hvacman

There are a number of reasons that the blower will start at the instant you have a call for heat; t'stat wired wrong, no delay on fan board selected ( doubtful), fan relay bad ( stuck "picked" ) and if relay is on the units system board...the board is bad.......

NTC6125KJG1 was made by ICP and is rated to be either up-flow or Horizontal applications, it is a 125,000 btu/hr input rated for 5 tons of cooling

GARY...funny that you mentioned that (zipper head) me too, I spent 20 years there as a fire / safety , code inspector....left there went to a two year HVAC school, and two years at BCC (electrical engineering)...now a technical troubleshooter for a very large HVAC / R wholesale company in NY, solving service related issues on boilers, furnaces, and AC systems all over NY and into PA....thanks for saying Hi....Ken

It was made in 1993 and the 5th week ( 05) of the year....

As "Charlie" stated....there is NO subsitute for the factory install manual. But a few key points, is the unit taking combustion air from outside or inside through a coaxial (dual) vent pipe. If it is taking combustion air from inside the space/home, you have to meet the square foot space to btu/hr requirement of all appliances in that space as per NFPA 54 fuel gas code. NOTE: then it can't be installed in a closed closest / room ! Watch out for flexible gas whips and gastite feeding the unit, Noritz cautions the installer NOT to use them, due to the restriction they cause for proper gas flow, or in the case with Gastite....size the feed line way up to compensate for the flow restriction. Black iron pipe is best. Water feed lines in and out of unit should be 3/4 inch for best flows.......

One of the reasons that the turbulator, does this melt down....is when a contractor throws the water in his truck on its side in the box and the turbulator comes off the top hooks during this rough handling. Now the turbulator is sitting on the burner head while firing, which will cause this issue. Like "Jim from Oregon" stated......install a new turbulator, and re-check gas pressures to factory specs to be sure that reason number 2 for this failure (does not happen )an over fired unit.........hvacman

The other very missed aspect of the direct venting of 90% furnaces is the vent pipe size. Manufactures state different pipe sizes based on BTU input of unit and venting length, where say a 75,000btu/hr unit may use 2 inch and a 100,000 btu/hr unit will use 3 inch. The install manual and the respective venting chart is really the key, there is no rule of thumb here. ........hvacman