no need to equalize lengths if you have balancing valves. and you should. if it's just one big open room, you still at least want loop shutoffs even if you length balance.

max lengths depend on desired pump, heat load, temperature drop, on center, etc. 250 is usually safe. depends on what you're trying to do though. Our max loop lengths for 1/2" vary from 150 to 500 feet, sometimes on the same project.

Maybe. "the book" is comprehensive but a bit much for the novice. One can "gloss over" if one know the subject.

I would suggest that the design is more important than the contractor. There are many good mechanics in the field but few who can design and install radiant systems to high standard (bare tube below the floor comes to mind). I correct many system problems created by professional and DIYers alike. Before you buy, learn the lingo and higher a designer before buying products you can't or shouldn't use.

Sizing plate heat exchangers is beyond the scope of this venue and more appropriate for advanced design seminars.

Start with a heat load analysis performed on dedicated software buy an experienced professional and put the book money on a sure thing.

I do have balancing valves on each circuit. I am also planning on putting shut offs on the supply side of each circuit. I really like the idea of having more than just the balancing valves to control the circuits.

I tried to get the loops as close in length as possible, but room size and distance to the manifold ultimately dictated the circuit lengths. I used 300 ft as my max limit, but aimed for 250, though exceeded that in 2 circuits - one 258 feet and one 270.

One of these days I will actually get the manifold built and then the proof will be in the pudding as to how well I designed and built the whole thing. My last back ordered parts just shipped today.

-Rosalinda

I am getting down to the nitty gritty of putting my manifold and control system together, and i have a couple of awkward runs to make. Is there any problem with using flexible stainless steel water connectors instead of putting together a variety of fittings to fill the gap? I am using 3/4 inch ID copper and brass and they make the SS connectors in many ID sizes including 3/4 ID. Any thoughts?

-Rosalinda

Went to Home Depot this evening and they had 3/4 ID corrugated copper connectors at a not unreasonable price. so I went with 2 of those for 2 troublesome areas. I did not like the look of the woven SS connectors as they did not hold their shape and kinked too easily when bent.

No one seems to carry the corrugated SS waterline connectors locally, and I want to get this darn thing FINISHED so don't want to wait for an online order.

-Rosalinda

I am still messing around with the system. I finished all the wiring today.

I am now trying to find out what the PSI should be for the closed radiant side. I have seen many different answers.

15 psi, 12 psi, and a formula that said divide the highest point in the system, in feet, by 2.3 to get your psi for the system, and add 5 psi.

For my system, the highest point in the system is 6.5 feet from the floor, and 3 feet above the pump. Using the formula, that would give me 7 psi for the system and that sounds very low. Anyone have an answer/rule of thumb for this?

-Rosalinda

12-15 psi is typical for a residential system. anything else requires expansion tank charge changes and such.

Thanks Rob, that is what I will set it for.

-Rosalinda

Posted By NRT.Rob on 18 Mar 2011 09:09 AM
12-15 psi is typical for a residential system. anything else requires expansion tank charge changes and such.

One of our local engineers is of the opinion that higher pressures result in better efficiencies. Both in solar thermal and hydronics. I had never heard of this before so am wondering if you or anyone else would like to express an opinion on it? Bob

I don't think so - AFAIK all it does is prevent cavitation in the pump and negative pressures at high spots.

The heating system is all hooked up and running. I purged it 3 times and though once in a while I hear a gurgle, everything appears to be running smoothly and the 3 air removers seem to be doing the job of getting the last of the air out. I have it set at 15 psi.

It took about 2 hours to raise the floor temp 10 degrees, but the water in the system was at 39 degrees and the floor surface was at 50, so that Vertex hot water heater is getting a workout. I have the radiant pump set on low and am running around .59 gpm per circuit. The HWH is set at 130 with a 20 degree differential, the water temp coming out of the flat plate on the radiant side is 120, and the return water is running at 80 degrees F.

Once everything is warmed up I will make adjustments.

The noisiest thing is one of the flow regulators jitters.

