Sachs Consulting

 

HVAC and Building Controls Commissioning Experts

 

 

Why commission?

 

Today’s building and office facilities are very high tech. Design engineers go through a lot of effort to design a system that meets the needs of the customer and will perform efficiently and with minimal maintenance. Today’s HVAC systems are also very energy efficient. Of course all this depends on the finished product being properly installed and then accurately tuned before the design and construction teams leave the project.

 

All the good intentions will not get the job done. When a design engineer writes a sequence of operations it is very critical that the system operate in the order that it was designed, otherwise energy efficiency will not conform to what was expected from the design. Let’s look at just one critical example:

 

Let’s say the system design calls for the cooling tower condenser water system to provide for “Economizer Cooling” or free cooling at a certain outdoor air temperature and humidity.  This design option would allow for the air distribution system to provide cooling even though the refrigerating compressors are not running, thus saving energy and lowering electric bills.

 

There are a number of things that could jeopardize the effectiveness of this process. The sensor measuring outdoor air temperature may not be accurate or installed in a poor location. The sensor measuring outdoor air relative humidity could be reporting incorrectly, out of calibration, located poorly or being effected by an excessively long wiring run. The actual sequence of the staging of the fans off and on and from low to high speeds may not operate correctly. If the tower fans are variable speed, the 0-100% signal from the building control panel output may not match the Variable Speed Drive input, causing the fans to run at 85% when they should be running at 40%.

 

All of these could affect the free cooling initiation process and efficiency.

 

The most interesting point of all these details is that typically, the person performing the start up and check out will assume that the sensors are “Factory Calibrated” and don’t need any further attention. Not true!

If a start up technician does perform a quick check of the device to see if it is sensing accurately, what test equipment is he using? My experience dictates he will probably use a meter or measuring device he has on his service truck and truly does not know if it is accurate. So now we are checking and calibrating a sensor with an inaccurate measuring device. Not good.

 

The overall result is an economizer system that comes on to soon or too late. If it comes on to soon it is running tower fans and system pumps to attempt to reach a set point that’s not possible under those conditions, wasting electricity for no gain. If it comes on too late the system wastes energy by running compressors unnecessarily.

 

The result to the facility is a higher electric bill! What was mistaken as an insignificant detail could effect your electric bill by as much as 10%. A combination of insignificant errors could affect your electric bill by as much as 20% or more.

 

How much would 20% of your electric bill equal for one month? $1,000 or even $5,000.  I’ll bet you could pay for the cost of the commissioning fees in one month!

 

Today’s DDC control systems are capable of trending electric consumption along with many other useful figures. Unfortunately, if the first months electric bill is based on an HVAC system operating inefficiently due to a control system that does not function up to design, the baseline numbers are now set on poor performance. 

 

There are other reasons to commission besides energy efficiency.

 

Better overall operating comfort levels, lower maintenance costs, eliminate nuisance calls and receive a detailed report of the results of the commissioning process. The report will contain original settings, calibration readings, status and sequences which will provide you with a base line for future reference.

 

If you are the installing contractor effective commissioning can reduce your warranty costs substantially by eliminating nuisance call backs during the warranty period.

 

 

With over 25 years experience in the commercial building trade, you can count on our expertise. We can develop a commissioning plan that is right for you.

 

 

 

 

 

 

 

 

       

Sachs Consulting 608 Park Crossing Way Lilburn Ga 30047   Cell – 770-337-0735    Business – 770-381-3843