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-   -   DIY Hydronic Floor Heating (https://ecorenovator.org/forum/showthread.php?t=728)

Drake 02-20-15 11:39 PM

This is all great info, at least for me. An Alpha is what I am watching to get a good buy on as I have some time. I don't plan to pour floor for another year, till I get addtn framed, roofed and enclosed. Second floor loop is minimal pex cost and will most likely to heated by future solar panel experimenting for fun. I will have two solar powered loft ceiling to first floor ducted fans to mix stratified air(I have one in existing cabin and it really makes a difference) it is off at night but by than I want heat to rise to sleeping area which it does.

Drake 02-21-15 06:06 PM

In better understanding an outdoor reset mixing valve the outdoor sensor controls the actual valve, making it operate differently(reset) than it would if it was just a mixer valve? I have been search engining for info many ways and when mining just "outdoor reset" I am finding much on it controlling boilers as well.

buffalobillpatrick 02-21-15 10:38 PM

The idea of ODR is to match & minimize the water temp going to the floors to the expected heat loss to Outdoors. This is done so that condensing boiler, solar, or heat pump can provide the minimum temp water, this may minimize energy consumed, depending on pumping energy.

ODR is not perfect, but can be better than not using it. It does not consider wind effect or cold clear night radiation into space.

If not using any type of heat source that I mentioned, ODR helps little. I have done it both ways & currently do not use it as my current boiler condenses very little (very high altitude).

AC_Hacker 02-22-15 12:02 PM

1 Attachment(s)
Quote:

Originally Posted by Mikesolar (Post 43965)
AC, It is all great to understand how turbulent and laminar flow affects heat transfer but there is something you forgot to mention. If you increase the diameter, your flow will become more laminar and the reynolds number will drop.

I think I did address that when I indicated that extra pumping would be required, and I indicated that the increased volume could be achieved with less power (linear increase rather than quadratic increase).

It was after that section that I included my statements on reynolds number, as it needs to be re-calculated. If I failed to make that connection clearly, let me know and I will re-edit.

Quote:

Originally Posted by Mikesolar (Post 43965)
The increase in heat transfer is not as great as you may think and you must think of the whole package (tubing, flow rate, concrete....and it ability to transfer the heat) including whether you need to use that heat. Not in this case. Drake is at the low end of the scale and the tubing choice is due to it being free (otherwise I would use 1/2"). He will never need to pump fast enough to get turbulence in the tubing.

NEVER?

I think this is where the kind of thinking that is needed for Low-Temperature Heating departs from conventional thinking that has worked so well in the past.

Fortuitously, I came across THIS_PAPER just today, that addresses certain aspects of Low-Temperature Heating. Here is a segment that talks about the need for increased flow rates when using low-temp heating.


I ran into Low-Exergy Heating and this whole different way of thinking when I was researching the possibility of heating my house with solar, in Western Oregon, where I live, where direct winter sun is rarely available. It turns out that even on an overcast day, a solar collector can produce 80 degree F water. So I started researching if it would be possible to do that. I learned that first of all it was necessary to drastically reduce the heating load (this is where Passive House ideas are so useful), and also the heating system itself would need to be substantially different from conventional designs.

So I pursued radical radiant floor designs, and began computer modeling them to see if 80F feed temp (or less) would work. This lead me the the LowEx consortium, and their work. It was during this phase that I was spending a lot of time with the RadiantWorks hydronic modeling program, to see if the physics of radiant floors would allow me to achieve my goal.

It turns out that really close spacings (<= 6") are key. RadiantWorks was not designed to go narrower than 6", so I called one of their Tech Reps on the issue and he said that narrower spacings were required and that flow rates would need to be increased above what is commonly used, to make it happen.

The interesting thing to me is that the radical approaches to heating with low temperature sources will also have a tremendously positive effect on conventional fuel sources, because far less of them will be required.

Who knows, maybe less of Canada would need become a Sacrifice Zone if we designed heating systems as if the availability of fossil fuels could someday decline.

