undersized ac vs room temperature

[aungkyawtun]

sensible heat gain is 108 kW.installed ahu is 103 kW@ 5.3 cmh. what will be the room temperature .100% return air system
Thank u in advance

 

[LittleInch]

Hot.

No where near enough info. Is this a school question?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[marcoh]

reset the room temperature in your heat load software until you get a sensible cooling load of 103kW, noting you need to also check the change in sensible capacity as air-on conditions change.

But then read ANSI/AHRI STANDARD 210/240-2008 "Performance Rating of Unitary Air-Conditioning & Air-Source Heat Pump Equipment" and realise what the allowable margin is on stated capacity and an AHU with 103kW capacity, could legally be doing quite a bit more (or less) and so what is the real capacity of the unit?

But in the real world with a conservative 10% safety factors etc, for most of the year, you would be able to achieve the design room temp in any case.

 

[317069]

- 103 KW is a sensible capacity or a total capacity.?
- 100% return, do you mean there is no outdoor air.?

 

[RandomUserName]

I round a lot.

Assume:

Qs = 108 kW (368 MBH)
Qhvac = 103 kW (351 MBH)
RA = 75°F
SA = 58°F

Qhvac is 100% sensible load capacity; also includes fan heat gain
100 % RA system with no OA; therefore RA = MA

Qhvac = (1.08)(CFM)(deltaT)
CFM = (Qhvac)/(1.08)/(deltaT)
CFM = (351,000 BTU/hr)/(1.08)/(75-58°F)
CFM = 19,100 CFM

Holding CFM constant:

Qs = (1.08)(CFM)(deltaT)
deltaT = (Qs)/(1.08)/(CFM)
deltaT = (368,000 BTU/hr)/(1.08)/(19,100 CFM)
deltaT = 17.8°F

RA = SA + deltaT
RA = 58°F + 17.8°F
RA = 75.8°F

Seems negligible unless critical.