 |
| Author | Post |
|---|
Bob in Canmore
Member
| Joined: | Mon Mar 10th, 2008 |
| Location: | |
| Posts: | 3 |
| Status: |
Offline
|
|
Posted: Tue Mar 11th, 2008 04:52 am |
|
I'm a newbie to this forum, but have been looking at the posts on the pros and cons of tanlkess vs tank systems.
I am building a new house, a 1800sqft bungalow. I am making it as efficient as possible. it will have raadiant heat inthe floors. The plumbers gave me options for the DHW:
A coil in a well insulated tank- Aeroso, if I recall correctly, indirectly heatedby the boiler that does the floors.
A condensing tankless heater by Navien.
http://www.navienamerica.com/
With this I could downsize the boiler somewhat. Has anyone had any experience with this? Are their other brands of condensing type heaters? Am I trading one set of problems for another? Between the two types of tankless sytems, I mean.
Pretty cold here in Alberta in the winter. Groundwater seems to have been ice a few minutes ago? Haven't actually measured it yet...
Thanks for your help!
bob
|
elenano
Member
| Joined: | Sat Sep 11th, 2004 |
| Location: | USA |
| Posts: | 1322 |
| Status: |
Offline
|
|
Posted: Wed Mar 12th, 2008 05:40 am |
|
There is another forum that specializes in radiant and steam heating and a lot of pros hang out there. It is Dan Holohan's The Wall at http://www.heatinghelp.com. You might do better to ask this question there.
Randy Schuyler
|
eleent
Member
| Joined: | Sat Sep 11th, 2004 |
| Location: | |
| Posts: | 1567 |
| Status: |
Online
|
|
Posted: Wed Mar 12th, 2008 09:31 pm |
|
Hello: "The Wall" will have good feedback for you, but here are a few thoughts anyway. Heat loss calcs are the foundation for good decision making. You'll need that info for good radiant design also. There is a "mod-con" type of boiler, which means modulating and condensing. Hooking up an indirect tank to such a boiler is probably the Cadillac system. A tankless could be used, but you need to be sure to separate domestic and space heating waters with a heat exchanger. With heat loss calcs, you'll be able to see what equipment exists that will fit your needs. Don't forget to do whatever can make things work better and be more efficient. If you design a central equipment core to the house, a manifold system using 3/8" tube could serve nicely for hot (and cold) water distribution. A GFX shower heat exchanger could help. Have you considered a SIPS shell? With the reduced air infiltration and better insulation SIPS can provide, you could save money on heating equipment through downsizing.
You may be past the point of using some of these thoughts, but hope some of it is useful 
Yours, Larry
|
srdenny
Member
| Joined: | Mon Feb 4th, 2008 |
| Location: | |
| Posts: | 6 |
| Status: |
Offline
|
|
Posted: Sat Mar 15th, 2008 02:14 pm |
|
As mentioned above, a properly designed mod-con (with outdoor reset) is state of the art , giving you heat and domestic hot water as efficiently and cost effectively as is presently possible. Furthermore, modulation is the answer to your concerns about having to oversize the boiler for peak (winter) demand. Go to "the Wall", as suggested, and perform a search on mod-cons. Lots to read, but very informative.
As for Navien's condensing tankless water heater, I'm very excited about it. However, their"new" tankless offering is so new, I can't buy one here in CA yet. Even their website is still under construction. And, even if I could, I'd be leary about being a beta tester until it has a track record.
Good luck,
Scott
Last edited on Sun Mar 16th, 2008 01:23 am by srdenny
|
PeterT
Member
| Joined: | Wed Mar 19th, 2008 |
| Location: | |
| Posts: | 1 |
| Status: |
Offline
|
|
Posted: Thu Mar 20th, 2008 04:39 am |
|
Larry,
You mention using mod-con boilers with a indirect tank as the Cadillac system. The question I can't seem to get answered is how do these systems perform on an efficiency basis in the summer on 90 deg. F days? We seem to have more and more of those days every year. It still seems to me that using a mod-con boiler is overkill for domestic water only.
Peter
|
eleent
Member
| Joined: | Sat Sep 11th, 2004 |
| Location: | |
| Posts: | 1567 |
| Status: |
Online
|
|
Posted: Thu Mar 20th, 2008 11:13 pm |
|
Hello: I'd agree that a boiler and indirect are going to be overkill for domestic hot water, unless you have a rather large family. With that kind of heat outside, there should be a way to use solar. I do like heat recovery as it has very little to go wrong. You may want to look at the Phoenix Solar by HTP. Basically it has a mod-con boiler installed halfway up in a stainless tank. At the bottom is a coil that gets hooked up to solar to do the bulk of the heating. Doing both DHW and space with this solar/mod-con appliance could be a good thing
I suspect that as ambient temp goes up, you're going to get less condensation of flue gasses... but if it's also hooked up to solar, the boiler isn't going to be firing then anyway. The bigger problem to me is if the water being heated is too hot to allow condensation. Particularly if space heating is involved, keeping distribution piping temperature low is a worthy goal.
