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Instant water heaters being used for heating

well, then you are not continually flushing your pipes in the summer when the heat isn't running by running the domestic through them.. I guess you're relying on "pump exercising" to do the job?
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Comments

  • Christopher Haley
    Christopher Haley Member Posts: 14
    Rinnai instant water heater used for heating

    Greetings
    I was wondering if anyone has had any experience used an instant water heater for DHW as well as heating. I imagined it would be possible by creating a loop between the hot and cold and using a stainless steel circulator pumping through a stainless steel heat exchanger. On a call for heat this circulator and one on the other side of the heat exchanger would come on. Water would move through the water heater, through the exchanger and pump and then start over. On a call for DHW, the SS circ would stop, and start again when the call for DHW ended. Any suggestions would be great.
  • Al Letellier_9
    Al Letellier_9 Member Posts: 929
    instant water heaters

    Not sure of your layout based on your description but most plumbing codes do not allow mixing heating water with domestic and Rinnai tells us here that if you use on of their continuums for heating you must use the commercial unit or you will void any warranties.
  • Perry_3
    Perry_3 Member Posts: 498
    Perhaps... But usually not

    I am a homeowner and not a heating professional. On the other hand I have some experience...

    Perhaps a "hot water heater" could be used as a stand alone (not for DHW) where there was only a small heating load - say a lot farther south than I live. You would have a separate unit for DHW.

    While very small boilers can be purchased in Europe (10,000 BTU/Hr) there is nothing like this in the US. In a case with a heat load like this - perhaps your idea has merit.

    Keep in mind that if you did this - these would be not be expected to necesarily last a long time. But it may be a lot cheaper than installing even the smallest boiler out there - and could be rigged with quick disconnect type fittings (couplings) so that it could be easily replaced.

    This could not be done if a code stamped home heating boiler was required.

    However, for larger heat loads - I think you would be best off with a regular boiler.

    Perry
  • Ray Darby
    Ray Darby Member Posts: 20
    Instantaneous Wtr Htr Space Heating

    I've had experience with this subject going back 20 years. In a nutshell, to engineer such a system you need to review the heater manufacturers technical specs. In particular, the pressure drop through the unit at the design input/output temperatures (with most units its pretty high) and the output capacity under those conditions. For example, the Rheem folks don't seem to know (much less have) a flow vs head curve! The Noritz folks (nice unit!) have the curve all right - but upon close inspection it seems the (194k input) unit won't put out more than 55,000 Btuh assuming a 20F delta-t; and that'll take two Taco 0011 pumps in series to get the (approx) 55' of head to pull it off! Kind of excessive pump-wise. I'm checking out the Bradford White Everhot (Rinnai) for lower pressure drop.....

    Years ago I worked with Aquavac (now defunct) on their instantaneous and learned its possible to decrease the pressure drop through a modulating instantaneous. I'm hoping to "resurrect the dream" with one of today's units.

    Anyone with more research tidbits to add to this is encouraged to do so. I'll backfill whatever new info I get here on The Wall (isn't this place great!?!?)
  • EJ hoffman
    EJ hoffman Member Posts: 126
    bradford and noritz

    I use bradford mostly, it is a rinnai with a built in remote control. Noritz is really nice but getting all the parts stocked in my area is difficult. I do constant circ with injection mixing and most of the time all you need is a 006 you have to keep the flow rate just right to keep it from cycling minimum 3/4 gpm on most units. Also i only go with a 15 delta t Most design temps in 108-120 this is only a 2 pump system. Constant circ on the floor loop with the injector pulling off the water heater and getting it to fire. the injector allows you to eliminate the need to keep up the 2gpm flow and with the 3/4 gpm flow the heater usually runs on the lowest fire most often 10000 btu for most heaters I use a tekmar 356 to controll the injector
  • Plumdog_2
    Plumdog_2 Member Posts: 873
    Internet sales

    Guy I know bought a kit off the internet and installed it himself. Takagi water heater, heat exchanger, huge pumps, manifolds, the whole enchilada. He now lives in a cold house with monster gas bills. Wishes he would have got a real boiler.
  • Ray Darby
    Ray Darby Member Posts: 20


    Plumdogs point is well taken. Its important to appreciate the instantaneous heaters are designed to heat cold water, not recirc hot water like a boiler does.

