NuClimate Chilled Beams vs. VRF ( First Cost, Service & Efficiency) 2

[Chesapeake]

OK now that US engineers have been introduced to both of these design solutions, who has some real numbers to discuss? I cannot find anyone who has unbiased data, especially on first cost and service. Anyone have any feedback after 1 to 3 years installed, etc.
Thank you in advance!

 

[cry22]

These are European "Chic" systems shoved into US engineers' throats, no more.
Chilled beams are nothing more than Induction units, which were widely used in the 50's, 60's in the US. Chilled beams are OK when you have 6 Watt/SF or more of sensible load (justifies the savings in ductwork and fan energy), for conventional office building, they are TOO EXPENSIVE.
VRF are another European climate friendly system, over there, they have exorbitant utility rates. Heat pumps are common in Europe, and AC is still a delicacy in Europe (even in hospitals).
Chilled water/cooling towers are not used that much in Europe, so they just try to find a way to export their system with their product.

Yes, you are right, There is absolutely NO Scientific data to back up any of these systems in a LCC. No one will give a first cost price, let alone a maintenance cost.
There isn't even data on their effectiveness (Ok, they work, that's about it).

GSA does NOT recommend the use of Chilled beams in its buildings.

 

[marcoh]

Advice I have had from facility managers is that the chilled beams are essentially maintenance free, and fewer AHU's to maintain so that is all positive. Of course that that assume the system is correctly designed and installed.

Issues I have see include dehumidification systems not operating correctly and thus resulting in condensation forming on the beams, doors to outside being left open, even both doors on areas acting as air locks, beams being selected to serve too large an area, resulting in downdrafts under the beam.

Whilst expensive they can be energy efficient if the chiller chilled water temperature is reset to as high as possible which results in making the chillers more efficient. But if you still need cold water for dehumidification, then you need two chilled water systems which becomes very expensive.

You also loose out on using economy cycle operation.

 

[ChasBean1]

I’ve commissioned a few — buildings that have chilled beams successfully installed do save. These are basically induction units reinvented and you are correct cry22. Principle is moving water for cooling provides a lot more energy transfer per unit volume than moving air to accomplish the same purpose. This is true and the principle does work. For air handlers, you dump a quarter or a fifth of the airflow that you would for a conventional cooling and ventilating system. I became a believer in these systems after seeing some operating costs per square foot. Positive building pressure and dehumidification by central AHU systems becomes important however to prevent dew point/condensation issues.

 

[cry22]

The trouble we see with these systems in the US, is the fear of the unknown from designers.
chilled beams should be coupled with no more than 0.35 to 0.4 CFM/SF of air handling equipment. i.e achieve all the sensible load using water as medium instead of air.
What we see instead is designers applying this 1 CFM/SF plus of AHU with VAV systems (sometimes dictated by life safety, such as Min ACH for smoke control).
Designers are simply not comfortable with the level of psychrometrics involved to control dew point. Psychrometrics is not taught in most Mechanical Engineering schools, people are learning on the job and getting by with only basics.

I've seen several active induction units using 100% OA units still in operation after 50 years, very energy efficient indeed.

But we have come up with a "chic name" and selling it as the latest high tech to charge an arm and a leg.

Like everything else, chilled beams have their applications and climate but if manufacturers want to sell these things, they need to do a lot of education in real application on chilled beams (especially psychrometrics), including their specific limitations (no operable windows as an example).

OK y'all, why don't you test your engineers to provide you with a detailed psychrometric chart using chilled beams in less than 2 hours. you will realise that 90% of your engineers and designers are so week in psychrometrics........
Then again, watch out, you might fire most of your engineers after such a test.

Another big problem we see in the US is that these new chic systems are always dictated by someone other than the Engineer (owner or architect, or both). Remember the UFAD craze? the Double Facade on buildings craze? same thing going on for chilled beams.

 

[ChrisConley]

I agree with you cry22 that the psychometrics involved with chilled beams are tricky. Not just tricky, but resistant to rule of thumbs and oversizing.

The main issue I found was that the 'industry standard' temperatures for chilled water and air temp have to be completely re-evaluated. Lower air temp (well, lower dewpoint) to ensure that latent load is met with ventilation air (without over ventilating) and higher chilled water temps (how high? depends on how much you can dry the space, which depends on how low you can drop the ventilation air dewpoint...).

However, once the work is done (and redone on every project), you can combine a very efficient DOAS (Dedicated Outdoor Air System... with heat recovery) to supply sufficiently dry air to control the latent load of the building at the same time as providing the proper ventilation to the building.

I've done many chilled beam projects now (moving from fan coils, to chilled ceilings to chilled beams) and the benefits really can out way the downside. I can list some of my happiest (repeat) clients as clients that have installed a properly designed chilled beam system. I've toured new clients through existing installations so they can get an idea of what the system is, and hear from the occupants and maintenance people what they think.

Once contractors have installed the system once or twice the 'chic' price disappears and you get a low profile (small ductwork) easily renovated, low maintenance, quiet, high efficiency system with a ~15% capital cost premium and a reasonable payback (climate and utility rate dependent).

EH Price recently put out a really good guide to engineers that has a large section on chilled beams that I recommend to anyone thinking of using the system.

Chilled beams aren't the 'solution' to every problem (and not every climate), but I have found them very applicable in many situations so far: offices, schools and labs.