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Thread: Furnance

  1. #1
    DIY Member Barry J's Avatar
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    Default Furnance

    On my oil burner (with on demand tankless, coil). My aquastat reads Hi 200, low 180 and diff of 12. And it seems like when we run the tub, it goes from hot, to warm, then if we shut it off for a little bit, it will come out hot for awhile, but back to just warm.
    The temp guage on the boiler, seems to stay around 130 degrees.
    But, when I go to my dad's house, he has seem boiler, ..his aquastat is set at Hi 200, Lo 180 and a diff of 10. But, his temp reading on his boiler reads about 175-180.
    What should I have checked on my boiler...the company is coming out on Wednesday.
    Thanks
    Barry

  2. #2
    Master Plumber nhmaster's Avatar
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    Normal differential setting is around 10 degrees. It's the amount past the setting that the control has to "play with" without it or set to 0 the unit will short cycle. Your problem is not the temperature settings or the differental, it's the tankless coil which is probably starting to plug up. Tankless coils are nororiously inefficent and possibly the least cost effective way to make hot water. Disconnect it and install an indirect. Which is the most efficient way to make hot water.

  3. #3
    Engineer Furd's Avatar
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    I agree with nh. The only thing worse than a tankless coil in a boiler is heating your domestic water in a kettle on a wood-burning kitchen range.

  4. #4
    DIY Member Barry J's Avatar
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    What is an indirect???? How would I do it and how much would something like that cost??? Because I just called my wife (I'm at work), and told her to start saving our money, but, she said she had plenty of hot water today...maybe she likes her money more than her hot water.
    Is there a way to check to see if the coil is gone, I just had it replaced 3-4 years ago??

  5. #5
    Engineer Furd's Avatar
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    An indirect water heater is a tank that contains a heat exchanger. It has all of the advantages of any tank-type water heater and also the advantage of utilizing the higher efficiency burner in the heating boiler for heating the domestic water. It is piped to the boiler as a separate zone, preferably with its own circulator pump rather than a zone valve.

    They come in various sizes and when used with a tempering valve can be sized smaller than one might first think yet still supply large amounts of hot water at usable temperatures. They have very low "standby" losses because they are very well insulated. Generally they will supply hot water at a lower cost than will a conventional gas-fired water heater and unless your electrical rates are quite a bit lower than average they will be much cheaper to operate than an electric water heater. Their biggest downside is that they have a higher capital cost than any other water heating device.

  6. #6
    DIY Member Barry J's Avatar
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    Default Furnance

    Ok, the oil company can over and did not replace the mixing vavle. They did not feel that, that would make a difference, since it was already cranked to max.
    He checked the temp at the kitchen faucet, and it was 120 degrees, he checked it at the bathroom sink and it was at 119-120 degrees. Then checked the bath tub faucet and it was about 100 degrees.
    He said he thought me problem was in my shower vavle and not in my furnance, since the difference in temps. He said I probably needed my shower valve changed.
    What's your opinion?????
    When i asked about the temp gauge (reading 130 degrees) on the furnance, ..he said they are unreliable and he could change it and charge me, but it probably wouldn't last.
    He said to just go with the aquastat.
    Any suggestions??
    Thanks
    Barry

  7. #7
    Retired Defense Industry Engineer jadnashua's Avatar
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    A pressure balanced shower valve has an adjustable limit stop. You may need to adjust this (assuming your valve has one) to allow it to go hotter.
    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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