    The best instant Ive found is the Rinnai (Bradford White uses it & calls it an Everhot).

    If you have a very small heating load (say 30kBtuh or less)the lowest-cost, simplest, most reliable heater is a Bradford White tank heater (energy factor in the 0.62-0.63 range; space heat eff approx 85%).

    Between 30 and 60 kBtuh the Rinnai 2532 appears to be blessed by the manufacturer but the warranty drops from 10 to 3 yrs (added expansion/contraction on HX due to cycling)...their tech support says its the least worrisome in a (low temp)radiant floor application (120F +/-). It requires a decent sized pump (such as Taco 0013) to get 6-7 gpm (& 60-70 kBtuh).

    The Takagi, Noritz, Rheem, etc units would need two Taco 0013 pumps in series and you still wouldn't quite achieve the Rinnai's flow rate with only one pump! Seems the only sensible application for these instants would be very small heating loads, in which case I prefer the reliability, simplicity and low-cost of the tank heater. I've used Bradford Whites for dozens of simple combined hydronic radiant systems over the last 20 years (my own home included) and, other than the occasional thermocouple, they last around 15+ years (a little longer, on average, than the tank heater used for DHW alone - a fact established by the industry about a decade ago).

    WARNING: Having worked extensively with do-it-yourselfer and owner-builder types over the years I am very concerned about them doing these installations safely/properly on there own. Fortunately there are companies that are great at helping these folks - one such company I like very much is here - www.radiantec.com
  • Ragu_5
    Ragu_5 Member Posts: 315
    My Take....

    I particularly like the replies of Plumdog and Ray Darby; this is bad territory to enter. Some Internet "Radiant Specialists" will promote these uses, but the longest running one I have seen is 8 years (an Aquastar).

    There is no free lunch, although there are lunches that are fairly cheap, but they make you ill. I like boilers.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • jp_2
    jp_2 Member Posts: 1,935
    chris?

    first off we should all be asking chris how large is the heatload?

    then the good reasons why not to use such a unit, such as relative poor efficience.
  • Bill de Jong
    Bill de Jong Member Posts: 15


    One of the writer's is quite right about the requirement by Rinnai to use their commercial unit if space heating is involved. Most of the Tankless Water Heater manufacturers have suggested schematics on their sites for combo space heating/domestic water heating. You will find with most of the mid size 180MBH units that you will need to create a "Heating Loop" of 1" Pipe and circulate that loop with a High-Head Bronze 1/6Hp Pump like a Grundfos UP26-99BF. However, I would be hesitant about using one of these units for anything but small heat loads. The designed purpose for these units is domestic water heating, and you are going outside the original design use, as well as adding extra cycles to the normal anticipated use. The jury is still out in North America as to the lifespan of these types of units.

    Good Luck!
  • We've often

    used a Noritz for combination service. We used to build our own boiler boards, but we are starting to use the Taco X-Pump Block where single wall heat exchangers (HX) are allowed.

    The HX in the Noritz is not very restrictive (1.58 gpm @ 10' head) and
  • We've often

    used a Noritz for combination service. We used to build our own boiler boards, but we are starting to use the Taco X-Pump Block where single wall heat exchangers (HX) are allowed.

    The HX in the Noritz is not very restrictive (1.58 gpm @ 10' head) and the Taco 008 circulator in the X-Pump Block has no problem.

    See photo below.
  • Jeff Lawrence_25
    Jeff Lawrence_25 Member Posts: 746
    You gotta be kidding?

    That company? They've done more harm than good for the radiant industry, in my opinion.

    An 'approved' open system? Not approved in my book.
  • EJ hoffman
    EJ hoffman Member Posts: 126
    Is the block a double wall for Cali?



  • I would further refine your estimate; at 30kBTUs/hr, if you have a low temp system AND are in a real heating climate, a mod/con is probably still your best choice.

