Chilled ceiling design

JStar

I have a project that I think will be a great application for chilled ceilings. If I have to suspend tubing in the ceiling, can I design the tubing size and flow rates the same as radiant heating? Does heat transfer work both ways?

paul_79

cooling

is this a residential or commercial install? if it is commercial look into passive or active chilled beam cooling.

NRT_Rob

.

Dupe

NRT_Rob

lot more to it than that

-your delta-Ts are smaller so you need tight coverage, higher flow rates and good install details.



-need to control your humidity.



-need to protect against condensation



-output is limited to a bit over 20 BTUs/sq ft in most cases for ceiling cooling.



-it's slower to respond than even slab radiant. no setbacks. set and forget.

JStar

Job details

This is a residential home. The house is nearly air tight. The cooling basically takes care of people and appliances. I'm aware that we will need a DOAS and humidity control system, as well as condensation, dew point, and maybe window sensors.



I'm looking for the ratings for different pipe sizes at different spacings.

NRT_Rob

heh

good luck on that one. best I've gotten is 1.9 BTU/sq ft per degree difference ceiling surface to room, assuming flat ceiling in typical rad ceiling height ranges.



I would recommend a high output panel like warmboard-R or Roth panel to be sure not to come up short in most cases. If you find anything better though please do share.

JStar

Well

Here's my situation. The guy built his house with absolutely no room for conventional ductwork. He doesn't want to see registers, or feel or hear airflow. And he does not want high velocity. What the hell am I gonna do?

NRT_Rob

I hear you.

the best I have for you until someone smarter than I chimes in is "be conservative". that's why I would generally use a high output panel... to ensure I can get that surface temp as close to water temp as possible.



we can do this kind of design but it's still bleeding edge for sure. not a mature process and some information, such as you request, as far as I know simply doesn't yet exist.

JStar

Sigh

I figured that I would't be able to find resources for a residential level job. This customer could be a curse or a blessing for me. Good advice about over designing. I think I'm going to see if I can translate the panel ratings into pipe/spacing ratings. I may even run extra circuits in the walls because he plans on installing floating acoustical ceilings. The only relief I have in the designing process is that the heat gains are so small that I'm sure I will have enough surface area to get the required BTUH.

SWEI

call your Uponor rep

They've put some money into radiant cooling for the US market and should be eager to assist.

JStar

...

Yah know...I'm still stuck in my old mindset of "figure it out for yourself". If somebody didn't stop to remind me that I can actually call the manufacturer to get questions, I'd be lost in the numbers forever. My first reaction is to always seek advice from field techs first.

Bart Vaio

Messana Ceiling Panel

Radiant ceiling is a tough nut to crack.  The Daikin Altherma paired with Messana ceiling panel and Messana controls is one of the better ways to do this.  The ceiling panels are a pre piped sandwich of Drywall pipe and foam board.  The controls are in every room to sense humidity temp etc. Every room is zoned, monitored etc.  They help with design and layout and controls.  It is a control intensive system so be prepared for a significant wiring and control cost as well as the ceiling panels cost.

 http://hydronicheatpump.com/messana/10_messana_TechnicalSpecsAndPerformance.html



Here is the panels performance spec around 25 btu/ft cooling



http://hydronicheatpump.com/messana/Brochure%20for%20webpages/MessanaTechSpecs.pdf

Deant

Self furring ceiling panel

Hi Joe,

We are using Xlath self furring ceiling panels for 1/2" PEX.



contact me offline at deant@talbottsolar.com

SWEI

radiant cooling ceiling tiles

I looked into some of these (from Switzerland IIRC) a few years back for a project and the materials cost alone came to almost $25 PSF.  Have they come down from that?



thanks~

pipeking

how r u

going to control the condensation (humidity) if your costumer doesn't have room (or doesn't want) ductwork?  i am very interested in this topic, cuz this is something i want to do in my place.

JStar

Chilled

This project became a dead end. The customer kept inventing more and more excuses for not trusting my design. Engineers!!! Anyway...



I'm planning to install chilled ceilings in my own home. I will convert my current air handler to take care of the humidity control.

pipeking

what do

u have to do yo convert your ac to dehumidify? i would think that all u would need to do is downsizing the tonnage

JStar

Air

The tonnage is WAY oversized for the humidity load. I plan to install a chilled water coil, and to degrade the blower speed to the lowest possible speed. I'll also have a reheat coil, using the compressor discharge, to condition the dehumidified air.

pipeking

this is

all uncharted territory for me, but i like it. let me see if my theory on your design is correct; u first heat the air using your compressor which increased the amount of humidity the air will hold. then use the cold hx to extract the humidity better, because it doesn't get nearly as cold a refrigerant. But then i ask,  if the cooling tower your using is cooling the water with refrigerant, and not a "swamp cooler type chiller", then y not just use a refrigerant dehumidifier, "a smaller ac system" insteed of a chiller and preheater?

