Reader Mail: 02/03/2003
Misdiagnosis
[Editor’s note: This letter is in reference to the letter “Elevated Head Pressures,” Jan. 20.]There seems to be some controversy on what will happen to the head pressure if you had a restricted liquid line. There is a very simple answer. If you have enough condensing area to store the system charge, your head pressure will go down. A good example of restriction is a pump down (out) on a commercial split system. If you observe your gauges, you will see the suction pressure respond immediately, and then you will see your head pressure start to drop until the LPC opens. Since you could be dealing with large and long liquid lines, the pump down (out) solenoid should always be located as near to the indoor unit as possible. Mr. McClure stated that he has seen the head pressure go up and down. My suspicion is the previous technician misdiagnosed the restriction as low on charge and added refrigerant trying to increase the suction pressure and ended up with an overcharged system and ended up with not enough condenser for the overcharge.
You will almost get the same indication on your gauges, but if you were to measure the subcooling, you would know if it were a restriction or not enough refrigerant.
David Anderlik, Wagram, N.C.
Laws Of Physics
I am writing in response to Scott McClure’s letter [“Elevated Head Pressures,” Jan. 20] concerning John Tomczyk’s article on the relationship between high-side restrictions and head pressure [“Diagnosing A Restricted Liquid Line Can Be Tricky,” Dec. 2]. I think Mr. McClure is thinking short term in his response.Mr. Tomczyk is correct; when the load is removed, head pressure falls. The experience Mr. McClure described (rising head pressure on startup) is similar to the action while pumping a system down. If the pressure was equalized when the heat pump was started, you are flooding the condenser coil as there is no flow, which could cause the high-pressure safety to trip, or (more likely) as the expansion valve began to fail, a technician added refrigerant in an effort to raise the suction pressure. When the valve completely failed, it had enough refrigerant in the system to force a condition approaching hydraulic lockup, thereby tripping the high-pressure safety.
If you consider the physics of a system with static refrigerant in the condenser, that is, with no content to remove, the high-side pressure should equal the corresponding ambient pressure-temperature figure. The physics involved in refrigeration are not variable; therefore any variation of the actions of a piece of equipment is due to an outside influence!
Greg R. Snyder, President, Edwards Refrigeration, Loveland, Co.
Fitting Eulogy
I certainly enjoyed Barb Checket-Hanks’ column on Jack Sweet [“Learn To Live And Laugh; Jack Sweet, 2002,” Jan. 20]. When I read the headline, I immediately said out loud “Learn to live and laugh, and thus delay your epitaph.” It was always fun to read his column and I invariably got a few chuckles out of it. Thanks for giving him the recognition, and bringing back some memories to me.We were also saddened to read of the passing of former News writer Joe Olivieri. He was a great man to work with, and we always had a lot of fun playing tennis, golf, and bridge with him.
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Mark Bumler, Bumler Mechanical/Exelon Services, Sterling Heights, Mich.
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Publication date: 02/03/2003