I will go out to the new house later tonight and see what's what.

-Rosalinda

I wonder?

How did you come to the water pressure setting. How did you size the water heater/heat exchanger? How did you size the pump? How did you figure the water temperature? What is an air remover and why do you have three? Why do you think the "flow regulator" jitters? How does the six inches of concrete effect the time it takes to heat up the slab?

Higher water pressure can not affect efficiency.

Mr. MA, to answer your questions:

Water pressure setting - rule of thumb appears to be 12 to 15 psi. Formula of distance to highest point divided by 2.3 plus 5 psi was 7psi, but that seemed too low. The system pressure is easily adjustable if you have any recommendations.

The water heater selection was based more on its features than size. I wanted a very efficient water heater, that was designed to do both DHW and radiant, that used propane, was condensing, and direct vent. I wanted to be able to set a differential on it so that it would not short cycle - the Vertex allows a 20 degree differential. I also wanted one that was a reasonable cost, so got the AO Smith Vertex for 2 grand rather than a polaris, or marathon for several grand more. If I decide to add other means of heating the floor - wood or solar, the DHW heater will still serve a purpose, unlike a boiler which would become an expensive wall ornament.

I ran several heat loss tools on the house and kept coming up with between 25,000 and 35,000 BTU/hr with a delta of 67 degrees required by code. 1/2 inch PEX spaced on average 12 inches in my 1399 ft2, would give me approx 35,000 btu/hr at 3.5 gal per minute, so the system was designed accordingly.

The pumps were sized based on head, the advice I received on this board, and was checked with the radiant guy at Pexsupply.com where I purchased them from.

The heat exchanger was sized to provide the 35,000 BTU/hr and Jeff Baron from this board was nice enough to send me a document on sizing heat exchangers that was very helpful. The advice on this board was that I should oversize it since my water has lots of mineral. I also asked the advice of the gentleman who sold the heat exchanger to me, and his rule of thumb was 10 plates per 500 sq ft. I purchased the 30 Plate Water to Water Brazed Plate Heat Exchanger from a supply outfit in Wisconsin.

Since I heated the house this winter with a very small electric heater supplemented with a propane garage heater, I was using less that 10,000 btu/hr to keep the house between 50 and 60, and we have had one of our coldest winters in the 32 years I have lived on my farm. I have a feeling that I will be using much less than the 35,000 btu/hr, but time will tell how all my experimental insulation placing will work. The temp probe that is 3 to 4 ft in the ground just inside the insulation perimeter on the north wall has risen 2/10ths of a degree. The probe on the northwest corner, where there is no PEX in the floor (cold room for root vegetables etc) has not changed.

I meant to say air separator, not air remover - I had purchased a B&G EASB-3/4JR Air Separator to put before the pump on the radiant side. I was looking for an more elegant way to add thermostats, pressure gauge and drain valves when I discovered that Zurn made a kit that fit the manifold I was using that included it all. these sections came with small air separators, so I got to add two more that went after the pump.

The system still has some air in it, so maybe that is causing the jitter - a slight rattling sound. And again I used the wrong term, it was the supply end flow meter that was making the noise, though today I think the sound is coming from the supply side ball valve. I will have to investigate more.

I don't think the 6 inch slab or the R5 insulation is having any affect on the time it takes to heat the slab. The PEX is tied to the wire mesh centered in the slab, covered by approx 2.5 inches of concrete. I took about 5 hours to get the floor temp to 65. The water temp started at 39 degrees F. The surface temp of the slab was 50 degrees and is now up to 70, with the house temp now 65 downstairs and 62 upstairs. There is only heat downstairs, none up and none planned, and the house continues to remain as it has all winter, with a 2 to 3 degree differential between the ground floor and the main floor. Since I have never done this before I don't know if that is a long, short or average time for system start up. The house feels very warm to me as I am used to a drafty 60 degrees and this is very non drafty.

I will post a picture of the system eventually.

