ReplyWhat kind of freon and evap temp is this refering to?
Regular Guest
this is for the guys that were asking for reference to my comments on another post.
copeland mandates a minimum compressor suction superheat of 20*.
exerted from the heatcraft refrigeration installation manual
"h-im-64d" a suction line superheat of 30-45 is to be maiuntained...
Professional Member
What kind of freon and evap temp is this refering to?
Member
new one on me. the only way any system should run that high of superheat is on an captube or orfice systems and then under certain circumstances.
do it on a freezer and youll be changing out the captubes because the compressor windings are breaking down.
Regular Guest
lwarren
did not specify. but if you wanna discuss further let me know. all in the interest of developing/ refining skills.
so as it turns out i did in fact mis apply the information. copeland says only 20*. carlyle is a range i am digging for it. tecumseh is a range, looking for it as well. none as i recall specified which systems or evap temps.
[Edited by hvac3901 on 07-01-2004 at 12:12 AM]
Professional Member
If you maintain 20 to forty .... it doesnt matter which refrigerant or system this is on.
The unit needs to run cool. Not too hot and not to cold either.
Make sence?
Professional Member
20 at the compressor, leads a lot a variables as to the length, I have heard that on res units, and they can be 10 to 50 feet away from the evap, I guess the comp. people want to ensure that the don't get slugging, sounds to general, rule of thumb thing.
there but for the grace of god, go all of us
Professional Member
I've heard 20>26 from copeland rep. Have found different on charging charts with AC's and HP's. From what I've read here 20 is min. on racks if refrigeration is included in this.
Be safe not fast. body parts don't grow back
Professional Member*
Isn't that 20° at the compressor suction valve? So, that heat would also include heat from the motor windings.
Regular Guest
jrbenny
6-8 or 10-12 inches away from the compressor inlet or service valve. whichever it is its not exactly at the inlet.
Member
you have to remember also that it dependeds if you have a orfice or txv. on orfice systems you can't control superheat when charged properly it will depend on temperture as to what the superheat will be like from 0 to 45 degrees.
on txv systems you charge by subcooling and the superheat should be anywhere from 8 to 25 degrees. the higher the superheat the less efficient the machine becomes.
superheat values for exvs on flotronic systems dependeds on the eprom chip. usually they range from 2 to 7 degrees superheat.
Professional Member*
Where did you get this number?Originally posted by hvac3901
copeland mandates a minimum compressor suction superheat of 20*.
Professional Member*
I think you've been given some bad info. When you measure superheat, it is at the service valve, and should be 5 to 45° if on a piston system or 8-12° if on a TEV system.Originally posted by hvac3901
jrbenny
6-8 or 10-12 inches away from the compressor inlet or service valve. whichever it is its not exactly at the inlet.
The 20-30° that you quote is suction superheat at the valve plate.
Why would every unit manufacturer completely disregard Copeland's superheat requirements? Yep, that's right. They don't because the number you've quoted is in regards to a superheat that you can't measure.
Regular Guest
quote:
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Originally posted by hvac3901
copeland mandates a minimum compressor suction superheat of 20*.
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Where did you get this number
jrbenny
uhhh, out of the copeland manual.
Regular Guest
What is Superheat – definition, function, setting and adjusting
Proper definition: The difference between the saturated temperature (pressure/temp chart) and the actual temperature of the suction gas.
Function: To protect the compressor! Other functions such as improving the efficiency of the evaporator are secondary. The two functions can become in conflict, however, protecting the compressor is the first priority of Superheat.
If Superheat is set to low: refrigerant may flood back, washing out oil. Leading to low oil pressure, bearing wiping and other damage may ensue. Refrigerant and or oil may slug back into the compressor resulting in broken valves, rods and other parts.
If Superheat is set to high: the compressor will get insufficient cooling. Oil breakdown and sludging, oil screen clogging, high ring wear and ultimate seizure.
Steps in setting Superheat:
1. With an accurate gauge, measure the pressure at the compressor suction service valve. Convert to temperature (°F) from the appropriate gas chart.
2. With an accurate thermometer measure the temperature of the suction line entering the compressor AT the compressor.
3. Subtract 1 from 2. The difference is Superheat in °F. Most manufacturers recommend setting at about 10-12 °F. It is essential to check the specific manufacturers recommendation.
4. Now, measure pressure at the evaporator (remote bulb location) and again convert to temperature to see if the evaporator is operating at design level. If it is, all is well in the circuit. If it is not, it may be necessary to adjust the thermostatic expansion valve. However, if this is done it is essential to remeasure at the compressor to be sure that Superheat setting is still within the manufacturers recommended range.
With multiple evaporators, the steps above must be repeated. Measure first at the compressor then at each successive evaporator, final measurement to be taken back at the compressor.
Professional Member*
carlyle requires superheat of 20 degrees 3 to 5 inches from the compressor suction valve
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