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Comments wanted (ME)

J.C.A. Member Posts: 349
no drawing capabilities . But the idea would be to make a zone from a HX heated by the Water heater and seperate like a typical zone(check, exp. tank circulator)

I would also most likley have to put in an anti scald device as the water temp would most likely be too hot for domestic use without it .Hope that helped. Chris


  • Proposed changes to the RPA installation guidelines


    I come here seeking input and advice from some of America's brightest.

    The RPA is seeking changes to its living document, The RPA Installation Standards and Guidelines book. Myself, along with John Felciano and Joe Kennard are making recommendations as it pertains to the use of potable hot water heaters as dual use appliances. I have prepared the changed text, which follows, along with a drawing showing the recommended piping practices for those installations that fall under its scope.

    The intent of this proposed change is not to differentiate between boiler versus non boiler applications. A heat source is a heat source provided that it properly addresses ALL of the safety concerns. Instead, the intent is to alleviate the possibility of Legionella growing a super culture during periods of non use, i.e. summer, and allowing this culture to mix with the potable system at the point of use, or worse yet, become aeresoled through the faucet aerator or shower head, and ingested into the lung, thereby causing possible death. This is not a practice in theory, it has happened and been documented thousands of times.

    The RPA is considering adopting the CSA standards. In fact, the current RPA standard is written exactly like the CSA standard.

    The Canadian Standards are allowing this unprotected use of the potable water as a space heating/DHW medium, provided that a timer is installed to cause the space heating circulator to turn on every 7 days to refresh the water lying stagnant in the heat distribution system.

    This, in my opinion and the like of opinion of other practing licensed master plumbers, is inadequate at best and is dependent upon things that can and do break, to insure that a healthy system is maintained.

    In the first place, why would a person intentionally subject his customers to the possibility of stagnant water mixing with their potable water?

    Secondly, just because the CSA makes a recommendation does not mean that we as an industry necessarily have to follow suit.

    Oddly enough, the CSA outlaws the individual use of water heaters as a space heating only applicaiton, which I do not agree with. Let me clarify that. If a person wants to apply a 30 gallon water heater as a heat source, and its not being used for heating DHW also, then I think it should be allowed. The CSA wants to disallow it.

    Thank you for your time and consideration. The proposed changes in RPA text follow. My comments are in CAPS and enclosed in parens.

    4.2 Combination of Potable Water and Hydronic Heating Systems
    4.2.1 Use of water heater for a combination of potable and hydronic systems must conform to one of the following methods:
    a. Hot Water Heater and Heat Exchanger - hydronic radiant heating and Domestic use water may be heated by the same water heater provided a heat exchanger is used to separate the heating fluid from the domestic water and the closed side of the system used for the radiant panel system. (see fig. 12, addendum F) The closed radiant panel side of the system should utilize all generally accepted plumbing practices for closed loop hydronic heating. This includes the use of a properly sized expansion tank, pressure reducing valve, fill valve, air eliminator, pressure relief valve and backflow preventer where required.

    The heat exchanger may be integral to the hot water heater or external and must meet applicable codes for the separation of potable water from other fluids. (see fig. 13, addendum G).

    If the heat exchanger is external to the water heater, it shall be piped as shown in the attached drawing, with a venturi fitting installed where the heat exchangers’ return line re-enters the cold water line of the domestic hot water heater. This provision will insure that each time there is a domestic hot water draw, that fresh water is moved through the heat source side of the heat exchanger, thereby eliminating the possibility of the water in the heat source side of the heat exchanger becoming stagnant during non use periods.

    b. A domestic water heater shall not be used as a heat source for both hydronic heating and domestic potable water heating when there is no separation of the two working fluids. (see fig. 11, addendum F)

    (WE ARE RECOMMENDING THE FOLLOWING BE DELETED) A control device should be installed on the radiant heating portion of the system to insure that the water will be periodically circulated through the heating system to avoid stagnation during the off seasonoff-season. This circulation should be equal to or greater than one complete water change every seven days.


    c. Additional requirements for use of a water heater in combined systems

    •no chemical additives to the system

    •no water heater is used to replace an existing boiler
    •tempering valve should be provided for proper domestic water temperatures on the potable side.


    Again, thank you for your thoughts and considerations. We will be making these recommended changes at the upcoming committee meetings on Saturday May 10th in Sacramento.

