Too much airflow and a gap between the unit and the wall

BACKGROUND

Located in the heart of the internationally recognized Texas Medical Center, this property is the ultimate destination for guests seeking a community of healing, learning and discovery.

The property engaged AirRevive to refurbish, re-commission and repair defective installation and inconsistent airflow from room to room  on 452 guest room vertical fan coil units that were manufactured in 1983.

This study compiles data collection on the following:

MOUSE OVER TO GO DIRECTLY TO EACH SECTION.

I.        Project Challenges

II.      Project Goals and Scope of Work

III.      Supply Temperature

IV.       Coil Temperature

V.        Airflow

VI.      Sound Decibels

VII.    Energy Savings

VIII.  Before and After Photographs

IX.     Results Summary

X.      Facility Benefits

XI.    Testimonial from Property Engineer

I.  Project Challenges 

SITE SURVEY FINDINGS

• 10% of surveyed coil’s fins deteriorated and corroding consistent with acid washing. The remainder in working condition.
• 10% of surveyed control valves water leaking by when closed.
• The coils and fins are dirty. Insulation lodged between fins. Organic material in core.
• Gap between the unit cabinet and drywall allows return air to mix with supply, and air from gap to mix with return and supply air.
• Cooling and heating not occurring as designed due to gap between cabinet and wall.
• Dust and debris lodged between the fins, in the motors, and in the blower assembly.
• Air filters held in place with tape and pins.
• The condensate pan is corroding.
• The cabinet components including blower assembly, wheel and wires dirty and covered in oily film.
• The drain lines clogged with corrosion and debris.
• Below the condensate pan in the bottom side of the cabinet there is a make up air hole no longer serving any purpose.
• Installed motors inconsistent from room to room. Airflow out of balance.
• Majority of units surveyed airflow over-blowing and not aligned with design specifications.

COIL TEMPERATURE CHALLENGES:

• Before service 90% of the unit’s coil temperature was 56 degrees and above.
• Before service 97% of the unit’s coil temperature was 53 degrees and above.

SUPPLY TEMPERATURE CHALLENGES: 

• Before service 88% of the unit’s supply temperature was 60 degrees and above.
• Before service 100% of the unit’s supply temperature was 55 degrees and above.

AIRFLOW CHALLENGES:

• Airflow significantly higher than design specification. Airflow passing across the coil too quickly to dehumidify, cool, and heat as designed.
• 60% of the unit’s airflow were above the manufacturer’s specification curve.
• 24% of the unit’s airflow were below the manufacturer’s specification curve.

NOISE

• Sound decibels averaged 62.68db which is above the acceptable sound range for a fan coil unit.

II. Project Goals:

The overarching project goal is to extend the life of the fan coil unit asset. The refurbishment process goals to improve the operation of the unit include:

• Extend the life of existing units and improve indoor air quality by:
  • Replacing fiber insulation with foam anti-microbial insulation;
  • Rejuvenating, deep cleaning, and disinfecting the coils and fins; and
  • De-rusting the condensate pans and re-coating with impermeable epoxy.
• Enhance heat transfer by rejuvenating the coils and aligning airflow with manufacturer’s design specifications.
• Construct sleeve to close the gap between cabinet and wall so that:
  • Return air passes through coil without mixing with supply air and gap air.
  • Gap air is not introduced into the return area and supply area.
• Construct sleeve so that it holds return air filter to eliminate use of tape and pins.
• Close the hole in the bottom of the unit so that cabinet is fully insulated.
• Reduce sound by replacing fiber insulation with foam and replacing motors with brushless motors.
• Reduce FCU fan motor energy consumption by rejuvenating the coils and retrofitting EC motors.
• Re-commission units so that airflow is aligned with manufacturer’s design specifications.
• Re-commission units so that heat transfer is like new.

SCOPE OF WORK

AirRevive’s fan coil unit refurbishment and EC motor retrofit process included the following:

• Deep clean coils and fins from back and front sides. Disinfect coils and fins.
• Replace as-needed corroded coils with custom made coils.
• De-rust condensate pan and re-coat with impermeable epoxy.
• Replace fiber insulation with foam anti-microbial insulation.
• Remove all debris from the blower assembly, motor, and wheel.
• Clean and disinfect the blower assembly and wheel.
• Clear out, clean and disinfect the drain line.
• Close hole inside cabinet below drain pan.
• Replace as-needed control valves.
• Design and install sleeve to close gap between cabinet and guest room and provide space for air filter to sit.
• Check operation of each unit and record before and after data.
• Program EC motor to supply airflow consistent with the unit specifications, room area, and building nuances.
• Install motor and controller.
• Wire motors to thermostat for proper functioning.

III. Supply Temperature

Supply Temperature Before and After Service

Summary: Supply temperature dropped by an average 9.9℉ from 63.4℉ to 53.5℉.