    The instantaneous water heaters.. There is one and only one thing they do better than a tank heater in radiant. That is, rapid recovery for mass systems. Which should not be the driving factor behind heat source selection in any system. As you note, a tank water heater will run at a decent, if not impressive efficiency (I personally wouldn't call it more than 80%, but that's me). The instananeous will, on the other hand, rarely achieve its rated 83% in a heating application.

    The mod/con, on a low temp system... maybe, with a cheap buffer... would achieve low to high 90's. run a degree day analysis and you'll find in most climates with real winters, that will give you a reasonable payback (as well as a better operational characteristic with built in outdoor reset) in all but the smallest of small systems. Or in mild climates.

    I'm a little stunned at your plug as well.
  • Ray Darby
    Ray Darby Member Posts: 20


    Regarding the Taco pump able to pass 1.58 gpm at 10' head - while that's a reasonable head for, say, a recirc loop we're talking space heating - with a 20F deltaT 1.58 gpm will deliver just 15,800 Btuh. As one of the other posts noted, the instant htr manuf's show schematics where the units are used for space heat or to heat a sidearm tank. Before anyone tries doing either one they need to investige the design requirements - other than what I've already posted earlier, I'd like to comment on the sidearm (storage tank) approach - briefly, and I'll use the (very nice) DHW heater from Noritz as an example - it'll only provide about 50 kBtuh of recovery (a small fraction of its input rating) in heating a sidearm tank and that's using two gigantamundo pumps in series! If heating a lot of hot water efficiently is what the job calls (ie, a restaurant, etc) PLEASE use a boiler!! As another post pointed out, the efficiency of an instant at a small delta T, unlike a boiler, is lower than nameplace.

    NOTE: I worked with industry and 3rd party test labs in the early 90's creating algorithms for the California code calcs req'd for combination (space & DHW) systems - a tank type heater in a combo system actually has a slightly higher recovery efficiency when it's used for space heating (in addition to DHW) - and it'll last a little longer too. Yeah it suprised me too! So did finding out some tank heaters maintained at 180F (instead of 120-140F) will last a little longer (according to American Appliance their res and commercial units use the same tank body - apparently stuff that lives in 120-140F water and eats tanks can't survive at 180F).

    On Radiantec I can't say I agree with everything they suggest - for example, the Polaris (despite redesign several years back) still burns out ignitors about every 2-3 years - fortunately we only have a couple installs using them and they're cheap (about $25 material and 10 minutes labor) to fix. What I can say is I've dealt with Radiantec since the early 80's and they've been very helpful to a large number of customers I steered their way. While they're not everything for everyone (who is?) their simple approach (see my earlier post for definition) using an open-loop combination system (with a mid-eff water heater) often has a lower LCC than a boiler-based system. A proper LCC needs to take into account EVERYTHING (initial cost, gas use, electricity use, energy escal. rate, maint/repair/replacement costs and frequencies, etc).

    Open systems aren't (generally speaking) illegal or improper (although its not hard to make them so!) but the customer needs to realize that, if there's a leak, it's gonna keep-on-a leaking until it's fixed! That beautiful wood floor won't have just a puddle, it'll be a lake! With a closed system, assuming the PR valve's upsteam shutoff valve is off after fill/purge, only a few gallons of water at most is likely to end up on the floor if there is a leak.

    Boiler-based systems were not the subject of this post - if they were, I'd be ranting and raving on the many blessings of boiler-based systems. Fortunately I think 99.9% of the people frequenting this forum appreciate that, in most cases, a boiler is their best choice. I was merely making the point that there's a niche for instantaneous and mid-eff tank heaters while touching on their limitations.

    Lastly I have to say I treasure this forum and ALL opinions expressed. This is probably the best place on the web to share and grow from our combined experiences. Thanks to all of you for taking time out of your busy day to help the rest of us evolve!