    Remember, its not about boilers versus water heaters, it's about protecting the health and the welfare of the nation.

  • Dan Peel
    Dan Peel Member Posts: 431

    I like this direction far better than the CSA approach. One exception which perhaps should be considered is floor warming applications where recirc and/or shower runout piping is embedded, but subject to induced flow. The simple venturi is a nice safety feature. Dan

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  • Sounds Fine

    I know this issue has been going on for some time; thanks for taking the time to get it in print in the Installation Standards. That is the way we pipe our water heater systems in the Bay Area except we don't use a Venturi tee on the return; good idea, though.

    If you don't mind me pulling you off the subject for a moment regarding your diagram, I've always wondered what happens when you've got a DHW return line in combination with a tempering valve on the supply. With no one using water, the return line is bringing back water that is below the setpoint temperature of the water heater which the water heater has to heat up again. Once heated, the hot water leaves the water heater only to be tempered down to a cooler temperature. If this is the case, the water heater is always working to heat up water cooled down by the tempering valve.

    Or does the return water enter through the cold port of the mixing valve insead of going to the water heater?

    Best wishes,


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  • hot_rod
    hot_rod Member Posts: 15,033
    It almost goes without saying......

    Open system construction is an open invitation for disaster.

    The CSA folks have wondered far afield with their unbelievably crazy approach. I exchanged several e-mails with them, but they will not reconsider or redraft the standard. This in spite of the fact that one Canadian study confirmed Legionella within a percentage of potable water heaters. That they disallowed the use of water heaters as stand alone hydronic heat sources while allowing open system construction flies in the face of reason and akll that is known about fostering Legionella bacteria growth.

    I like the approach Mark, but also feel a bit concerned about the reliability for ensuring the venturi was actually installed. OK if I "borrow" the drawing?
    Think about this. Even with all the world-wide panic regarsding SARS, Legionella from potable water systems kills more people per year in the USA alone than all of the deaths attributed to SARS to date. Unlike SARS, we do have the means at our disposal to regulate Legionella growth in our potable water systems. Why in the hell would anyone in their right mind create and/or promote systems that offer Legionella everything it needs for rampant and unchecked growth?

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    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Peelers concerns...

    could be addressed by putting a venturri fitting in the cold water supply where the return comes back in also. Wouldn't be allowed to use a zone valve that would stop guaranteed circulation on draw.

  • Allens concerns regarding DHW circulation return and 3 way valve

    Allen, when only circulation is occuring, the 3 way is not really introducing cold water into the mix, other than the tepid waters coming back from the return, and yes, you are correct. If the hot water port shuts down due to excess temperatures, the cold port opens, which is where the return water would flow, hence cooling down the three way and causing it to re-open its hot port, while closing its cold port.

    This set up is really no different than the way a person would set up a 3 way valve with a boiler, except that the pump is on the FAR end of the mixed supply.

    Thanks for your comments.

    Nice set up... Is that a hole in the flux can lid??? :-) Probably just a glitch in the photography ;-)

  • It goes without saying...

    anytime you or anyone else wants to use a drawing or a picture I've generated for the purpose of education, my permission is not necessary. Thanks the same for asking though...

    As for ensuring compliance, the standard can be written such that a venturri fitting with a "makers mark", i.e. Taco,or B&G can be required. Their fitting has a red ring where the venturri is at. No red ring, no compliance, no C.O. I think the fittings cost around $5.00 each...

    FYI, I've got it figured out so I can attend your Bugs-n-Water seminar. Prepare for hecklers!!

    In all honesty, thanks for continuing the battle, protecting the health and welfare of the nation as you have to this point, Dave. There's strength in numbers.

  • hot_rod
    hot_rod Member Posts: 15,033
    Cooking With PAH - \"From Soup to Nuts\"

    Be prepared for some heat in the kitchen and "No Soup for You" if you're a heckler who get's the wrong answers as we stir up a few recipes for disaster in my class!

    This ain't no Julia Childs!

    Tomorrow night the brand spanking new RPA Washington / Virginia chaper gets a preview. I wonder if Riles will get soup or nuts???

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    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • hot_rod
    hot_rod Member Posts: 15,033
    What about

    will the venturi overcome the pressure drop thru the HX? I suppose, also, double wall HX's may be needed in some areas.