-AC

Drake 02-23-15 11:00 AM

All of the writings I have come across so far on Exergy have been focused on the macro relationship of energy use in commercial or large scale buildings rather than the micro of single system energy use in small residential building. I think the concept is just as valuable on the small scale just not the economic incentive there yet for most to be interested in it yet at that small scale. I think most of us are already including Exergy thinking into our projects without really calling it that. Maximizing heat losses in structure, considering solar gains, passive cooling, minimizing inefficiencies, etc. For most of us the heating/cooling part is the components that needs improving and for that low temp heating is, as of yet, one of the best directions to be moving. This is certain for new construction because R values can be built in structure quite cost effective to make low temp heating very workable. Retrofitting for it depends on how much the R's can be increased in old structure, determining how low, if at all, low temp can be used. LT heating seems to be very limited documented or explored to its limits. At least in how we would like to apply it in our modern homes/lifestyle. This article is as yet for me one of the most informative on the idea of LT heating including some specifics on applications Renewable Hydronic Heating | Home Power Magazine. The note on the amount of heat emitter being a major factor in how low heating source can be makes me wonder what a fully explored and integrated radiant structure could one day achieve, floors, walls, ceilings. Reality though is we all have to choice a point to commit to the actual build of the what we hope we have best designed our projects and go from there.

P.S. here is a link to a new Passive House project in my area that is the most modest I have yet seen(though I am sure still has a non modest price) but in my mind going the right direction. They call it a "retrofit" but it is a full rebuild and only retro fit to the lot site, TE Studio - Residential Passive House Design Experts.

AC_Hacker 02-23-15 02:43 PM

Quote:

Originally Posted by Drake (Post 43991)
...LT heating seems to be very limited documented or explored to its limits. At least in how we would like to apply it in our modern homes/lifestyle...

Most people think that when they do a Google search, they are by default searching over all available on-line information in the world. It is not obvious that Google localized information.

So if you search for something like "Low Exergy" and you don't find much, it is because there's not much information in the localized range of on-line information that Google has pre-selected for you.

If you really want to know what is going on in the Sweden, for instance, do a Google search for "Google Sweden". The top search result will localize you in Google Sweden's search range (you can get Google to translate for you). There you will have a chance to see different results. Try it for other countries, you will be amazed!

There was a "Low Exergy" International initiative and study (AKA: LowEx), done about 10 to 15 years ago. The US was invited to participate, but declined to do so... pressure from the fossil fuel industry, I would guess. All of Europe joined in, and also Japan.

The information from that initiative was pushed out in an organized way and made public. It has been integrated into European practices. They probably don't call it Low Exergy (the most accurate description) any more. They probably call it Low Temperature Heating and High Temperature Cooling. In fact they probably call it "the best way to do things", that's how integrated it is.

The reason commercial installations are using the ideas, is that the savings from a big installation are big, thus the incentive to do things differently and better, are more persuasive.

People in Europe are implementing these ideas on a smaller scale, for homes, etc. because it is the best way to do things... and their energy costs (=> 2X of US) are not subsidized by use of the military to the extent that they are in the US.

People in the US, and Canada are implementing these ideas on a vastly smaller scale, because there was no involvement in LowEx, and there was no organized 'push' to get the ideas out and into general practice. So it is the fringe, radical, wacko DIY people who are carrying things to the limit (and saving money in the long run).

There is a gathering effort in this direction, even in the US. There is finally the dawning recognition that the lifetime of a built structure is rather long, and its inefficiencies run up a rather huge national energy bill.

A built structure that is created with the primary decision factor being financial, will limit investment to considerations of, "is it worth it", "will it pay off in two years", "will it pay off in my lifetime", "what do I care, I won't live that long".

But if the primary deciding factor is efficiency, then completely different decisions will be made.

If you stop to consider how the price of fuel has increased in your lifetime, you will understand that there is a fast-moving target when you frame the issue in financial considerations.

If you frame the issue in efficiency considerations, the target hardly moves at all.

Europe has codified many of the principles of very high efficiency in their building codes.

There is a very interesting story about the OPEC oil crisis and how it was handled by the US and how it was handled by Sweden.

The US made a heroic push to go solar... prez Carter wore a sweater, and put collectors on the roof of the White House. Solar businesses were subsidized, people going solar were rewarded.

Sweden made an in-depth, 2-year study of housing thermal efficiency, and integrated it into their building codes.

So... in the US, when Ronald Reagan became president, he ripped the solar collectors off of the White House, he ended the subsidies. The whole solar industry crashed.

Sweden, on the other hand, made it the law that all housing had to conform to the new higher standards. If a person wanted to build a home and couldn't afford the higher standards, the government was there to assist and make it happen. So today, all housing built in Sweden since 1975 is build to superior standards, and the practice persists to this day.

That's how things should be done.

So, taking the long look, I think that the fringe, radical, wacko, DIY people who are carrying things to the limit of efficiency, no matter what... they are the real heroes, and they deserve our respect.

-AC

AC_Hacker 02-23-15 03:22 PM

Quote:

Originally Posted by Drake (Post 43991)
...This article is as yet for me one of the most informative on the idea of LT heating including some specifics on applications Renewable Hydronic Heating | Home Power Magazine...