Yours, Larry
|
Bob in Canmore
Member
| Joined: | Mon Mar 10th, 2008 |
| Location: | |
| Posts: | 3 |
| Status: |
Offline
|
|
Posted: Tue Mar 25th, 2008 04:55 am |
|
Thanks for the info, fellas.
Haven't made a choice yet. I will have a boiler, and i believe it will be a "mod-con" if I remeber correctly. Will also have a separete forced air furnace. The Navien was suggested as an option for the DHW . I am inclined to go with the indirect tank from the boiler. Have an Aeroso tank in another house- seems to work fine. Will look at the options.
BTW, the place is made of SIPS, both walls and roof. Having some problems, thhough. Apparently the SIPS for the walls were "underblown" and got missed in QC. They were installed, and will now have to be taken out and new ones made...
Don't get many 90 degree days up here - I'm 6 or 7 hours north of Montana...
bob
|
eleent
Member
| Joined: | Sat Sep 11th, 2004 |
| Location: | |
| Posts: | 1567 |
| Status: |
Online
|
|
Posted: Tue Mar 25th, 2008 09:05 pm |
|
Hello: I built a SIPS house too. Randy has just added info about it to this site. But, what do you mean by "underblown"? Is the foam in the SIPS not of the right density?
Another thing; my place is about 1800 square feet as well and design heating load is 27,000 BTUs. I do most of it with solar and have the water heater as back-up, but haven't needed it. Depending on what your design load is, it could be hard to find equipment small enough to heat efficiently. If your load is small enough, it can cause a perceptual problem with radiant. That is the "warm floor" promise that radiant is often sold with. In a super efficient house, the floors never need to get to what feels warm  If you really want that feel, cut back on the feet of tubing and put it where you'll be walking, or spending time.
Yours, Larry
|
Bob in Canmore
Member
| Joined: | Mon Mar 10th, 2008 |
| Location: | |
| Posts: | 3 |
| Status: |
Offline
|
|
Posted: Tue Mar 25th, 2008 10:56 pm |
|
Hi Larry-
Don't know about the density, but there are voids, not all the way through, as well as foam pulling away from the studs. These are polyurethane foam panels, supposedly better than EPS, but...
There will be a lot of window in my place. It will be triple glazed, low-E, yadda-yadda, but the heat load is still there. I had an engineering estimate a while back but not at my fingertips right now. Solar is not a cost effective option right now as we are kind of in the trees, which will help with the summer heat load. Aside from the concrete floor there will be a fair amount of stone in the area exposed to solar heating which may help modulate the swings. I am plumbing in lines for future solar heat as well as PV.
About the warm floor- you are suggesting closer loops in high occupancy areas and less in otheres to delover the same total heat, ie, you wind up with the same number of loops?
bob
bob
|
eleent
Member
| Joined: | Sat Sep 11th, 2004 |
| Location: | |
| Posts: | 1567 |
| Status: |
Online
|
|
Posted: Tue Mar 25th, 2008 11:55 pm |
|
Hello: What is done with floor tubing really depends on the heat loss in the particular room. A lot of glass (even good glass) might create a need for more tubing. Wirsbo and others have programs for determining tube layout and spacing, based on heat loss. When a house gets really efficient, putting plenty of tubing in the floor can make the need of heat from each square foot of floor so small that it can actually feel cool, or neutral to the touch, but still be heating the room adequately. By reducing the amount of tubing, you force it to give off more heat per linear or square foot, increasing floor temp (in specific areas) and giving the homeowner something closer to what he/she expects. Actually, by the time you get down into such low loads, it could make sense to look at wall panels or some such low cost way of getting heat into the room. Heat emitter design is directed by individual room heat loss.
If I've just lost you in technobabble, think of it this way: You need a given amount of heat in the room. You can get it with a very big, luke warm surface or a small, very hot surface. For a floor you want a surface that's about 80 degrees. Calculations will tell you how big that area is and knowing how the room will be used will tell you where to put it to keep toes warm 
Yours, Larry
|
Current time is 07:49 am | |
|
|
|
|