  • I think you'll find some pretty strong disagreement around here about open systems not being improper. it's not always a boiler world, but these days, with energy the way it's been and the way it'll go, and with mod/cons here to stay.. it usually is. When it's not, a dedicated tank water heater, or tank and HE, is a far better idea than an open system. Everything else aside, constant introduction of fresh water into a heating system is bad for performance and longevity in many cases.
  • ALH_4
    ALH_4 Member Posts: 1,790
    drinking your radiant floor

    Bacteria are a bigger concern than leaks or function of the heating system. Radiant floor temps are ideal for Legionella to thrive.
  • Ray Darby
    Ray Darby Member Posts: 20


    Andrews point - Drinking Your Hot Water - is very important to consider, so I'm very glad he brought it up.

    I've heard about Legionella concerns like this for the last 30 yrs and have been told, when attempting to find a record of it in an open radiant loop (or other plumbing/piping system) that no such records exist; it seems to be limited to cooling towers and other (exposed to air) type applications. Nonetheless, I'm VERY interested in ANY documented case(s) in a hydronic application.

    Because of this concern alone, open-loop radiant circuits should have fresh water moving through whenever DHW is used. This is accomplished by having the incoming cold water circ through the floor before entering the water heater. In this configuration it's really no different than a hot and cold water distribution system in terms of the freshness of the water.

    What I've wondered about, however, are manufacturers providing a combo tank heater and a fan coil - no water moves through the fan coil during non-heating season. It would seem like this (stagnant) condition would be more of a concern, but, again, the manuf's I've spoken with (ie First Company, Apollo) have told me Legionella isn't a concern in such systems.

    Sounds like this may be a ripe subject for a new topic post! Anyone know of any Legionella in (water-filled) plumbing systems, combo systems or otherwise? If you have a source please post it.

    And, again, it should be emphasized (overemphasized perhaps) that open systems have their advantages and disadvantages(some of which have been discussed in these posts). It is my experience that they're an elegantly simple and affordable solution for energy-efficient homes with a not-so-big demand.

    Is a modulating condensing boiler always the best choice? I don't think so. Why? The analogy I give is to look at two extremes -

    1) I have a customer with a small home in the hills of Mexico with very little DHW and even less space heating load (couple days a year they need space heat). Will a mod-con boiler-based system be their best choice or would a simple combo system be more cost-effective? Answer - the mod-con has a much higher LCC in this case - a combo system (or wood heat with seperate tankless DHW, etc) option is the better choice.

    2) I have a customer in Lake Tahoe California building a medium sized home for a family of three. Which system now has the lower LCC? Answer - the mod-con.

    By illustrating the extremes, you can easily imagine there are a lot of cases in between. This is where the detailed LCC calc becomes helpful. If it's a wash I think I'd choose the higher eff mod-con system even though the maint/replace costs will be higher over time. The reason I would choose the higher eff mod-con is because I (personally, professionally) believe the 5% annual fuel inflation we've seen the last 30yrs is too conservative to assume for the next 30yrs - but I continue to use that assumption because to do otherwise is impossible to quantify for any professional (God only knows and he won't tell!) - plus I don't want to sound like a crazed doom and gloomer type! Sensitivity analysis, looking at different rates of fuel inflation, seems to be the most professional approach - then the customer can choose to believe whatever they want and choose their solution accordingly.
  • EJ hoffman
    EJ hoffman Member Posts: 126
    Delta T,s

    Delta T i think is being misunderstood In the systems I design the delta t between the radiant floor supply and radiant return is 10-15 degrees the delta t between the injector line and the radiant floor is 40-50 degrees with a 1/2 line at 1.5 gpm 30,000-40,000 btu/h this fits perfect for the areas we heat.

    Don't let water go stagnate. better recirc your cold water and use every fixture every day or so.
  • EJ hoffman
    EJ hoffman Member Posts: 126
    Ray I really like your post

    You have a great post. I like your thought process.
  • Ray Darby
    Ray Darby Member Posts: 20


    Nothing seems dumber than replying to my own post, but here goes (blush).

    I must admit I haven't looked at the Legionella issue for FAR too long - thanks again to Andrew for bringing it up!

    Check this out:
    http://en.wikipedia.org/wiki/Legionella

    Sorry - gotta leave - I'm off to crank up some aquastats really, really high!


