During our Lunch and Learn event, we discussed the following opportunities to realize energy savings and upgrade to meet the current energy code. The codes exist for a reason and for that same reason, all new construction adheres to them. You can create a building that is a “21st century state-of-the-art energy performer” without making prohibitive changes to the building envelope.
DEMAND CONTROL VENTILATION
This is an opportunity to minimize the amount of conditioned outside air being supplied to a space by monitoring the indoor air quality using CO2 sensors. In other words, monitoring how many people are in the space at any given time.
DOCUMENTATION, BALANCING, and VERIFICATION
Do you have someone that understands your HVAC design—an outside vendor or someone on your staff?
Do you have adequate documentation? Do you have system diagrams and written operating sequences that match the current use?
Has the control system operation, including all controllers, sensors, and actuators been verified to match the current system operating sequence?
Has the system been balanced to meet the current use of the building?
Any system that has been installed for 20 years has probably been modified as an emergency measure to meet some sort of crisis. In most situations, these modifications result in increased energy consumption and degraded performance. Balancing and Verification can be very important when it comes to analyzing these systems.
SUPPLY AIR ECONOMIZERS
They are now required on all units above 5 tons
Economizers are just automated outside air dampers on packaged mechanical equipment that utilize enthalpy sensors which allow for “free” cooling when outside temperature and humidity conditions permit. During these times the unit compressors, which are ENERGY hogs, will shut down to allow the space to be cooled by outside air.
This is a simple energy code upgrade opportunity that should be implemented whenever unit changeouts are proposed.
Whenever changes are made to a cooling tower system and related pumping or controls, the designer should take that opportunity to incorporate a water economizer for any system in the building that has significant wintertime cooling requirements.
You typically see water economizers on air handlers in multi-story buildings that are utilizing both chillers and cooling towers. The water economizer allows you to indirectly cool the space using the cooling tower water in lieu of using the chiller compressors which burn more energy.
VARIABLE AIR VOLUME FAN CONTROL
This opportunity involves removal of the inlet guide vanes and installation of a Variable Frequency Drive on the supply fan motor. The VFD can reduce the fan horsepower up to 70% when the design airflow is reduced by 50%. THIS is where the energy savings comes in.
An automated control sequence that monitors duct static pressure and adjusts the fan speed to maintain the conditions in the space is required.
HYDRONIC HEAT PUMP SYSTEMS
In many older multi-story or multi-tenant buildings, there are hydronic heat pumps that are spread out through the building and condenser water is continuously (24/7) pumped through all of them. This means the condenser pumps consume maximum horsepower at all times.
A Variable Frequency Drive (VFD) can be installed on the condenser water pump and two-way valves can be installed on all heat pumps, stopping the water flow through the pumps that are not operating. For a vast majority of the time, this modification will allow the condenser pumps to consume only a FRACTION of their rated HP—thus conserving energy
This opportunity should be considered whenever there are control upgrades.
HYDRONIC PART LOAD CONTROLS
This is an opportunity to modify existing chilled water or hot water systems by converting three-way valves to two-way valves and adding variable speed pumping.
Controls may need to be upgraded to allow the main system loop pumps to modulate down to at least 50% of capacity, based on building loads and system pressure requirements.
SYSTEMS WITH MULTIPLE CHILLERS
Whenever an upgrade is developed for a chiller plant with multiple chillers, the designer should incorporate primary/secondary pumping to significantly reduce energy consumption.
Also, water should not flow through the chillers that are shut down. This can be achieved by having a separate pump for each chiller.
HEAT REJECTION FAN SPEED CONTROL
This is an opportunity to add controls to any cooling tower work that is being done and does not require the presence of a building automation system.
Basically, VFD’s are installed on all motors to reduce the horsepower of the cooling tower fans to maintain the temperature of the condenser water to the chillers.