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Old 11-01-16, 10:53 PM   #11
nibs
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Angry

Thank you for the input. It is great to get the positive feedback. sounds like I will be putting in 2,000 lin ft.
Is it better to stay with 250 ft loops?
I was thinking that perhaps a good way to circulate the water is using an RV water pump for each room, (3 pumps) each on its own thermostat, less than $100 per room and inexpensive to swap if/when they fail, they are very long lived and can handle reasonably hot water.

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Old 11-02-16, 07:22 AM   #12
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Nibs -

I would not have thought of RV water pumps being especially reliable and long lived compared to the "bumble bee" and other highly efficient water pumps. I have found that most RV infrastructure equipment does not seem to be especially reliable and certainly NOT inexpensive.

Don't know the cost comparisons, but any water circulation pump is easy to replace.

Yes, the use of a common loop length means less balancing issues.

I would look into the costs/reliability of: one pump, one manifold and thermostat controlled values on each loop. Each of these valves has a small gate valve built in so you can fine tune water (heat) flow in each loop.

Equal lengths of pipe can can different resistances due to numbers of turns, etc. But this small effect can be handled easily with the gate valve.

Less large current wiring (one pump), higher operating efficiency with one pump and simplicity of using inexpensive and incredibly reliable zone values (See Uponor for some nice stuff).

Great project.


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Old 11-02-16, 09:01 AM   #13
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Have not researched other pumps, but am very impressed with the Shurflo style pumps, they operate on 12V, we will have a battery bank for solar so 12 v is no problem and if we use mercury switch thermostats can drive them directly with no 110 interface other than a backup 110v charger.
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Old 11-02-16, 10:05 AM   #14
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Nibs - I applaud the use of 12 volt solar and batteries . . . . but.

The use of a 12 V water pump will be far more energy costly compared to an equal flow 120 V AC pump. Ohm's law dictates that as power = current squared times resistance (i**2 x R).

Compared to a 120 V circuit, a 12 V pump must use ten times the current to get the same power (P=Ei). Assume the winding resistance is about the same for both. It is the square of the current that kills the efficiency. That is why higher voltage water pumps are more efficient than lower voltage ones.

These hydronic pumps are going to be on a lot of time so even small (and the above is not small) decreases in efficiency will cost you a lot over even a few years - a huge amount over ten years. Do your homework carefully.

I am a BIG advocate of rational use of PV and stored power when applicable. If you were off grid, then I might (and this is a might) suggest a 12 V pump - but it is a very inefficient way to pump water. Most off gridders all have a 12 to 120 V AC inverter for appliances/applications that work best on 120 VAC.

I might suggest the use of the 120 V AC mains for this hydronic application and the use of a PV system and inverter (highly efficient) to create the 120 V power you need for this application.

As a PV advocate, I appreciate the used of stored power, but the 12 V pump inefficiency, the cost of the 12 V battery, its upkeep/replacement and the associated costs just make this a 120 V application.

Hope I am not disappointing . . . .


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Old 11-02-16, 03:41 PM   #15
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Default European Advice

I think that this thread may have ignored a couple of very important contributions to this discussion.

Energy prices are currently low-ish, but as a very wise machinist said to me, "we are only a camel-fart away from skyrocketing energy costs."

Housing has a very long life, compared to cars, etc. so a house should be built not for today, but for 50 or 100 years from now.

Right now, Europeans are paying far higher prices for energy, in other words, regarding energy, they are living in the future, and we in North America would be well-advised to pay attention to their practices.

Fionn (Ireland):
6 inche PUR (rigid foam) insulation under slab

Zwerius (The Netherlands):
PEX spacings 6", preferably 4"

These seasoned EcoRenovators are using very thick foam (6") under the heated slab not just to support the foam industry, nor are they tending from 6" PEX spacings toward 4" spacings so that more PEX is created in the world.

They know that they will require less energy by doing this. This means less money required to heat and if you care about our impact on the earth, CO2 generation will be reduced.

We should not only thank them, we should act on their good advice.

-AC_Hacker
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Old 11-02-16, 10:00 PM   #16
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Steve, the main reason I thought about 12V pumps is familiarity, have been using them for years and know them well. Also they are inexpensive I have several, I buy them at yard sales, the weak link on them is the pressure sender, not a prob with heat loops; to be able to switch them directly by thermostat is handy as well.
Will research pumps over the winter probably.
Envy your southern insolation, we hardly get enough solar to pay for itself this far north. With grid tie inverters becoming so inexpensive will likely not build a large battery bank.
Since I have virtually no experience with in floor heat, many of my ideas will be changed as the build time approaches, as ideas flow from this and other sources, my thinking becomes more flexible, and the design evolves.
Am carving an elephant here, so we just keep knocking off the bits that don't look like the elephant.
Tony.
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Old 11-03-16, 08:37 AM   #17
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Tony - great analogy of carving the elephant! Had not heard of that one . . .

Spent time before you build. It has low cost, gets your mind "around" the problem and by the time you implement your ideas, they are well versed and worked out.


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