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#541 |
Apprentice EcoRenovator
Join Date: May 2012
Location: Atlanta, Ga
Posts: 142
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![]() No-the incoming cold water goes through the loops before getting to the water heater. They aren't heated unless a circulator pumps hot water through them. The only disadvantage to an open system is that zones calling for heat only see warm water instead of hot water during a DHW draw. Since that doesn't happen for very long, it doesn't matter and the benefits outweigh this drawback.
Here's a site with a schematic and a good explanation of open systems: The Open System | | DIY Radiant Floor Heating | Radiant Floor Company I have a single water heater, an Eternal GU145S. Once I finish the buffer tank/GSHP/etc, it will be replaced by a 100ft 1" corrugated stainless coil in the buffer tank. Everything now and in the future other than that coil will be 3/4", only dropping to 1/2" for individual plumbing fixtures and the hydronic loops. My biggest zone has 4 300ft 1/2" loops, fed by a 3/4" pipe and manifold. I originally thought I would need a smaller water heater to bump up the temp as I described in my "don't waste that heat" thread, but now it looks like my coil will be able to get the water within 5F of the tank temp, so I probably won't need it. If they were only 1/2" ports, I would parallel two.
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"I‘d put my money on the sun and solar energy. What a source of power! I hope we don‘t have to wait until oil and coal run out before we tackle that." Thomas Edison, 1847 — 1931 Last edited by Mobile Master Tech; 03-01-16 at 06:59 PM.. Reason: Extra content |
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#542 | |
Master EcoRenovator
Join Date: Aug 2012
Location: Toronto
Posts: 958
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#543 |
DIY Guy
Join Date: Jan 2011
Location: Mpls,MN
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#544 |
Apprentice EcoRenovator
Join Date: May 2012
Location: Atlanta, Ga
Posts: 142
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![]() Mike, I beg to differ on a few.
I am not knocking slab or advocating "staple up" per se, but rather systems with heat plates holding up the pipes and using a bead of heat transfer compound. I originally just had staple up. With 150F supply water it couldn't cope with a 40F night! I removed the staples and added the stamped u-groove heat plates, now it can keep up with at least 15F nights using 130F water. Pipe is cheap, and so are plates; completely remaking a house to add a slab is not. New flooring, new trim, adjusting door heights, resetting cabinets, less headroom, possible structural mods, etc. If I were designing from scratch I would probably plan for in-slab on all floors. Not as easy on an existing house. There may be complaints with staple up, but I and my pets love having slightly warmer areas of the floor-I find that a positive, not a negative. There is enough temp difference to notice but it is not obtrusive, especially with a radiant barrier hanging freely just below the pipes to create a "cocoon" of warm air under the entire surface and conditioned space below. The underside of the barrier won't ever get dirty, so the barrier remains effective. The noise isn't a big problem and I believe a change of thermal compound wil address most of it. Both these problems pale in comparison with my larger complaint with retrofit slab systems: cost and effort! Failures and problems are far more likely to be caused by improper design or install rather than system type. Failing to radius the end of the plate channel so the edge chafes the pex is a prime example. Do you have some examples to back up your claim that a properly designed underfloor system is inherently less reliable than slab? Recall that I said bronze valves, not pumps. These one way check valves are just a loosely hinged slab of bronze falling by gravity against a seat. They don't have to seal perfectly, just stop the bulk of the flow. Those will probably never fail. I'll report again on my system more than 10 years down the road instead of just 4 so far. As for pumps, are you familiar with the Laing/Bell & Gossett e3 design? No seals, no bearings, and the only moving part is a freefloating rotor, positioned and driven by magnetic force, spinning on a ceramic "pinhead". Bronze isn't why other style pumps fail, it's their moving/sealing parts, just like any conventional pump. Could you please back up your statement with examples of the Laing style pumps failing? Bronze or stainless is what allows pumps to be used in potable systems, and it has the benefit of not corroding. For fun, check out hvac-hacks.com, especially the screw-ups and burnt n'crispy categories. Plenty of "don't do it this way" examples. 