24 Reasons to STOP Specifying VRF 3

[nglty]

1. No documentation on energy savings from the industry. The industry claims energy savings, but no independent studies have ever been made available from the industry. Even GSA white paper indicates that they could not find any documented energy savings, and that is the reason GSA does not allow it in their buildings.
2. Claims of heat recovery substantially exaggerated. The system as typically piped serve zones with similar loads, especially for schools where all spaces have day light, making the cassettes ALL either in cooling or in heating mode. There is no heat recovery.
3. Oversizing of Equipment, especially Condensing units for a heating dominant climate. By as much as 30% of cooling load. We’ve seen shop drawings showing VRF (connected to a cooling tower mind you) sized at 1.5 KW/ton.
4. Heat pumps do not perform at low temperatures, according to their AHRI testing. They perform because their compressors are oversized (sized for heating, not for cooling). Lack of supplemental heat requires cassettes and condensing units to be oversized to match the building heating load. The elimination of electric supplemental heaters is hidden into the cooling oversizing of compressors.
5. Use of DX rooftop units for large spaces such as Multi-purpose rooms, Gym, cafeterias. A chilled water system will not have DX RTU’s. A chilled water system will have a 50% cooling block load compared to VRF system.
6. Claims of energy savings available are always comparing VRF with DX RTU with electric reheat, the comparison is to the least efficient HVAC system. DX RTU with electric reheat does not even meet ASHRAE 90.1 for large commercial spaces.
7. Studies comparing Geothermal heat pumps to VRF indicate that GSHP beat the VRF in energy savings for a lot less first cost and LCC.
8. First cost is the highest of any system. As much as twice of a 2-pipe CHW/HW system using air-cooled chiller with condensing boilers.
9. No LCC available for VRF anywhere.
10. Many cassettes and Branch selectors in ceiling space to maintain.
11. High pressure refrigerant piping in space. Resulting in installing multiple units to comply to ASHRAE 15.
12. Proprietary systems for government projects.
13. Proprietary control system – Not BacNet compatible.
14. No data available to engineers on cost or on drawback of proprietary system on client.
15. System is not ducted type distribution. Low static pressure capabilities for ducting. Additional ducts make the system even more expensive.
16. Cannot add any additional units to the piping system.
17. VRF piping requires higher skilled labor for installation, resulting into higher prices and elimination of competition.
18. No high efficiency filtration capability.
19. No local humidification capability.
20. Requires DOAS system.
21. They tell you their compressors have inverted VFD, etc, they can go down 50%. What they don’t tell you is that in heating mode, their compressors (already oversized by 50% remember) will go to 150%, i.e go from 60 to 90 Hz to address the heating load. The same affinity law applies. You go down in cubic root in when slow the compressor, you also go up by cubic power when you speed the compressor in heating mode. If you oversize a system by 50% and then speed it up by another 50%, where are the savings exactly?
22. This is just another craze, just like the UFAD and the chilled beam fads (aka induction units that came from Europe with a chic name). No disrespect to Europeans. The same way raised floors for electrical wiring in office space craze.
23. The system hurts the local Economy. The VRF system puts ALL the money only in two pockets
a. The VRF manufacturer - exclusively Japanese and Korean
b. The local Vendor
24. Many trades are put out of business – Many jobs are lost in local economies:
1) Piping manufacturers and installers
2) Boiler manufacturers and installers
3) Pumps manufacturers and installers
4) Insulation manufacturers and installers
5) Chiller manufacturers and installers
6) Valve manufacturers and installers
7) Sheet metal workers
8) Air device and accessories manufacturers and installers
9) Welders
10) Pipe fitters
11) Controls manufacturers and installers
12) Balancing contractors
13) So many jobs are lost in various parts of the country due to the VRF system
14) Design MEP firms when renovating projects in the future

 

[EnergyProfessional]

1-6: this is a case of misapplication by design engineer. Any system can be made inefficient. you need to find the right application for it.
16: you can add units if the branch selecors are sized for it.
7: you may not be aware, but VRF also can be combined with geothermal
17 seems to contradict 23; the higher skilled labor is local and earns more money. and this is not relevant to the building owner
20: doh, every VRF manufacture is very upfront about this
21: you know those are DC motors, there is no frequency.

There are uninformed people that see VRF as the solution for every problem, and equally uninformed people that see VRF as no solution at all. VRF is a niche for relatively small systems and where space for ducts is an issue.

 

[nglty]

Energy

1-6 is what is pushed by the manufacturers, you are one of those pro VRF, and I would love some tangible data that backs up the use of a VRF for a school for example.

I do not disqualify anything, I have designed VRF for historic building, remote places and the likes, but I see it applied in large projects where they do not belong, such as schools.

I see it applied in electrical room, storage rooms, corridors, and of course schools where we waste our tax dollars.

What's bothersome in your post, you just criticize, you do not bring anything constructive to the subject. I wish that you would comment on the main topic, i.e. the energy savings claimed by the manufacturers. Unless you have some Daikin stock of course.

Everybody is aware of VRF can be applied to geothermal, which is stupid to begin with, you spend the money on non-proprietary system only to add a proprietary system.

What was the last time you were able to predict the future to size a refrigerant line for expansion?

Let's keep thing constructive, will you?

