Introduction to VRF Technology
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- เผยแพร่เมื่อ 29 ก.ย. 2024
- This introduction to VRF technology class from the HVACR Training Symposium was taught by John Chavez. John explains the basics of how VRF technology works and why people might want to use it in commercial structures. The adoption of VRF technology is regulated by ASHRAE.
VRF heat pumps are capable of some extraordinary feats, including achieving 100% cooling capacity down to -10 degrees and 78% heating capacity down to -15 degrees. The software that controls the HVAC system is the heart of VRF technology; the software controls the refrigerant flow throughout the structure, which adjusts the HVAC system performance.
VRF and VRV technology are the same thing; VRV is just a marketing term used by one company, and it means “variable refrigerant volume” instead of “variable refrigerant flow.” As with all heat pumps, VRF heat pumps have indoor and outdoor coils that can reverse their functions depending on the operating mode (heating or cooling) via a reversing valve. Modulation is also an important function in VRF technology, as they have stepper motors that control EEV, compressor (inverter-driven scroll), and fan operation. The variable-speed compressor satisfies a wide range of load requirements while saving energy.
VRF systems also appear as ductless 1:1 systems, have multiple zones (up to 8:1), and come in single-phase and three-phase varieties. VRF technology architecture consists of a central controller that connects to an outdoor unit, which then connects to a remote controller and one or multiple indoor units. All units share the same system control and refrigerant charge, and they may contain heat recovery systems. A heat pump with heat recovery differs from a typical VRF heat pump in that it has an extra component: a heat recovery box. Systems with heat recovery may have two-pipe or three-pipe systems and can perform simultaneous heating and cooling. (The two-pipe configuration is standard for regular heat pumps.)
Algorithms control VRF technology by assessing the conditions and telling the equipment to operate a certain way based on those conditions. Whereas many heat pumps have difficulty providing heating in cold temperatures, VRF heat pumps optimize several parts of their system to allow the system to heat efficiently and effectively.
VRF technology allows you to mix and match indoor units, use a flexible piping design, and get 150% connected capacity (connecting 15 tons’ worth of indoor units to a 10-ton outdoor unit). However, you must know your building profile (diversity) before making use of connected capacity effectively. VRF designs tend to be flexible and can have their controls easily manipulated by DIP switches. The compactness and economic nature of VRF systems also make them attractive due to their small footprint, low energy consumption, quietness, and cost-effectiveness.
The variable-speed compressor allows VRF systems to match part-load conditions and regulate the discharge temperature for maximum compressor longevity. Lower electrical loads allow compressor startup to be relatively soft, as there is no inrush current. A variable-speed compressor also tends to have a high power factor and low reactive power, making it energy-efficient and able to handle precise temperature control without high kWh usage.
In many cases, warranty returns are also very low, meaning that VRF systems are also beneficial to contractors. These systems also tend to be less expensive to operate and maintain over time than conventional HVAC systems.
VRF systems use a remote controller to manage the set point for the indoor unit. These controllers are more complex than thermostats, as they can also control vanes and other parts of system operation. The outdoor unit works as a function of the connected capacity, thermistor readings, compressor hertz, LEV position, and pressure and temperature targets. The voltage gets converted from AC to DC, smoothed, and then back to AC power between the control section, microcomputer, and compressor. The system can also manipulate the cycles per second (hertz or Hz) from the power supply to match the equipment.
PID (proportional, integral, and derivative) controls continuously adjust the EEV, which allows the refrigerant flow to vary based on the changing conditions. VRF systems also use smart coil technology, which are sensors that determine target superheat and subcooling temperatures.
Some VRF heat pumps also come in the water-source, ground-source (geothermal), and hybrid varieties. Indoor units can come in high-wall, ceiling-suspended, or floor-standing varieties. They also have varied ceiling cassettes with built-in drain pumps.
You can download this presentation from John’s LinkedIn page at / johnkchavez .
Read all the tech tips, take the quizzes, and find our handy calculators at www.hvacrschoo....
Man, put this guys smarts into Bert’s entertainment value and you’d have the perfect instructor. I appreciate the video and I’m very interested in learning more about VRF. Thank you HVAC School. 👍
Great video, it gave me a better insight of VRF and preparing me to be a better tech. Thanks
Great presentation! I am, however, curious why at 1:05:00, it was implied that using a VRF and/or ductless system in a computer room would be inadvisable? Wouldn't the same energy efficiency, humidity control, and temperature control benefits still apply to a computer room?
Typically, designers or building owners select an inverter driven variable capacity system to save on energy usage. In the case of a IT room, the loads are generally constant year round. There is no load shedding or part-load scenarios to take advantage. In reality, server rooms grow and increase loads. Also, although humidity control is a concern, it is typically not an issue with high humidity but low humidity. IMO, it is better to select a fixed capacity system. This topic deserves more time and attention. Contact me if you are interested in discussing it further. Cheers!
