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annakah
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Posts:1
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| 05/16/2008 1:01 PM |
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I live in a modified house/duplex. I have lived here for 4 years, it was a house that was modified into an upstairs/downstairs duplex. It has radiant heating on the floors. It has a boiler system that says on it GPH hydronic heating system. I have liked this system, but we have had several problems with it and the landlord has had to send out a many of technicians. Of these techs, only 2 of them have really known what they were doing really. This system uses what appear to be copper tubing.
My question is, I do hope someone can answer me, is there a way to switch the water to cool temperatures for summer time cooling? I live in Salt Lake City UT, it gets pretty humid here in the summer time. And if there is a way to do that could I get it explained to me so I can explain it to the technician who will need to come out to fix the system as it breaks regularly and broke in March, we just dealt with the colder air, since there is no reason to get your heater fixed near the end of the season. |
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NRT.Rob
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Posts:384
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| 05/17/2008 11:39 AM |
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| If you had a very low cooling load and a method of humidity control tied in, you could maybe work it to do some cooling, but not many people are fluent in radiant cooling and it's pretty weak, especially in the floor. Typically you'd have to have designed the house to be able to cool from the floor to make it work well. |
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-=Northeast Radiant Technology=-
NRTradiant.com |
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Brock
Registered Users
Posts:201
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| 05/17/2008 11:25 PM |
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| In playing with a radiant floor we had in a garage, I thought in summer I would cool the garage (floor) and pre-heat the water running in to the hot water heater. So I connected the well to one side and the other side to the hot water input. It did warm the well water about 10F while running and 25F if it sat there for a while, but drastically reduced the hot water flow (should have thought of that) and made the floor in the garage all wet from condensation. So cooling with cold water in humid conditions will is likely to cause condensation and dampness. Because of this I would be very leery of trying it in a home setting. |
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Green Bay, WI. - geothermal heated indoor pool with a small solar setup |
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BillN
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Posts:38
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| 05/24/2008 10:07 PM |
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if its on the edge, you probably dont want to touch it. If you owned it and wanted to play, you could get a small refrigeration unit, like one from a refrigerator box and connect it to the circulating loop for cooling. you just cant go below the due point or water will condense on the floors. the rooms would be cold and damp without an air system removing humidity.
At that point you better own the system or know somebody to take care of it because you will be on your own. |
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chad
Registered Users
Posts:6
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| 06/12/2008 3:03 PM |
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I am looking into an open direct system from Radiantec that pipes the incoming cold water through the slab in the summer via a valve that can be turned for summer operation. In order to deal with the possible humidity issues, we are going to do three things - install a room dehumidifier, install ceiling fans to keep air moving over the slab and reduce the possibility of condensation and install an ERV that will help ventilate with fresh air while controlling the humidity.
I agree with the others that this is tricky and an application that is "on the edge" and would be leary of installing without consulting an engineer on the setup. I had an engineer friend run some quick calcs on when condensation would occur in the house and the corresponding humidity levels we would need to maintain in the house. Good luck! |
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Build It Green Philly - Philadelphia Green Building specializing in cost-effective new construction and major rehabs. |
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NRT.Rob
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Posts:384
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| 06/12/2008 3:28 PM |
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It's also a bad idea doing freshwater systems (aka "open direct"). but you can do a search on this or any other forum discussing radiant heat and get dozens of threads to sort though on that topic so I won't bother here. I'll leave it at, a heat exchanger is a very good idea.
Also, unless you are doing some active pump and dump schemes (which, if you're on city water, would be very expensive), the cool water coming in from regular water usage is minimal. the phrase "limited" free cooling isn't just cute, it's a massive understatement; you get a little cooling while you are actively running the water, and then you can absorb a little into the water left sitting in the pipes: it's not much at all. Certainly not a benefit that would tilt the heat exchange argument in my book. |
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-=Northeast Radiant Technology=-
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KCMOKen
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Posts:14
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| 06/12/2008 4:52 PM |
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I have a friend living in Kansas City (humid climate) that uses radiant cooling and has for the past 30+ years. He has that radiant tubes high on the walls, and a water collector trough that collects the condensation. It is the craziest thing I have ever seen, the water collection troughs have the Edwards Engineering label on them, and the company is here - http://www.edwards-eng.com/, they clearly sell chillers I just don't see anything like what he has nor do I see anything that looks even remotely residential (although the logo is the same).
