{"id":79,"date":"2021-01-27T14:10:11","date_gmt":"2021-01-27T19:10:11","guid":{"rendered":"https:\/\/opentextbc.ca\/basichvac\/chapter\/pressure\/"},"modified":"2023-03-02T11:42:08","modified_gmt":"2023-03-02T16:42:08","slug":"pressure","status":"publish","type":"chapter","link":"https:\/\/opentextbc.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:\/\/media.bccampus.ca\/id\/0_gc9qt73g?width=608&amp;height=80&amp;playerId=23449753\r\n\r\n<strong>[pb_glossary id=\"212\"]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<strong>[pb_glossary id=\"213\"]Velocity pressure[\/pb_glossary]<\/strong><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<strong>[pb_glossary id=\"214\"]Total pressure[\/pb_glossary]<\/strong><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 <strong>[pb_glossary id=\"211\"]air-handling unit[\/pb_glossary]<\/strong> will have a maximum value of pressure that it can produce. If <strong>[pb_glossary id=\"212\"]static pressure[\/pb_glossary]<\/strong> is too high relative to <strong>[pb_glossary id=\"213\"]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 <strong>[pb_glossary id=\"212\"]static[\/pb_glossary]<\/strong> or <strong>[pb_glossary id=\"214\"]total[\/pb_glossary]<\/strong> pressure, from which the <strong>[pb_glossary id=\"213\"]velocity[\/pb_glossary]<\/strong> pressure can then be derived.","rendered":"<p>Click play on the following audio player to listen along as you read this section.<\/p>\n<p><iframe loading=\"lazy\" id=\"kaltura_player\" title=\"3.22 Pressure Terms\" src=\"https:\/\/api.ca.kaltura.com\/p\/148\/sp\/14800\/embedIframeJs\/uiconf_id\/23449753\/partner_id\/148?iframeembed=true&#38;playerId=kaltura_player&#38;entry_id=0_gc9qt73g&#38;flashvars[leadWithHTML5]=true&#38;flashvars[streamerType]=auto&#38;flashvars[localizationCode]=en&#38;flashvars[sideBarContainer.plugin]=true&#38;flashvars[sideBarContainer.position]=left&#38;flashvars[sideBarContainer.clickToClose]=true&#38;flashvars[chapters.plugin]=true&#38;flashvars[chapters.layout]=vertical&#38;flashvars[chapters.thumbnailRotator]=false&#38;flashvars[streamSelector.plugin]=true&#38;flashvars[EmbedPlayer.SpinnerTarget]=videoHolder&#38;flashvars[dualScreen.plugin]=true&#38;flashvars[Kaltura.addCrossoriginToIframe]=true&#38;wid=0_bcuc1nr8\" width=\"608\" height=\"80\" allowfullscreen=\"allowfullscreen\" sandbox=\"allow-downloads allow-forms allow-same-origin allow-scripts allow-top-navigation allow-pointer-lock allow-popups allow-modals allow-orientation-lock allow-popups-to-escape-sandbox allow-presentation allow-top-navigation-by-user-activation\" frameborder=\"0\"><\/iframe><\/p>\n<p><strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_79_212\">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<p>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<p><strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_79_213\">Velocity pressure<\/a><\/strong><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<p><strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_79_214\">Total pressure<\/a><\/strong><strong>: <\/strong>The sum of static and velocity pressure inside an HVAC system; the total opposition to airflow in a ducting system.<\/p>\n<p>An <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_79_211\">air-handling unit<\/a><\/strong> will have a maximum value of pressure that it can produce. If <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_79_212\">static pressure<\/a><\/strong> is too high relative to <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_79_213\">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<p>In testing HVAC systems, it is sometimes necessary to test the pressure at various places. Direct measurements can give values for <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_79_212\">static<\/a><\/strong> or <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_79_214\">total<\/a><\/strong> pressure, from which the <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_79_213\">velocity<\/a><\/strong> pressure can then be derived.<\/p>\n<div class=\"glossary\"><span class=\"screen-reader-text\" id=\"definition\">definition<\/span><template id=\"term_79_212\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_79_212\"><div tabindex=\"-1\"><p>The force resisting the movement of air.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_79_213\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_79_213\"><div tabindex=\"-1\"><p>The force exerted by a moving air stream, in the direction of the moving air.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_79_214\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_79_214\"><div tabindex=\"-1\"><p>The sum of static and velocity pressure that must be overcome by an air handling unit.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_79_211\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_79_211\"><div tabindex=\"-1\"><p>The component of an HVAC system which drives air through the building.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><\/div>","protected":false},"author":90,"menu_order":1,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-79","chapter","type-chapter","status-publish","hentry"],"part":78,"_links":{"self":[{"href":"https:\/\/opentextbc.ca\/basichvac\/wp-json\/pressbooks\/v2\/chapters\/79","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/opentextbc.ca\/basichvac\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/opentextbc.ca\/basichvac\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/opentextbc.ca\/basichvac\/wp-json\/wp\/v2\/users\/90"}],"version-history":[{"count":3,"href":"https:\/\/opentextbc.ca\/basichvac\/wp-json\/pressbooks\/v2\/chapters\/79\/revisions"}],"predecessor-version":[{"id":348,"href":"https:\/\/opentextbc.ca\/basichvac\/wp-json\/pressbooks\/v2\/chapters\/79\/revisions\/348"}],"part":[{"href":"https:\/\/opentextbc.ca\/basichvac\/wp-json\/pressbooks\/v2\/parts\/78"}],"metadata":[{"href":"https:\/\/opentextbc.ca\/basichvac\/wp-json\/pressbooks\/v2\/chapters\/79\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/opentextbc.ca\/basichvac\/wp-json\/wp\/v2\/media?parent=79"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/opentextbc.ca\/basichvac\/wp-json\/pressbooks\/v2\/chapter-type?post=79"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/opentextbc.ca\/basichvac\/wp-json\/wp\/v2\/contributor?post=79"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/opentextbc.ca\/basichvac\/wp-json\/wp\/v2\/license?post=79"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}