A/C orifice tube question
Pro
Joined: Dec 2014
Posts: 683
Likes: 275
From: Cincinnati Ohio
Do you have a link to this flow control? I’m interested in what the manufacturer is claiming.
i worked on a number of flow controls some years ago for automotive HVAC. TXV’s, electronic expansion valves, two stage orifice’s. The basic idea was to decrease the size of the orifice at idle while increasing its size to maintain reasonable high side pressure at down the road speeds. You may have noticed that if you have found yourself stuck in city traffic on a blistering hot sunny summer day, the air temperature will rise as you sit, and sit, and sit in traffic.
i worked on a number of flow controls some years ago for automotive HVAC. TXV’s, electronic expansion valves, two stage orifice’s. The basic idea was to decrease the size of the orifice at idle while increasing its size to maintain reasonable high side pressure at down the road speeds. You may have noticed that if you have found yourself stuck in city traffic on a blistering hot sunny summer day, the air temperature will rise as you sit, and sit, and sit in traffic.
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Le Mans Master
Joined: Jan 2001
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From: Hilton NY
For climates under 105 degrees, it's AC Delco professional part #1550120 at Rock Auto for $21 that replaces alternate OEM part #9189841 or #89032868. The normal non-automatic professional AC Delco part #155151 is $3 and replaces alternate OEM part #03033879 or #3038790. I was curious if anyone tried one and what the results were.
Pro
Joined: Dec 2014
Posts: 683
Likes: 275
From: Cincinnati Ohio
I think I see how it works. It has two smaller diameter orifice tubes. One is always open and the other opens or is blocked based on condenser out liquid temperature. Theoretically, at low speed and idle conditions, the condensed gas temperature is high enough to cause a bimetallic spring to close off one orifice. This will raise the discharge pressure and enable more of the discharge gas to condense to high pressure liquid (or increase the sub cooling of the high pressure liquid if it is already fully condensed). This will improve the refrigerating effect at the low speed and idle conditions. If you drive in hot climate low speed and idle conditions, the trade off for improved ac comfort is higher compressor out pressure and temperature with the smaller orifice. As long as the cooling fans can keep up, there would be some small impact on compressor durability. If the fans cannot keep up, the system will cycle on and off due to high side pressure and your comfort will suffer. In theory the compressor clutch life will be impacted as well because it will be cycling on and off at high discharge pressure conditions.
