Does anyone know if there is such a thing as a simple air cooling system that could just “pump and dump” cold well water through a handler and a regular duct/blower set-up? I’m lookin’ to cool a RFH new build. Thanks.
–Solo
Remember, measure twice… then keep cuttin’
’til it fits really fine.
Replies
There is a thing called a "swamp cooler" used in America's south western deserts. It is all about evaporation to cool air not necessarily about the temperature of the water. Kind of a strange device that sits on the roof with a 1/8" copper tube feeding the water.
I believe that enviornmentally the pump'n'dump is not well thought of .... now that everyone is finally realizing that groundwater is a limited resource. Saw on the TV during the drought that the groundwater level in the eastern part of I think it is NC is down about 185 feet since about 1850. Part drought, part overuse of resources.
Groundwater is a limited resource. Yet so is oil,gas, nuclear fuel,coal, etc.
I'd have to think the desert community would have found some equilibrium of economics with respect to water use and electricity pumping freon.
I don't know the economics of it, but Palm Springs CA and the surrounding communities (desert communities) all have great usage of the "swamp cooler". There must be some overriding value of these coolers that makes it stay as the airconditioner of choice. I assume the rest of the hot world doesn't use them because our humidity is too high.
In the simplist sense it uses water and a circulating fan. The fan is constant (power user) in in swamp coolers and a freon type air conditioner....
So the question in my mind is :
1. Spray water and collect the heat from the house by utilizing the energy required to evaporate the water. (water escapes into the environment)
Or
2. Burn coal, boil water, turn a turbine, transmit the power (at a 40 percent loss of energy) and then turn a compressor to wring the heat out of the house.
The second method seems to give entropy more room to 'play' (waste resources)
I know I'm over-simplifying it but tell me what I'm missing. Seriously. I saw the first one 3 weeks ago and I thought it a magnificent simple contraption.Jack of all trades and master of none - you got a problem with that?
"Groundwater is a limited resource. Yet so is oil,gas, nuclear fuel,coal, etc."
You listed several different options for fuel. Try to list one option for water!
Ice.
Seriously water is a part of the world closed cycle isn't it. It may no longer be water in California but it does go into the air to be rained somewhere else. It isn't like it is chemically altered or reduced in state. It is purely a phase change.
Jack of all trades and master of none - you got a problem with that?
Beer
Solo,
What you describe is sometimes used to cool the condenser side of a system, but it will not work for air conditioning (with "standard" components). For most cooling coils, the temperature difference between chilled water supply and leaving air is 10 degrees (i.e. 45 CWS and 55 LAT). The best you will be able to get from ground water is 55 degree CWS. Trying to cool a space with 65 - 67 degree air (which is about the best you could expect) will require twice the air flow and will do no dehumidification whatsoever. With a very large and very deep coil, you could get the LAT down to maybe 60, but it still wouldn't do what you would like. One of the main drawbacks of RFH is that, for all practical purposes, it is good for heat only.
Tim
Tim, any experiences with the hydronic a/c systems? At least they avoid the need for ductwork, since you don't need it for the rfh. Multiaqua and Hydro-Air are two brands that come to mind.
I am planning on building homes starting next year with the following heat/cool setup:
Heat with radiant floor (PEX in concrete).
Cool by running the (closed loop) RFH water thru an in-ground cooling loop. Handle the dehumidification with a ventilator/dehumidifier (say an Ultra-Air 100) using its own small ducts from a centrally located utility space.
Any thoughts?
>Cool by running the (closed loop) RFH water thru an in-ground cooling loop.
Not sure I follow. You're going to cool water with ground source tubing (loops buried in dirt) and then pump the X degree water through the in-floor tubes? Something other than this?
Do you know your cooling loads? How much tube are you burying?
You are correct. I am looking for a way to make the entire RFH package more cost effective by eliminating redundant systems, in this case (part of) the A/C system (I currently live in a house with RFH and a separate A/C system). I also like the idea of using natural systems to accomplish heating/cooling goals (e.g. passive solar, ground temps).
With that said, this is more conceptual than concrete at this point. I have read an ASHRAE article about doing this and it was positive. Main issue was to not make the floor too cold (maybe 67F min) and keep humidity down to prevent condensation on the floor.
I did take a stab at the heat gain and came up with around 21000 btu. The floors will be colored concrete with no coverings. I have not attempted to convert this info into feet of tubing required or even if I can extract the necessary btu's. Note that I am not a mechanical contractor. I am a just starting very small time new home builder who will be doing most non-licensed work myself (or at least that's what my business plan says). I will be utilizing a mechanical contractor to aid in the design and install. Also am assuming that there are controllers that can do what I am describing (even if I need to manually open and close the exterior loop / bypass the boiler).
I'm thinking the condensation on the concrete will make the floors slippery. I have a home near Lake Michigan That gets uncomfortably hot in August but by opening the windows I get a healthy breeze that makes the world OK. HOWEVER If I open the basement access doors (Bilco like) I get a wonderful breeze and tremendous condensation in the basement.
