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  1. #21
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    Nov 2007
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    42

    Default Re: Weather Response Heating Control System

    Quote Originally Posted by Blue RidgeParkway View Post
    sparky,

    here is a link for you.

    http://www.heatinghelp.com/heating_howcome1.cfm

    i'm suprised you don't have a bypass by now.
    Thanks for the link!... a great refresher on gravity-feed and another chance for me to see all the variations on old installations.

    I now see the bypass you are talking about and read about all the reasons these were installed.

    My system is 100 years old but the boiler is a Burnham V3 and the burner is a Blue Angel, both from the 1980's and professionally installed at that time.

    According to my original Burnham V3 instruction sheet, they simply show a supply and return pipe as the recommended installation for a gravity system with no bypass valve. However they do mention the need for a bypass in the situation where a gravity feed system is "converted". Mine is not converted... it's all original (no pumps).

    My guess is that since water is flowing so slowly and has such a huge mass that there is little chance for water temperature differential to get so great as to shock the boiler. i.e. water returning from my radiators is never cold unless water flowing into them from the boiler is cold.
    Last edited by sparky672; 11-18-2008 at 02:47 PM.

  2. #22
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    Aug 2007
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    The Great White North
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    Default Re: Weather Response Heating Control System

    Quote Originally Posted by sparky672 View Post
    I wasn't considering the circulating portion of the circuit when I replied.

    However, my boiler has no mechanical circulation. I have a gravity feed system with one zone. The thermostat calls for heat and the boiler fires until the thermostat is satisfied. Blocking the operation of the thermostat (when the water temperature is warm enough and it's warmer outside) is the only way I could use such a device.

    On warmer days (40s & 50s), my boiler fires for a long time since it take a long to heat up and circulate that much water. By the time the radiators get hot and the thermostat is satisfied, the boiler stops but the radiators are still getting hotter. The system overshoots the thermostat by a large margin. Such a device by tekmar would prevent this but shutting down the boiler sooner on these warmer days when the boiler water reaches the lower temperature... thus giving the water more time to circulate and warm the large radiators.
    Sorry about that ... you hadn't made that clear in your previous postings.

    As mentioned earlier .... I'm no expert on boilers .... forgive my elementary thoughts about them .........

    If I understand a gravity fed system ...... the thermostat would call for heat .... signals the boiler to fire ...... which heats the water to the temperature set by the high limit ..... the water eventually rises and flows through the rads constantly heating them.

    When the set point at the thermostat is met it signals the burner to shut off ..... meanwhile warmed water is still flowing through the rads and heating them. It's understandable the temperature is over shooting because of the slow response of the hot water still flowing and the rads are still radiating ..... however .... the burner has been shut off not wasting any fuel.

    Question ....... instead of using the controller ....... couldn't you accomplish the same thing by manually adjusting the high limit to a lower temperature for heating the water .... raising as needed ?
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #23
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,824

    Default Re: Weather Response Heating Control System

    On a gravity fed system it would have to control the boiler high temp not the thermostat control. Other wise yiou would not be able to get any heat until the ouside temp got cold. By setting the high temo limit it would cycle the firing to maintain a boiler temp of 137 degrees rather than having it heat up to q80 degrees.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  4. #24
    Join Date
    Nov 2007
    Posts
    42

    Default Re: Weather Response Heating Control System

    Quote Originally Posted by JLMCDANIEL View Post
    On a gravity fed system it would have to control the boiler high temp not the thermostat control. Other wise yiou would not be able to get any heat until the ouside temp got cold. By setting the high temo limit it would cycle the firing to maintain a boiler temp of 137 degrees rather than having it heat up to q80 degrees.
    Jack
    There are are two temperature inputs on the Tekmar unit. Outside temperature and boiler water.

    If it's warm outside and boiler water is colder than 137, boiler would still fire as called by the thermostat.

    But there's no need to debate me on whether or not the unit is in the thermostat circuit, the Tekmar data sheet is pretty clear about that.
    Last edited by sparky672; 11-18-2008 at 08:19 PM.

  5. #25
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    Aug 2007
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    The Great White North
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    Default Re: Weather Response Heating Control System

    Sure could use JacktheShack's input.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  6. #26
    Join Date
    Nov 2007
    Posts
    42

    Default Re: Weather Response Heating Control System

    Quote Originally Posted by canuk View Post
    Sorry about that ... you hadn't made that clear in your previous postings.

