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Thread: Question regarding tankless boilers and which is best

  1. #1
    DIY Member flamefix's Avatar
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    Default Question regarding tankless boilers and which is best

    No doubt this will upset a few but that's not my intention, I'm generally interested in opinions not starting a conflict. And I have no vested interest in the product only I use them myself here in the UK.

    I've been looking through the boilers discussed here and I'd like to know your experiences with
    http://www.viessmann.ca/en/products/...odens_200.html

    And why when you look at the design of these units you'd pick anything else?

    Over here the domestic boilers are nowhere near as good as the German/Dutch units not all but when you look at the designs of burners used for example I'm not afraid to say a UK produced boiler is less reliable less well built. And I prefer the Viessmann or Vaillant brand personally.

    For example and I don't know all your boilers just ones I have seen talked about and figuring out from their website (Incidentally I struggled to find the Takagi site and the navien site didn't seem to work) I think this is the latest Noritz model.

    http://www.noritz.com/professionals/..._water_heater/

    how is that superior to the above unit from Viessmann.

    Or what boilers do you rate and why?

    Finally i know that in these economic times and in general I'd like to buy British boilers for example as you'd like to buy made in the USA but can we leave that aside in this instance.
    Gas, Oil, solar and renewable service and installation in Devon UK- Please note my advice is not based on USA regulations as I am UK resident. Therefore I will try to avoid posting where confusion may be caused or make that clear.
    http://www.flamefix.co.uk

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    DIY Member flamefix's Avatar
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    Quote Originally Posted by jakeru View Post
    A "boiler" is not a "tankless water heater".

    The technical literature confirms this is not a tankless water heater:
    "The Vitodens 200 is designed only for closed loop, forced circulation hot water heating systems"

    A boiler gets activated by a thermostat. An electric pump drives water through it, and the burner heats the water at a fairly constant rate.

    A tankless water heater heats domestic hot water (DHW.) It is activated by water flowing through it. It fires up the burner very quickly to heat up the water (minimizing cold water sandwich), and it responds quickly to varying flows to maintain a fixed output water temperature.
    Apologies, I simply assumed they offered the same combi and system boilers as they do in Europe, my mistake.
    http://www.viessmann.co.uk/prod_vitodens200w.php

    I know perfectly well what a combi boiler is.

    So now the argument is is it relevant if they don't supply it hmmm? So humour me, I've taken your response as sarcastic humour or should I re-post in the forum for system boilers only (those are the ones you first described)

    Sorry again for any confusion on my part.
    Gas, Oil, solar and renewable service and installation in Devon UK- Please note my advice is not based on USA regulations as I am UK resident. Therefore I will try to avoid posting where confusion may be caused or make that clear.
    http://www.flamefix.co.uk

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    DIY Senior Member Runs with bison's Avatar
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    Boilers boil water, not just heat it. If there is not vaporization going on and steam being produced, I wouldn't refer to it as a boiler. Just my process design background kicking in.

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    DIY Member flamefix's Avatar
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    Quote Originally Posted by Runs with bison View Post
    Boilers boil water, not just heat it.
    I can see this is going to be hard work..

    Compact Oxford English Dictionary


    boiler

    noun 1 a fuel-burning apparatus for heating water, especially a device providing a domestic hot-water supply or serving a central heating system. 2 Brit. informal a chicken suitable for cooking only by boiling.

    Sorry just my English root language kicking in Whats it say in the American equivalent dictionary?
    Gas, Oil, solar and renewable service and installation in Devon UK- Please note my advice is not based on USA regulations as I am UK resident. Therefore I will try to avoid posting where confusion may be caused or make that clear.
    http://www.flamefix.co.uk

  5. #5
    In the trades Dana's Avatar
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    In the US, the Noritz 0842 retail price is less than half that of the Vitodens 200, (which may explain something... )

    But since the Noritz is marketed as a water heater, not a heating-system boiler a more apt comparison to the Vitdodens 200 might be the TriangleTube Prestige Solo 110:

    http://www.triangletube.com/Triangle...?CatID=1&PID=1

    ...which is a very reliable unit with a good reputation, at 2/3 the price of the nearest Viessmann equivalents. (This could be the sad state of the dollar vs. the euro at play.)

  6. #6
    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by flamefix View Post
    I can see this is going to be hard work..

    Compact Oxford English Dictionary


    boiler

    noun 1 a fuel-burning apparatus for heating water, especially a device providing a domestic hot-water supply or serving a central heating system. 2 Brit. informal a chicken suitable for cooking only by boiling.

    Sorry just my English root language kicking in Whats it say in the American equivalent dictionary?
    I didn't realize you were using Old English prior to the Norman Invasion. I use modern English and common sense so that it is possible to distinguish between modern objects and so that people can understand me. What you appear to be using is a colloquial form of English and misapplying it to other regions.

    In my Webster's New Collegiate Dictionary (English by the way, I don't have any dictionaries for American or Australian, etc.) it has the following.

