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Old 02-28-16, 01:03 PM   #551
buffalobillpatrick
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More info on Legionella:

MMT, Please note that I have removed many references that "bad mouth" Open or Combined systems.

I agree with you, that either type of system, closed or open can be very dangerous if the water is allowed to stagnate.

Here are some selected quotes from hydronic heating experts on this topic:

"The CDC estimates that upwards of 10,000 people die from community acquired Legionnaires each year. They also tag water heaters and potable hot water distribution systems as amplifiers."

"the aspiration of small sized water droplets into the lower 1/3 of the lungs that represents the pathway for Legionella bacteria.

Drinking legionella does not pose a known risk, although the same can't be said for many other water borne pathogens.

Showering is often thought to be the only distal site within the home, but faucet areators and flushing a water closet also emit micron-sized water droplets.

Amplification of Legionella becomes a concern with water temperatures below 133F. If you couple up the other favorable growth issues (stagnation, pH and biofilms), you've managed to create a perfect hydroponic bacteria growing amplifier. "

"First point: Non-reported cases. As I understand it, the CDC only addresses outbreaks of Legionella. Events where many people are affected... they are focused on epidemics, not isolated incidents that may occur in individual homes.

Second point: Misdiagnosed cases. Bacterial pneumonia kills a LOT of people in the U.S. every year. No-one knows how many of these cases may have been Legionella.

Third point: Healthy people aren't likely to get LD unless exposed to massive amounts of the bacteria. Our immune systems are generally able to handle it quite well. Grandma isn't so lucky, especially not if she smokes. Cancer suppressing drugs can also weaken the immune system. The Legionaires - old guys that smoked and happened to be near a cooling tower. Outbreaks in hospitals - weakened immune systems.

A healthy person CAN get it if the bacteria are present in numbers sufficient to overwhelm the immune system, as in cooling towers."

"reality is ....
I won't live long enough to see our code bodies enact this common sense solution that addresses both scalding and bacterial issues. Politics at the code enacting level is fierce and intense. One code official I spoke with likened it to turning a battleship in heavy seas using only a trolling motor.

Min tank temperature of 140 F (source). Distribution systems temp min of 133 F with constant circulation (distribution). All points of use with final step-down of temps via certified scald-guard devices (points of use)."

"Chlorine is ineffective against Legionella bacteria at concentrations found within potable water systems. If chlorine levels are raised to a point where it can begin to kill off the bacteria, the water becomes far too agressive for metal or plastic piping and combines with organic materials to form carcinogens.

Furthermore, as water is heated chlorine dissipates. That's one reason why we see more pitting in the hot water piping.

Pasteurization of hot water is quite effective for keeping the bacteria numbers suppressed if the water temp is held above 133 F with a contact time of at least 20 minutes.

So much for the storage tank or source of hot water. Let's call that part #1 of a 3-piece puzzle. Part #2 is the distribution system or maze of piping. Part #3 of the system are the points of use (faucets).

If we are to have bacterial safety within the potable hot water system, all three must be treated.

Here's how that could work. Elevate the storage tank's temperature to 140 F minimum.

Install a certified ASSE 1017 thermostatic mixing valve at the tank's outlet and set it for 133 F.

Install a bronze circulatory to move water through the distribution system 24/7.

Part #3 of the puzzle comes next but we've got to bring scalding safety into the picture due to the elevated temperatures (which we had anyway as the current Z21.10.1 regulations allow for water temps of up to 190 F from stacking in residential water heaters of 75 gallons or less). We'll need to add certified ASSE 1016 scald guard faucets or devices at points of use where human contact occurs.

106 F is the human threshold for pain. 120 F, the current mantra for so-called safe water temps - is not. Third degree burns are still a reality and thousands of people continue to be scalded annually. If the delivery temp is limited to 110 F, actual safety for bathers begins. That's why old folks homes are limited to 105 - 110 F. But that's also why most test positive for Legionella bacteria.

There are three types of certified ASSE 1016 valves: pressure balancing; thermostatic; and the best of the three - thermostatic combined with pressure balancing. Pressure balancing valves are blind to seasonal temperature fluctuations (incoming water service temps can vary by as much as 50 F between winter and summer - also, if the homeowner runs out of hot water, their first reaction is to turn up the tank's thermostat, which changes the PB faucet's upper limit - who's to know?).

