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Thread: natural gas boilers

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  1. #1

    Default natural gas boilers

    Hi guys, new to the forum, I was wondering if any of you are experiencing problems with condensing gas boilers.
    I am converting from oil to gas (can't wait) and would need approx. 130kbtu for baseboard and indirect domestic hot water. I was told that the stainless and aluminum heat exchangers in condensing boilers were falling apart (acid build-up?). I had a plumber recommend an energy kinetics system 2000. Just wondering about opinions on that system or other recommendations? Thanks in advance Lou.

  2. #2

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    Lou

    I have been running my buderus for about a year now with no problems. I will let you know what it looks like after we do service some time this summer. I did see one at the supply house that was all messed up but my guess would be it was replaced under warranty and thats why it was there.

    I think in europe all anyone buys is condensing boilers due to thier energy policies that actually work. Best I can tell they have a good track record over there.

    If you want the most cost savings make sure the person who sets it up takes the time to read the manual and knows a little somthing about temperature set points and installing out door resets. Baseboard (especially copper tube) is not an idea heat medium for getting the boiler to be run in condensing (highest efficiency) mode. I can get mine to run in condensing mode about 75-80% of the time which has lead to huge cost savings over oil.
    I will have paid for the system and be about $3500 ahead by the end of next winter, so for me anyhow the cost savings were huge

    Lou

  3. #3
    DIY Member Squ1rrel's Avatar
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    Also, the grade of stainless can have an effect on corrosion. the 400-grade (I think 444) they use in Polaris won't stand up to squat, while 300-grades will generally resist corrosion far better.

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    Big Lou do you think it wouldn't be cost effective for me to go with the condensing boiler? Because of my baseboard heat. While I haven't ever read the return temp, anytime I've touched the return piping at the boiler it was hot to the touch.

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    DIY Member cattledog's Avatar
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    Any time you can run lower water temperatures and take advantage of the extra efficiency to be gained in condensing mode you will be saving. Given the price of natural gas and issues of greenhouse gas and global warming you really need to give a high efficiency modulating/condensing gas boiler a hard look.

    You need to start with a heat loss calculation for your structure and determine the amount of existing radiation. There should be btu/ft/degree tables available from the baseboard manufacture. If you are currently over radiated for your load, you can run lower water temperatures and get into condensing range. If you have outdoor reset, you can also run lower temperatures in the swing seasons when the weather is warmer and the heat loss is less.

    You may be able to estimate the balance of radiation vs load by knowing your current water temperature, and how long the system runs when it is very cold outside.
    Last edited by cattledog; 05-29-2008 at 07:29 AM. Reason: spelling error--change head loss to heat loss

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Older boilers typically ran at a fixed temperature. On a mild day, it might fire up and only circulate the water for a few minutes, then stop. This isn't particularly efficient. More modern systems can adjust the water temperature to the load, so on a mild day, instead of 180-degree water, it might only produce 120-degree water, and run longer. On a condensing MODULATING boiler, it can also adjust the heat output to match the load, and actually gets more efficient at these lower outputs since the heat exhanger can be more efficient.

    As you lower the temperature, you also limit the maximum amount of heat you can release into the room, so on a very cold day, you may need that 180-degree water to be warm. Getting a boiler that can adjust can save money during operation that has to be reviewed against the extra costs up front to pay for the higher complexity. Reliability plays into this as well, so pick a reliable brand with good warranty and hope for the best.
    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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