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  1. #1
    Join Date
    Oct 2016
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    Modcon vs. old-school cast iron boiler for residential hot water radiator system?

    I have a hot water radiator/baseboard system and live in New England. It's an old house but well insulated, about 1600 s.f. or a bit more. The house no longer has a chimney other than for the fireplace, so some sort of side-venting option will have to do.

    I need to have my boiler replaced. (My old 170,000 btu unit is oversized and leaky: 37 years old!) I called a number of contractors and they all wanted a lot of money to install a modern Navien-/ Rinnai-/ Munchkin-type condensing boiler. However, one contractor who is well regarded and has been extremely generous with his time told me that that's a bad idea, and strongly recommends that I simply go with an old-school cast iron boiler (his particular recommendation is a Weil-Mclain CGI-5). He says he'll install anything I want, but recommends a cast-iron unit because he claims the following:

    1. In a hot water system, the return line is about 160 degrees, which is too hot for a condensing boiler to go into condensing mode where most of the savings lie.

    2. The cost savings of a modern modcon boiler -- maybe 20% a month in gas bills -- aren't all that significant at least if gas prices stay more or less where they are.

    3. The service life of a cast iron boiler is 15-20 years; a modcon would be lucky to get half that.

    4. A modcon unit requires annual servicing, which eats up almost all of the annual fuel savings anyway. A properly set up cast iron unit requires little if any maintenance other than a few drops of oil on the direct-vent fan bearings once a year.

    5. A cast iron boiler is far cheaper up front than a modcon.

    6. A modcon is much more complicated and as such would be far more likely to break. It includes things like an exterior sensor and the like, which are just more things to go wrong. He has had terrible luck with units like the Naviens and Munchkins and so on.


    He advises that the two downsides to a direct-vented gas boiler are the slight noise of the fan and the fact that there are no rebate programs in place for same. Other than that he says it's no contest, dollar for dollar.

    What do you guys think? Is this sound advice? I mean, people don't drive pushrod V8 cars very much these days. Is this guy stuck in the past, or is he just being honest?

  2. #2
    Join Date
    Jun 2016
    Location
    Plano, TX
    Posts
    3,016
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    Ok. I know this sounds odd but I disagree. High efficiency is MUCH more reliable than standard 80% boilers. Weil-Mclain Ultras are tremendously reliable (if they are installed regularly) & every boiler needs to be inspected early, regardless of efficiency. It's a matter of carbon monoxide poisoning & a general tune up. Weil-Mclain Ultras even have a summer/winter switch (if you're looking to use it for domestic water it lowers the temp at the push of a button decreasing fuel usage) & there's also an outdoor temperature sensor that works as an outdoor temperature reset. This basically means it will raise your boiler water temp as it gets colder & lowers it as it gets warmer outside, again, saving you money. If your house is zoned you can actually get away with a smaller boiler as most zones won't call at once. High efficiency boilers are phenomenal. They also have extremely LONG parts/labor warranties. I have personally worked with Weil-Mclain & their engineers during the first days of their development. Weil-Mclain used to recommend my company & my partner to breakdown catastrophic failures so they would not happen again. I can attest that I do not work for them, nor have I ever, I would also steer clear of their boilers, they sooted up way too much for my liking. I work for a competing corporation that also sells high efficiency gas boilers & I would buy a Weil-Mclain Ultra over anything else. I would look into their products and I think you'll find the ROI is well worth it. Ultras are sealed & actually pretty quiet too.

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  4. #3
    Join Date
    Jan 2004
    Location
    PA
    Posts
    78,377
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    A properly set up modcon should get you into the high 30% savings, if it also does your domestic hot water. 40% plus if home heating use only.

    Newer modcons are more reliable then the ones of 10 years ago.

    However, the contractor that told you all of the reasons not to get one, is probably not the contractor to use to install one. He doesn't like them, and probably doesn't know how to properly install and set one up.
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