 

[EnergyProfessional]

It is the responsibility of the design engineer to use the manufacturer's data properly and select an appropriate system. You can't blame the manufacture for wanting their system to be used a lot. A chiller manufacturer also wants chillers to be used, even in a 1-ton office if they could convince someone to design it.......

Potential energy savings can be shown with an energy simulation (with all their limitations). IMHO space limitations typically are the deciding factor for VRF, not energy savings.

If you see them mis-applied, you should talk to the designer. I see all kind of HVAC systems used in inappropriate applications, VRF is just one of them.

 

[nglty]

The intent of this discussion is purely technical.
I am talking about what I see out there when I review projects, my intent is to alert engineers out there to engage in a debate and weigh things up before deciding on a system, not just because it is easy.

Now, the cooling load is ALWAYS much larger than normal in order to deliver the heating capacity, so saying "right-sizing" should be done is easy to say. The minimum size VRF is 130% of cooling needs to address the heating load. Always oversized, always.

The HVAC engineering community is overtaken by the vendors, because engineers feel that they need the vendors to select equipment. Manufacturers refuse to publish their equipment data so that engineers cannot make informed decisions on their own.

Look at the local ASHRAE Chapters, they are taken over by all the local vendors in the board of directors.

It is through these kinds of forums that we can alert each other of systems being pushed by manufacturers at the consumer's expense.

I hope that everyone will pitch in to a debate instead of arguing you about what an engineer should or should not do.

I will give you an example: How many of you will specify a VRF for a school? If you say yes, please state why you would specify such a system.

 

[Drazen]

Well, that's a good subject. With modulating capabilities of water hydronic networks, chillers and fan coils, water systems are back on track. It is noticeable that VRF sales reps have become overly aggressive in last few years, and they less and less cooperate with designers, trying to bypass them.

As regards to chilled beams and Europeans, however, the main point is that Europeans prefer comfort provided by radiant heat exchange. Convection, especially forced convection is deemed necessary evil. I had number of high luxury projects where clients insisted on form of radiant heating despite of DX systems anticipated for cooling. In some areas climate is such that heating requirements are easily satisfied after DX is sized for cooling, yet clients want supplementary radiant systems for winter.

 

[itsmoked]

What is VRF?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[willard3]

VRF is simply a Carnot cycle whose efficiency, at best is in the 30% range.

The Carnot cycle efficiency increases as the delta T decreases so that in temperate climates where the heating load predominates, a Carnot cycle for heating is very inefficient

VRF is just a heat pump with too much refrigerant piping.

 

[itsmoked]

Thanks Will.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[lukaiENG]

I'm not sure if I should kick this hornets nest, but anyway...

I would back up EnergyProfessiona's statements. VRF is just one of many systems and it is useful in space constrained installations.

I would comment further that the local climate is a major consideration as well. Nglty's states an opinion that the systems are typically deployed where they serve spaces which are all in the same mode may be true in extreme climates (say Arizona or the Midwest). In these cases I would agree it is not a good application. There are other climates where the systems may be more applicable - say a marine climate where exterior zones may be heating modes and interior zones in cooling.

I worked in Australia for a while a few years back, literally every project I worked on was being designed around VRF. While the system may not have been applicable in every case, a typical project would be a retrofit to a building which had never had AC before. The buildings typically had restricted ceiling which allowed for just a outdoor air duct from a DOAS system. To achieve space cooling would require terminal units - either refrigerant (VRF) or CHW/HHW fan coil units. When comparing these 2 options the VRF option is typically much more cost effective as you have half the equipment and piping (albeit different equipment/piping). The climate was a marine climate, so there were many hours per year where the buildings would require simultaneous heating and cooling.

I think we all agree that (some) designers need to be educated on system selection and not be tricked into a 'simple, easy to design' solution that the sales reps try to market. I do however think that blanket statements that designers should stop specifying a system type altogether is unhelpful, even if there is a good body of evidence to support this viewpoint (in some scenarios).

 

[nglty]

Luka

The post was about my observations of VRF being "the system of choice" nowadays. just because engineers don't want to deal with boiler and chiller design.
They also push it as equivalent to water source heat pump to obtain LEED points. I am looking at a project where a corridor gets 3 VRF units a high end adjacent office space gets RTU with electric reheat.

I designed VRF systems myself, for historic buildings mainly. Yes, of course their have their limited niche application, which is not what I am talking about.

What I did not get from the replies so far, is opinions of claimed energy savings by VRF.

Good on y'all

 

[EnergyProfessional]

My problem with VRF is that the controls are so proprietary and auxiliary heat is so hard to implement in meaningful ways when you have a building automation system. Same with controlled ventilation.
I'm in WI with winter design temp of -15°F, so any air source heatpump is out. I could see a boiler radiant heat for heating and cooling-only VRF. A smaller 10 ton application maybe.
Heat recovery VRF sounds nice, but this makes meaningful control of heating even more complex.

I once studied the above and compared to a VAV system (cooling only VAV, also hydronic radiant heat). since there was not much internal space with cooling load in winter, energy savings were in favor of VAV. Especially fan energy is bad for VRF since you need ducted units and the tiny fans are less efficient than large AHU fan.

But I'm sure there is a scenario where energy savings are better for VRF. You just need to understand and analyze each system. No matter what sales people say, thermodynamics still rules.