Tips & Tricks

Technical Tips & Tricks:

1) Always allow any system heating or cooling to reach Steady State Operation (SSO) before taking temperature or amperage readings.

2) Don’t waste time waiting for a system to reach SSO.  Use the time to complete paperwork or complete the client and system information on the worksheet header.

3) Always set the thermostat 20 to 30 degrees above or below the indoor temperature to avoid the frustration of a system shutting off before you finish collecting all readings.

4) Don’t attempt to use the program when it is raining outside, or the condenser is wet, or the outdoor ambient is below 68 degrees F … or in any other condition in which it would also be unreasonable to properly charge a system using  the subcooling method.

5) By “ambient temperature” on the technicians work sheet:  we mean  outdoor ambient temperature.

6) When taking outdoor ambient temperatures avoid direct sun light (radiant heat) or other heat sources.

7) Take return air WB and DB readings at the return air grill (and not inside the plenum at the air handler/furnace.)    All WB readings should be to the nearest tenth (56.8) of a degree) Collecting this reading at the return air grill is  easier, and by utilizing this practice … air leaks in the return air  plenum will show up on the TPD report as a loss in BTU production.

8) Take supply air WB and DB readings at the register nearest the air handler/furnace.   Readings taken inside the plenum, too close to the air handler/furnace, may result in distortions caused by unmixed air conditions and/or the radiant heat effects of elements and heat exchangers.   All WB readings should be to the nearest tenth (56.8) of a degree)

9) Always record the lowest WB and highest DB reading at the supply register.  Some registers may show different temperatures across the register face due to common air vortex effects.    All WB readings should be to the nearest tenth (56.8) of a degree)

10) When in doubt, it’s quicker and easier to double check your temperature readings than it is to put on a set of refrigerant gauges.

11) Take all WB and DB readings with same meter.  Using two meters (one for return and another for supply) increases the potential for a skewed report due to differences in the two meters calibrations. If a single meter is slightly out of calibration … it is at least … always calibrated with itself.  (as my old pappy used to say …”A man with one watch always knows what time it is, but a man with two watches is never quite sure”)   All WB readings should be to the nearest tenth (56.8) of a degree)

12) Altitude/Elevation:  Those living in any place above sea level are familiar with heating and cooling capacity losses associated with air density/mass and the necessity of adjusting cooling fan speed.   This somewhat generic chart may help when it comes to better understanding the relationship between CFM, elevation and system performance diagnostics.  In order to match the same sea level cooling BTU output of 400 CFM , the same equipment at 5000 ft would be required to move 481 CFM.  What you can’t adjust for is the BTU loss associated with a non adjusting condenser fan.  Click on chart to enlarge or print.  

CFM altitude Equilavent

CFM altitude Equilavent


Commercial Package Systems:

1)  Block off any economizers or fresh air dampers using plastic. If you’re looking for accuracy, do not simply “close the damper” as some air  will always leak past.  Measuring any mixed air stream will compromise accuracy.

2) When taking voltage and amperage readings on 3 phase equipment accuracy can be increased (normally by only a small percentage) by taking reading across all three legs and then dividing the results by 3.  Technicians should always be on the hunt for any voltage phase imbalance greater than 2%.   In a perfect world the voltage reading between any all phases would be the same and the amperage reading on any one line would match the others.  As you may have noticed … this is not a perfect world.

3) TPD only provides one entry field (per component type) for entering equipment amperage readings.  This will mean that on systems with multiple compressors and/or condenser fans … the combined amperage of like components should be added together before entering the information.

4) If indoor supply and return grills are hard to access, Wet Bulb reading may be taken at the unit if adequate care is taken to insure that all temperature reading are taken at a location where the air has become adequately “mixed”.  Readings taken too close to an evaporator coil, heat exchanger, or electric element will often be compromised by their proximity.  Removing access panels to take temperature readings may present problems (especially on the return air side). Small access holes in the equipment panels work very well for taking temperature readings.  These holes can be plugged and then re-used over and over again.

5) The Commercial PKG version of TPD allows technicians to select different electrical phases for condenser fans, indoor fan, and compressors.  When using the TPD commercial version be certain to select the proper phase for the component being measured.


Practical Tips & Tricks:

1) Start small …   Run several reports in the office before attempting to run any report in the field.  Next run several reports by yourself (alone)  in real time (in the field).  Once you are comfortable with the process, run a report in front of a client.

2) Make sure you fully understand the report before you try explaining it to a client.  Practice explaining the report to a client before you actually attempt to explain the report.

3) Allow skeptical technicians to waste a little time verifying their TPD findings on a few jobs.  Eventually, however, technicians will need to trust the TPD report with the same health skepticism they have for any other meter or tool.

4) It never hurts to have a firm grasp on the science behind what you’re doing. Review these blog posts …. It’s just Science  … Cooling Capacity Dynamics

5) If your readings “don’t make sense”…  a)  take the readings again  b)  check your meters  c)  verify your method of taking readings.

6)  Don’t be too anxious to explain the client report or your technician worksheet readings to a client.  Allow clients time to view the information for 20 to 30 seconds minimum.  Explain only the report’s findings first … then wait another 20 to 30 seconds minimum for the client to absorb the information.  Most people when confronted by an obvious problem will ask for a solution.   Your explanations and recommendations will be better received when requested.

7) Always use the TPD email function when possible.  It is the fastest way for a client to share the findings with a spouse or to brag about your service to a friend.

8) E-mail yourself a report so you will be familiar with how the e-mail will appear when it arrives in your clients email in-box.

9)  All WB readings should be to the nearest tenth (56.8) of a degree)