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.

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Originally Posted by flatcroaker

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.

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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.