HVAC RETRO-COMMISSIONING | SCHOOL
HVAC
Retro-commissioning
ASHRAE Chapter 42, HVAC Building Commissioning
Retro-commissioning (RCx)
involves commissioning the building HVAC equipment after the equipment has been
installed, commissioned, is running and usually after the warranty period has
expired.
The performance of building HVAC equipment
normally degrades with use and time.
The rate of performance degradation
depends on the quality of maintenance and operations applied to the HVAC
equipment. The quality of maintenance also impacts the life expectancy of the
HVAC equipment.
A facility retro-commissioning
effort should include development of an Owner’s Project Requirements (or
owner’s intent), documentation of the existing system, a survey identifying
operational inefficiencies for the facility, quantifying and prioritizing the
inefficiencies found, determining how to best optimize the equipment or
operation, implementing the change and training the existing staff and then
re-verifying with on-going measurements that the retro-commissioning
activities produced and continue to produce the desired effect.
Other definitions specify RCx as a one-time event with a different set of
project phases.
All of these approaches provide
methodologies to improve the operation and lower the energy use of a facility
with direct consideration given to the current operational requirements.
Retro-commissioning activities include:
1. reviewing utility bills and building
documents;
2. optimizing the chiller and boiler systems;
3. implementing various equipment operational
scheduling;
4. optimizing the air delivery systems;
5. setting up temperature resets for the
water and air side operations;
6. optimizing indoor air quality control; and
7. Verifying control systems are functioning
as needed.
When existing systems may not have the
capacity to meet the Owner’s Project Requirements, the system deficiencies need
to be documented with a decision on when or if upgrading will be done.
For
example, indoor
air quality (IAQ) objectives may not be met because of system limitations due
to a system designed under an older Standard or Building Code. Temperature objectives may not be met because
of additional computer equipment loads added to some spaces since the original
system was designed to handle a lower load.
In each case, a documented recommendation should be provided to the
owner on the options available.
RCx has demonstrated to be a very cost
effective method to improve occupant comfort and lower costs. Energy savings of over 20% with a 2-year
payback have been reported. Also, others
showed that RCx typically achieved 40%+ more
savings than was estimated during a range of audits. These costs are also supported by the LBL
study on a large data set of projects.
Buildings with systems ranging from older
pneumatic controls to newer building automation systems (BACS) have been
successfully retro-commissioned.
Modern BACS enable a lower cost RCx activity and also allow trend logging of
various parameters to sustain the achieved savings.
Σχόλια
Δημοσίευση σχολίου