Percentage of Adequate Airflow on 5-Ton Systems

[udarrell]

In your opinion; Where you live, what percentage of 5-ton residential air conditioning systems have adequate ductwork systems that will support 2000-CFM at .5" of ESP?

Here in the USA it's not a very good percentage...

[nike123]

In my country, we don't have at all 5 ton duct residential systems.

Mostly in high class residential applications we have natural ventilation and hydronic systems (chiller-heat pump and natural gas heating - and floor/radiant heating or/and fan coil units). Rarely, in that systems, it is controlled fresh air and exhaust ventilation with heat recovery.

Normally we use small ductless split systems in residential applications (for cooling and heating in mild climate area ) combined with hydronic central heating in cold climate areas.

Duct systems are mostly for commercial purpose here and their shape is very bad due to lack of maintenance, bad craftsmanship and very scanty investors during building phase (and therefore pure construction).

[udarrell]

Evidently Inches of Water Column (IWC) is not used here.

Therefore, how many 4 & 5-ton duct systems are within the blower's rating?

Here in the USA, very few duct systems are sized to meet the blowers & system requirements.

Many 4 & 5-ton systems deliver up to a half-ton to a ton or more under their ratings.

[Abby Normal]

call it 125 Pa darrel

[udarrell]

call it 125 Pa darrel

Yep, there is 250-pascals to one IWC.
We don't use it much here, but it can be more precise a measurement where small precise increments are needed.

Personally I like it for air infiltration & other applications.

However, guess there is little interest over-here concerning my original thread question.

Thank you for the good input. - Darrell

[cadillackid]

in really old systems I used to find way oversized ductwork... you were lucky to get .25" on high speed cool on the older systems....

now what i find is cheap flex duct used,, twisted and curved around through joists and trusses.. oftentimes the inner pipe squeezed from a circle to an oval... along with its inherent "ridgy" interior causes for a High buildup of static pressure at the plenum only to find a lackluster performance at the end of the run....

the contractor often getting complaints from the homeowner that the HVAC system.. (esp cooling) performing inadequately on the second floor... so the contractor wires a higher blower speed in... never considering it might be the ductwork installation / and / or design...

ive tested more than one residential system pushing .75" at the plenum... and they wonder why the energy bill is high and the blower motor fails or creates a lot of heatload on the system.....

along with High static pressure not only comes higher energy bills wasted on making that pressure.. but also on lots of air lost often to unconditioned spaces.. (crawl spaces, basements, garages, attics...). you can only tape up the ductwork so well and residential ductwork plenum and trunk will swell under that kind of pressure.......

-Christopher