    "1: one that boils 2a: a vessel used for boiling 2b: the part of a steam generator in which water is converted into steam and whichy consists usu. of metal shells and tubes 2c: a tank in which water is heated or hot water is stored."

    Note that a tankless water heater does not fit the definition of a boiler at all, so your audience is rightly confused as to what the heck you are actually talking about. Using more precise terms is generally desirable in technical discussions rather than devolving to describing everything vaguely or using words that imply something else.

    And even 2c is such a weak and broad definition that any tank containing hot water, whether boiling or not is a "boiler." If I referred to all of my hot water containing vessels as boilers people would have no idea what I was talking about. At any rate I've never heard it used that way, certainly not industrially. If you called a storage tank with hot water in it (and no heating device) a "boiler", nobody would know what you were talking about.

    The definition you are relying on appears to be a corruption that occurred because hot water often came from boilers in the past. That corruption seems to have fallen into disuse decades ago.

  7. #7
    DIY Member flamefix's Avatar
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    Quote Originally Posted by Runs with bison View Post

    In my Webster's New Collegiate Dictionary (English by the way, I don't have any dictionaries for American or Australian, etc.) it has the following.

    "1: one that boils 2a: a vessel used for boiling 2b: the part of a steam generator in which water is converted into steam and whichy consists usu. of metal shells and tubes 2c: a tank in which water is heated or hot water is stored."
    clearly there is American/English as there is English/English otherwise the terms colour and color wouldn't exist or gas meaning petrol here and gas here reffering to natural gas for heating/cooking with.
    Hence you will have American/English dictionaries because if they were English/English dictionaries there would understandably be confusion.


    Quote Originally Posted by Runs with bison View Post
    Note that a tankless water heater does not fit the definition of a boiler at all, so your audience is rightly confused as to what the heck you are actually talking about. Using more precise terms is generally desirable in technical discussions rather than devolving to describing everything vaguely or using words that imply something else.
    A Tankless water heater could be either an instantaneous water heater here or in the case where it is combined with the boiler for space heating then it is called a combination boiler or combi for short and from the triangle site Dana linked to Americans it appears would call a combi a combi heater. Which surely must fall into the category of tankless as it heats water and doesn't store it in a tank (unless it has a small buffer store) and the Hot water has priority over space heating.


    Quote Originally Posted by Runs with bison View Post
    And even 2c is such a weak and broad definition that any tank containing hot water, whether boiling or not is a "boiler." If I referred to all of my hot water containing vessels as boilers people would have no idea what I was talking about. At any rate I've never heard it used that way, certainly not industrially. If you called a storage tank with hot water in it (and no heating device) a "boiler", nobody would know what you were talking about.
    Nobody seemed to have a problem using the boiler forum or http://www.terrylove.com/forums/showthread.php?t=29655 in this thread


    But they also call it a boiler http://www.triangletube.com/document...Literature.pdf

    I can understand confusion in Poland they call a boiler a heated storage tank which we in the UK would call a hot water cylinder, or a thermal store or a buffer tank depending on application. A tank is something we would use for storage of water but only cold, or the expansion tank on an open vented heating system.

    The expansion vessel is the small cylinder that is connected to a sealed water system this is the small vessel with a EPDM rubber membrane.


    Now we have cleared up tanks cylinders and boilers anyone like to get back to the topic? If you'd like to talk off topic further then please feel free in your own thread.




    Thanks Dana I suspected price might be a pertinent issue I don't know the prices in the US myself perhaps if you have the prices of the two makes I'd like to compare them with the prices here.

    For example the Vitodens 200 35kW system boiler lists here at 1773 = $2836 trade on that would be around less 40% so 1063 = $1702 the combi version is bizarrely 1796 or 1077 trade. The trade would depend on volume and history with the merchant.
    Gas, Oil, solar and renewable service and installation in Devon UK- Please note my advice is not based on USA regulations as I am UK resident. Therefore I will try to avoid posting where confusion may be caused or make that clear.
    http://www.flamefix.co.uk

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    Viessman sells both combi and 'normal' boilers in the USA...just depends on what you want. They are pretty up-front about the capability of the combi for DHW use. It does require the system to maintain a higher temp, and run more frequently than it would with an indirect.

    A typical tankless system is designed for intermittent use. A boiler is designed for continuous use. To achieve decent life, it typically needs to be built more robust, and that costs money.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member zl700's Avatar
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    "But they also call it a boiler http://www.triangletube.com/document...Literature.pdf"

    Combis fall into both boiler or "combi heater" classification depending on which side of the heating medium fluid falls, direct or indirect.

    Since the Triangle Tube Excellence Combi heats hydronic water directly, and the DHW indirectly, it is a BOILER.

    CSA-

    Coverage in the water heater standard is being developed to handle combination appliances.
    Combination appliances cannot be used for space heating only
    If appliance has separate space heating and water heating circuits:
    Appliance must be marked with the working pressure of both the space heating and potable water heating circuits
    The space heating circuit must comply with hydrostatic pressure test of 2 times working pressure of space heating circuit but not less than 30 psi (2 bar)
    There are no efficiency requirements established for combination appliances. Combination appliances certified as a water heater must comply with the efficiency requirements as a water heater.