Gordy

Cost prohibitive

Unless you live in an arid climate where humidity is not such an issue to control. Radiant cooling in humid regions is really a control/equipment nightmare. You will need ductwork for humidity control anyway may as well implement conventional ac. The cooling season say in the Midwest is humid, but last year was arid, and an intense duration of 3-4 months.



I find the Messana cooling output numbers hard to swallow. I would be more inclined to believe Rob from NRT depending on the panel assembly, and the envelope. Where is Geoff Mcdonell when you need him.



I have ceiling radiant with tight tube spacing, would love to try it, but in the end I have to control humidity so I need conventional fa any way. Why run two systems when one , or the the other would fall short. May as well go with the one that will meet the load

JStar

Ac

The humidity control system only needs one supply and one return. The air in the house will blend. Humidity travels. So, the air system can be VERY small (less than 1 ton), and take up a very small area of space.



I guess the advatnage of chilled water,is having a system that does not rely on airflow. It's quiet, clean, and more comfortable. It will also help to reduce the amount of refrigerant in the world.



Pipeking: it would actually be the opposite. You dry the air first, then heat it back to room temperature. Hot air doesn't hold humidity. Humid air holds heat. You want to dehimidify the cold, dense air.

Gordy

Jstar

Would the ductwork for dehumidification not depend on an open design? At least,with one supply, and one return.

NRT_Rob

dehumidification

in our case is a single chilled water coil in an ERV duct system... all air in is dehumidified.



has limitations if you have a leaky envelope, then you need recirc. but you don't have to dehumidify every room, as the fellow says, humidity travels pretty well.

pipeking

i new that

cold air is more dense and can hold more humidity then hot air, brain fart i guess! know why not just put the cold dry air back into the home without reheating it? is i because it will cool down the home to fast and inturn short cycle and not pull the humidity out? but then why can't u just down size? maybe i should find an artical on this and read it!lol!

Gordy

So Rob

If your using an ERV to dehumidify with a single coil. What tonnage, and brand brand chiller are you partial to? if i require a 3.5 to 4 ton conventional ac unit, does chiller size compare to the conventional tonnage?





I think I got the tubing between ceilings, and floors to get some decent output. Ceilings are 6" on center floors are 8 and 12" oc some rooms have both ceiling and floors 4 of them. A concern of mine is that the ceiling tubing being embedded in plaster, and we through a greater contraction rate on the tubing then it has ever seen with 55-60* water it may do some unwanted results, but my better judgment thinks plaster, and copper have all most the same expansion coefficients so all is good.



Thoughts anyone?

NRT_Rob

cold water

we are using a daikin altherma air to water heat pump. I am not up to speed on all the chiller options... I will say that may require super high head pumps so doing a tank with them and turning off the pump is often a great choice.

Gordy

Rob

I shot you an email on innoflex piping for lufta ervs. this is a german product with some distributers here. this is one in Minn. http://www.peakbp.net/innoflex.html



Let me know what you think of this system if you get a chance. They have some other pretty amazing energy efficient products.

Gordy

Flow rates

Yeah I hear you Rob, system head is just under 11.5 ' at 15 gpm with heating. Wondering if there is a trade off here with erv distribution being sized bigger to trade off some gpm?

NRT_Rob

with chilled water

flow rates must be high unless you can make really cold water. whether you tie to air or radiant this remains true.

FR

Mr.

Regarding the inability of chilled ceilings to handle latent heat loads, would it be reasonable to have a minimal valance cooling unit just large enough to handle the latent heat and have the chilled ceiling handle most of the sensible heat load?



I would expect valence systems to work well for cooling, but they seem to be rather large and unsightly. One just barely large enough to handle latent heat would presumably be much smaller, but it would have to be operated with lower temperature water than the ceiling. Probably that would require two water chillers, i.e., one small low temperature one for the valence units and a larger higher temperature one for the ceiling. To keep the controls simple, a two-stage thermostat could activate the valence cooling first then operate the ceiling cooling.



Does that sound like a reasonable thing to do?

NRT_Rob

unlikely

even the smallest valance unit is sized for real cooling loads so unless you have a very large area it's unlikely you can just dehumidify with it without also doing some significant sensible cooling.



Typically this is handled with very low flow chilled water coils in the ventilation system, or standalone dehumidifiers, or chilled fancoils with reheat. I prefer the vent coils.