The manual says Furnace Rated at .5" ESP.
There are some things I don't understand though. In the chart are TAP, LOW, MEDL, MEDH and HIGH. Are these for cariable speed blowers? Having a single speed blower, which do I refer to?
Also, I'm in the natural gas business and have a draft range differential pressure transmitter than can accurately measure down to a few fractions of an inch. Basically a digital manometer rated at .1% of 30" (0.03" I think).
Do I tap into the inlet and outlet of the furnace or what?
Sounds like you have a multispeed motor,very common,variable speed is a DC motor and different altogether.
If thats a fan chart it should list cfms,at varios ESP's or static ,for varios fan speeds so you have a choice,higher speed will deliver more cfms at higher ESP's.
Measure sstatic at inlet to furnace,and note where the filter is located and it's size and type.
Then measure at a point between the coil and the furnace,Don't drill holes if you don't know what's behind that area!!!
If you can't get to a pont between the two,measure hust above the coil,and post the model number of the coil,someone may have the specs on the coil.I'm assuming it's a ne coil.
Was a load calc done on your home? Unless you live in Arizona under 110 degree heat 5 ton for a 2500sq ft home seems a little overkill! Even though it previously had a 5 ton unit still does not mean it's correct? How is the humidity in the house and did the last unit short cycle?
[Edited by kevinmac on 08-01-2005 at 10:18 AM]
2500-sq.ft. home, 14-SEER, 5-ton; sounds like the old 500-sq.ft. per ton rule.
That 16" round return duct is about right for a 2.5-ton system, not a 5-ton system! Even if it had a 4-ton condensing unit on it before, it wouldn't deliver anywhere near 4-ton.
That could be leading you to oversizing even more, which won't work either. Have a "manual J" done and size it right with a duct system and blower to match the tonnage.
You need at least a 20" round duct return for 5-tons.
After the Man. J,get a Man . D ,duct design,and you'll find the correct sizes for Your duct system,it can vary ,a lot.
20" could be right so could 22 or more.