Sensible duty is King
We spend most of our days, in comfort air conditioning, striving to give an occupants dry bulb temperatures of their desire (eg 21oC).
Our heat load sums give us a duty (say 8kW). Whilst the Total Cooling (Sensible Cooling + Latent Cooling) is important, it can sometimes lead to confusion.
Sensible duty is King
Modern buildings and fresh air make up results generally in all heat loads being calculated to be mainly Sensible Cooling.
- Sensible Cooling is related to the dry bulb temperature (that shown on a remote controller & mentioned in the weather forecast)
- Latent Cooling is the heat energy used in changing state (ie making the condensate, reducing humidity, freshening the room)
- Total Cooling is the sum of them both.
The Technical Bit
The mass-produced AC units for the UK and global market have a set `Sensible Heat Factor` designed into their cooling/heating indoor coil.
Unlike a custom-made DX coil for an AHU for instance, where the manufacturer creates a coil specifically to do `X` Sensible Cooling and `Y` Latent Cooling to match design, these are set at factory production line.
Air passing across the High Wall DX Coil with a SHF of say 0.7, will do 30% Latent Cooling and 70% Sensible Cooling.
The linked brochure shows the 9kW high wall (Largest) and that at UK conditions it has a Total Cooling of 9.28kW and a Sensible Cooling of 7.22kW (Latent being 9.28-7.22 = 2.06kW)
This is a SHF of 0.778
Take from the Sensible Cooling shown a `little bit` for piping lengths (we calculate this on Toshiba`s Airs selection software) then a 7.0kW or even 6.5kW Sensible Cooling system is supplied.
Confusion Sometimes
When we do our sums and need 9.28kW of Sensible Cooling we may fall into the trap of using a single 1101 High Wall thinking we`re getting 9.28kW Sensible Cooling.
We are only getting 7.0kW or even 6.5kW
Larger Indoors
10kW Sensible Cooling (+/- a wee bit) can be achieved with an Under Ceiling, Ducted or Floor Mounted Unit – but not a High Wall.
Twin (2 high walls) or Triple (3 high walls) Systems, having a single outdoor, can be supplied too for larger duties.
Summary
Sensible duty is King