-Rosalinda

http://www.rnrgroup.net/heat1.jpg
Image of heating system


It took approx 8.2 gals of propane to bring the system from cold to current temp.

I have the heat off, and want to see how long it holds the temp for.  Should be in the low 20s tonight.

How are you measuring that propane usage?

Just a safety note for other DIY radiant floor folks:

In the unlikely event that your water heater flashed to steam, at 1400 times its original volume, the T&P valve should open turning any flexible plastic extension thereof to a live steam hose (while it lasts). Think letting go of a 250°F fire hose while it is at full throttle.

Many T&P and PRVs weep over time for various reasons and give warning of their imminent failure...unless you hide the discharge end in a waste pipe precariously close to cross connection.

In a typical combi water heater/radiant floor job, at least 4 licensed trade skills are involved (5 here in Minneapolis). To assume you can learn them all, without supervision, on your first job, is a stretch, but Kudos for the work ethic and Yankee ingenuity.

DIY is great and can save you real money...if you live.

Always have a professional check your work before firing up gas-fired appliances and more especially pressure vessels of any kind.

ICF Hybrid, I purchased a 500 gal propane tank, and it was filled with 409.1 gallons to an 82% fill on the gauge. This propane has not been used for anything but the hot water heater, barring a little used to test the gas lines and fire up the kitchen range to make sure all was working. (and YES Mr.MA I did hire a professional to help me install the propane system, though I designed it, and the Propane company came down and inspected, tested and fired up the system for the first time). The hot water heater used 2% on the tank gauge for the first 52 firings, so that is 8.182 gallons, giving me .157 gallons per firing. Actually that included the 6 times I had fired the water heater previous to the heating system startup - to do some laundry - so it was actually 7.22 gals to bring the system up to temp.

Mr MA, what do you suggest I use to safely take the hot water from the pressure relief valves, to the drain? Copper? That is doable.

The system is working beautifully. The hot water heater fired three times last night keeping the temp in the house stable. It got down to 19 here last night. The sun is shining today so the hot water heater is off, and the system just cycles the water through the floor as needed, picking up the sun warmed water from the circuits on the south side of the house. The temperature is 2 degrees cooler upstairs as always this winter, so the concerns folks had about the ground floor radiant not being capable of heating the main floor due to its being conductive rather than convective, were groundless. Obviously I will have much more information once the system has run for a full heating season, but so far all seems to work perfectly as designed and installed by this DIY radiant system novice with much appreciated help from the folks on this board.

-Rosalinda

"In a typical combi water heater/radiant floor job, at least 4 licensed trade skills are involved (5 here in Minneapolis). To assume you can learn them all, without supervision, on your first job, is a stretch, but Kudos for the work ethic and Yankee ingenuity."

Thanks for the kudos Mr MA. though I don't agree with you about the premise. Given the ability to learn, the ability to research, ask questions and understand the answers, the self knowledge of ones abilities and limitations, I do not think there is anything in building a house that one can't tackle. None of this stuff is rocket science, and none of it is being done by rocket scientists. I did check my work, for example, the stuff that was completely new to me - such as wiring the Taco relay switch - I contacted Taco and made sure the way I wired it was correct before I turned on the electric. I had figured it out correctly, but I made sure first. I am sure you have had to correct the mistakes of others, but I would wager there were as many "professional" jobs that needed correction as there were DIYers. No one is or could be as meticulous as I am in doing the work on my own home, as no one has my motivation and self interest for getting it right, and that self interest is true for many DIYers. If it all went wrong, I would have no one but myself to blame, but it all went right so I can take the credit for a job well done, with much thanks for all who gave advice and assistance along the way.

-Rosalinda

And by the way, those gator bite push fittings are amazing. I used a couple just because I wanted to try them out, I could not believe they would work with 3/4 copper tubing, but they did, and exactly as described. I even took one apart and put it back together with the little plastic tool they say to use, and hey presto it worked! Radiant heat systems are great DIY projects because the components to build them are extremely user friendly, and getting more so all the time.

-Rosalinda