I have a ruud furnace that wont stay running. The unit goes through
the start up cycle. The electronic igniter will start sparking, and
the flame will ignite. It will run good for about 5-7 seconds, then
it it will go out like the unit cut the gas off. I think it is a
flame sensor, but I am not sure what it is called.
This furnase has a circuit board with 3 leds. two are green and one is
yellow. It says Flame. This light flashes, but the other two stay
solid green. I cant find a manual to see how to read these. Any help
or pointers would be appreciated.
Does your furnace have a draft inducer fan? There can be one or two
safeties with a draft inducer. A centrifugal switch on the fan motor
and a diaphragm operated pressure switch to detect the air pressure
cause by the running fan. The diaphragm switch will be round plastic or
metal with a silicone rubber tube connected to the draft inducer
housing. The air line could be bad or the connection to the inducer
housing could be clogged. A piece of wire can be used to clear the
connection and you can blow gently on the tube and listen for a click
from the diaphragm switch. You can jump out the safeties to test them
but never leave the furnace running like that. There are several sites
where you can post a question about your problem. You'll need to post
the model number and such because the folks reading your question can
be dealers for your specific equipment.
http://www.hvacmechanic.com/index.php
http://toad.net/~jsmeenen/index.html
TDD
Couold there also be a thermocouple to sense thast the flame is
actually on?
No, it has an electronic igniter. Most new NG furnaces use a hot surface
igniter which is a silicon carbide or nitride resister which glows red
hot and will ignite the pilot when gas hits the igniter.
http://homerepair.about.com/od/heatingcoolingrepair
/ss/furn_electr_ign_4.htm
http://preview.tinyurl.com/2g27es8
The igniter is used in conjunction with a flame sensor which is a heat
resistant metal electrode that sticks into the pilot flame. Both devices
are hooked to the control module which will turn off the igniter when
a flame is detected by the flame sensor circuitry.
TDD
What you can do is find the flame sensor and clean it with fine steel
wool.
On this
http://www.acdirect.com/shop/images/products/Ruud_UGPH_G22_448_Rev10.pdf
it's called "remote sensor" on page 2.
You might have to remove a plate/baffle to get at it, or just contort
your hand/wrist.
If that doesn't work, you might try a new flame sensor.
Bring your part AND your furnace model/serial number with you to the
HVAC supplier.
These things often have different parts than the drawings show.
After that I would get a pro in.
I went through this sensor cleaning, inducer diaphragm replacement
crap for years with my furnace after I had it installed.
Every damn season I had to tinker with it.
Hours of farting around.
Always guided by control board LEDs and troubleshooting charts.
Always got it going again, but never felt good about it, because the
problems seemed too random and flaky.
Even the control cycling would sometimes change - like the inducer
running for 20 seconds after shutdown, etc.
My wife hated that furnace, and I got to hating it too.
It's -20 out and you hear it try to start in the night and it has to
cycle twice to get going - you wonder if it will start.
Then it usually starts, but you lost an hour's sleep thinking about
it.
Then the main fan got stuck on low speed only.
I tapped around everywhere hoping to unstick what I supposed was a
stuck relay, then called a pro in.
The guy had the thing fixed it 10 seconds by twisting the control
board hard.
I agreed with him it would happen again and had him put in a new
control board.
ALL THE OTHER PROBLEMS WENT AWAY TOO.
We haven't given it a thought in about 4 years,
Best $470 I ever spent. The board was about $320.
Not saying what your problem is, and there's a couple things you can
do.
Clean/replace a flame sensor. Replace an ignitor/sparker.
New inducer diaphragm if indicated.
That's all inexpensive parts.
But if you have a flaky control board you'll spin your wheels.
I'm glad a relay got stuck on mine, otherwise I'd still be dealing
with that BS.
I used ServiceMagic.com to find my HVAC guy.
Think I'll mention that in a new thread.
--Vic
Flame sensor.
The ignition cycle won't start if it's doesn't detect that the draft
fan is running. Sometimes cleaning them will fix them but usually
they are marginal and should be replaced. Starting and shitting down
are always the flame detection phase of the cycle. Could also be the
control board but the flame sensor is the cheaper of the two and fails
more often than the boards.
I know the file name says "Rgph" but when you examine the file, it is
the 40 page installation manual for GPH models as well. Might match
your furnace, or be close enough to be helpful.
Thanks!!! I was searching for this installation manual and couldn't
find it.
I was able to clean the flame sensor and all is well. Thanks for the
advice. My Yellow Flame Led is flashing which means it is a weak
signal. I will order a new flame sensor and install it when it
arrives.