[Mic865hvac]

I need to locate an operation manual for an Intertherm G4RA096C-16, to calculate the system CFM based on static pressure. Can this manual be located on line?

[drtom4444]

What are you trying to do? It's more complicated than that. The furnace puts out 400 cubic feet of air per ton of air conditioning capacity or slightly more. You have to measure duct size and shape along with static pressure to get CFM, but mobile homes are high static pressure systems and Intertherm furnaces are designed to run at a high static pressure. There is a tool you put over each outlet to get airflow in CFMs and then you add them together. You must make sure the coils are very clean along with the filter before testing to get your max. Mobile home coils get very dirty and if not cleaned yearly will clog up completely. If they have not been cleaned well with coil cleaner and high-pressure water your air flow will be killed almost entirely or entirely. If the unit has been freezing up you know it's clogged up with dirt.

[Mic865hvac]

This unit is not installed in a mobile home, it is in the basement of a three level home. I have taken static pressure readings with my magnehelic gauge and now I need the manufacturers literature for the equipment, in order to see where the CFM and static pressure meet. The coil and filters are clean, there are no filter grilles or. I've taken two readings, (1) before the filters and after the coil (2) before and after the coil. I need the info to determine if I need to increase the duct size for a changeout that includes new duct to the top level that has been served by a window AC unit, and a radiant panel in a wall. I need the manufacturers literature in order to complete the calculations.

400 CFM to 600 CFM per ton is a rule of thumb that varies based on duct construction, home construction etc. I have changed out many 3 ton units with less than 1000 CFM in the supply duct. So I'm really needing the manufacturers literature for the unit I am replacing with a new unit. Before I demo the existing unit, I want to make sure any duct modifications are made first.

[drtom4444]

I would recommend that you find a dealer to get a copy of the specs you want. Those charts are in books that only the dealers have. I have never seen them anywhere else. If you are supplying air to more space than you had before I know you will need larger supply ducts to account for the extra CFMs you will need. In Florida we have to be extra careful to have at least 400 CFM per ton because we are using air and heat and any shortage on CFMs will be noticed right away by a hot room. There are even extra requirements for the new 13 SEER units that require either vents in each door or returns in each room to keep air flow up. If you try to run more air through too small duct work you will have either a very noisy system or one that will not deliver the air flow you need even though Intertherm units are high static pressure units. Adding a little size to the plenum should not be too expensive and will insure that you have enough air flow and a quiet system.