He says it was designed by an engineer, and it has worked flawlessly the life of the house, and somewhat efficient. I have been to his house many times, and I can agree when I was there both temperature and humidity were well controlled. I have also seen his gas bills (natural gas based chiller, you don't see these every day either) and he is definitely paying less to cool his similar sized house than I am. He has a New Old Stock gas chiller in his garage, still on the pallet, in case he ever needs to replace the one he has, but still the original.
I have never seen the like of such a unit, but I can vouch that one exists and it does the job quite well. My next house gets radiant heat, I just want to find that engineer that designed his system although I am sure he has long since retired. |
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bartman99
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Posts:35
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chad
Registered Users
Posts:6
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| 06/17/2008 4:50 PM |
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Posted By NRT.Rob on 06/12/2008 3:28 PM
Also, unless you are doing some active pump and dump schemes (which, if you're on city water, would be very expensive), the cool water coming in from regular water usage is minimal. the phrase "limited" free cooling isn't just cute, it's a massive understatement; you get a little cooling while you are actively running the water, and then you can absorb a little into the water left sitting in the pipes: it's not much at all. Certainly not a benefit that would tilt the heat exchange argument in my book.
In a very tight SIPs home that is well insulated and has a high amount of thermal mass from a slab on grade foundation, a very limited amount of cooling may be all that is needed in the Northeast. I hear you on the freshwater system and need to do more research on this subject. The bottom line for our project is that if we are able to eliminate an expensive active cooling system by using the existing radiant system and free cool water from the city, why not?
Another option I have considered is simply running an extra loop of PEX through the slab for the summer cooling feature only and sticking with a closed system for the heating season. Worse case scenario, the summer cooling feature doesn't work or creates condensation, and we switch it off never to be used again. For a couple hundred in extra PEX, it is an inexpensive experiment. |
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Build It Green Philly - Philadelphia Green Building specializing in cost-effective new construction and major rehabs. |
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NRT.Rob
Registered Users
Posts:384
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| 06/17/2008 4:58 PM |
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Let me try again. I'm not tryin
By "limited", I mean "negligable", "not worth considering". If your house needs cooling, this will not cool it. If your house does not need cooling, then this is unnecessary. It's a little marketing spin to add one more "check" to the "pros" column that, in reality, does nothing worth even thinking about.
It's like saying you get limited free cooling from your existing domestic piping when you run your cold water; it's true. It's just not useful or worth thinking about. This is slightly more than that, but only slightly... unless you use huge pipe. I suppose you could rig up loops and some kind of pump and dump scheme like I mentioned (where it dumps water down the drain to keep cooling going, I know a contractor who did that with good results) but just "harnessing" your regular usage is very, very minimal. |
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-=Northeast Radiant Technology=-
NRTradiant.com |
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chad
Registered Users
Posts:6
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| 06/17/2008 5:15 PM |
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OK, I see your point. I am looking at a report made for the DOE a number of years ago. It gives the following figures for radiant cooling in a slab:
- 720sf slab 5.5" thick in a 2-story, 1400sf home
- water temp of 55 degrees and a design temp of 78 degrees
- household consumption of 300 gallons per day
- head exchange efficiency of 90% in the radiant slab
- 51,667 BTUs extracted per day
Is there a glaring error in these assumptions from the report in your opinion? I am not an expert in these types of calcs so I am certainly not claiming they are correct. |
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Build It Green Philly - Philadelphia Green Building specializing in cost-effective new construction and major rehabs. |
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NRT.Rob
Registered Users
Posts:384
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| 06/17/2008 9:31 PM |
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whups, my last post got chopped there, sorry, that sounded a little snippy. I must have hit submit while I was on the phone. I wonder what I was going to finish saying with "I'm not tryin" ?
so, wow. Those numbers assume that you pull all incoming water up to 75.7 degrees before it gets out of your house, which seems a bit optimistic to me, first of all. and that you use 300 gallons a day of water which seems fairly high to me when an 8 minute shower at 2.5 GPM/minute is only 20 gallons, but hey, maybe that's just me, maybe. I guess with a family of 3 you're almost halfway there if you all take a shower every day.