The graph below shows supply temperature sorted from high to low before coil rejuvenation.

The red line demonstrates that before coil rejuvenation the supply temperature ranged from 77℉ to 55℉. The average supply temperature was 63.4℉. The supply temperature was above 55℉ on 100% of the units.

The blue line demonstrates that after coil rejuvenation the supply temperature fell below 56℉ on 99% of the units. The average supply temperature after refurbishment and coil rejuvenation was 53.5℉.

IV. Coil Temperature

Coil Temperature Before and After Service

Summary: Coil temperature dropped by an average 10.68℉ from 58.71℉ to 48.03℉.

The graph below shows coil temperature sorted from high to low before coil rejuvenation.

The red line demonstrates that before coil rejuvenation the coil temperature ranged from 73.6℉ to 50.1℉.  The average coil temperature was 58.6℉. The coil temperature was above 53℉ on 97% of the units and above 56℉ on 90% of the units.

The blue line demonstrates that the refurbishment and coil rejuvenation reduced the coil temperature to below 53℉ on over 95% of the units.  The average coil temperature dropped to 48℉.

The AirRevive refurbishment resulted in the coil and fins operating at “as-new” performance.

• Coil rejuvenation resulting in unrestricted airflow
• Coil temperature dropped by an average 10.68℉ from 58.71℉ to 48.03℉.
• 90% of coil temperatures at or below 49.9 degrees
• 8% of coil temperatures between 50 degrees and 53 degrees

Lowered coil temperature combined with unrestricted airflow prepares the coils for the EC motor retrofit.

V.  Airflow

Airflow Before and After Motor Retrofit – Type FC1 & Type FC5

The graph below shows high fan airflow sorted from high to low before the motor retrofit and airflow programming.

Summary: Unit types FC1 and FC5 manufacturer’s high fan airflow design specification is 410-425 CFM. Before the EC motor retrofit the unit’s average airflow was 498 CFM.  After the motor retrofit the unit’s average airflow was 420 CFM.

The red line is airflow before motor retrofit. The red line’s slope down to the right demonstrates that the units’ airflow before service ranged from 1099 CFM to 173 CFM.

The blue line demonstrates that after motor retrofit each unit’s high fan airflow is within the original manufacturer’s airflow design specifications of 410-425 CFM.

Airflow Before and After Motor Retrofit – Type FC3

The graph below shows high fan airflow sorted from high to low before the motor retrofit and airflow programming.

Summary: Unit type FC3 manufacturer’s high fan airflow design specification is 420-440 CFM. Before the EC motor retrofit the unit’s average airflow was 671 CFM.  After the motor retrofit the unit’s average airflow was 438 CFM.

The red line is airflow before the motor retrofit. The red line’s slope down to the right demonstrates that the units’ CFM before service ranged from 1331 CFM to 294 CFM.

The blue line demonstrates that after service the majority of the unit’s high fan airflow is within the original manufacturer’s design specifications of 420 – 440 CFM.

Airflow Before and After Refurbishment – Type FC4

The graph below shows high fan airflow sorted from high to low before the motor retrofit and airflow programming.

Summary: Unit type FC4 airflow design specification is 525-540 CFM. Before the EC motor retrofit the unit’s average airflow was 578 CFM. After the motor retrofit the unit’s average airflow was 524 CFM. The majority of the units fell in the range of 530 CFM.

The red line is airflow before the motor retrofit. The red line’s slope down to the right demonstrates that the units’ CFM before service ranged from 986 CFM to 229 CFM.

The blue line demonstrates that after service each unit’s high fan airflow is within the original manufacturer’s design specifications between 525 and 540 CFM.

VI.  Sound Decibels Before and After Refurbishment

Summary: Sound decibels dropped by an average 11.25db from 62.76db to 51.51db, a decrease of 17.74%.

The graph below is sorted by sound decibels from high to low before refurbishment, installing insulation and the quiet EC motor.

The red line demonstrates that before refurbishment and motor retrofit the sound decibels ranged from 83.20db to 56.1db.  The average for the sound decibel readings was 62.78db. 100% of the sound decibel readings were above 57db.

The blue line demonstrates that after refurbishment and the motor retrofit the sound decibel readings for the majority of the units fell below 53db. The average sound decibel reading was 51.51db.

VII. Energy Savings

Fan Motor kW Consumption Before & After Refurbishment

Below is the average before and after fan motor kWh energy consumption by unit type, based on a random sampling of 10% of each type of unit.

Fan Motor Energy Savings

The projected annual energy savings per fan motor is $97.55, which for the facility is about $44,000 annually.

The EC motor retrofit on an AirRevive refurbished unit is the proven best practice for re-commissioning fan coil units. If the coils are not working uniformly before installing EC motors then the EC motor program will not be optimized.