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Oil Furnace for Hot Water heat settings?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by babalu87, Mar 1, 2006.

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  1. babalu87

    babalu87 New Member

    Joined:
    Nov 23, 2005
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    1,440
    Loc:
    middleborough, ma.
    Hearth related because the only thing my furnace kicks on for anymore is hot water

    What should the temperature difference be set at for optimum efficiency
    Choices are 10 15 20 and 25 degrees

    I have to judge the hi-low at the upstairs shower to set the temperature where it needs to be for hot showers the wife likes to take but since I wont be using it for heat any longer I wonder what the optimal settings should be?

    Thanks

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  2. elkimmeg

    elkimmeg Guest

    Couple of things one can do: Anti scald codes about 120 degrees. I would not want to increase it too much beyoud that. IT's one thing to have a hot wife but scalded one is never too pleasent.
    Most shower valves have adjustments beyond what your is currently set. Yours could be adjusted to introduse more or less hot water.
    I would adjust your simmons valve first, before messing with the boiler settings.
    Another word to the wise, boilers are not designed to be turned off long periods of time. If turned off, expect a lot of leaks when turned back on. When they loose heat, the gaskets and fittings srink. and are no longer water tight, Hopefully when turned back on they expand and regain the water seals, but before they do expect a lot of water pissing out the connections. In some cases shrinkage
    actually re seats them and they will leak till replaced. One also runs the risk of freeze up pipes, located in or near outside walls. Cold drafts if exposed long enough and no circulation, will freeze up. I know it has happened 4 occasions here. My wood stove provide the heat to shut down the zones. Finall solution was to glyccol my system. 29 years ago I made a few location placements when plumbing my home. If doing it over now and knowing I could correct them, but you know tearing down good walls and ceilings to get at concealed pipes is expensive. Last night I know my stoves are carring the heating load but still my burner will cycle a few times.
    You know something is wrong when you do not here it come on, then you check and water is weeping out the joints. There is something wrong with the boiler. We all want to reduce oil/ gas dependency but a fine balance must be met effeciency vs foolishness
    Just like you learn how to get the most out of your wood stove, one also must learn the right ballance with your burner/ boiler usage
  3. Sundeep Arole

    Sundeep Arole New Member

    Joined:
    Nov 18, 2005
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    Loc:
    Framingham, MA
    Those numbers are the differential. Adjusting that will only decide how far above the low limit the boiler will go before it cuts off. Set that too low, and the boiler will short cycle. Set it high, and you may win provided you have a separate dhw tank. If you have a tankless coil and your dhw comes directly from the coil, without a separate dhw tank with aquastat, you will wild temprature swings at the shower. You can try adjust the low limit lower, though.

    I of course struggled with finding the right balance between boiler/wood usage too. Based on the thermostat alone, burning 24/7 means my circulator will never come on, and there is a risk of water freezing in the heating circuits which run through the slab. If I turn the thermostat up to run the circulator, I have to turn it down manually since the thermostat is basically confused.

    I turned the low limit down, but it just made the dhw get too cold. Then I bumped up the differential, and the temp swings were wild.

    In the end I spent money and went with a somewhat expensive solution for the shower - it is a bit of a risk since I don't know if it will work. A thermostatic and pressure balancing (not just pressure balancing) shower valve. This guy allows you to set a specific temprature for the shower water (within a range) and senses the tempratures of the incoming hot and cold water and adjusts the mixing ratio to keep a set outgoing temprature. My hope is that this will allow me to set a lower low limit, and perhaps a higher differential, and still have a comfortable shower water without ridiculous temp swings. At the sink, the swings don't matter as much.

    The other solution was to get a separate dhw tank with its own aquastat - that would not be very practcal in my case as there isn't the physical room to put a tank. Both practically and costwise, the thermostatic shower valve just was the best option.
  4. Sundeep Arole

    Sundeep Arole New Member

    Joined:
    Nov 18, 2005
    Messages:
    237
    Loc:
    Framingham, MA
    Also, depending on how far you want to go with this, there are controls available for boilers which sense the outdoor and indoor temperatures and automatically adjust the low set-point for boiler operation. Google "outdoor reset control" and you will likely be able to read about these. One relatively new gadget for residential applications is a microprocessor control called the Beckett HeatManager. This device doesn't have a outdoor sensor, but rather a indoor sensor which measures the rate of temperature drop of the boiler supply water (hence the heat load) and adjusts the burner firing pattern to match the home heat load. In a case where your boiler is oversized you can have a lot of short cycling - which is wasteful of energy. This device eliminates that. It is interesting in a house with a woodstove, since what the woodstove does is reduces the heat load as the boiler measures it, effectively making the boiler oversized in relation to the amount of heating it has to do.

    I installed one of these on my system, but only because I am a geek by nature and love to tinker with stuff, and home heating systems just seems to be the new thing I have gotten my head into for now.
  5. velvetfoot

    velvetfoot Minister of Fire

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    Loc:
    Sand Lake, NY
    I too have installed an outside temp reset control (Argo) on by Beckett fired Burnham unit with baseboard hydronic. I am still trying to get used to it; it is not as flexible, programming wise as others (more associated with floor slab hydronic) but the price was right and it was a direct plug in to the existing Argo controller. The factory setting on mine was 10. I saw the effect on the high temp. when the outside temp was nearer to 40F or so. I have an indirect hot water tank. The hot water 'zone' has priority. I am not totally sure what priority means: I know the other zones are turned off while the priority zone is on but I'm not sure if the boiler temp is allowed to go to the max programmed in the reset unit (in my case 180), or it gets turned down in response to higher outside temps. My situation would be how low I can keep it in the summer, or how low the reset keeps it in summer, to get sufficient hot water (for the wife's daily bath!) without causing flue gas condensation. What is the lowest reasonable temp... 140?
  6. fbelec

    fbelec Minister of Fire

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    Loc:
    northern massachusetts
    i wire the computers for boiler control, either the built in or after market tecmar systems. usually on those controls with the outdoor reset the priority is that until the priority zone usually the domestic hot water is satisfied nothing else gets heat. and as far as boiler control when the domestic hot water tank calls for heat regardless of outdoor temp it will make the boiler go up to 180 or 190 what ever it is set at.

    if you have a tankless hot water on your boiler set it for ten degrees differential. it will help on those oh we ran out of hot water. by the time the boiler kicks in and heats the cast iron you'll be cold if you have it at 30 degrees.

    budarus boilers computer is very nice. it has about 8 or 10 programs built into the computer depending on your situation with who is home and when. customers say it's saving them oil.
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