  • Ray, no one is saying a mod con is the only choice. Water heaters have their place on small loads.

    What we are saying, is that when using a water heater, it should be dedicated or should use a heat exchanger.... period. This is not a dramatic elevation of cost. It is however a very prudent move for the safety of the inhabitants, the future flexibility of the system, and the longevity of the system.

    Also, running cold water through the mile of pipe you have in your floors in the summer with no regard for condensation is a recipe for mold growth, yes?

    Seems like an awful lot of chances to take on a client's home that you are not familiar enough with to say it can be done safely, for a very small benefit. I respect your thought process and you are obviously intelligent, but as far as I'm concerned, that's a poor design decision. One I used to make for myself for long time I might add, but do no longer.

    It's about more than LCC. It's about making sure the system performs well over time, and about safeguarding the home and occupants as well.
  • PJO_5
    PJO_5 Member Posts: 199
    How about a Radiantec System Homeowner's Opinion?

    Ray,

    I'd like to hear from a knowledgeable homeowner who has a Radiantec system as you describe...then I will post my own experience.

    Fair enough?

    Take Care, PJO
  • Home Depot Employee
    Home Depot Employee Member Posts: 329
    Legionaires from Plumbing?

    You betcha!
    Read below!
  • Home Depot Employee
    Home Depot Employee Member Posts: 329


    ROCHESTER, N.Y.

    Rochester's largest hospital is dealing with its third case of a patient with Legionnaires' disease.

    The case was announced yesterday -- two days after another patient died, with the disease partly to blame.

    The bacteria that causes the pneumonia like illness was found in Strong Memorial Hospital's water supply on February 13th.

    About 500 patients have been on bottled water since then as the hospital cleans the system.

    The disease kills about 10 percent of people hospitalized with it, but people with weakened immune systems are two or three times more likely to die. That's according to the Centers for Disease Control.

    Two cancer patients have Legionnaires'. One is in guarded condition, and the other is satisfactory.

    A third patient with hepatitis died Sunday.

    Legionnaires' infects fewer than 100 people in New York each year.

    This was found in the drinking water system.

    Now imagine standing in a shower with tepid water misting you that is heated with a combi unit that is shared with a heating system with out a isolating heat exchanger??

    NOW THATS THE MAKING OF A LEGIONAIRES BREATHING CHAMBER
  • Ray Darby
    Ray Darby Member Posts: 20


    I appreciate everyone's comments. I'll address both Rob and Patricks questions in this post -

    Patrick - I've lived in the same home for 25 yrs and for the past 20 yr I've used the open loop water heater system (a Radiantec-style design I designed/installed myself). [note - Radiantec didn't invent this system - there are quite a few that came before and after)

    My system doesn't have any problems (all I've replaced is a pump and a wtr htr thermocouple)and it works extremely well. I've got dozens just like it with happy customers (thank God, as most of my relatives have one). Please post your own experience(s) with this system config as I'm interested in what might have gone wrong.

    Rob - No mold growth. Condensation isn't a problem in summer and, if you think about it, if it were, wouldn't all my incoming cold water pipes be dripping with water and mold growth too? Keep in mind the floor surface is not as cold as the incoming water temp and, if it were, I still wouldn't have condensation or mold. Metal frame windows and toilet tanks in homes is where I typically see condensation, but that's in winter. Chilled water cooling of slabs is where the problem you mention typically comes up (or very cold wtr pipe in very humid climate).

    In terms of cost, adding a heat exchanger, secondary loop pump, flow meters and thermostats, PRV, fill valve, controls, etc is not a small added cost - neither is oxy-diffusion barrier PEX. Of course non-ferros components are more expensive, but component costs overall all far less. My potable-PEX tubing is the same stuff we use in DHW, all components are non-ferros, etc. How would all those extra components be a benefit in my case? I honestly haven't experienced any problems with this system config - at least not yet - but I'm always willing to be educated!

