[Experiment 1: Refrigeration And Mechanical Heat Pump Experiment.pdf
Oludare Padilla
Despite the lack of windows and insulation, I was already looking ahead with nerdy engineering glee to building a home-brewed heating system for this place, and I told you about it in the article called The Radiant Heat Experiment.
In a nutshell, this involved running thousands of feet of PEX pipe under my existing wood floor via the crawlspace and circulating hot water through it with a pump and this high-end Rheem tankless water heater.
Experiment 1: Refrigeration and Mechanical Heat Pump Experiment.pdf
DOWNLOAD ⚹⚹⚹ https://t.co/9koBpgw8Nv
Last time I presented you with a daunting list of parts. The list makes a lot more sense when you stick everything together. Here is a picture of the heart of my setup as it stands now, with everything screwed onto a plywood board:
It took only about two hours to attach all this together, and then I confidently crawled down under the house with it to get to work on the rest of the installation. Little did I know that the real work was yet to begin.
This system proved to be quite torturous to build, but it was because of plain old physical challenges rather than anything technical or mental. The problem is that to install radiant heat below the floor of a wood-framed house, you need to thread a huge length of stiff, fussy pipe through an unyielding grid of tightly spaced floor joists. I divided my house into six zones, each one about 250 square feet in area. For each of those zones, I had to do the same steps:
But weather adjacent to the Rocky Mountains is anything but consistent, and this winter we have also seen an all-time record low of -14F (-26C) as well as a daytime high of 77F (25C) just a few weeks later. This is why you still need a heating system with some juice.
On the positive side, you can get really creative with radiant heat, embedding the tubes into tile walls, or making heated towel racks in your bathroom that tie into the system. Each extra heated feature will deliver more BTUs. Also, installing under a tile floor instead of wood floor will increase heat transmission.
The main drawback of combining them that you need to keep the water heater set very high (140F) to get enough heat output to the floors. This means somewhat fussy water temperature balancing in the shower, whereas with a dedicated tankless heater you just type 110F into its remote control unit, crank the hot water handle, and enjoy a computer-regulated perfect shower every time.
A second issue is that the hot water can sometimes smell like new plastic pipes. This effect faded to zero after about three months, but it is worth noting, especially if you are installing your system in a house with people likely to complain about this. All components I used are after all specifically designed for potable water.
On the positive side, I found that if you run hot water when the pump is off, water is drawn through the system through natural pressure differences. This means that in the summer, my floors will actually be cooled down by the cold water supply as it sucks unwanted heat from the house. So the floors will pre-heat the water before it hits the water heater. Double energy savings and free air conditioning.
It has been a worthwhile experience. Loads of learning, plenty of hard labor, a luxurious end project, and an $8,000 savings over having a new forced air furnace and duct system installed into this house. Although DIY radiant heat is not for everyone, I can declare this particular experiment a success.
** The temperature drop is configurable with a little knob inside the computer-controlled circulator pump by Taco. I set my own pump to maintain a differential of 20 degrees F, which is typical for a system like this. Then if the pump starts seeing a drop of more than 20 degrees, the pump runs faster to compensate. If it is less, it means your house is already warm so the pump runs slower.
Good to see success. A similar alternative is to pair a hydronic air handler with a tankless water heater. Its the same principle except the in-floor pex is replaced with a furnace that has a water-to-air heat exchanger (instead of a burner). This might be a good alternative if you need to keep your AC coil and duct system, have a basement, have thick wood/carpet or otherwise insulating floors, or need a higher output for a cold climate (say 40,000-80,000 btu/hr). You can also get the return temperature very low, which will increase the efficiency of your condensing water heater (if you have one). We completed a study of these types of systems a few years back. They work well, but as noted in the article, you need to pick the right water heater. Cycling at low loads can destroy many different parts of poorly designed units.
I agree. I am just wondering if this will work under the brick floor I have in my living room on the far end of the house. It gets pretty cold in that area during the long Michigan winters. Any thoughts on whether it will heat the brick up and thus create a warmer living room on that end?
I am wondering if you have two floors, did you run this system on the second floor or is it just in the basement area. and also if it isnt ran on the second floor, how well did it heat the second floor?