Scald guard faucets are readily available and if the codes would change to this new "standard", plumbing inspectors would be required to verify proper setting was performed by the installer. Safe hot water systems, safe bather temperatures and reduced liability for the water heater manufacturers, the plumbers and others involved (such as the supply houses)."

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Old 03-01-16, 11:41 AM   #552
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Quote:
Originally Posted by buffalobillpatrick View Post
Gas hot water heaters loose convective heat up the stack constantly and are not nearly as efficient as advertised.

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)

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
BBP,

His weather forecast shouldn't show the temp in degrees, instead just the acronym "TDC!"

Of course, you must design for the demand of the building and climate. An awful lot of the population lives in a climate and house that could get by with 40kbtu because of the "buffer factor" and the fact that their homes don't spend very much time at the design temp, if only they will do the basics like low-e windows (or at least mitigating heat loss from their current ones), recommended insulation levels, and sealing air leaks using the interior wall surface as your infiltration barrier, especially behind baseboard trim and electrical boxes on exterior walls. Just sealing the boxes allowed the first room I inexpertly retrofitted with staple up hydronic stay at setpoint with a 20F night when previously it would lose 5F overnight, running nonstop.

Since that design temp is typically in the middle of the night when DHW use is low or nonexistent and many people like their house a little colder in the night, a slight deficit of available btu's won't drop the interior temp very much.

I'm mainly trying to point out there is more than one good way to get a good result, allowing more people to afford a warm floor system. A "good, better, best" mentality serves us here.

Good: Energy Star storage heater with open system. True, the flue losses are an issue. Energy Factor on standard models is typically 0.59 and worse in real conditions. The Energy Star's are at least 0.67EF, which includes the storage losses. Since those losses are nearly constant, using the water heater for more than one use brings the average efficiency close to the burner efficiency, around 80%. Probably 1/4 the component cost of a system with a good boiler, separate tank, exchangers, additional pumps, etc.

Good with caveats: a condensing tankless heater with open system. 92% or better efficiency, but won't condense as much when inlet temps are warm-more like 85% then. Head loss issues, "cold water sandwiches," etc.

Better: A condensing storage heater such as AO Smith's Vertex 100kbtu and open system. 95% or better efficiency under nearly all conditions, proven and reliable, standby losses under 600btu/hr.

Best: A stainless condensing storage heater such as Westinghouse's WGR050NG076 (76kbtu, $2,000 or so) and open system. Or, one of the Phoenix or Polaris models. Cupronickel heat exchangers, up to 199kbtu, 95% efficiency under nearly all conditions, might last a lifetime, 300btu/hr or less standby loss, still significantly cheaper than a separate boiler system.

Alternate best: systems similar to BBP's. Widely understood, more components and cost, complexity, standby losses, good for locales prohibiting open systems, avoids short cycling of a traditional burner system. There is a surprisingly large amount of surface area on a separate boiler, tank, hx's, pumps and all the plumbing between. Only the tank is likely to have 2" or more of insulation. Standby losses will be much higher than 600btu/hr.



Here's an interesting link from a few years ago about condensing heaters. And of course, getting the heat nearly free from something other than fossil fuels as I am planning is the king of "Best!"

BBP, thanks for the Legionella and "scald safe" info, especially the need for an easy way to step temps up then down. I will be installing scald safe fixtures any time I am changing/adding one. They should be code mandated.

I have personally run 150F water in my DHW system as a test. If you are quick of reflex, you can get your hand out of harm's way in a blink, but it will hurt. If you aren't or your senses are impaired, you will be scalded. It's awfully hard to get your whole body out of a shower spray in a hurry, no matter who you are.....
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Old 03-01-16, 01:20 PM   #553
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MMT,

Even though Outside Design Temperature is reached very seldom, we who must obey the IBC, have to design systems for that temp.

My house has Propane for heat, at 8500' altitude, ModCons don't condense as much up here, and when it gets cold outside the LP isn't cooperative.

Boiler manufactures usually state heat output at IBR & DOE
IBR is lower by about 15% from DOE, IBR assumes boiler room heat is lost (not inside heated space) DOE is higher as it assumes that the boiler room is inside the heated space & isn't lost.

All 3 ModCons that I have installed (1 is neighbor buddy's) have had intermittent ignition problems. I have and use an expensive combustion analyzer to set mixture.

