A/C problem

[hermanus]

I have a 1100 sq foot home in Florida and recently had a 2,5 ton 14 seer split unit installed.
I have had the unit installed hanging from the carport rafters and the return duct runs directly into the crawl space and to all the various drops. The supply duct from the filter housing to the air handler is 25 ft with a 16 inch duct.
My questions are: is my supply duct too long , and what sould my suction press be at an outside ambient of 80F and indoor at 78F , as my neighbour hooked up some guages to the unit and at the above temps it was at 88psi on the suction side.
I asked him to check this out as the unit runs a lot I feel.
He felt that this is way too high and has me worried.

The house has R30 insulation recently installed

[16x80]

hermanus

Welcome to the Home Repair Forums


Your 2.5 ton 14 seer ac unit is 30,000 btu's that works out to be 400 cfm per ton of ac, which for your unit is approximately 1000 cfm. A 16 inch flex duct carries 1500 cfm! It does not matter if its 3 ft or 25 ft! Air can be pulled thru anything just cant be pushed!

As for your suction pressure! Well it varies on the the ambient temps. In an optimum setting you should be running at about 68-70 deg on the suction side. My question is to you, What is the differential on your intake air and your supply air. you should measure this with a digital stat at the supply register and the return register. It should be about 17-18 deg differential. If this is the case your unit is doing all it can do to cool the home. If its lower than that you could possibly have bad supply air flow. The next check would be static pressure measured at just before and after the air handling unit with a manometer, This measurement should be ideally .10 static pressure. This can vary to a 1.5.

Check your temp differential and get back with me, I will help as much as possible.

16x80