@@hvacmensch @hvacmensch6220 Great points, thanks for explaining! However, in most climates, the cooling load will still vary quite a bit depending on the outside temperature and sunlight. Obviously there are a ton of variables such as the climate, insulation, sun exposure, etc, but the heat load at, for example, a 60 degree ambient in the middle of the night (or potentially much lower if the AC is used all year instead of fresh air) is going to be significantly different than with a 110 degree ambient and the sun shining on the building.
Of course the difference won't be nearly as drastic as in a normal comfort cooling application since the heat gain through the walls and ceiling will be a much lower percentage of the total heat load, but I'd think the overall difference in load would still be significant.
Also, if higher efficiency computer equipment is installed in the future or equipment is removed (lower heat load) or, as you said, equipment is added to meet increasing demands and the heat load increases, a properly sized VRF system will be MUCH more adaptable and won't be nearly as likely to suffer penalties from undersizing or oversizing.
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Great video, I loved the ending...leave those gauges in the truck.
Yeah Brother! Speak the TRUTH
Is This system only designed for the West Coast or Hot Weather cause many of these systems don't perform well in the Mid west. Where I live and often one must add a heat pump to this system to get Max performance
Thompson Mary Martinez Laura Thompson Susan
It seems that a shorted compressor takes out an indoor coil due to acid contamination, causing a preference for system replacement. That seem untenable for VRF, so what's the solution? Replaceable core filters, a different flushing system or what?
Well done Mr mike pipe. When will you going to open a branch in Maryland? I will love to apply.
I installed a VRF 8hp ac controlling 3 indoor unit but it always show me p02 and trips of the compressor and later shows p13 so I am confused right now pls what can I do
Great info but the audio man. Truck on the highway I can’t hear !
These systems sound like very versatile. I have questions though. Weren’t there restrictions about how much refrigerant can be circulated through a building, due to the breakdown of the refrigerant into toxic gasses, if the building catches fire. If a compressor has a running burnout, I guess it would make every head connected to this outdoor unit inoperable. How would one clean up a contaminated system, with all the delicate components? Seems like it would be a service nightmare. What about oil return? Seems like the compressor could run short of oil with all the piping. Is there a separate oil reservoir, which maintains a specific oil level, until enough oil can be returned through the piping?
I guess a brazed system would have to be very clean install. I heard some of these systems use aluminum piping with shoulderless connectors. These seem like they will be the systems of the future. I am concerned about the amount of components, scattered all over the place. I think I would prefer all of the refrigerant and controls located in one package chiller
I’m not knocking these systems. My guess is the installation has to be a very clean, and the installation installation quality would determine the reliability of these systems. Is there a separate ventilation system required for fresh air? Seems like it would have to be supplied from an outside source, which is critical for indoor air quality. This would require a fan, ductwork, etc. usually outdoor air has to be conditioned, as to not add to the heat load of the building. Then there is the problem of maintaining building static pressure requirements. Seems like separate makeup air units, with the ability to supply conditioned outdoor ventilation air would be required, adding to the cost.
All of your questions can be addressed by contacting the speaker.
Need a hands on vid
Every time I watch one of your videos, I learn a lot of new things. Thanks for sharing the knowledge with us. Greetings from Salamanca, Guanajuato, Mexico.
VRF has so many configurations... the interface control with technology like iOS and Android is amazing
It's kinda funny that he says at the end leave your gauges in the truck when im currently using gauges on a Daikin VRV to make sure the pressure transducers are working properly.
I think he meant that initial troubleshooting should be by using the computer service tool.
@@jonsnow5943 I'm being pedantic lol
Great video. Thank you HVAC School for this training. I am new to VRF systems and I'm trying to learn how to troubleshoot them. You have so many great videos on traditional HVAC systems and I'm hoping there will eventually be more videos on VRF systems. We work at a large resort where some of buildings are equipped with Samsung VRF systems and we know very little when it comes to figuring out the problem. The manufacturer's provide very little online training. Thanks again for all you do.
Me saludas a Juan Chavez
Thank you for the video.
This a good subject to go in Depth mr. Been waiting for some like this.
Hi, what is the brand and model of the white HVAC mechanical thermostat in the background of the Amber and Depp Trial? You can see it when Amber or Depp are talking. Thanks for your help.
1.25x speed with this guy
Feeling bittersweet about the future but, well put! Thank you Hvac school!
I would love to see the TEWI number for a VRF against a Water system. VRFs use huge amounts of refrigerant when compared to a water CH, HP or 4P. The greenhouse effect sent you a hug! :(
Good video and I like Arabic caption thanks
Insightful and very educational
This is really thorough - thank you for posting. Some of this I knew, but it's great to see it all stitched together like this. A great explanation for a homeowner like me.
Hey MR TOM......... YOU ARE LIKE OMNIPRESENT ON ALL THOSE HVAC TALKS
Great video, thank you
Not even watched it yet, but I'll go ahead and say it... Great video, as always!
All about diversity bro
This is the most annoying video ever heavy on speech and boring, it makes me fall a sleep 😢
Gave up watching after 10min😢😮
That's okay. It will be here when you are ready. Take care.
Your a parts changer..
What did you want the guy to do come dressed as a clown and dance.. this info should cost you thousands in some tech inst. if they went over it at all
my brother in Christ, you need to reatore your attention span, youre cooked