Category Archives: Engineered RTU

Recommended tools

 

Fluke 116/322 HVAC combo kit basic multimeter and amp clamp that will do anything in residential diagnostics.

Fluke 87V Digital Multimeter if you are working on any Engineer MUA (Make Up Air) or RTU (Roof Top Unit) you need the percent duty cycle option to set up combustion motor speed sensor properly.

Cooper SH66A Multi-temperature thermometer instrument. Good for measuring temperature on pipe or airflow

Ritchie Yellow Jacket LCD Vacuum Gauge 69075 senses the full range from atmospheric pressure down to 1 micron. I have had mine for 6 years and have never had any problems with it. It will give you exact number read out not just lights to indicate vacuum pressure

D-TEK Select Refrigerant leak detector this leak detector is the best one I have used it is very sensitive and will find the smallest leak. Some people believe it is too sensitive, because sometimes when it is moved fast it will beep. If you use the meter properly by moving it slowly around the leaks it will prove to be the best meter on the market. I would rather have a few false readings then to miss a leak that would cause me to return to the same job site a few times on callbacks.

Fluke Alert Voltage Detector A/C 90-1000 Volts-1AC-A1-II & A/C 20-90 Volts. I always carry one of these detectors around sometimes I can diagnose a problem with it or double-check the power for safety. Always test detector against known power and use meters to insure all power is turned off.

Testo 510 Manometer is the best manometer I have found that will measure differential pressures. The unit has many switchable units of measure. Very accurate as mine is 6 years old and has never required calibration. Only complaint is max pressure 1.5 PSI.

Powers Pneumatic Calibration kit 832-177 comes with Siemens adapters should buy Honeywell and Johnson adaptor kits as well in order to do all thermostats.

Procore Ratchet Wrench 17-9568 only 5 degrees of operation is needed to use this wrench. All wrenches have opened end and ratchet box end, which makes easy work in tight places.

If anyone has a better meter they use please send a comment to me and I will add it. I know fluke has a new one with flexible amp clamp, but I do not have the meter so I can’t comment on it

Thank you for visiting my blog I would appreciate any feedback I can get, Please leave a comment on whether my information has helped you. I am always interested in more topics to write so feel free to leave a comment asking about anything related to HVAC-R (Heating, Ventilation, air conditioning, refrigeration).

Thanks for reading my blog

Engineered air rooftop units

Engineered air pre-purge error
Combustion motor on engineered air units are variable speed, which are controlled by the hertz to the motor. Voltage will always remain constant and to slow down the motor the DJM2 controller will run between 15-59 Hz. If the reading it over 59 Hz then the speed sensor is grounded and the wire and/or sensor need to be replaced, 3450 RPM equals 59 Hz.

  • If combustion motor is running first check tachometer signal, Y to G should run between 4-6 VAC. If AC is not present check that the sensor is 1/16 inch from magnet at the end of combustion motor shaft. Also insure the sensor is not over the centre of the shaft, But rather it is off to one side of the magnet.
  • If voltage is within 4-6 VAC, The DJM2 is sensitive to the shape of the waveform produced by the speed sensor. You will need a fluke 80 series similar multi meter that can measure percent duty cycle. Connect meter to Y and G press Hz for Hertz then second time for duty cycle. Speed sensor will output a signal close to 50% duty cycle and must be accurate within 2.5%. If the number is outside those parameters the pre-purge problem light will flash
  • Many time the only thing wrong with this system is the magnet at the end on the motor shaft. By flipping over the magnet sometime will fix the problem

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Thank you for visiting my blog I would appreciate any feedback I can get, Please leave a comment on whether my information has helped you. I am always interested in more topic to write so feel free to leave a comment asking about anything related to HVAC-R (Heating, Ventilation, air conditioning, refrigeration).

Thanks for reading my blog