Carrier 58mvb Intake Issues

[superdale]

Hey guys! I have a 60K BTU Carrier (13 years old) that I went to tonight to fix and I have a couple questions for you.

It was tripping on Code 34 "Ignition Fault"

The furnace runs great with the Burner Cover (2 pipe) taken off. The intake/exhaust venting runs about 16' with 4 - 90's outside (2" ABS). I'm looking at an air delivery issue here. Nothing has changed in the 13 years they owned it. (Good friend's of mine)

What I've Done:

Cleaned and re-aligned burners
Cleaned Orifices
Manifold pressure (3.45" W.C.)
Checked I.D. Motor EFF
Cleaned drains

I have to go back tomorrow to cut out a 2X4 to be able to remove the intake from the furnace to see if there's any obstruction in the venting system. The intake snorkels up outside about 6' to back to back 90's (to meet code).

I just wanted to know if you guys had anything else I could check before i do that.

Thanks for your help guys,

Dale

[jamessnevets]

One possibility is a plugged secondary hx, characterized by a powerful sulfuric odor coming from the exhaust pipe or seeping from the combustion chamber when the cover is off. LP fuel applications are notorious for this in the midwest where I am. Sometimes the furnace will be able to ignite, but quickly use up the available oxygen for combustion, and shut down on that fault code or a code 32 (it pays to check the fault memory, as it covers the last 72 hours of operation), b/c the secondary hx is not permitting proper airflow. Another way to check is is to pull the main blower and look at the back underside of the hx. If you see white mineral deposits forming along the lower seams on the outside of it, then the hx needs to be replaced. That is a huge undertaking, as it usually involves replacing the primary hx, secondary hx, and a host of other parts connected to them. Hopefully it's just a blocked intake pipe, for your sake, I hope it's not a plugged hx. Another possibility to check is if the ground for the furnace has a good connection to the breaker box.

[SAILFISH]

if the furnace runs ok with the burner door off look at a blocked intake tube. Blow with nitrgen to the out side. Also check the screen where the intake pipe goes into the furnace for bug, trash debris.

[Cosmicmuffin]

Had one do this after installing an after market ignitor.,it did not tightly "seal the closed combustion box. Factory rep told me air will "swirl" and not lite properly. Thought he was nuts.,but had no other ideas. Sealed up..,no problems.,been over a year!

[Kevin Weaver]

After you get it to light, have you tried putting the burner door back on? Sounds like leaves at the intake screen where pvc pipe connects to furnace.

[pauls heating &]

After you get it to light, have you tried putting the burner door back on? Sounds like leaves at the intake screen where pvc pipe connects to furnace.

at combustion disc...

[superdale]

Thanks for the replies everyone. I'm going back there today to take the intake off to inspect it. I have put the burner door back on once it's running and the flame goes a little yellow then comes back to blue. I'm assuming its the screen that has a slight blockage. It was just one of those days where you just second guess yourself.

I'll post back asap once I fix it.

Dale

[markvilleman]

HE has blockage, then the resistance increased. But when you removed the cover,the total resistance would dropped again. So the pressure made and burners were lite up.

[gravity]

check the furnace drain trap!

i have seen this many times.

pull off all 3 hoses. put ure finger on 2 ports of trap and blow thru the 3rd hole. do this to all the holes. then run HOT! water thru the trap and shake it around real good. also check for the color of the water that comes out and if its sludge or not. this will tell the condition of the secondary h/x.

you can also use a manometer and check pressure thru h/x. if your reading hi pressure then its most likely clogged. you should also be using a combustion analyzer. this would tell you real quick how the furnace is burning.

if this all checks out then pull the tubes off the pressure switch and see if there is water in them. if there is replace pressure switch and shorten tubes so no water can travel in them

[superdale]

check the furnace drain trap!

i have seen this many times.

pull off all 3 hoses. put ure finger on 2 ports of trap and blow thru the 3rd hole. do this to all the holes. then run HOT! water thru the trap and shake it around real good. also check for the color of the water that comes out and if its sludge or not. this will tell the condition of the secondary h/x.

you can also use a manometer and check pressure thru h/x. if your reading hi pressure then its most likely clogged. you should also be using a combustion analyzer. this would tell you real quick how the furnace is burning.

if this all checks out then pull the tubes off the pressure switch and see if there is water in them. if there is replace pressure switch and shorten tubes so no water can travel in them

Hey there, I did clean the trap out as that was part of my basic check list (I do a lot of testing). Also I did a Combustion Analysis test on it and I was getting proper readings through the flue so I know my burn is good. 17PPM through my exhaust with proper O2 levels. Did a manifold test also at that time.

I went back tonight to check the venting out and there is nothing wrong/blocking the venting/screen. I started scratching my head for a few minutes :P. It's dual vented so there's no perforated disk installed. The idiot who installed it glued the intake pipe into the intake collar inside the furnace (arrrgggg......).

NOTE

I believe I found the issue to be the ignitor not glowing on the right side of the "M" (weak). I am ordering the part tomorrow and I'm sure the problem will be resolved . It's been a stressful week so my brain is cramping and second guessing myself which I usually don't do.

I appreciate the help about the "Aftermarket" Ignitor as it sparked in my head tonight.

Update to follow later....

Dale