    A combination appliance can only be classified as a water heater if the primary heat exchanger directly heats potable water. Proposed definition is as follows:
    Combination Water / Space Heater. A water heater that heats potable water directly within the appliance, and may be connected to provide space heating either directly or indirectly for distributing heated fluid to either a fan coil or similar appliance for space heating purposes. The design is such that the heating fluid temperature cannot exceed 210 F (99 C) under any circumstances during normal operation of the water heater.

    A combination appliance that indirectly heats potable water cannot be classified as a water heater. It must be a boiler and meet the ASME pressure vessel requirements.
    There has been no coverage proposed in the Z21.13/CSA 4.9 boiler standard for combination appliances.


    For boilers being certified for the United States, compliance with ASME Boiler and Pressure Vessel Code, Section IV (Heating Boilers) is required.
    CSA International cannot provide this approval. ASME (American Society of Mechanical Engineers) must be contacted for approval requirements (www.asme.org)
    Evidence of compliance with ASME Section IV must be provided before certification of a boiler can be provided. The required ASME mark is the H stamp.
    Testing of the boiler can be conducted concurrently with the ASME process of obtaining the ASME certification.

  10. #10
    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by flamefix View Post
    Nobody seemed to have a problem using the boiler forum or http://www.terrylove.com/forums/showthread.php?t=29655 in this thread
    Perhaps because it was in the BOILER forum???

    Using incorrect or at best ambiguous terms is your problem, not ours.

  11. #11
    DIY Member flamefix's Avatar
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    Quote Originally Posted by zl700 View Post
    "But they also call it a boiler http://www.triangletube.com/document...Literature.pdf"

    Combis fall into both boiler or "combi heater" classification depending on which side of the heating medium fluid falls, direct or indirect.

    Since the Triangle Tube Excellence Combi heats hydronic water directly, and the DHW indirectly, it is a BOILER.
    And so does the Viessmann unit it does the same, the radial heatexchanger contains the hydronic water and is heated directly.
    This hydronic water is also the medium to heat the domestic hot water via a plate heatexchanger. Both are indirectly heating the hot water whether via a plate to plate or a tank in tank the basic principle is the same.


    We're agreed then the Viessmann unit is a boiler. and if heats water indirectly via a secondary heat exchanger within the boiler itself this is a combi also. But you wouldn't call this type of combi boiler a tankless or a combi tankless or anything remotely related to a tankless.

    We now have two products for comparison are there any others? It would seem that Triangular is part of the AVC group and they're sold here in the UK http://www.acv-uk.com/tech.htm but I'd never heard of them.

    Quote Originally Posted by zl700 View Post
    CSA-

    Coverage in the water heater standard is being developed to handle combination appliances.
    Combination appliances cannot be used for space heating only
    that makes sens as why would you, but it wouldn't affect the operation of the Combination units in the UK if it was run as a space heating boiler only if the cold inlet and hot outlet were capped off.

    In fact it is not uncommon for someone have solar installed with a combi only unit to do something like this and set up a separate zone off the hydronic circuit to indirectly heat the cylinder as a back up heat source, in essence reverting the combi back to a system boiler only.

    Quote Originally Posted by zl700 View Post

    A combination appliance that indirectly heats potable water cannot be classified as a water heater. It must be a boiler and meet the ASME pressure vessel requirements.
    There has been no coverage proposed in the Z21.13/CSA 4.9 boiler standard for combination appliances.
    Boilers boil water, not just heat it. If there is not vaporization going on and steam being produced, I wouldn't refer to it as a boiler. Just my process design background kicking in.
    Thank you for that clarification clearly a boiler then - no confusion there.

    So the upshot of all these boiler posts is that of the question of tankless water heaters and my placing of a combination boiler into the tankless forum. So it would be preferred if it was in the boiler section? ( I do recall posting a few days ago for clarification on what is the meaning of 'tankless' seems indirectly I have been kindly informed in a roundabout fashion.

    But since I can't move the post could we get back to the topic now?
    Gas, Oil, solar and renewable service and installation in Devon UK- Please note my advice is not based on USA regulations as I am UK resident. Therefore I will try to avoid posting where confusion may be caused or make that clear.
    http://www.flamefix.co.uk

  12. #12
    Senior Robin Hood Guy Ian Gills's Avatar
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    All of the European combi boilers I have ever had the priviledge of seeing/owning beat the crap out of anything we have in the US in terms of longevity and efficiency.

    Take Worcester for instance...


    It's just a different world. But most houses do not have AC in the UK, which complicates things.

    It is funny though. During my last visit to the UK, I had the privilege of going round some new built luxury apartments (US$1 million plus). Guess what I found in the closet....a US-style water heater!
    Last edited by Ian Gills; 09-14-2009 at 06:52 PM.

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