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domestic central air conditioners (cac) and outdoor air system (oas) are developing rapidly as people are more and more demanding on comfort of environment and air quality. questions arise about whether it is duplication or complementation to install both cac and oas.
to answer this question, we need to look at it in two aspects: is it duplication or complementation to install both and is it necessary to do so?
1.oas cac = duplication or complementation?
firstly, oas and cac do not duplicate in functions. cac is utilized to regulate indoor temperature with cooling and heating whereas oas is utilized to ensure indoor air quality through outdoor-indoor air circulation.
secondly, the two are complementary for improving comfort for life. with cooling and heating functions, cac provides a relatively comfortable temperature environment. oas, on the other hand, can maintain fresh air indoor. generally, indoor temperature can be kept fresh and clean at around 25℃ in summer with doors and windows closed even for 24 hours when both cac and oas are installed.
finally, combined use of cac and oas can reduce damage rate and balance energy consumption. with “total heat exchanger”, the oas can lower entering outdoor air temperature during summer time when outdoor temperature is very high. as a result, cac doesn’t need extra energy to cool down inlet air.
2.oas cac = necessity?
people are hesitant to install oas and cac at the same time mainly for three reasons: tight budget, remote location from first-tier cities, and cognitive blind spots on cac and oas.
if you can afford a hundred-thousand- or even million-dollar house, the budget for a healthy and comfortable living environment would be just small money for you. affected by haze, oas becomes popular for its function of pm2.5 filtration to ensure safe breathing air and reduce indoor air formaldehyde (hcho) concentrations.
cognitive blind spot actually makes things not as important as they were in some way.
when you are interested in oas and cac and start collecting information, you will find that many shops claim that their cacs come with built-in total heat exchanger and produce “fresh air” as well as heating and cooling. as a matter of fact, they are misleading consumers by contradicting oas and cac. consumers may feel difficult to make a choice between the two and be misled to a cognitive blind spot.
so what is the cac’s built-in “fresh air” function and how does it differentiate from the dedicated outdoor air system?
cac’s key function is temperature regulation rather than “fresh air” supply. its “fresh air function” is fulfilled in the following way:
outdoor air is drawn in through the air inlet, going through a rough filtration and then becoming cooling or heating air to be delivered indoor while contaminated indoor air is drawn back through return air inlet. in this way, the indoor air circulation repeats.
oas adopts a different way of air circulation. it draws outdoor air through fresh air unit, fresh air ducts and air vent, delivers fresh air indoor and then expels indoor air through air vent, exhaust air ducts and fans. simply put, oas is ventilation process to reject contaminated indoor air and introduce fresh outdoor air, forming air circulation between outdoor and indoor.
it seems that there is little difference between the two. but cac’s air intake action is a process of indoor pressurizing. when indoor pressure is higher than outdoor pressure, a closed circulation will form between the room and the air conditioner, which fails outdoor-indoor air exchange.
in short, the most competitive advantage of oas over cac’s “fresh air function” is that oas can reject contaminated indoor air and provide a more thorough and reliable air filtration.