    As mentioned earlier .... I'm no expert on boilers .... forgive my elementary thoughts about them .........

    If I understand a gravity fed system ...... the thermostat would call for heat .... signals the boiler to fire ...... which heats the water to the temperature set by the high limit ..... the water eventually rises and flows through the rads constantly heating them.

    When the set point at the thermostat is met it signals the burner to shut off ..... meanwhile warmed water is still flowing through the rads and heating them. It's understandable the temperature is over shooting because of the slow response of the hot water still flowing and the rads are still radiating ..... however .... the burner has been shut off not wasting any fuel.

    Question ....... instead of using the controller ....... couldn't you accomplish the same thing by manually adjusting the high limit to a lower temperature for heating the water .... raising as needed ?
    As I stated in an earlier post, with the huge mass of water and the slower response time, my boiler water only reaches the upper limit of 180 on the really cold days. On warmer days, it runs cooler as the boiler fires less.

    As far as overshooting the thermostat, it only happens on really warm days when the boiler starts cold... this problem can be manually solved by my killing the thermostat before things get hot.

    Originally when I saw the episode, I thought this unit could save energy. However, after thinking about how my water temperature isn't always at the high limit, this device would do very little for me on my system.

  7. #27
    Join Date
    Aug 2007
    Location
    The Great White North
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    4,045

    Default Re: Weather Response Heating Control System

    Quote Originally Posted by sparky672 View Post
    As I stated in an earlier post, with the huge mass of water and the slower response time, my boiler water only reaches the upper limit of 180 on the really cold days. On warmer days, it runs cooler as the boiler fires less.

    As far as overshooting the thermostat, it only happens on really warm days when the boiler starts cold... this problem can be manually solved by my killing the thermostat before things get hot.

    Originally when I saw the episode, I thought this unit could save energy. However, after thinking about how my water temperature isn't always at the high limit, this device would do very little for me on my system.
    Somehow that point was overlooked and if that is the case I would have to agree .
    "" an ounce of perception -- a pound of obscure "
    - Rush

  8. #28
    Join Date
    Jan 2008
    Posts
    731

    Default Re: Weather Response Heating Control System

    Quote Originally Posted by sparky672 View Post
    Thanks for the link!... a great refresher on gravity-feed and another chance for me to see all the variations on old installations.

    I now see the bypass you are talking about and read about all the reasons these were installed.

    My system is 100 years old but the boiler is a Burnham V3 and the burner is a Blue Angel, both from the 1980's and professionally installed at that time.

    According to my original Burnham V3 instruction sheet, they simply show a supply and return pipe as the recommended installation for a gravity system with no bypass valve. However they do mention the need for a bypass in the situation where a gravity feed system is "converted". Mine is not converted... it's all original (no pumps).

    My guess is that since water is flowing so slowly and has such a huge mass that there is little chance for water temperature differential to get so great as to shock the boiler. i.e. water returning from my radiators is never cold unless water flowing into them from the boiler is cold.
    your welcome for the link.

  9. #29
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,824

    Default Re: Weather Response Heating Control System

    Quote Originally Posted by sparky672 View Post
    There are are two temperature inputs on the Tekmar unit. Outside temperature and boiler water.

    If it's warm outside and boiler water is colder than 137, boiler would still fire as called by the thermostat.

    But there's no need to debate me on whether or not the unit is in the thermostat circuit, the Tekmar data sheet is pretty clear about that.
    Just went back over the data sheets and wiring diagrams. As I understand it you set a max temp and a min temp and when heat is called for (by the t-stat, you were right) the unit will cycle the boiler to maintain a temp on a scale some where between the two extremes based on the outside temp. Advantage would be you save fuel on cool days, disadvantage would be it would take longer from a cold start on a cool day to reach room temp called for.
    Jack
    Last edited by JLMCDANIEL; 11-18-2008 at 11:38 PM.
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  10. #30
    Join Date
    Nov 2007
    Posts
    42

    Default Re: Weather Response Heating Control System

    Quote Originally Posted by JLMCDANIEL View Post
    Just went back over the data sheets and wiring diagrams. As I understand it you set a max temp and a min temp and when heat is called for (by the t-stat, you were right) the unit will cycle the boiler to maintain a temp on a scale some where between the two extremes based on the outside temp. Advantage would be you save fuel on cool days, disadvantage would be it would take longer from a cold start on a cool day to reach room temp called for.
    Jack
    Yes, exactly.

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