N.gas carrier furnace. wont fire?

Unknown

you have a Hot Surface Igniter which does glow.

You have a seperate sensor for sensing flame. Make sure the sensor is into the burner flame at least 3/4 to 1" and about 1/4" to 1/2" above the burner.

I assume by your statement on it reaching limit you mean the number of attempts at ignition.

Make sure your gas pressure is correct, check your orifice size and calculate your input. It should be as close to rated input as you can get it.

It is possible that the combustion air blower is pulling the flame away from the sensor. Try restricitng the air flow to see if it will stabilize.

One very important question does the igniter come on light and then go out immediately?

OR

Does it ignite stay on for a few seconds then go out?

Some Carrier units also require a turbulator in the air shutter area, does your service/installation manual mention this anywhere and if so is it in place. If it is LP gas the turbulator has to be removed by the way.

Does the Integrated Furnace Control (assuming you have one on this unit)go into any failure code mode?

Mark The Plumber

N gas furnace won't fire ,right,

It will fire up, maybe. I watch it try, it goes through the cycles but hits the limit. I think 5 tries. my last attempt it flamed up, but went out immediatly.
I took out the flame sensor cleaned it that didn't do anything it. I ordered a new one, but it is not here yet. Is this a good guess, or where should I have started. if that doesn't work where. I can smell the gas some and the glow pilot is working,
Thanks, Plumber,

jim lockard

condensing

or non condensing?

Timco

if it gets to that point, the inducer motor is pulling in the pressure switch, and all the rollout sensors have to be good to get that far....sounds like the flame sensor.

T

Empire_2

try this

Cleane the sensor with 400grn sand paper to remove dirt and crap. Also I'm sure the furnace is grounded, but make sure. Is this existing or a new install?. If new, check the ground and make sure your polarity is correct on the incomming 110vac line. Try to switch just so see if there is a difference. Visually, is the flame reaching the sensor on the cross over of the burners?

Jeff Lawrence_25

not sandpaper

Emery cloth.

The silica on the sand paper could possibly cause a glaze on the sensor so it will need replacement sooner rather than later. I've heard that if you don't have any emery cloth, you can use a fairly new dollar bill.

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Terry

seen it a million times

Check the Polarity of the 120Volt power feed.

I'll bet lunch on Friday that it's reversed...

(I've had a lot of free meals on this type of call)

gl.

EIN

Mitch_4

the key words in your post

were it cycles and hits the limit. Is it the high limit? is the unit overheating? then its an airflow problem.

Mitch

will smith_4

check

The flame signal before condemning the sensor. Wouldn't be surprised if it is a reversed polarity. Would be surprised if the homeowner has a happy relationship with the furnace. I think Carrier is the best marketed Edsel ever to crawl out of the swamp; personally, I'd rather have a well maintained 20 year old Trane than a brand new Carrier, but that's just my experience talking.

S Ebels

How old is it?

If it's fairly new, the integrated control should have an idiot light on it that will flash in a sequence. Three long and two short for example would be failure code 32. If your furnace was made within the last 6-7 years it should have this onboard diagnostic capability. Take the bottom (blower compartment) door off to access the control and observe the lights. On the back of the blower cmpt door, there should be a table interpreting the number and sequence of the flashes. This will at least get you looking in the right direction.

Other than that, don't overlook the obvious stuff like gas pressure, polarity, grounding, etc. I have seen a number of newer furnaces work just fine for years and then freak out because there is no ground wire connected. I for one, don't know why some furnaces take that long to exhibit a problem but it happens.

I have also seen HS ignitors that would glow but not get hot enough to reliably ignite the air fuel mix. They seem to just get weak and lose the resistance required for correct temperature. I can't tell what exactly you are saying is happening in the ignition sequence but if the ignitor glows and you don't establish any flame when the GV opens I'd install a new ignitor first. (They should be changed every 3-4 years just for the sake of reliability anyhow) After that I would check your flame current, providing you have a meter that will read microamps.