IntelliPak (Legacy) - Space Pressure Sensor Failure

Issue:

Space Pressure Sensor Failure

Resolution:

IMPORTANT NOTE: Voltage and pressure readings in (PARENTHEIS) indicate values for all Ipak 2 units and Ipak 1 units built after 02/2009

The space static pressure sensor is used on units with 100% exhaust with Statitrac. This diagnostic occurs when the voltage output from the transducer is outside the range for normal building pressures. Normal pressures range from -0.20 IWC to 0.50 IWC (-.67 IWC to .67 IWC). During normal operation if the voltage dips below 0.04 VDC or rises above 0.75 VDC the diagnostic will be generated.

Note: The sensor is capable of responding to pressures from 0 to 5.0 IWC (-.75IWC to 9 IWC), but the controls can only read values in the range of -0.20 to 0.50 IWC (-.67 IWC to .67 IWC) as valid for space pressure.

This diagnostic can also be generated if the calibration solenoid is not functioning properly. For one second every minute, the calibration solenoid is energized to zero out the transducer. It connects the high port and the low port to outside air static reference. The controls expect to see 0.25 VDC @ 0.00 IWC (0.53 VDC @ 0.00 IWC) during this time. Any difference from this value is used as an error amount and used to adjust the sensor reading for the next minute. If the calibration solenoid is not functioning, the controls will not receive the correct error signal and will interpret the sensor reading as zero pressure. In these cases, if power is cycled to the unit, the sensor will read correctly for one minute and then read decline to 0.00 IWC before giving the diagnostic.

Items to check include:

1. wiring
2. sensor
3. calibration solenoid
4. control module 1U52
5. pneumatic tubing connections

Here are the steps for Intellipak Rooftop

Step #1 Wiring Errors

The space pressure transducer connects to the Exhaust Comparative Enthalpy Module (ECEM) at pins J3-1 (+5 VDC), J3-2 (signal from transducer), J3-3 (common). Verify that the wiring is correct, all the plugs are connected, and the voltages are present at the transducer. Refer to the unit schematics for wire numbers. (As a note, on units with Variable Frequency Drives (VFD), it is very important for the sensor raceway wiring to route high through the unit and the power wiring to route low. If this is not the case, the VFD can interfere with the operation of the sensor, and the wire routing will need to be corrected.) If the wiring checks good, continue to the next step.

Step #2 Pneumatic Tubing

Refer to above diagram for proper tubing connections for the transducer. Verify that factory installed tubing is correct and there are no air leaks. Also verify that outside air static pressure reference is properly installed. If the outside air static pressure reference is not properly installed, rainwater can enter the tubing. If this is the case, correct the installation and dry out the pneumatic tubing. The customer installed tubing should be connected as shown in the above diagram. If not installed, the sensor will see a large negative pressure when the supply fan is energized and report an error. The customer installed tubing should also be checked for kinks and obstructions. If all appears to be correct, continue to the next step.

Step #3 Sensor Checkout

0 to 5 IWC Transducer

-.75 to 9 IWC Transducer

Tee a manometer/magnehelic into both the high and low ports on the transducer. Verify that the voltage read at J3-2 and J3-3 on the 1U52 module corresponds to the pressure indicated on the manometer using the chart above. If it does not and Steps 1 and 2 have been performed, replace the transducer. If the voltage corresponds to the pressure, proceed to the next step.

Step #4 Calibration Solenoid Checkout

The calibration solenoid is energized for one second every minute. During calibration, the ECEM should see 0.25 VDC @ 0.00 IWC (0.53 IWC @ 0.00 IWC) at pins J3-2 and J3-3. The coil voltage is approximately 23VDC and is supplied from the 1U52 module at pins J6-2 and J6-3. If a squeeze bulb is connected the Normally Closed (NC) port and pressurized, it should be relieved for one second every minute. If not, verify that the 1U52 is supplying the 23 VDC every minute. If not, replace the ECEM. If the ECEM is supplying the correct voltage but the solenoid does not function, replace the calibration solenoid. If the solenoid checks out, proceed to the next step.

Step #5 Control Module

If all the previous steps have been performed, the diagnostic remains, and no errors are found, replace the ECEM module.

Other Question/Problem/Cause Statements:

• Space Pressure Sensor Failure

Facts:

• Intellipak Rooftop 20-130
• Intellipak I - 20-130 Ton Packaged Rooftop R-22 (S_HF, S_HG)
• Intellipak I - 20-130 Ton Packaged Rooftop R-410A (S_HL, S_HK)
• Intellipak 2 - 90 - 162 Ton Packaged Rooftop

WARNING:

Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.