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Backup boiler controls

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rich p_4
rich p_4 Member Posts: 25
How about a real simple aquastat, set to 120
or whatever, have it fire the gas boiler when its
the waste blr drops below it.
I am sure there is many varied ways of doing the same thing
How did you pipe the boilers?
Rich

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  • Mike Dunn
    Mike Dunn Member Posts: 189
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    Backup boiler controls

    I am installing a waste oil boiler with a natural gas backup boiler in an auto repair shop. I need to find a way to only fire the back-up boiler when:
    A. the waste oil boiler is not working
    B. the waste oil is not keeping up due to whatever reason

    I am not really staging the boilers because theoretically the backup boiler may never need to run.

    Any thoughts on possible controls would be appreciated.
  • Brad White
    Brad White Member Posts: 2,398
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    Offset Thermostat Setpoints

    Set the controlling thermostat/aquastat for the backup at 2 degrees or so below the setpoint of the primary boiler control. If you set back the primary boiler setpoint you must of course set back the back-up boiler setpoint or the backup will come on.

    Thus the secondary/backup boiler will fill in regardless of the reason for the failure or inadequacy of the primary boiler.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • Mike Dunn
    Mike Dunn Member Posts: 189
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    The waste oil is directly connected to the primary loop and the backup boiler is piped injection style into the primary loop
  • Mike Dunn
    Mike Dunn Member Posts: 189
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    are you talking about using a two stage stat like the Tekmar 512
  • rich p_4
    rich p_4 Member Posts: 25
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    Injection style, do you think this would inject Gas blr water into the waste blr? You probably don't want that
    it would waste fuel. If each boiler injected into the primary loop that would be better. I am sure some one here
    has a drawing or a better way
    Good Luck
    Rich
  • Brad White
    Brad White Member Posts: 2,398
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    I was thinking

    in general terms, but a 2-stage would do the trick so long as setbacks (if used) are done in parallel. The 512 would serve the function although I have not deployed one. If there is enough setpoint differential range for you, why not? Seems simple.

    You can do either space control if that is what you are doing now, or line temperature control (aquastats for example maintaining a particular line setpoint) if that is your method.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • Mike Dunn
    Mike Dunn Member Posts: 189
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    What you said is what I meant. Sorry. They are both piped into the primary injection style.

    That being said would you drive the waste oil boiler with an aquastat to maintain a constant temp or would you have the injection controller control it's on and off
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