Yeah. John Siegenthaler is the go-to guy for radiant in North America.

I actually sat in on a free webinar by him on the subject of Renewable Hydronic Heating. It was pretty good... but somewhat of a product presentation. Some equations were presented that were very valuable, I think his target audience was contractors & installers.

In my opinion, John Siegenthaler is very intelligent, very well informed, but I think that he is constrained by local codes and building and trade practices to get out on the cutting edge (European standards). I understand, because he needs to be relevant to the current building community, otherwise no one would listen to him. I don't fault him... he has a job to do and he does it very well. But I don't think that his word is the last word in efficiency.

I asked him some questions in the webinar about ultra high efficiency, I even used the "Low-Exergy" word... he answered a few questions and finally quit because I was going too far off script.

He did say that he was writing a book on Low-Temperature Heating. I'll be interested to see what he comes up with.

-AC

Drake 02-23-15 04:34 PM

Agreed, Agreed, everyone has their self interest and in the US little of it is to help make the end consumer more energy independent or less out of pocket. Using less energy is fine by the Corps if it means selling less but getting the same price or more. The wacko DIY'ers may literally need to be the ones "where no one has gone before".. Green is good is the propaganda as long as it can keep corporate profits high.

Thanks for the tips on inter web searching. I so old school I still know where the reference libraries are and work with the original search engine - the card catalog. Now modern knowledge is mostly digital. Searching digital archives takes different skills.

Drake 02-23-15 04:52 PM

In the install procedures I have come across on thin slab application of in-floor radiant some have stated the need of a bond breaking barrier(poly) between concrete material and subfloor others haven't. Poly can be a moisture barrier also and maybe a benefit

Mikesolar 02-23-15 05:40 PM

Quote:

Originally Posted by AC_Hacker (Post 43980)
I think I did address that when I indicated that extra pumping would be required, and I indicated that the increased volume could be achieved with less power (linear increase rather than quadratic increase).

It was after that section that I included my statements on reynolds number, as it needs to be re-calculated. If I failed to make that connection clearly, let me know and I will re-edit.



NEVER?

I think this is where the kind of thinking that is needed for Low-Temperature Heating departs from conventional thinking that has worked so well in the past.

Fortuitously, I came across THIS_PAPER just today, that addresses certain aspects of Low-Temperature Heating. Here is a segment that talks about the need for increased flow rates when using low-temp heating.


I ran into Low-Exergy Heating and this whole different way of thinking when I was researching the possibility of heating my house with solar, in Western Oregon, where I live, where direct winter sun is rarely available. It turns out that even on an overcast day, a solar collector can produce 80 degree F water. So I started researching if it would be possible to do that. I learned that first of all it was necessary to drastically reduce the heating load (this is where Passive House ideas are so useful), and also the heating system itself would need to be substantially different from conventional designs.

So I pursued radical radiant floor designs, and began computer modeling them to see if 80F feed temp (or less) would work. This lead me the the LowEx consortium, and their work. It was during this phase that I was spending a lot of time with the RadiantWorks hydronic modeling program, to see if the physics of radiant floors would allow me to achieve my goal.

It turns out that really close spacings (<= 6") are key. RadiantWorks was not designed to go narrower than 6", so I called one of their Tech Reps on the issue and he said that narrower spacings were required and that flow rates would need to be increased above what is commonly used, to make it happen.

The interesting thing to me is that the radical approaches to heating with low temperature sources will also have a tremendously positive effect on conventional fuel sources, because far less of them will be required.

Who knows, maybe less of Canada would need become a Sacrifice Zone if we designed heating systems as if the availability of fossil fuels could someday decline.

-AC

AC, that is a good paper. I may have overlooked something in your comments to misconstrue your points. Regardless, if you look back through any posting I have made, I have stated over and over that tighter spacing is better and that some people I know in europe are using 100mm (4") spacing.

It is true that an increased flow rate is needed but it is an increase in pumping rate OVERALL, not necessarily per loop. The paper you noted indicates that constant flow is desired, which is also consistent with the advise given to Drake and others regarding how to move the solar heat to the cooler areas.

Also, the max temps and flow rates are needed at heat load conditions, so what will happen at, for example, 0C where only half the energy is needed. We can heat at 28 or 30C but if we go much below 23-24C the comfort level of the floor may be affected. We therefore have a condition that the paper does not talk about (unless I missed it) which is what to do during part load, run at full and open a window? It is a bit of a conundrum for any heating designer.


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