Whisper furnace by lennox. Model # G20Q3/4E-100-1-M SER # 5891B11187-S... I AM ADDING A/C UNIT COIL TO MY SYSTEM... no one can tell me what size coil I need ! Need to know cfm on this furnace to match a coil with. What tonage of a/c do I need to match this system? Furnace is 100,000 BTU according to label. All original equipment still on this unit. Please help me with this matter. THANK YOU.

whisper furnace by lennox. model # G20Q3/4E-100-1-M SER # 5891B11187-S......... I AM ADDING A/C UNIT COIL TO MY SYSTEM..... no one can tell me what size coil i need ! need to know cfm on this furnace to match a coil with. what tonage of a/c do i need to match this system? furnace is 100,000 btu according to label. all original equipment still on this unit. please help me with this matter. THANK YOU.

You will need to do a manual J to see exactly what size A/C unit you need then you will have the correct answer. This is not a item you guess at or use a rule of thumb. Follow the link below and read what it says. Since you are the contractor you will need to answer the questions.