Installing VRF Systems: Give Your Customers The Comfort They Want
From their ‘on demand’ operation to their low carbon footprint and energy efficiency, VRF systems come with lots of benefits. According to a 2012 General Services Administration study, VRF technology has the potential to achieve 34% energy savings when compared to its older counterparts. As energy costs and consumption continue to rise, VRF, the primary HVAC technology used in Europe, China and Japan – where it was created – is steadily gaining mass appeal in US markets.
One of the main keys to ensuring end users reap the most from the many benefits these systems offer is to ensure they are properly installed. In addition to the actual installation techniques, some steps for proper installation include:
a) Giving careful thought to the system’s design and software, ensuring that the design takes into consideration any installation limitations.
b) Training technicians, not only to install VRF systems, but also in accordance with manufacturer specifications.
c) Job planning, both on paper and pre-construction walkthroughs.
With these three pre-installation steps taken care of, focus should be squarely placed on the techniques employed during the installation process, since this is where most errors occur.
MAIN INSTALLATION PROBLEMS
VRF systems can be divided up into four major components: outdoor units (condensing units), indoor units (fan coils), accessories and controls. Installing these components is very specific and varies from one manufacturer to the other. This level of specificity means engineers should not approach installation in a generalized way. Instead, consultation and frequent communication with the system’s manufacturer or sales rep is vital to ensuring VRF system installation pitfalls are avoided.
According to Fujitsu General America’s South West Sales Engineer CJ Corbet, common installation errors fall into two categories: leaks and communication errors.
“When you have a leak, you are leaking out the refrigerant, and this brings in non condensables,” Corbet said. “So you are losing the ability to keep cool, which obviously causes major issues since keeping cool is the goal of your VRF system.”
The series of piping that comprises VRF systems require a greater level of specificity than traditional ductwork systems. Failure to comply exactly with the manufacturer’s design will likely interfere with the system’s ability to run efficiently.
“This is a much more complex system, so it requires working more closely with tech support to ensure things run smoothly,” QCS Operations Manager Willis Hurley said.
The Las Vegas-based HVAC company has, on more that one occasion, been called in to fix VRF jobs that were botched by other contractors for this very reason.
“People often think they can change pipe sizing,” Hurley said. “But it’s not the same as with a typical system where you change the pipe sizing one up, or one down. With VRF systems, it’s all about precision.”
Pipes must also be properly flared, and torqued to the proper specification. If pipes are not flared, then brazing is necessary, and technique is key to avoiding leaks. One of the most vital components of the brazing process is nitrogen purging.
“Your biggest worry about brazing is getting rid of the toxic gases produced from heating the copper,” Hurley said. “So purging is necessary to clean out any contaminants put inside the piping during the brazing process.”
Once the system has been properly flared or brazed, it’s crucial that the contractor performs a pressure test to ensure there are no leaks, and an evacuation of the system to remove all non condensables.
System communication errors are the second most common issues encountered with VRF installations. Communication is facilitated by a set of wires that are connected to each piece of equipment – indoor units, outdoor units and remote controls, and this wire is specific to the system’s manufacturer.
“We have had some installations where technicians did not use the proper, or recommended wire, and the system did not work,” Corbet said. “So following the manufacturer’s recommendation with regards to wire selection is the first step to beating communications issues.”
The second is ensuring that all of the units are wired according to specification.
“This is essentially where the wire goes,” Corbet said. “So from what unit to what unit, and then what terminal blocks they need to be terminated on.”
The final step technicians should take to avoid communication failures is ensuring everything has been addressed correctly. Indoor units and outdoor units have rotary dials or dip switches above, and making sure that they are properly addressed is crucial to the communication system.
The design element and high level of precision needed for a successful VRF installation mean even the most skilled HVAC technician must be re-schooled in accordance with the manufacturer’s guidelines. He or she must also be very thorough.
Fujitsu recommends a seven-point checklist to ensure no elements of the installation process are missed, and the system runs smoothly and efficiently. Numbers 1, 2 and 3 on the checklist apply to the entire project, while 4, 5, 6 & 7 are specific to each system/refrigerant circuit on the project.
1. Notate the following project information: Total number of refrigerant circuits, total number of outdoor units and total number of indoor units.
“This aids with verifying between design, and the actual installation,” Corbet said.
2. Check your transmission wiring to ensure the correct wire (as recommended by the manufacturer) is being used, is configured or connected to the respective terminals as indicated in the manufacturer’s diagram, and that the resistance at both ends of the communication line is within the acceptable range.
3. Ensure that all central controllers and communication devices are within the manufacturer’s guidelines or specifications.
4. Check the electrical supply of both the indoor and outdoor units to ensure they are also within the manufacturer’s guidelines or specifications. These include checking the circuit breaker capacity, ensuring the ground fault equipment breaker is installed where applicable – or as per local code, ensuring the power line wire meets the local code and checking line voltage.
5. Outdoor units should also mounted and piped according to the manufacturer’s specifications. This includes checking power source wiring connection points and tightening any loose screws, ensuring refrigerant piping is insulated without any gaps, ensure the largest outdoor unit is set as the Master and is closest to the indoor units. Outdoor units should also be elevated above average snow level, and gas and liquid pipe service valves should be completely open.
6. For the indoor unit setup, notate the unit name and model number for each unit, and check to ensure drain lines are pitched downward, that there are no traps or kinks in the drain lines and that condensate pumps are installed for each unit.
7. Ensure pipe sizes are consistent with design, are properly brazed or flared and nitrogen purged to remove all contaminants. Refrigerant lines should be properly insulated and supported. Pressure test to check for leaks, and ensure pipe lengths and height differences are consistent with the manufacturer’s standards.
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