{"id":46,"date":"2021-01-27T14:10:11","date_gmt":"2021-01-27T19:10:11","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/basichvac\/?post_type=chapter&p=46"},"modified":"2021-03-25T17:21:19","modified_gmt":"2021-03-25T21:21:19","slug":"pressure","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/basichvac\/chapter\/pressure\/","title":{"raw":"Pressure Terms","rendered":"Pressure Terms"},"content":{"raw":"Click play on the following audio player to listen along as you read this section.\r\n\r\nhttps:\/\/video.bccampus.ca\/id\/0_jbqrm141?width=608&height=70&playerId=23448552\r\n\r\n[pb_glossary id=\"463\"]Static pressure[\/pb_glossary]: <\/strong>The force required to move air through various components, such as filters, dampers and diffusers. This represents a resistance to air flow.\r\n\r\nStatic pressure is the outward force of the air in the ducts and represents a waste or loss of available pressure. Anything that adds air resistance, such as corners in ducting and filters will increase the static pressure.\r\n\r\n[pb_glossary id=\"465\"]Velocity pressure[\/pb_glossary]<\/strong>:<\/strong> The force exerted by a moving air stream. It is produced in the direction of the moving air. This represents the useful value of pressure that moves air through the ductwork.\r\n\r\n[pb_glossary id=\"467\"]Total pressure[\/pb_glossary]<\/strong>: <\/strong>The sum of static and velocity pressure inside an HVAC system; the total opposition to airflow in a ducting system.\r\n\r\nAn [pb_glossary id=\"461\"]air-handling unit[\/pb_glossary]<\/strong> will have a maximum value of pressure that it can produce. If [pb_glossary id=\"463\"]static pressure[\/pb_glossary]<\/strong> is too high relative to [pb_glossary id=\"465\"]velocity pressure[\/pb_glossary]<\/strong>, the fan will be unable to circulate air throughout the ducting system. Most air handling units will have a maximum pressure rating that they are designed to deliver.\r\n\r\nIn testing HVAC systems, it is sometimes necessary to test the pressure at various places. Direct measurements can give values for [pb_glossary id=\"463\"]static[\/pb_glossary]<\/strong> or [pb_glossary id=\"467\"]total[\/pb_glossary]<\/strong> pressure, from which the [pb_glossary id=\"465\"]velocity[\/pb_glossary]<\/strong> pressure can then be derived.","rendered":"

Click play on the following audio player to listen along as you read this section.<\/p>\n

https:\/\/video.bccampus.ca\/id\/0_jbqrm141?width=608&height=70&playerId=23448552<\/p>\n

Static pressure<\/a>: <\/strong>The force required to move air through various components, such as filters, dampers and diffusers. This represents a resistance to air flow.<\/p>\n

Static pressure is the outward force of the air in the ducts and represents a waste or loss of available pressure. Anything that adds air resistance, such as corners in ducting and filters will increase the static pressure.<\/p>\n

Velocity pressure<\/a><\/strong>:<\/strong> The force exerted by a moving air stream. It is produced in the direction of the moving air. This represents the useful value of pressure that moves air through the ductwork.<\/p>\n

Total pressure<\/a><\/strong>: <\/strong>The sum of static and velocity pressure inside an HVAC system; the total opposition to airflow in a ducting system.<\/p>\n

An air-handling unit<\/a><\/strong> will have a maximum value of pressure that it can produce. If static pressure<\/a><\/strong> is too high relative to velocity pressure<\/a><\/strong>, the fan will be unable to circulate air throughout the ducting system. Most air handling units will have a maximum pressure rating that they are designed to deliver.<\/p>\n

In testing HVAC systems, it is sometimes necessary to test the pressure at various places. Direct measurements can give values for static<\/a><\/strong> or total<\/a><\/strong> pressure, from which the velocity<\/a><\/strong> pressure can then be derived.<\/p>\n

definition<\/span>