    Also a bit of pressure drop for the DHW flow thru the venturi port.

    I have been using Polaris with FP HXs mounted tight to the extra tappings. Seems with a real tight connection the HX gets flow.

    Finding venturi fittings in every market could be a challange. Not many "younger" installers and dealers know what the are! I think you are on to a good fix, as long as installers understand the reason, mechanism and proper installation of the fitting.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • leo g_39
    leo g_39 Member Posts: 1

    i know that you sent away for the BC RHWHA guidelines. i'm wondering if you got the sixth edition, march 1999. in it are the acceptable configuration drawings for this set-up. NO OPEN SYSTEM IS ALLOWED! i am not sure if this is how it will come out in the national building code, but i do know that most of the hydronic rules for that code were taken from the alberta and BC guidelines.

    keeping my fingers crossed!

  • J.C.A.
    J.C.A. Member Posts: 349
    OK , maybe I'm simplifying this....

    But why not just put a heat exchanger in the loop and avoid all the nonsense involved with puting domestic water with the heat ?

    It does cost a bit up front, but in the long run doesn't it make sense? JMHO. Chris
  • bill clinton_3
    bill clinton_3 Member Posts: 111

    I think what you are trying to do is mandate heat exchangers. I'm with you on that, but the wording is not clear:
    b. A domestic water heater MAY SHALL NOT (which is it?) be used as a heat source for both hydronic heating and domestic potable water in an open system -----

    I suggest you simply say: "shall not"

    Given that, I would revise the rest:

    "when all the pipe,regardless of whether or not fittings and fixtures used within both the heating system and domestic system are suitable for potable water and pressure tested to regulatory limitations for each. (see fig. 11, addendum F)"

    to simply read:

    "regardless of whether pipe, fittings, or fixtures are otherwise suitable for potable water systems."

    Regarding the diagram: It's fine, put specifying it alone precludes other and perhaps better arrangements. I like to pipe the return into the drain tapping and mount the pump low relative to the tank: This assures the circulator will not run completely dry and burn itself out if water supply is cut off.

    Also, my very favorite method to connect up a heat exchange module is to mate it with a water heater tank that has extra side connections specifically for heating. That makes for a much cleaner installation and also solves the problem of getting an air-bound ciculator: it can't happen unless you drain the tank. No need for the venturi tee here either: One connection is higher than the other and thermal stratification will induce thermo-siphoning. Trust me, it will.

    I'm with you on allowing water heaters as dedicated heat sources for radiant. Not an ideal choice, but sometimes appropriate. Trouble is that there is no certification for them in that use, so you're at the mercy of the "local administrative authority."

    All in all, a good rule.


  • Bill...

    Thanks for the proof reading. This is why it's important for other people to take a gander. Here's what I re-wrote;

    b. A domestic water heater shall not be used as a heat source for both hydronic heating and domestic potable water heating when there is no separation of the two working fluids. (see fig. 11, addendum F)

    As for the system config drawing, it's only one of many potentials. If there needs to be another drawn to comply with your needs, then I see no problem with that provided it complies with the intent of the design. Nothing is cast in stone. Even if it is, it can be reshaped to meet anothers idea, so long as then end product (safety to the consumer) is met.

    Thanks for your input. I value it coming from someone with your experience.

  • Chris,

    Can you clarify your thoughts to me with a drawing?


  • Leo,

    I'm not sure which standards I have from RAHWA, they're at work, and I'm not. That said, it's kind of a moot point because the CSA folks are allowing the use of dual use, single fluid systems, but are outlawing the single dedicated use of water heaters as heat sources.

    Beats me...??


  • leo g_40
    leo g_40 Member Posts: 1

    the reason i was given that a hotwater tank should not be used for space heating solely:

    a) was that it was never designed for that,

    b) that theprice AND life span of a tank was not comparible to a boiler, therefore to help keep the fly-by-night fellows from hoodwinking potential customers with a lowball price.

    also, as far as i know, the CSA is no longer a government facility, but now is a private lab (maybe mr bean could verify this?), that like underwriters, is an accepted method/testing facility. the building code would take precedence over the CSA.

    leo g
  • Steamhead
    Steamhead Member Posts: 14,840
    Mark, I agree

    that potable water and heating-system water should never mix.