I think realistically, smaller demands like washing your hands or filling a pot will give the full benefit of their usage, but a real demand like a shower is probably not going to raise its temperature 90% at a 2.5 GPM draw in one pass through a slab, not even if you use the big pipe to slow down its velocity and split amongst multiple loops.. you might be able to make that happen but you would be trying awful hard and you'd basically be trying to make a storage tank out of large diameter pex in your slab. and most of your demands that are going to contribute significantly to your 300 gallon usage are likely to be "real" demands.
so I guess I'd call that "wildly optimistic". I've been wrong before, maybe all those assumptions are totally sane, all I can say is that they aren't assumptions I would make. Don't put in low flow heads though or you lose half of your cooling ability ;)
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-=Northeast Radiant Technology=-
NRTradiant.com |
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BillN
Registered Users
Posts:38
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| 06/17/2008 10:39 PM |
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I use radiant cooling in my house given certain conditions. I have a small closed loop geo heat-x that I circulate the slab water to.
I guess that you could call it limited. Generally I call it supplimental, or auxillary, but not insignificant.
I get about 1 free ton of cooling with about 2 degree delta on my water loop. I bring my exposed concrete floors 1 or 2 deg below the room temperature, but not below 70. |
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chad
Registered Users
Posts:6
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| 06/18/2008 9:56 AM |
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1 Ton of free cooling would be more than enough for my homes but I don't think I'll get that much. This will be a LEED home and we will be installing low-flow fixtures. If the assumptions in the calcs above are correct, then our home will most likely yield about 15K BTU's of free cooling per day according to our water usage figures.
I found this very informative document on radiant heating and cooling by following one of bartman's links above. "Possibilites and limitation of radiant floor cooling" by Bjarne W. Olesen, PH.D.
After our discussion here I am leaning more and more towards a hybrid system with two separate loops for heating and cooling. My main concern is condensation and if we are saying here that the radiant cooling scheme I am looking at will produce negligible results, then there should be no risk of condensation. However, if I do experience condensation, I can simply just turn a valve to turn off the radiant cooling altogether. Some more calculations on the install height and spacing of the cooling loop are in order I think. |
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Build It Green Philly - Philadelphia Green Building specializing in cost-effective new construction and major rehabs. |
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NRT.Rob
Registered Users
Posts:384
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| 06/18/2008 10:19 AM |
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I remember you posting on that awhile back I think Bill; very cool stuff! oh man, that was the worst pun ever. does your closed loop system maintain its contribution throughout the summer, or does it degrade as you dump more and more heat down there?
Chad, that 15kBTU may even be high. even an eight minute low flow shower head 1.5 GPM shower is 12 gallons. If you have less than 1200 feet of half inch pex in the floor, or 600 feet of 3/4", you have less than 12 gallons to clear all the lines of water that absorbed heat. then you're back to assuming that the water can absorb all that heat on one pass through, which I don't think is the case. Meaning water left sitting in the pipes gets 100% transfer, but water that sneaks in and out without ever stopping I strongly doubt gets a 90% efficient transfer.
But if it is good, 15kBTUs represents about 4 kwh of electrical capacity in resistance heating; not sure how to translate that to cooling, but it would be that or less since AC is a heat pump, I think? anyway. that, in the cooling season only, has to offset your installed costs.
If that makes sense, and you can be reasonably assured you won't get condensation, then go for it! |
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-=Northeast Radiant Technology=-
NRTradiant.com |
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Brock
Registered Users
Posts:201
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| 06/18/2008 12:12 PM |
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| A bit off topic but in summer I usually put a fan on our water to water heat exchanger during the day when we are not taking showers in the morning. During showers it takes the 50F water to 70F or 71F with the drain water. It easily brings water for the dish washer and hands and cooking up to room temp before it hits the pre geo water tank. I am not sure how much extra cooling we get. I have found aiming a fan at the basement floor warms up the floor and cools the space a bit, and you can really tell where the footings are because the concrete is much cooler in that area (not insulated). |
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Green Bay, WI. - geothermal heated indoor pool with a small solar setup |
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BillN
Registered Users
Posts:38
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| 06/21/2008 2:08 PM |
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when it first turns on there is a bigger delta, about twice as much as the steady state.
It doesn't usually run continously for longer than a few days. So every startup I can see a big delta, then it decreases.
The floor temperature is not too cold, kind of nice, like a basement floor in the summer. I have some small slabs on a different loop that dont get the cool water, and they are noticibly room temperature or above. |
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