Chilled water cooling

John R. Hall

I attended a meeting of the Eastern Michigan Chapter of the RPA last week and met a gentleman named James Turnquist, who has published a book called "Where's the Chilled Water?" I've started to read it and I'm interested in the subject of chilled water as a means to cool a home.

Is this something that is highly specialized with a limited market? Or is this something that some hydronics people are doing to fulfill a "niche" market? Your thoughts would be appreciated.

dave connors

Especially good in large applications

If you need more than 5 tons of cooling it is an excellent choice. There are a few economical 7 ton chillers available online. Works real well with the high velocity equipment.

Brad White_2

I agree with Dave

on the five ton and up scenario. Issue is cost but you cannot beat the flexibility. Multiple zones on one cooling machine. Keep in mind system volume and use a 3-5 minute flow rate volume tank on the return side so the chiller does not cycle on and off at part load.

I have a problem with Servel type gas fired absorbers. They take about 96,000 btus of gas to produce 5 tons (60,000 btu's) cooling. At the cost of gas ($1.25-1.40 a therm?) that is $5.00 to $7.00 an hour, sort of like having your chiller earn minimum wage (absent a favorable summer rate). If electrical and 1.2 kW/ton and 12 cents per kW, that is 72 cents an hour for the five tons, unless I am missing something.

Personally, I like TSI Chillers, out of Pryor, Oklahoma. Good equipment, stock parts available anywhere, and custom flexble. I have used them in the 3 to 8 ton range and in fact designed a 46 ton chiller for a house (some house!) several years ago.

rb_5

Schematic

Some would say this is a cool two pipe schematic...

Dan Peel

and beyond

I'm in the middle of a heat/chill with common piping feeding 3 air handlers in two buildings, radiant floors for heating season only and a couple of indirects that the boiler needs to see year round plus a remote chiller. All the runout piping is spec'd "K" copper and fully insulated. This one is going to need more than just a few days. Enjoy.....Dan

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doug_16

Yeah, way cool!

How do you do that?

GMcD

Large scale radiant cooling

Yes, There are beginning to be quite a few more large scale radiant slab ceiling cooling installations in my area (Pacific NW). The radiant cooling systems only need 64-65F water for enough cooling, so a geothermal heat pump plant or a simple roof mounted closed circuit cooling tower that runs at night does the trick for very low energy building climate control. The "enertia" of the radiant slab allows the re-cooling of the slab to occur at night when the outdoor temp is suitable for generating the required 64F water at peak cooling conditions.

The key is a high performance building envelope, especially the glass, to keep out those nasty short term, high amplitude transient solar loads that the slab cooling can't handle at it's operating temperature (lower limit=ambient dewpoint). Expensive glass, but really inexpensive, low maintenance mechanical system - win - win.

Now for residential applications- the "economy of scale" is the challenge. There was "almost" a large scale residential development in the SE United States that I was providing design assistance with, that never got off the ground due to the lack of any local Engineers and Contractors willing to "take the risk". The technical issues were all worked out - Karo ceilings, small water cooler and an HRV with dehumidification capability, good thermal mass and good glass. Too bad. Radiant cooling has been going on in other places in the world for at least a couple of decades, and it is not some black art, it's simple laws of physics in action, but requires a "whole building design effort" to pull it off. The North American building design and construction industry just isn't set up to accomplish this- too fractionalized and reactive. Did you know there are no "building physics" courses or faculty programs at any North American University or College? Yes, there are lots of specific "building systems" courses that focus on specific aspects of building design, but no one set of courses that puts it all together. Don't even get me going about the "Architects" that are being turned out of Universities....To clarify- there ARE some good Architects that DO recognise the value of the high performance passive envelope design, but they are few and far between.

GMcD

Nice schematic

Very similar to the systems I've been involved with, but with the exception of the chiller being replaced by a fluid cooler (closed circuit cooling tower) that runs at night to "re-charge" the slab cooling system. The boiler would obviously be a condenser to run at the very low heating temperatures required. Plug in a geothermal heat pump unit to replace the chiller and boiler, with a direct bypass to the ground loops for "free cooling" direct from the geo-exchange side. In many areas, the ambient ground temperature is less than the fluid temperature required for radiant cooling, so direct geo-exchange can work out for an ultra-low energy cooling system. Can we say "ground coupled structure"?

Carl PE_2

Huh?

1 therm=100,000 Btus, at least according to my gas company. That puts the operating cost at $1.20 to $1.34/hr using your gas rate.

My gas rate (Ameren) is about $0.65/therm, making the chiller cost $0.62/hour to run vs $0.72.

I agree that there's a limited application for gas cooling, but it's a great deal if you've got the right rate structure.

Tell us some more about this 46 ton house..

Weezbo

I personally Like it:) It has a certain je ne sais pas:)

Carl PE

Small Absorbers

Hey, as long as we're all on the subject of tiny chillers.. Does anybody know of a 1-5 ton hot-water-fired absorber, like Servel used to make?

There's a Japanese company that makes them down to 10 tons, but I can't find anything smaller. I'm about to cut open a couple RV refrigerators and make my own.

rb_5

believe it or not....

Have been test driving different software for some upcoming reviews...

This drawing was created in - are ya ready – drum roll please - Microsoft’s PowerPoint ...not exactly a CAD program but hey...as they say its not the instrument that sings its the musician...was a little awkward at first had to forget the AutoCad habits and develop a new set...three hours later and voila...the hybrid schematic with the chiller addresses the components of ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy.

I know Geoff is familiar with 55 but its interesting that in an industry based on health, wellness and comfort that over 97% of its participants don't know of its' existence...

We'll be discussing the recently updated Standard 55, November 2 & 3 at CIPHEX West in Calgary...radiant cooling and chilled water will most definitely be included.

RB

Lurker_2

re\"

www.articool.com

small but expensive chillers.

must be a lower cost source
seems to me the units need to be much cheaper to be competitive with minisplits

Brad White_2

Brain Faht....

I have no idea what I was thinking- You are absolutely correct.

I had it in my head at a btu for btu...therms per ton...96,000 BTU's for 60,000 BTU's. My bad. That should have jumped out at me. Time for vacation.

The 46 ton house is a shingle-style, about 20,000 net SF with lots of south facing glass and ventilation load, in Massachusetts. Two (2) Viessmann Vertomats (one standby) for all heat, the pool(s) and domestic hot water.