    I use a lot less electricity by using just one pump too, which is important because I'm striving for a Zero Net Energy Home (solar PV and hydropower render by elec bill close to zero every year, despite driving an electric Ford Ranger PU as my primary mode of transportation - I put about 15k miles/yr on it). Also, my tank heater is preheated by an active solar system with a tank built for the life of the home (polypropylene liner, 3" polyiso insul); turns out this was more cost effective than a higher efficiency heater in my case.
  • Ray Darby
    Ray Darby Member Posts: 20


    It's extremely serious all right!!

    After doing some research I found MANY similar stories, mostly in institutional settings such as your example. The solution typically offered is to set the water heater at 140F (or higher) and use an anti-scald valve.

    If there's any comforting news in all this its this (from pg 12 of Government report, citation follows):

    What does real-world experience tell us?
    While it is recognized that legionnaires’ disease is under-reported, experience in the United States is encouraging. For over a decade, local laws and nation-wide industry practice in the US have required that water heaters be installed with the thermostat set at 49°C in order to prevent scalds. Yet the Centers for Disease Control has not reported a significant increase in cases of legionnaires’ disease, a reportable condition, during this period. The state of Washington has been practising reduced thermostat settings by state law since 1985, and the rate of legionnaires’ disease in that state is similar to the national average.

    The full report is here:
    http://www.sickkids.ca/SKCPublicPolicyAdvocacy/custom/TapwaterscaldsDISCUSSIONPAPERrevised2005.pdf


  • Ray: I have seen open systems clog and corrode in short periods of time. This is not common, but unless you are doing full water quality testing, and you know it's stable, on the homes of your clients, this is dice rolling.

    I see condensation on cold water plumbing in the summertime all the time up here in maine, which is not arid... nor is most of north america... Luckily, this is a relatively small amount of piping in a home typically. You don't see summer condensation on cold piping? sweating toilets? I'm not saying the floor surfaces should be condensing or crawling with mold.. I'm talking about what's happening around the pipes, say in the joist bays, when you multiply this potential condensation surface area by a factor of, what, 100? Not a problem that would be noticeable for quite awhile perhaps, but certainly one that does not serve the long term interests of the structure nor the occupants.

    non barrier pipe isn't the greatest idea ever either.. use a cheaper brand of o2 barrier pipe if you really want to save money ;) Obviously you can do it.. and as long as you, or the next owners of the home, don't need antifreeze, it's not a big deal. But o2 penetration can compromise antifreeze products which someone, someday, might need. Given how fast homes "flip" on average, you have to think beyond the current owners too... If you really want to though, nothing says you HAVE to use o2 barrier pipe in your separated system, it'd be open to oxygen, but at least it wouldn't be a "fresh water" system.

    to make a water heater system closed, you add a heat exchanger, expansion tank, PRV/Fill, and one pump, and that's about it. If you WANT to add a couple hundred to turn the HE pump into an injection pump (and ditch the tempering valve you'd otherwise need unless you're running the water heaters lower than they are supposed to be run) and vastly improve the operation of the radiant in most cases, that's a choice you can make, but you don't have to. Compare that to the cost of the rest of even a cheap radiant system, and while it's noticeable, it's rarely a deal breaker.

    In your case your heater is backup.. I have no doubt you're right when you say a high eff heater wouldn't make sense for you. Again, no one is saying mod/cons are the only thing that make sense; but when you are servicing a load over 20kbtus/hr in a real heating climate, and it's your primary heat source, it usually DOES make sense. Usually.

    The issue here is entirely with what an appropriate system design is. Open systems save a small amount of electricity, and a few hundred bucks up front; that's it.

    In return, you risk compromising the system's operation with the constant introduction of new minerals to react in the system. You risk possible health issues. You reduce the system's flexibility to adapt to the needs of future owners.

    If HE systems were a LOT more money, maybe I'd consider it more strongly. But frankly Ray, from where I sit it looks like a pretty poor trade for me. A one shot insurance policy of this caliber, at this price, doesn't come along every day.
  • lots more to do Ray

    Go look up bacterial "amplifiers + water heaters" too.

    Cooling towers take the heat, but where do they get their water?