My 1st ModCon was a Heat Transfer Products Voyager, it had a tank so it was self-buffering, they also make the Phoenix & Polaris models.

I lived with that noisy blower, igniter eating, fail to fire, POS for 10 years. HTP NEVER AGAIN

2nd modcon that I still have in my house is better (Triangle Tube Solo 60) but still has issues.

I have 3 zones in my house & the TT couldn't modulate low enough at 50* outside, so it would short-cycle.

When it did it had problems with E02 Errors (fail to ignite) and if it would ignite it would make a loud foghorn noise. Many owners have reported these problems, worse at high altitude & on LP.

TT support is of no help as they know that they have these design issues & don't help DIY home owners.

I solved these problems by configuring system as I described above, so it never short-cycles, but it don't modulate as it is in DHW mode, & condenses very little at start of run.

From now on, it's Cast Iron boilers for me, vs ModCons , CI cost much less, are more reliable, last 3-4X longer, with much less maintenance $$

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Old 03-01-16, 02:18 PM   #554
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My Eternal also "foghorns" sometimes, but at it's lowest modulation while on, around 26kbtu. Spooky and comical low hoot sound-almost as if the flamefront has resonant pulsation. Ignition is sometimes a problem so I get an occasional failure to ignite code if it is shortcycling frequently while the inlet temp is warm, it's fine if igniting with cooler inlet temps. Seems like warm inlet temps show less of a temp change for it to recognize the burner has lit. If it ever shut off due to a code while I was away for a while in subfreezing temps....oh my.

I imagine the condensing storage heaters I describe would be more reliable, as they don't modulate or don't modulate very far (say a 3:1 modulation ratio, instead of 5.5:1 like my Eternal) and are meant to ignite while already seeing warm temps because the tank is already warm. I likely wouldn't choose an Eternal again and BBP's comments would make me yearn for field knowledge if I were choosing a new heater. I know many utterly reliable tankless water heaters with high modulation exist. My Grandparents had at 20+ year old Bosch that never had a problem.

For those considering gas for their heat source, anyone want to chime in with practical experience on condensing water heaters similar to BBP's reports on boilers?
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Old 03-01-16, 02:36 PM   #555
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MMT, very interesting that U see the same issues on totally different heat sources!

I have my TT boiler wired with a line cord, plugged into a simple cheap mechanical timer, every 3 hrs. it turns boiler off for 15 min. This insures a Power on Reset to boiler that resets any errors & it always fires off as it has cooled a bit.

It may, once every few Winter months, sit with the boiler locked out, I haven't seen this yet with boiler room door open next to kitchen table where I eat, but if it did happen, the large buffer tank will still be sending heat to floors.

Both my house & my Son's new house have suspended 1/2" pex below subfloors.

This requires hot to very hot water temps. depending on outside temp. & passive solar gain.

Not a good match with any low temperature heating method: ModCons, solar, Heat Pumps, etc.

But still 85% efficiency isn't too bad, considering high reliability. Boiler rooms are within heating envelope. Sealed combustion helps.

Most of my house has the 1/2" pex 8" on centers, 4" OC near large window area. (zone 5)

My house is VERY well insulated, ICF basement, R35 SIP upstairs walls, R45 & R70 ceilings, all windows are triple pane, low-e, Argon filled & most have an outer 4th layer of glass 1/4" tempered glass storm windows (high winds)

Infiltration is my major heat loss when wind is blowing hard (sometimes gusts > 100mph) but this high wind never happens when it's below 10*F outside.

When it's -10*F outside & no wind, IR gun measures floors @ 75*F so about 10btu/ft2/hr

As my Son's house has way too much glass (views) I did 4" OC + all possible interior walls + a large upstairs cat-walk. Upstairs bedroom & bathroom floors also add heat to Great Room where most of the South facing windows are.

Still his is at the very upper limit of mostly under subfloor heating, 35btu/ft2/hr

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Old 03-01-16, 03:44 PM   #556
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BBP, yes-weird we have some of the same heatsource problems.

Do you have any heat transfer plates on your pex? HUUUUUGE difference compared to staple up/suspended. I call straight staple up worthless and pex with transfer plates pretty good. My system can keep up when water temps are 125F.

Also, since my AC blower runs slowly any time the main zone is on, I added a water/air HX after it using the return water from the zone to prevent cold drafts from the air movement. It doesn't add a lot of BTUs since it sees 100-110F return water and then only after the water has made a complete lap through that zone. This way the floors always warm first, the air doesn't blow cold for long, my air is always filtered, and there is a bit more output if the zone has a long duty cycle.

