty find the pressure switch online, do you have a source?
Thank you Erik
Customer reply replied 1 year ago
HI Phil,
Spoke with HouseNeeds.com in Vermont, they are checking on the part 1004f-2051.
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Hello again, had you tried Sears parts.

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HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Rinnai head offices,

https://www.rinnai.us/contact-us

give them the part number and the following numbers:

Rinnai Energy Saver RHFE-263FA II-P Serial C8-00-000380

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HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

You can also locate the nearest dealer on that page, you need your zip code only

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HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Its time to rate my work, locate the 'finish and rate' link and click on it, I will appreciate that greatly and hold the question open for any needed follow up on an unlimited time basis... lacking that the question could time out on us.

Thanks!

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Customer reply replied 1 year ago
Thank you Phil, I am checking other sources, HouseNeeds wants just shy of $110 for the part with freight.
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

`Good luck, stay in touch

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Customer reply replied 1 year ago
Hi Phil,
The new pressure switch arrived this evening. I have installed it and again I have the same problem. Initial start up is correct, combustion air purge, igniter starts, gas valve opens, good blue flame, few seconds pass, then system shuts down, and error code 12 flashes on the screen.
What steps do you suggest?
Thank you Erik
HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Hello again, looks like the error code may have been incorrect (that happens a lot). lets do a heat stress test on the printed circuit card that the flame sensor rod plugs into.

Use a hair drier to warm it up to 130F or so, not over 140F. Then while its hot try the furnace again, any change, for better or worse indicates a bad printed circuit board. (cracked micro circuits expand and either get worse or better when warmed up).

We can go from there

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HVAC Technician: Phil, Mechanical Engineer replied 1 year ago

Next step if needed will be to fit a U tube manometer to the 1/4" pressure switch tube and measure the vacuum... it is possible that the combustion air blower wheel is clogged with dirt or disintegrated or that the vent is still blocked or you have a split in its 1/4" rubber sensing tube.

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