best way to check superheat

[-1994]

what is the best way to check superheat on any equipment

[bama 101]

Take low side pressure and p/t chart .convert low side press. to temp. then take line temp of suction line near condensing unit and subtract the two and the diff. is superheat.

[fitter638nyc]

P/T Chart,Good set of gagues Thermometer and a Fluke Line Clamp

[hvacpope]

Originally posted by bama 101
Take low side pressure and p/t chart .convert low side press. to temp. then take line temp of suction line near condensing unit and subtract the two and the diff. is superheat.

I never hear of taking condensing temp for superheat. or a suction line near condensing unit. you may want to re-check your post!

[bama 101]

hvac pope care to give more info ? I was tought to take saturation temp of evap and suction lin temp 8 in from compressor and or suction line on outside of condenser please correct me if i'm wrong

[bama 101]

Evaporator Superheat
Check Your Superheat. After the box temperature has reached
or is close to reaching the desired temperature, the evaporator
superheat should be checked and adjustments made if necessary.
Generally, systems with a design TD of 10¢ªF should have a
superheat value of 6¢ª to 10¢ªF for maximum efficiency. For systems
operating at higher TDʼs, the superheat can be adjusted to 12¢ª to
15¢ª ¢ªF as required.
NOTE: Minimum compressor suction superheat
of 20¢ªF may override these recommendations
on some systems with short line runs.
To properly determine the superheat of the evaporator, the following
procedure is the method Heatcraft recommends:
WARNING: If the condensing unit has no flooded
condenser head pressure control, the
condensing unit must have the discharge
pressure above the equivalent
105¢ªF condensing pressure. See refrigerant
charging instructions on page 30.
1. Measure the temperature of the suction line at the point
the bulb is clamped.
2. Obtain the suction pressure that exists in the suction line
at the bulb location by either of the following methods:
a. A gauge in the external equalized line will indicate the
pressure directly and accurately.
b. A gauge directly in the suction line near the
evaporator or directly in the suction header of the
evaporator will yield the same reading as 2a above.
3. Convert the pressure obtained in 2a or 2b above to
saturated evaporator temperature by using a
temperature-pressure chart.
4. Subtract the saturated temperature from the actual
suction line temperature. The difference is Superheat.
Alternative Superheat Method
The most accurate method of measuring superheat is found by
following the previous procedure, Temperature/Pressure method.
However, that method may not always be practical. An alternative
method which will yield fairly accurate results is the temperature
/ temperature method:
1. Measure the temperature of the suction line at the
point the bulb is clamped (outlet).
2. Measure the temperature of one of the distributor
tubes close to the evaporator coil (inlet).
3. Subtract the inlet temperature from the outlet
temperature. The difference is Superheat.
This method will yield fairly accurate results as long as the pressure
drop through the evaporator coil is low.

[Dad]

Also for your viewing pleasure.

Troubleshooting with Superheat - by Norm Christopherson

[adammemin]

The super heat can be measeure leaving the evaporator or at the compressor. You want to take you pressure reading at the suction line on the evaporator, convert oressure to saturation temp. Measure suction line with clampo on meter just out side of the evaporator case. Make sure box is at temp other wise false readings. Suptract the saturation temp from the line temp and that is your evap superheat.

[jdaug1]

Good link Lusker!

This one is my fav.

http://www.hvaccomputer.com/hvac/sizer.asp

roflmao!

Also for your viewing pleasure.

Troubleshooting with Superheat - by Norm Christopherson

[MRcoolingMAGIC-]

The super heat can be measeure leaving the evaporator or at the compressor. You want to take you pressure reading at the suction line on the evaporator, convert oressure to saturation temp. Measure suction line with clampo on meter just out side of the evaporator case. Make sure box is at temp other wise false readings. Suptract the saturation temp from the line temp and that is your evap superheat.

The temp.taken by the compressor can be a few degrees higher,so the best way is to be taken by the evap.

[bob_scheel]

I never hear of taking condensing temp for superheat. or a suction line near condensing unit. you may want to re-check your post!

You can't be sure your superheat readings will be correct unless the liquid to the TXV is adequately subcooled to prevent flashing. What is adequate depends on liquid line lengths/sizes and relative elevation of the condenser and evaporator.

There are two places to measure superheat and BOTH should be checked. The first is at the evaporator suction line. The second is at the compressor suction line. All hermetic and semi-hermetic compressors have minimum and maximum superheat requirements and some have desuperheat injectors and hot gas bypass that further complicates the issue.

[BamaCool]

Good link Lusker!

This one is my fav.

http://www.hvaccomputer.com/hvac/sizer.asp

roflmao!

That's the one I use! By far the easiest sizing calculator. I swear by it, and anyone can use it!

[adammemin]

The temp.taken by the compressor can be a few degrees higher,so the best way is to be taken by the evap.

The temp taken at the compressor will be more than a few degrees higher. A tipical walk-in cooler set up with a copeland recip. requires 6-8 deg of super heat at the evap and 20 deg of superheat at the compressor. Now there are a lot of factors to take in consideration. How well is the suction line insulated??? Should have at least 1/2 armaflex on a cooler and 3/4 on a freezer. How long is the line set???? Now there are a lot of units that the suction line insulation has worn off from the elements and if you check the superheat at the evap it may be correct, but the superheat at the compressor will be high. The compressor needs that liquid to keep it cool.