I really enjoyed the information since I am where the MMM project was a year ago. 6- 250ft 1/2 in PEX loops under a 1200 sf 1938 home that has extensive upgrades (r-19 walls & r-23 ceiling + high efficiency windows and doors) here in the hills of north central Arkansas. Also 1- 300ft loop under a slab installation as part of the over all project. Test run this past week for leaks & water circulation, Will be happy to see the results when the winter gets in full gear. I can personally attest to the PAIN of crawl space PEX installation. It nearly got the best of this 80 yr old dog,
Pete
Awesome. Thanks for the great write up. I too am an engineer and I designed and built a similar do it yourself, pex radiant system in a 2000 sq ft, passive solar, super insulated, ranch style, concrete slab house we just built in upstate NY. My system is similar except I have adjustable mixing valves to knock down the water temps for potable use and for the floor heat delivery. I have a high efficiency condensing propane tank hot water heater. My concrete slab is a huge thermal mass. The heat has to be on for many hours straight to make the slab warm and move the air temp even one degree (supply temp 100 deg F, return temp 80 deg F).
At least here in New England, radiant floor heating is falling out of style. Mostly because of installation costs, but also because of the lack of efficiency when compared to the new generation of air source heat pumps.
Last year, when I was looking at how we were going to remodel a home we purchased, I came to this same point. The home is on a 4 inch slab, and had been retrofitted with pex floor heat, above the concrete with 1x framing. We resolved to remove all interior walls, lay fresh pex, and repour a slab.
The SlabShield then acts to radiate the heat up, and prevent heat from dumping into the old, 4 inch slabs. I also used triple layer Pex-Aluminum-Pex, which holds its shape when formed, and made install quite enjoyable.
I was at a startup competition in SLC recently and heard this professor from the U pitching for start up capital to produce this product that is a replacement for forced air, but cheaper than radiant heating. It was so fascinating: =mJKKsH-YUh8
I installed radiant in-floor and under-floor heating in a home I built about 10 years ago. Here is what I found out.
The project was completed by myself, my wife and one employee. The lower level of the house, with a concrete floor poured after the PEX was installed, topped with ceramic tile, was easy, fast and worked like a charm. The upper level, engineered joists and sub-floor, topped with hardwood,was much more time consuming (maybe 2X-3X) and worked nowhere near as well. The lower lever would heat up n a very short time and retain that heat for quite a while. The upper floor (separate zone) would take longer to warm and required more frequent cycling of the pumps to maintain a given temp.Were I to do this again I would use the radiant in the concrete floor and min-splits on the upper level.
My best advice: sun orientation and roof overhang for shading are the most important consideration when deciding on the heating and cooling requirements for a structure. For those of you interested in a serious DIY take, find a copy of Your Engineered House by Rex Roberts (long out of print.)
I know you guys are pretty dry out West, but if someone were to do this somewhere with high summer wet bulbs, should we be concerned with condensation on the floors, or even worse, condensation IN wood floors?
Also, how do you think this system will affect resale value? This design is unique enough that most buyers will not have a thorough understanding of the system. Contractors likely will be confused by the novelty as well. Any thoughts on this?
Our furnance might need replacing in the next 5 years and any alternatives like this would be interesting to look into. I think with our cold climate though the standard gas forced air option might end up being the most economical. My parents have radiant heat in their bathrooms and having toasty feet is definitely nice.
Averages out nicely to just under $100/month year round, and that includes our hot water, but out of context the winter months do seem absurd (and we do keep the place at 15 degrees max). No matter the math I do, living here is cheaper than buying a house/condo in the current market.
We installed a geothermal system in 2009. It was coming to the time to get a new furnace (3 repairs over a few months), and the governments were offering huge rebates from a variety of programs. We live outside of Haliburton, Ont., which is about 4 hours west of Ottawa, and directly south of Algonquin Park, so winters can be very cold.
What a cool idea! How did you decide how many lines to run between each joist? It looks like you ran two rows on lines between each. Did you contemplate running a third row? Is there any efficiency to be gained running more rows?
795a8134c1