Yep on sealed combustion-you're creating a cold draft and possibly negative pressure/CO poisoning if you sealed up the house tight without it.

Yep on equipment within envelope. My winter gas usage with 2 scorched air furnaces, one of them in the attic, was 300-350 therms/mo, heating 2 stories. Now it is 150-200 therms/mo even though I am heating 3 stories plus the garage!

You certainly insulated the h**l out of it! I have R13 walls, R30 ceilings(for now), air filled double pane aluminum frame windows with no low-e (for now) and zero slab/basement wall insulation (for now).

Thanks for the timer idea! Will use it while away until I get the new heat source done. Won't run it regularly, as Murphy says it would probably cycle off while I was taking a shower....
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Old 03-01-16, 05:23 PM   #557
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MMT,

I feel that insulation is cheep $ that saves $$$ heating bills over time.

No heat transfer plates.
Don't want noise, expense of plates & instilation time.

Cast Iron boilers love to run hot, most need the return water above 140*F to prevent condensation which leads to rust & and an early grave, Son's Burnham ESC6 it's 120*F

Heat transfer Plates are not needed with high water temps. & suspended 1/2" pex 4" OC.

There is a convective plenum under the subfloor of about 4" with the pex in the middle, R30 below.

This is now a method recommended by Uponor (Wirsbo) largerst pex producer in world.

I was actually offered an engineering job interview (free flight meals & lodging trip) with them in Minneapolis St Paul 10 yrs ago, after I retired from IBM. I asked if I would have to live there in winter, manager said yes so I said no thanks.

In my Son's house @ -20*F outside, the hot water going through the pex is 165*F on average, the convective plenum air reaches about 145*F on average,

With a 30:1.5 ratio, about 95% of the heat fights it's way up through the R1.5 (3/4" subfloor + 3/4" hardwood flooring),

With a room AUST (room average unheated surface temperature) = 70*F
the hardwood surface reaches 87-88*F,

& releases 35btu/ft2/hr through radiation + convection.

I actually tried to talk my Son into doing it like we did my neighbors house.
It has 2x4 sleepers on 12" centers above subfloor with 1.5" x 8.5" of concrete (no rocks) around each 1/2" pex run, Hickory flooring nailed to sleepers.

We could have run cooler water temps. with more margin for extra heat if it gets down to -30*F outside

He said NO, as my house works so well.

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Old 03-01-16, 07:02 PM   #558
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I understand about the noise, but I don't find mine very obtrusive. I think silicone plumbers grease would lick that problem. If I do or redo any plates with it, I will post.

I found that 2-4ft plates sourced from a vendor I found on ebay were hardly more expensive on a per foot basis than the special staples for PEX though, assuming around 60% coverage with plates.

165F. Yup, great for cast boilers. Stainless, bronze or cupronickel equipment gets around the need for high temps. I wanted to be able to combine DHW in an open system for simplicity and to use lower exergy sources.

You mentioned using heat exchanger and two pumps to heat or draw from the tank, your controller makes your boiler see 25F delta, and that the hydronic zones see water from the boiler before going to the buffer tank. How do you regulate DHW temp?
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Old 03-01-16, 09:16 PM   #559
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MMT,
Honeywell (lead-free) DHW tank typical output Temperature Modulating Valve (TMV) set at 134*F with scald protection fixtures.

I don't use pex staples, I use Talon 1 nail clips on 36" centers.
When pex gets hot it droops down between the clips a couple inches.
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Old 03-02-16, 05:59 AM   #560
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Originally Posted by Mobile Master Tech View Post

Also, since my AC blower runs slowly any time the main zone is on, I added a water/air HX after it using the return water from the zone to prevent cold drafts from the air movement. It doesn't add a lot of BTUs since it sees 100-110F return water and then only after the water has made a complete lap through that zone. This way the floors always warm first, the air doesn't blow cold for long, my air is always filtered, and there is a bit more output if the zone has a long duty cycle.
This is a well thought out and intriguing concept to provide a small BTU source to low volume rate circulating air. One of my clients has all radiant flooring and also uses the low blower speed to circulate air. His wife complains about the "cold air" drafts. This would fix it.

MMT, thanks!

Steve

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