If you cool every floor that way you may have a slip and slide on each floor. The essence of A/C is not the temperature change, it is the reduction in humidity contrary to popular belief.Jack of all trades and master of none - you got a problem with that?
As my first post noted, I know I need to dehumidify and will do so within the context of the ventilation system.
CH,
No, I do not have any direct experience with what I think you mean by hydronic AC. I think you are refering to what would be Radiant Floor (or panel) Cooling. I see and work with chilled water systems (which I suppose is technically hydronic cooling) frequently, but these always involve air handling units with CW coils, fan coil units, or unit ventilators.
I looked into it when I was investigating RFH for my house years ago. The problems with cooling without forced air is humidity control/mitigation. Every system that I saw had some sort of fan coil unit to dehumidfy the air so there would be no condensation on the cold floor. Air at 75 degF and 50% rh (good conditions for an AC'd space) has a dew point of about 62 degF. If you use tubes in the floor to cool and it is colder than 62, condensation will form. You could cool with the floor at 65 or 70, but I don't know how effectively. And unlike the heating version, which by all standards provides superior comfort as compared to alternatives, RFC(?) would be marginal at best, IMHO. Thorough understanding of psychrometrics and controls are necessary to make something like this work. It can be done.
As you(?) or someone else stated, the dehumidification of the AC is system is a great deal of the benefit. 70 degrees at 80%rh is oddly uncomfortable(clammy), where 80 degrees at 40% rh is relatively nice.
Tim
Edited 3/12/2003 8:37:01 AM ET by Tim
What I mean by hydronic cooling is running a supply and return line of 3/4 or 1" pex to the walls of different rooms. The Hydro-Air unit, for example, installs in a 2x4 stud bay, and includes a coil and a whisper-fan. It also includes a condensate drain. Multi-speed fan for greater cooling or greater dehumidification. Each unit has a rated cooling/dehumidification capacity. You size it to the room needs.
I used the term hydronic, because it's "energy" source is chilled water. I'll take a more accurate term if you got one. And it's a ductless solution, so you avoid the expense of installing that. From my standpoint as a designer, I'm also avoiding the need for allocating space for ductwork! I have one design that is two domes separated by a long breezeway. The thin-shell construction doesn't leave room for ducts. But it'd be easy to run the supply and return between the foam and the shotcrete, or under the slab, or wherever.
It's a more easily-installed and distributed alternative to the Unico approach some people (me, here) have taken to providing A/C and dehumidification with rfh. Curious if you're seen it...
I considered RFC (radiant floor cooling) in my own house and I have about the best possible combination of factors: 38F unmetered city water, low heat gain (mostly solar input), and moderate absolute humidity in the summer air. And I have an HRV operating all the time to maintain the indoor air quality. But I decided not to do it. Partly for fear of swelling the wood floor on the concrete when it is the coolest thing around and therefore sucking up the moisture. Partly for general, eco-groovy reasons of preserving groundwater resources, even though they are not in shortage up here (yet). Mostly because the BTU/sq ft absorbed by RFC would be so low. In heating mode, there is a lot of convection as the lowest, warmest air rises and is replaced by cooler air. But in cooling mode, the cool air stays low and the hot air stays high. Your ankles would be nice and cool but your head would be up in the hot air and would be feeling radiant heat from the even hotter ceiling.
So I open a window when it is sunny and outside of my heating season (outside temps above 40F). If you don't have that option (because your outside air is hotter), then you have even greater heat gain to overcome and not such cold water to work with. And a RFC system would be even more marginal.
Although a forced air system would stir things up a bit, the velocities would have be much higher (more kwh's) to distribute cold air from the floor. Hot air from floor registers is easier to distribute evenly. And RFH is inherently very even heat.
To correct a psychometric factoid from another post, namely, "Air at 75 degF and 50% rh has a dew point of about 62 degF." This is not true. 75F and 50% r.h. has 0.009 pounds water vapor per pound dry air. That has a dew point of 52 F. A handy rule of thumb is that (around typical ambient temperatures) increasing the temperature by 20 to 22F halves the relative humidity. Reducing the temp by about 20F doubles the r.h. While I double checked my figures on a chart, the error noted above stood out because it's easy to do a good estimate in your head.
However, I agree with Tim?s conclusion that, "RFC would be marginal at best".
David Thomas Overlooking Cook Inlet in Kenai, Alaska
Edited 3/12/2003 1:21:04 PM ET by David Thomas
Dave! Still here! Still giving out some of the best advice! Good job!
I have not seen or designed an installation as you described, but I have read about them. Sounds like a viable option. I seriously considered this type of system for my home and planned to use a ground source heat pump as my main heating/cooling source. Life is such that that didn't happen. The drawbacks to such a system are minor and beyond the considerations of the average residence. I do not know realtive costs. Some might have a problem with asthetics.
"Hydronics", to my understanding, is water based heat transfer and applies equally to cooling as well as heating.