Radiant Floor Heating Question (boiler vs water heater)

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In a hydronic floor heat system, what is the best way to heat the water in the pex tubing?
The initial study of the building design recommends a 16800 BTU 85% efficient boiler ($2000 US). I am hearing about possibly a more efficient way using two 90% efficient 60 gal water heaters.
Can anyone make some suggestions to me? I live in Northern Colorado.
Project description:
42 x 80 Pole style building, single level (metal siding + metal roof), 12 ft side walls
FLOOR: 1 1/2" "Blue board" foam insulation on top of pea gravel - 5" concrete slab w/ pex tubing on 12" centers - 3 zones (3750' of 1/2" tubing in approx 250' runs
INSULATION: Walls- R-26 -- Ceiling- R-38
Thanks!
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It is possible to make hot water heaters work with radiant flooring but in most cases the duty cycle is far greater than the hot water heater was ever intended for. You can figure what that does to the life expectancy.
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Interesting floor construction.
In the UK for a non structural floor we would typically build he following top down...
2.5" concrete with heating pipe in 3" foam insulation Damp proof membrane (plastic sheet) Sand "blind" (to stop plastic sheet being punctured) 6" Compacted stone chips (called hardcore in the UK)
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In the us, slab floor construction is typically under the entire house so it is structural.
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5" doesn't sound very thick for a house. Is that timber frame?. Over here a garage or shed base is typically 4".
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Is this a troll, 16800 Btu has to be a typo, you do mean 168000 I hope I hope. You want efficency and you discuss 85% efficent boilers when up to 98% are made !! What boiler are you looking at.
Tell us all who makes a 90% efficent tank water heater... Answer nobody makes a 90% efficent fossil fuel water tank. Learn about EF- Energy Factor ratings, and show us the tank. And a tank isnt designed for long life but it truely aint efficent.
1.5" Blueboard is R 7.5,, 1.5" foil faced Polyisocyanurate is R 10.5 with an added radiant barrier, which is still not optimal R value for concrete radiant heat.
Walls R 26, Ceiling R38, it sounds off. What is construction and type of insulation You have lots a learnin to do wilma fingerdo, cause someones lyin to you.
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ransley wrote:

You seem pretty sure of yourself ... for being wrong. http://www.americanwaterheater.com/products/pdf/lpg100.pdf

More than one person is lying to Wilma.
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I see your as dumb as her if you dont know facts. Gees, what ignorant folks believe.
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ransley wrote:

What part of the Polaris efficiency specification did you not understand?
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Polaris, Ao Smith, condensing, are not 94-96% efficent. www.energystar.gov publishes efficency ratings for all tanks made. Efficency of a tank is rated as EF or Energy Factor, the number rating of 85 means 85 cents of every dollar you spend heats the water. I have a $2000.00 Ao Smith Cyclone condensing tank of thermal and burner efficency of 93% but its EF rating is about 83, and all boilers are at least 82% efficent today. 95 or so % of all Tank water heaters sold today in the US even the ones labeled High Efficency are in fact only 55-65 EF. The government still hasnt set a standard yet, its a scam to the uneducated. The lowest gas tankless is 83 EF and a condensing Takagi is 93EF. that is the highest efficency water heater I know of made today, so what you see is most always no better than 55-65 EF or 45-55 cents of every dollar you spend heating water goes up the chimney !
Boilers can be much more efficent, the AFUE ratings reflect use, like EF rating does on tanks. There are many 93-96% efficent Ng condensing boilers out, that are the best for Radiant tube sine Radiant uses realtivly low water temps and Condensing boilers drop dramaticly in efficency at over 140F, there is one I know of from canada that is AFUE 98% efficent, and the best tank is maybe 83 EF that I know of.
EF is not a rating Tank manufacturers publish often, or like to talk about, because it highlights tank limitations in true efficency
OP doesnt discuss Condensing units, but is in fact looking at 83% boilers, when 96 is easily avalaible, and most likely is looking at Two, 55-65 EF tank, now thats a waste of money. First 2 tanks would be less efficent than one and she doesnt need 2, but tank are not designed to last as home heaters.
The last I read Energy Star is still working on a tank specification.
Op is best with a 96-98% AFUE condensing boiler, not a 55-65 % efficent water tank made for showers. Find the EF rating on Polaris and post it, Ao Smiths site wont post all EF numbers on their super expensive Condensing units, but I own one.
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wrote:

I guess they aren't mandatory in the US? In the UK all new installations or replacement boilers (tank heaters) have to be condensing. Been like that since 2005.
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I did not say Energy Factor, wait one minute, I am the ONLY person to talk EF
Sure my heat guy said condensing is an issue, his stupidity was the issue.
Show me one study the states condensing wont pay off, I mean wake up, at a minimum you get 10% savings.
How many folks here have tankless water heaters in the US, Naw you guys are all to smart for those. I have one in my house and in summer my gas bill went down from 45$ to 9 month, mine was a 450$ Bosch, I get a 4 yr payback and its maybe 6yrs old now
The only way a 55-65% efficent tank makes sense is if you are dumb, and you cant drink or shower from water for heating so if OP has 2 tanks to heat the OP needs a 3rd unefficent junk to heat water.
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You mean you went with an 82% unit, right. My installer tried to talk me out of condensing, in fact 90% still do. They key is to get what works. Condensing furnaces have been a non problem issue for at least 10-15 years, condensing boilers at least 6 years, condensing Oil boilers are new, but furnaces have been out a long time, its up to you to learn facts. Bottom line condensing have a minimum savings of 12%, no honest study that reflects true energy price increases and future trends will show non condensing best.
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No, I went with a Lennox Elite that is ~92% AFUE rather than the top of the line ~95% unit. Both are condensing designs. The difference is that mine has a single speed blower motor and, I believe, a two-stage gas valve. I haven't checked the specs lately, but at this time (8 years ago) the top of the line Lennox had a variable speed blower motor and a variable flow gas valve. Word was that both were causing problems at the time (again, 2000 era).
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Yes the GE VSDC motor was an issue and still might be, even with a redesign by moving the electronic to keep them cooler, I have a Lennox like yours at a location its a good unit and efficent. If you get VSDC the 10 yr warranty is necessary.
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ransley wrote:

I figured at a lost of only 2% AFUE, it was worth it to avoid the problems and stay with the slightly less efficient, yet apparently vastly more reliable model.
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I was looking at vsdc when I put mine in, luckily I didnt do it either, but you say yours is 2 stage gas, so your blower is 2 speed, and you must have the 2 stage stat, right, the blower must go go high on high fire or the furnace exchanger overheats and its life is being shortened alot. Listen for the blower kicking on high , Mine is set for maybe 2-3f for when high fire is called for, you should get a probe thermometer like a meat thermometer and insert it at the top of the furnace to check the temp output, there is a specified range and exceeding it really shortens the life of the aluminum heat exchanger, I found my tech never checked mine and I was over the limit so I lowered gas input. I think I have the same model as you and have a 2 stage thermostat. One thing that will fail is the heat exchanger its aluminum or steel, not Stainless steel and I have heard they are failing, keeping temp in the low recommended range will increase its life alot.
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Voyager wrote:

Thanks for the reply, I mean 168000 btu. Its spray foam and cellulose insulation. "Pole Barn" type construction.
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Voyager wrote:

How much does that puppy sell for?
--
Art


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