125F water IS efficient and so is 130-145F, if your source heat temp is high enough. Being able to combine systems for less complexity or points of failure is also efficient and elegant, which is why I am combining 6.1kw of PV, GSHP with a 70F+ source temp due to the annualized heat storage, hydronic with DHW, etc. I referenced my other thread to explain where I was going with this-completely fire my energy companies and eliminate most of my transportation energy with a Chevrolet Volt, under $15k for a 2013 model these days. Look at any heatpump COP chart that shows multiple inlet temps and you will see that the COP for any combination of higher inlet/discharge temps is 95% or better of the COP for lower temp combinations with the same spread, assuming you don't try to run near the supercritical temp of your refrigerant. Again, proper system design. R410a with a supercritical temp of 163F would be difficult in a system designed to be capable of 145F output. Hydrocarbons or their blends like the R600 series, R134a, even R22 would all give better "fudge factor". The insulation recommendations from IECC and others for climate zone 4 (which I am on the edge of) for abovegrade mass walls is R-5 when more than half the insulation is on the exterior. The total R value of the assembly is 6.7-7.6: wall and drywall (R0.4-R0.7), air on both sides (R0.6 interior, R0.2 exterior) , radiant barrier with 1/4" gap (R 1.9-R2.5), and R3.6 of polyiso. The exterior is at least R5.5 (barrier, airgap, polyiso). I could go thicker, but I don't want it to stick out further than the existing siding above it. I don't plan on having insulation on the interior so moisture won't be a problem, plus the belowgrade areas will be part of my passive annualized heating system described in my other thread. R10 is recommended if more than half is on the interior, so you are correct if the insulation was on the inside. There is more than one good way to do something. I'm trying to show that underfloor with plates (I'm going to quit calling it staple up-what a hotbutton word!) can be successful and much easier than slab when done properly, and there are ways to combine systems for simplicity and a sum greater than parts.
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"I‘d put my money on the sun and solar energy. What a source of power! I hope we don‘t have to wait until oil and coal run out before we tackle that." Thomas Edison, 1847 — 1931 |
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#545 |
Apprentice EcoRenovator
Join Date: May 2012
Location: Atlanta, Ga
Posts: 142
Thanks: 38
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![]() Yes it is difficult for a heatpump system to be designed for 12million btu/month, hence the storage buffer tank with PCM described in my other thread. It can run during the day while the PV panels are warm, PV output is easily available to run it, and source water is likely to be 80F+, only running at other times during high demand periods.
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"I‘d put my money on the sun and solar energy. What a source of power! I hope we don‘t have to wait until oil and coal run out before we tackle that." Thomas Edison, 1847 — 1931 |
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#546 |
Supreme EcoRenovator
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![]() In Atlanta, I don't imagine dew point would be much of a problem in heating mode. Winter and Spring temps are all over the place, but rarely stay below freezing for more than 48 hours at a time. It gets into the cold range often, freezing range occasionally, and frigid range hardly ever. Freezing rain and sleet are much more common during winter than snowfall.
For example, on any given Sunday in January, the daily high may reach 65 degF. A cold front rolls in, and rain turns to sleet on Monday. The temp bottoms out at 28 when the sleet stops. Tuesday morning, school is called off. The black ice on the roads Tuesday morning causes wrecks everywhere, due to driver inexperience. By noon Tuesday, the ice on the roads has melted. Wednesday's high temperature reaches 52 degF. Due to the lack of deep temperature troughs of frigid weather in the region, most housing infiltration and insulation efforts would be classified as "severely lacking" by Canadian standards. More effort is put into dehumidification, as RH regularly rises into the 90's between February and October, especially during after-work hours through the night. Most of the year, the weather conditions could be described as "cold and clammy, muggy, or tropical" in nature. Not surprisingly, most modern homebuilders are more concerned with tight vapor barriers than raw insulating power. |
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#547 |
Master EcoRenovator
Join Date: Mar 2014
Location: Florissant, Colorado
Posts: 599
Thanks: 814
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![]() I have done 2 systems as follows & love it:
A large (buffer tank / DHW tank) that does both jobs. Mine is 80gal & my Son's is 115gal There is a flat plate heat exchanger between the boiler and the tank, pumps on both sides. Heating system is on boiler side of heat exchanger. System can heat during a boiler cycle or after, by pulling heat back out of the tank via the flat plate heat exchanger (tank acts like a buffer here) This is KEY: there is no short cycing of boiler. Zones calling for heat can sip out of the tank. The boiler is controlled by a Tekmar 256, Universal sensor on tank + outdoor reset sensor, continuous call for heat is jumpered on with a 25* delta programmed. This works great, long efficient boiler cycles heating the tank with ODR control of water temp. The boiler is not controlled by system, only the Tekmar 256 controls the boiler. |
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#548 |
Apprentice EcoRenovator
Join Date: May 2012
Location: Atlanta, Ga
Posts: 142
Thanks: 38
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![]() Jeff, add that upon any news of frozen water in the forecast, the majority of the population here rushes to the stores picking the aisles clean, stocking a month's worth of perishables that will go bad in a week! Other than that, you nailed it!