    Wikipedia as a resource? Isn't that the so-called "encyclopedia" that allows folks to post changes?

    Look up the conditions that give Legionella exactly what they need to thrive while you're at it & then explain how an open system avoids meeting all of those conditions & tell me why it shouldn't be labeled an "ideal amplifier". Check for Ph, water temps, food sources, and that old reliable - stagnation. Find out if all four must be present at the same time while you're at it.

    Look up "Legionella - The Coming of the Third Plague" on Google.

    You have a long way to go and a lot to learn. To assume open systems are safe simply because no credible scientific study has ever been performed to test for Legionella Sero Group #1, is an astounding leap of judgment for making the claim that they are, therefore, safe. Since you evidently feel that open systems must be safe simply because you never got sick, look up just who might be at risk and what varying levels of wellness may have to do with this issue.

    You might ask Mark Eatherton about water heaters and LD too. He's had a little experience.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • EJ hoffman
    EJ hoffman Member Posts: 126
    Swimming pools

    Swimming pools are responsible for more deaths than legionaires disease.
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,599
    Well,

    Mark Eatherton recently nearly died from Legionella. Got it from his own shower. You might check with him.
    Retired and loving it.


  • they kill more kids than guns too... so it's ok to leave a loaded handgun on the table when you go to work?
  • EJ hoffman
    EJ hoffman Member Posts: 126
    He did not have an open heat system

    Mark did not have an open heat system he had a 20 year old 30 gallon tank with hard well water and a limed up shower head. How about testing some water from open systems I send anybody some samples
  • EJ hoffman
    EJ hoffman Member Posts: 126
    Heating flushes the tank more

    less sediment build up less chance of growth in your pipes moving water many open systems are turned up max temps also
  • Ray Darby
    Ray Darby Member Posts: 20


    Dave,

    You may not have caught my last post. My understanding (please correct if I'm mistaken) is that Legionella is best controlled by setting the water heater to 140F or higher. Whether its an open hydronic (with fresh water introduced) or a simple DHW system, it seems to me the water heater setting takes care of it. It seems to me the hydronic distrib system is no different than a PEX-based DHW system - both are open systems with hot and cold running water flowing through them. Therefore wouldn't a hot and cold water PEX distribution system suffer from the exact same risks? Why wouldn't a higher hot water storage temperature, as recommended by health org's, do the trick?


  • Less sediment? Huh. where does it go?

    Less chance, sure, if you run higher temps in the system, while you are heating. This isn't a death sentance. Just not a good idea.

    I don't know about you, but I design low temp systems anyway, so the client can do things like use solar later on. If you're running the water heater at max temps (140, I presume) then other design decisions should, IMHO, be questioned.
  • Ray Darby
    Ray Darby Member Posts: 20


    Thank you Dave, I did just what you suggested (googled Legionella - The Coming of the Third Plague). And I'll continue to educate myself on this important issue.

    I'm sorry you don't sense my concern for Legionella - text alone doesn't always carry the full message. I am VERY concerned about public health as I hope we all are.
  • PJO_5
    PJO_5 Member Posts: 199
    More Info. Please....

    What is the heatloss of your home? How is the spacing on the radiant tubing? Do you have plates? How much insulation?

    How many feet of what diameter tubing do you have? Does the fresh water flow through the entire system and then go to your HWH?

    I have a "modified" (thanks to The Wall) partial Radiantec system...but since I work in the water/wastewater field I NEVER even thought about the open-type of system. We have substantial labs where I work - and they do microbiological tesing all day - and you wouldn't believe what's in the city water. Let that sit for a while and then expose it to your lungs or drink it while in the shower? And on top of that a person in immune deficient? Sorry, but none of my loved ones will risk that while I'm on this side of the grass.

    I'll post my heating experience with Radiantec after I get a thorough description of your system...how's that?

    Take Care, PJO
  • PJO_5
    PJO_5 Member Posts: 199
    Actually...

    Using it for heting would cause more sediment...especially if you have well water. More fresh water flow through the system and then it gets heated = more sediment.

    What is "Hoffman Hydro"?

    Take Care, PJO
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