    I have never seen such a setup around here. I think it would be illegal in these parts since all Baltimore-area jurisdictions require backflow preventers on boiler feed lines. The reason? Potable water and heating-system water should never mix!

    Illegal or not, I will never install a system that mixes potable water with heating-system water.

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  • Larry Drake
    Larry Drake Member Posts: 2
    Changes in RPA Standard Guidelines

    While the RPA appreciates Mark's efforts and input regarding the RPA Standard Guidelines, the comments and changes are his own and do not necessarily reflect the position of the RPA. The RPA is not currently seeking to accept the Canandian standard nor has it made any suggestions to the revision of the current RPA Standard Guideline.

    A RPA Action Group committee is being formed to investigate the use of water heaters as a heat source for radiant heating systems and to make recommendations, if any, for modifications to the Guidelines as a part of its work.

    Since this committee will have its first meeting at the RPA Conference next month, any conclusions are only speculation.

    Any RPA member who is interested in this topic and would like to participate on the Action Group is welcome to attend the meeting. For more information, contact John Fantauzzi, RPA Technical Director, at [email protected]
  • Paul Pollets
    Paul Pollets Member Posts: 3,428

    Sounds like you've got this can of worms labeled. I've little disagreement with the use of water heaters for low temp hydronic heating, provided they use an RPZ, PRV and expansion tank. I support combined DHW/Hydronic use through a FPHX or a specialty water heater (combicor) Are you excepting their use for high temperature applications, such as baseboard, radiators or air handler coils?

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  • hot_rod
    hot_rod Member Posts: 15,033
    Seems to me

    virtually every plumbing code in this country address the cross connection aspect regarding boilers and the legality of combo systems. Perhaps the RPA Standards Guidelines needs to merely mention that "all radiant systems need to be connected in compliance with all current plumbing codes." This puts the responsibilty for proper connections in the lap of the AHJ, where it belongs!

    I would guess they are in a better position to regulate, enforce, and watch that the "health of the nation' is protected as the code intends. I'm not sure the RPA is in a position to enforce code compliance regarding cross connection.

    Yet another reason homeowners should contract with licensed installers. Under the code here ONLY licensed plumbers are allowed to permit and connect boilers and heating equipment. Licensed heating and mechanical contractors are not allowed to make this connection, and the inspectors know this.

    If the legionella apocalypse is upon us, the plumbing and health officials at the local, State, National (including the CDC) level surely are taking steps to update and better codes to protect the end users. In my area the AHJ now requires RPZ's on all boiler connection. A step up from the dual checks previously accepted. Even the newly formed Homeland Security department is looking closely at potable water safety.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Code authorities...

    do in fact address the cross connection issue. They state that they are not allowed. Cross connection is a subjective term, as is degree of hazard.

    No documented cases of anyone becoming ill or even dying as a result of DRINKING Legionella exists. The problem is when it is INHALED, such as micro mist from faucet aerators, shower heads etc.

    It never, was nor has it been our intent to set the RPA up as code enforcement entity. In fact, the Standards and Guidelines book is just that, installation standards and guidelines. If it is ever to become a true code document, it will need to change all of it's "Should" language to SHALL language, and grow some teeth. A major step in and of itself, and I'd love to see it happen, but it will take a more powerful organization than currently exists. At least it will require that some toes get stepped upon.

    You can't keep all the people happy all the time. All you can do is to do everything within your power to protect them from known, readily identified hazards.

  • hot_rod
    hot_rod Member Posts: 15,033
    the corporate structure

    of the RPA, as a not for profit corp regulated by IRS codes section 501 c (3),I read it, strictly prohibits code writing.
    "No substantial part of the activities of the corporatrion shall constitue the carring on of propaganda or otherwise attempting to influence legislation, or any initiative or referendum before the public, and the corp shall not participate in or intervene in (including by publication or distribution of statements) any political campaign on behalf of, or in opposition to, any candiate for public office,"

    Probably take an attorney to un-wind that statement, but, it clearly states why the RPA will not be involved in any code legleslation. Hence the language, as written, in current Guidelines. Larry is well read on the "can and cannots" of the RPA regarding this, since he has been part of this from the founding day.

    Still I agree the RPA should be able to suggest guidlines regarding protection of potable systems connected to radiant.

