Carrier 58sx furnace

[Rmarshall]

Hey group question on a Carrier furnace. Lines coming off pressure switch. Pressure switch on bottom and line connects to box by IM which closes switch. Bit there's another line that comes on pressure switch into a T then into GV and burner box. What's it for, do etc? System works without it , read it's just a reference point?

Thanks guys

[bja105]

The gas valve's regulator and the pressure switch use it as a reference point.

Its a differential pressure switch, measuring the difference between the burner box and collector box, not ambient pressure in the basement.

[Rmarshall]

Differential pressure switch that makes sense from multiple locations that easily explains why it's there in the burner box. Thanks bro