Guardian furnace problem

Woodworker

I have a 40,000 btu 95.5%eff up-flow furnace. It has approx. 10' of 2" PVC for vent and combustion air each have 1 elbow.

The furnace trips out due to multiple attempts to ignite. It actually ignites every try but the burner will not stay lit unless the front door is open for about 10 seconds after ignition. Then the door can be closed and the furnace works fine. I tried removing the combustion air pipe and had the same problem.

Any ideas?

Charlie from wmass

clogged heat exchanger

I had a furniture restorer with a similar furnace. the heat exchanger was rusted shut.If this is for the shop or an area where you are doing a lot of wood working try a remote furnace with duct work supplying from another area. Not all sealed combustion units are all that well sealed.

DanCanDo

Fault Code?

Can you provide a more detail fault code?  I wondering if its a 3 or 4 fault code, indicating a problem in the pressure switch circuit.

Woodworker

failure code

Thanks for your reply.

I am not in the shop so I don't have the actual text but It blinks 7 times which per the manual is a multiple failure to start.

If it is the pressure switch would it shut down the furnace down after I close the door i.e..... door open only a few seconds after ignition and everything works fine.



Andy 

Tim McElwain

Check the microamps

from the flame sensor, should be between 2 to 10 microamps, normal is 3 to 5.



Clean the flame rod if  you are not able to get those readings.



Try temporarily disconnecting the flue from the unit and see if it will work.

World Plumber

New furnace?

Is this a new furnace? There was a problem with the grease they used in the manufacturing process in some unites that blocks the heat exchanger on start up. Does the flame look lazy and orangish? Can you feel a lot of heat radiating back behind the burners toward the cover if it were on?  If so The secondary heat exchanger may be blocked. Oh! does the condensate look milky?

World Plumber

baffle

Is there a baffle installed where the intake pipe connects? Usually we find something in the pipe. If it's doing it with the pipe off, look in the connector for a restriction.

Woodworker

check the microamps results

Thanks,

I will have access to my amp meter in the morning but, I went ahead and pulled the flame sensor and cleaned it with steel wool. The cleaning actually made it start more speradically with the door open. I'm expecting the flame sensor will need to be replaced.  

I pulled the flu and stuck a 5' piece of PVC in it's place. This did not change anything.

Woodworker

check the microamps results

Thanks,

I will have access to my amp meter in the morning but, I went ahead and pulled the flame sensor and cleaned it with steel wool. The cleaning actually made it start more speradically with the door open. I'm expecting the flame sensor will need to be replaced.  

I pulled the flu and stuck a 5' piece of PVC in it's place. This did not change anything.

Woodworker

New Furnace Reply

Thanks for the post

No it came with a property I recently purchased. I believe it is a 1998 vintage. It came out of a small house that we demolished. I just set it up in my woodworking shop.  

The flame is bright blue and I do not feel heat behind the burner

I ran the condensate into a 5 gallon bucket and it looks clear 

Woodworker

baffle reply

thanks for your post

I removed the intake pipe completely and got the same result. I stuck a 4" piece of pipe in and an elbow and got the same results