Professionals who care
MICHAEL YOUNG
Michael Young is a trainer , coach and mechanical engineer in the HVAC industry . He graduated from the University of the Witwatersrand in the field of Mechanical Engineering ( B . Sc . Mech Eng .) in 2008 and qualified as a Professional Engineer ( Pr . Eng ) in 2013 . Michael is passionate about promoting knowledge and helping other young engineers grow within the industry through his training workshops and coaching sessions .
HOW GEOGRAPHICAL LOCATION AND APPLICATION CAN AFFECT THE DESIGN OF AN HVAC SYSTEM :
By Michael Young ( Pr . Eng )
How climate change is causing HVAC systems to fail .
PART 3
46
Global warming was reported in the news about 30 years ago and since then , policies have changed and protocols have been implemented to help combat the effects of climate change .
Climate change is very real and many of us have experienced it first-hand with the milder winters and heatwaves during summer . The biggest problem that we face is drought , which has affected many parts of South Africa .
Increasing ambient temperatures also impose many different problems when it comes to the design of an HVAC systems and the type of technology that is implemented .
Engineers of the 21st century will have to consider the following moving forward :
• How do existing HVAC systems that are older than 8 years cope with the new operating ambient conditions ?
• What are we going to change in the designs of new HVAC systems ?
• How are we going to tackle the problem of water shortages while still meeting the cooling requirements ?
One issue with existing systems is the shutting down of an HVAC system on a ‘ high pressure ’ alarm . This problem occurs when insufficient heat is rejected from the condenser . When ambient temperatures rise , the temperature difference between the refrigerant and the ambient air decreases which then reduces the total heat of rejection ( THR ) of the condenser .
To solve this problem , either the ambient air condition must be lowered or the condenser capacity must be increased .
Decreasing the ambient temperature can be accomplish by implementing adiabatic cooling . Implementation of such a system however requires the use of water which doesn ’ t really help in addressing the water consumption problem .
RACA Journal I February 2021
Replacing the condenser involves a compatibility issue . Older refrigerant systems may still operate with R22 or R407C refrigerant . Most of the new direct expansion ( DX ) systems use R410A refrigerant .
It is still possible to get a system like this to work as unit setpoints and pressure transducers can be changed for different refrigerant gases . The R410A construction is also able to accommodate the higher operating pressure , so replacement of the condenser is still possible .
The final limiting problem is capital costs and looking further into the future . R22 gas is already illegal in Europe and one can expect R407C to follow . Replacing condensers can be an expensive process as refrigerant has to be reclaimed , condensers have to be rigged and there is no guarantee the indoor unit will last for another 5-10 years .
So , one needs to do an investigation to ask : “ Is it really always worth it to replace an existing condensing unit when the indoor unit may break within the next 5-10 years ? Will spares on these old units still be available , and is this exercise a good investment ?”
Climate change is not only affecting our weather patterns , it is also causing new problems for systems that were designed on old ambient condition guidelines . So , what does climate change hold for the future designs of HVAC systems ? Find out in next month ' s publication of RACA Journal . Wishing you a successful month ahead and chat soon . RACA
Michael can be contacted on michael @ myhvaccoach . com or 073 171 2311 for any questions or HVAC training needs .
www . hvacronline . co . za