11-30-14, 02:29 PM | #41 |
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Heat transfer between the water and the inside tube wall is usually better than heat transfer through the tube wall and from the outside tube wall to the room. In that case, laminar vs turbulent flow has only a small effect on overall heat transfer.
If the system had copper tubing embedded in concrete, that might be different. |
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12-01-14, 06:49 PM | #42 |
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"copper tubing embedded in concrete" is a very bad idea. Many older homes had this & many developed leaks & were abandoned.
Like the skylight saying: There are really only 2 types, those that leak, and those that will leak. I like the "home run" method using 1/2" O2 PEX limited to 250' each. Home run means no fittings in floor, all loops start & end at above floor 1" manifolds. A ball valve at each end of each loop, allows air purging by shutting off all loops but 1 at a time. Also allows for return loop temperature to be balenced. Yes it can be done. If a loop gets a nail driven into it, that single loop can be shut off at both ends. I know that your not suppose to use a ball valve for flow balencing (suppose to use a gate valve) but at these low water flow conditions they seem to work just fine. Where each 1/2" PEX line enters/exits the concrete a 1" 90* grey plastic electrical sleeve is placed, to protect the PEX. I like some of Blue Bomber Man's logic in post #33 above. Much more heat is lost along exterior walls & windows, so the hotter source water should be run there 1st. (I think?) Last edited by buffalobillpatrick; 12-01-14 at 07:04 PM.. |
12-01-14, 08:12 PM | #43 |
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[QUOTE=buffalobillpatrick;41997
Much more heat is lost along exterior walls & windows, so the hotter source water should be run there 1st. (I think?)[/QUOTE] This is important in poorly insulated houses, with old leaky windows. It is not necessary with modern well insulated low leakage houses with modern windows. My own house has all the hot air vents toward the middle of the house without any noticeable cold areas, even at -20 deg F outside. But the house was tested at 0.85 ACH50, and the heat loss estimated at 13,000 BTUH at -20 deg F. I want gold pipe. No corrosion, excellent heat transfer. |
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12-02-14, 10:47 AM | #44 |
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JRM, that's a very impressive house. Is it at Passive House standard?
Heated with ASHP? My house has 6" SIP walls (5.25" EPS) & tripple pane Argon Low-E windows with 1/4" storm windows outside, so 4 layers of glass. Brick exterior. Still way too much infiltration at front door & windows though. I didn't crowd the pex close to the outside walls & measure about 4-5*F colder floor surface temps. there with IR gun. "I want gold pipe. No corrosion, excellent heat transfer." and I thought copper was getting too expensive, hehe Diamond or graphine conduct heat best so far, but a bit too exotic. |
12-02-14, 03:38 PM | #45 |
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Not even close to Passive House standard. Air sealed to 0.85 ACH50, compared to Passive House standard of 0.5 ACH50. Walls are R32, ceiling R96, windows Anderson 400 series, 4" foam under crawlspace and under footings, 1300 square feet.
Heat is from a Triangle Tube Prestige Solo 60 with three zones: House heat, domestic hot water, and shop heat. Calculated heat loss is 11,000 BTUH house plus 2,000 BTUH ventilation air at 90 deg F temperature difference. I originally wanted better insulation and windows to get that down to 9,000 BTUH for the house, but $12,000 extra to save $50 per year on the heating was too much. |
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12-03-14, 10:19 AM | #46 |
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Graphene boosts thermal conductivity of popular plastic - physicsworld.com
"Our results reveal that the thermal conductivity of PET increases by up to 600 times when it is coated with the graphene laminate films." This gives the laminates a similar thermal conductivity to metals such as iron and lead, approaching that of silicon." Possible use in future. I also have a Triangle Tube Prestige Solo 60, on LP at 8,500' altitude & 3 zones. Up here it don't condense very much & only puts out about 25-30mbh. About 1/3 less O2 vs sea level. I really like the self-cleaning SS Fire-tube type HX. At outside "design temp -20*F" it only runs about 1/3 of time for my 2400ft2 house. It had some issues firing off (E02 errors) when it modulates all the way down (bouncing off the bottom) & also made a loud foghorn noise at fire off. I bought a UEI C50 combustion analyzer & have adjusted the mixture screw quite a bit & replaced the LP regulator, no help. TT tech support was no help. Heatinghelp.com was no help. I even designed & installed a circuit that operated a solonoid that pushed the reset button upon E02 error. Ckt. had a thermal switch on boiler output pipe & a 5 minute Time Delay Relay. After messing with it for a year, I finally fixed both issues after noticing that it didn't have either issue on heating the DHW on full fire. I made the Lochnivar 80g Solar DHW tank (4 ports) the boilers only load. DHW tank now also operates also as a buffer tank. The boiler now fires only on high. A flat plate external heat exchanger between the DHW/Buffer Tank and the boiler/floor system exchanges heat in both directions, into and out of the DHW/Buffer Tank. Works great now but don't modulate down the fire, So-what, it never did modulate low enough for 1 zone & 32*F outside anyway. Last edited by buffalobillpatrick; 12-03-14 at 11:01 AM.. |
12-03-14, 10:39 AM | #47 |
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JRM, "under footings"
this is interesting, I don't think my building code inspectors would allow this? You must have used expensive high compression rated foam? " I originally wanted better insulation and windows to get that down to 9,000 BTUH for the house, but $12,000 extra to save $50 per year on the heating was too much." This is the delima we face in USA and why I think trying to meet Passive House standard is excessive. I realize that our "Green at any cost" brothers will disagree. Last edited by buffalobillpatrick; 12-04-14 at 06:38 PM.. |
12-05-14, 12:28 PM | #48 |
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Foamular makes three different higher strength foams for use under footings. I used Foamular 400. They also make 600 and 1000 for even higher loads.
The builder had to buy a pallet load of foam, which was more than needed. Insulation under the footing was important because the water table is right at the footings. The drain tile runs most of the summer. I did not want 40 degree water flowing right next to heated space. I still want a Passive House, but the economics are not there. I'd be spending several tens of thousand dollars just for the bragging rights. |
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12-05-14, 04:26 PM | #49 |
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JRM, you are way up North by Lake Superior. Cold Winters?
How deep below grade are the bottoms of footers? I don't have any water table issues at my new property. I'm thinking of using Frost Protected Shallow Footers (FPSF) only need to go 16" below grade, with quite a bit of EPS on outside footers, not under unless it's an un-heated building. They are approved by IRC 2009 Code. Last edited by buffalobillpatrick; 12-06-14 at 11:14 AM.. |
12-05-14, 08:35 PM | #50 |
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Cold winters, yes. Last winter was colder than normal, about 9,900 heating degree days. A normal winter is about 9,000 HDD. Burned 627 therms of natural gas to heat a 1300 square foot house plus a 600 square foot shop. The shop is kept at 65 degrees.
Our footings are four feet down, with 4 inches of Foamular 400 under the footings. |
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