Before commissioning a hydronic system, a good technician learns the best way to assure a successful water balance is to use a pre-balance checklist. This question-and- answer document, completed by the installing contractor, will ensure the equipment and system installation is complete and the commissioning process is ready to begin.
Contrary to industry opinion, a commercial HVAC air and water system that is not 100% complete cannot be balanced. All too often, if a balancer shows up to begin his or her work and the project is not 100% complete, the balancing will be delayed and no one wins.
A Hydronic System Checklist Prior to Balancingshould be sent from the balancing contractor to the mechanical contractor’s installing supervisor several days before balancing is expected to begin. This document is usually sent with an email requesting it be completed and returned before the balancing can be scheduled. This benefits both parties and assures the systems will be ready for testing.
Air Balance First
When balancing a hydronic system that has an airside, ideally the air balance should be completed before the water balance commences. Each fan and duct system including registers, grilles and all outside air, should be set-up, tested, adjusted, and balanced first. Adequate airflow through each coil should be plus or minus 10% of design unless the balancing specification requires tighter parameters.
A hydronic system can be started up, purged of air, cleaned and rough balanced before the air balance, but full and final air balancing should be completed before the water balance begins.
To be certain the system can be tested and that water can flow through its components, verify that each piece of equipment related to the water side has been started up and is operational.
Questions asked in the Checklist Prior to Hydronic Balance may require the installing supervisor to check with other subcontractors on the job.
The first and obvious questions posed in the Checklist Prior to Hydronic Balance should be: Has the wiring for each piece of equipment on the job been completed? Has each piece of equipment been verified to have adequate power? Is each pump or fan shaft rotating in the correct direction?
If required by the specifications, you may ask if a factory representative or service personnel has started up the equipment. If so, ask if start-up reports are available and if you can be sent a copy of each report. Factory start-ups with start-up documentation are often included in the job specifications by the engineer for pumps, boilers, chillers and cooling towers.
If there are Variable Frequency Drives on some of the equipment on the project, ask if the VFD’s have been set up and verified to be operational?
Ask if provisions have been made to measure pressures near the pump. Ideally the plans call for installation of pressure ports in the piping or by permanently installed pressure gauges with appropriate shut off valves. By opening and closing valves near the pump, the pump pressures can be read and the pump can be deadheaded to enable the balancer to determine installed impeller size and then plot pump flow in GPM.
Inquire About the Water Distribution System
Once you’re sure the equipment is operational, the next step is to inquire about the state of completion of the piping system. There are several steps required of the installing contractor before the water balancing can begin.
Is the piping system installation 100% complete?This is an easy question to answer “yes” to, but additional questions should be asked to assure the job is in fact, 100% complete and ready to be balanced. A single yes rarely guarantees the system is ready for balancing.
These additional questions may include:
Are all valves, flow meters and temperature or pressure taps accessible? To test and manipulate valves requires room for your hands and room to insert test instruments where the pressure taps are installed.
Are all valves in the correct position (open or closed)?The installation supervisor should have walked the system to verify each valve is installed and set as it should be to match the current mode of operation.
Have the piping systems been cleaned and flushed? During construction all sorts of debris and construction materials as well as dirt and pipe dope get caught in the piping. The system has to be operated and cleaned and often filled with the specified percentage of antifreeze.
Have all construction strainer screens near the pumps and coils been cleaned and replaced with permanent screens? Is the cooling tower water clean? Water systems have built in filters or strainers that must be removed and cleaned once the system has operated for a short time. Debris is captured in a fine construction strainer and then replaced just before balancing after the system fluid is cleaned up.
Is the system air free?Are air vents properly installed and operational? Is the expansion tank filled properly? Once the system is cleaned and filled properly, the air in the system must be removed in order for it to operate as it should. Air vents are installed at the high points in the system. The process of removing all the air in the system is the responsibility of the mechanical contractor prior to starting the water balance.If possible, a water system should operate under live conditions a day or so before water balancing begins to be certain all air is removed from the system.
One last question: Will the HVAC installation supervisor be available to make any needed repairs during the balancing? Inevitably defects are found during the water balancing that must be corrected. Balancing valves are installed backwards or upside down, pumps run backwards, strainers are not cleaned, coils may be installed incorrectly, and the wrong valves, gauges, or pressure devices may be installed. You name it, it’s been found by a balancer.
Nobody looks at a water system like the balancer. Balancing is a testing and auditing process designed to inspect, measure, adjust, and prove the system was installed and adjusted to meet the intent of the design. There is no such thing as a self-balancing system.
Consider using a checklist prior to hydronic balance for the benefit of both the installing contractor and the balancer on your next hydronic project.
Rob “Doc” Falke serves the industry as president of National Comfort Institute an HVAC based training company and membership organization. If you're an HVAC contractor or technician interested in a free NCI how-to procedure to plot pump GPM on a pump curve, contact Doc at [email protected] or call him at 800-633-7058. Go to NCI’s website at nationalcomfortinstitute.com for free information, articles and downloads.