![]() BBP, you are absolutely right on preventing short cycling. I'm sure yours works well. The simplest way to do it though is to use an Energy Star conventional tank water heater (most are certified for hydronic/DHW combinations) and an open system (safe and approved in most locales). A 40Kbtu burner on a 40 gal 12 year heater for $600 is plenty because of the "buffer factor" of the tank AND floor/house unless your house and household is huge. I'm assuming anyone would already have a decent building envelope and water efficient fixtures such as Water Sense. The water heater will have less work to do, since it will never see inlet water temps below your interior temp. The incoming water replacing the DHW being used is drawn through the floor first. More simplicity, less cost. You would have to have a LOT of DHW use combined with a peak heating time before you would overwhelm the burner and heat already in the plumbing and house. Energy Star's have a 67% or greater energy factor, which is probably about an 80% efficient burner. Tankless, tankless hybrid and boiler systems have trouble if they can't throttle down to the lowest demand level (say, a faucet trickling warm water, or a single 0.5gpm heating zone). Conventional tankless has an awful lot of head loss in it's coil. My Eternal water heater is a condensing "hybrid" with low head loss and a few gallons onboard storage but it still can't throttle lower than 26kbtu. It's 96% efficient unless short cycling or when warm loop water is returning. At 110-115F return temps, it does still condense some, but I imagine the efficiency is more like 85% then. The newer, smaller Eternal can throttle down to 14kbtu, but I'm not sure even that is low enough, and I would replace the plastic pressure sensor with a metal one before I would even consider an Eternal again. A condensing boiler won't condense much as you have it installed since it is circulating already warm water, but condensing and noncondensing boilers will still work fine. It will operate most of the time with an efficiency not much better than a conventional Energy Star tank style though. Of course, I'm advocating and switching to a solar/geothermal hybrid system to get heat for "free".
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"I‘d put my money on the sun and solar energy. What a source of power! I hope we don‘t have to wait until oil and coal run out before we tackle that." Thomas Edison, 1847 — 1931 Last edited by Mobile Master Tech; 03-01-16 at 03:08 PM.. Reason: Typo |
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#549 | |
Master EcoRenovator
Join Date: Mar 2014
Location: Florissant, Colorado
Posts: 599
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Heating requirements at high altitude in Colorado are MUCH different than Southern states. My Son's house is in Crested Butte Colorado at 8,888' altitude, climate zone 6, as is much of Alaska (read too damn cold). IBC 2009 states that the heating system has to be able to keep every room at 70* at design temperature (-20*F) It was designed & specified by a great architect who used REScheck to calculate the UA = 1,194 The Design Delta between 70* -> -20* = 90* The output of the boiler must be at least: 1,194 x 90 = 107,460 btus/hr I decided on a Burnham ESC6NI-TH (high altitude version) Sealed combustion via side wall. Efficiency=85.2%, DOE=130,000, IBR=113,000 A proven design cast iron boiler like this costs about 1/2 of a good ModCon boiler. But it is way more reliable, will probably last 30-40 years, & requires MUCH less maintenance. This is why plumbing/heating shops love ModCons, they weigh a lot less & there is way more profit $$ A large boiler needs a large buffer tank to prevent short cycling, especially if only 1 zone is calling for heat & it's 50* outside. Last edited by buffalobillpatrick; 02-28-16 at 11:48 AM.. |
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#550 | |
Master EcoRenovator
Join Date: Mar 2014
Location: Florissant, Colorado
Posts: 599
Thanks: 814
Thanked 59 Times in 55 Posts
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![]() MMT, your post #228 in this thread has lots of good info:
Quote:
Last edited by buffalobillpatrick; 02-28-16 at 01:17 PM.. |
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Tags |
diy, heat pump, hydronic, pex, radiant |
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