    Also prohibited from endorsing "Bean for Radiant Prime Minister" :)

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Steve Ebels
    Steve Ebels Member Posts: 904

    If this verbage is inserted into RPA's guidelines, does that mean they will cease to endorse companies that continue to recommend these types of installations? I'm just waiting for one of these to rear it's ugly head and "bite" someone. Like the installer (HO or not) and the manufacturer/designer.

    As to the HX and venturi Tee, I'm 100% for it. I rarely use a water heater as a heat source. Only for small loads and only with an HX installed to prevent contamination.

    Go fer it pal!!!
  • Reply to HR

    HR, sorry for the late reply. Yes, the venturri will induce flow through the heat exchanger. If it is a high pressure drop concern, a person could put a venturri on the HX's supply AND return connections to the tanks Hot and COld and induce even more flow thru the HX.

    Under the right circumstances, these venturri tees could suck the chrome off a ball hitch :-)

    The PD on either side is negligible. Probably wouldn't be noticed under normal opearting conditions on either side.

    Taco is available virtually in all of North America. I think you're right, its just a matter of education of the masses. Especially the younger plumbers. Maybe we can break them of their bad habits early;-)

    Thanks for your input.

  • High temp use....

    I guess I'm not aware of any residential type water heaters with a temperature output capability that would do baseboard any good. I've always thought the limit for residential DHW was around 140 deg F. As with any heat source, the designer would have to work around the devices operating limits, or there abouts.

    As you are aware, I'm heating my home with a 40 gallon dedicated water heater, soon to be replaced with a beta testing high efficiency condensing boiler. I designed my system around the availaiblity of 140 deg water. It meant bigger panel radiators, but I got them for cost and it works great.

    As for fan coils, I think they've been used for that for about 20 years,and they have their share of problems. If I'm not mistaken, the recent failures you discovered up there in the great Northwest were tied to DHW /fan coil systems...

    If and when I decide to base load my house with a ground source heat pump whose limitations are 120 degrees, I may have to add more radiation. Got plenty of ceiling space:-)

    I figure I got room for about 3 wells in my back yard. Probably get a deep discount, or a free demo for them holes.

    Sorry for the rambling answer...

    Trying to do too many things at once.:-)

  • I guess maybe...

    your code officials have seen something they have not seen out West yet, eh...

    Thanks for your confirmation to a basic, proven belief. The health of the customer (and ME!) come first.

  • Thanks HR..

    You taught me something I did not know. Maybe it's time to re-visit the charter and possibly reorganize into an organization that CAN write code without fear of repraisal... But that's not a decision for me to make. That's a definate US decision...

    My director was telling me today, he asked the president of a local Home Builders group why people wanted to join his organization and he stated "Lobbying power..."

    Guess that's what "they" are worried about. Nuff about politics.

  • Thanks Steve...

    I appreciate your input. As to what happens to the people promoting theses systems, I guess that's up to the AHJ. However, if it becomes against the code, which I think it will, then they would be in violation of a law. As it stands right now, they are perfectly legal.

    Until someone comes out with a good small boiler that is ultra efficient and relatively inexpensive, water heaters make sense. However, I firmly believe that's all about to change. Think hydrogen fuel cell generator.;-)

  • Paul Pollets
    Paul Pollets Member Posts: 3,428
    high temp apps

    I've seen many water heater installations tied into baseboard, wall convectors and HW coils. Just fixed (replaced) 3 water heater systems featured on the KIRO-TV sting. Put in a CombiCor (with auto fill and RPZ) While the blame is tied to failure of the tubing, which was apparently stored in the sun for too long, we found 90% of the pex nuts fastened incorrectly to the tubing. This is more of a mechanic's problem than a materials issue. Still, here we have water heaters installed in high temp applications. Bad idea and not recommended. I guess it will be the attorneys who make the code changes, not the hydronic experts.

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  • Dave Yates (PAH)
    Dave Yates (PAH) Member Posts: 2,162
    a few thoughts

    Codes governing water heaters are poised for change - increased minimum water storage temperatures.

    A single lawsuit could include the RPA if an open system is verified as the source of LD.

    Once insurance co's discover installers are walking on thin ice, they'll rapidly distance themselves from coverage. They've already demonstrated a willingness to run away from problems by their reaction to mold.

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This discussion has been closed.