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Ignoring the outdoor reset on Lochinvar Knight

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russiand
russiand Member Posts: 73
I need to have just one of the built in heating zones on a Lochinvar Knight ignore the outdoor reset. Whats the easiest way to do this? Thanks in advance!

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  • Ironman
    Ironman Member Posts: 7,379
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    Is the zone for space heating or domestic hot water?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • russiand
    russiand Member Posts: 73
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    Space heating, but don't want to honor the outdoor reset just on that one.
  • Henry
    Henry Member Posts: 998
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    You will not reap the benefit of the Lochinvar condensing mode due to O.R. You will have to run the boiler at high temperature.
  • Ironman
    Ironman Member Posts: 7,379
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    Do you have an indirect connected?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • russiand
    russiand Member Posts: 73
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    Yes, I do have an indirect already connected. And yes I do realize that I will not enjoy the benefits of ODR on the zone I am trying to make ignore it. But I still want to find a way to do it.
  • Henry
    Henry Member Posts: 998
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    You will have any ODR for any zone. You will have to run the boiler at high temperature continuously
  • russiand
    russiand Member Posts: 73
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    So it's all of them or nothing, there is no way to get just one zone to ignore ODR?
  • Ironman
    Ironman Member Posts: 7,379
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    The Knight is capable of accepting 3 thermostat (heat demand) inputs. Each can have its ODR curve programmed differently. Simply program the ODR curve for that zone to give you the same SWT that you want at the top and bottom of that curve. Also, set the WWSD for that zone as high as needed.

    The demand signal will have to be wired to the corresponding terminals on the Knights control board.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    Leon82Boon
  • Dave H_2
    Dave H_2 Member Posts: 556
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    or.....
    Use a zone controller. Depending upon how your system is zoned, pumps or zone valves you can use a multizone controller for that one zone and the DHW indirect zone.
    Take the XX terminals from this controller and go to the DHW input of the boiler. Use the priority setting on the controller so that the DHW still runs in that mode.

    Dave H
    Dave H
  • NY_Rob
    NY_Rob Member Posts: 1,370
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    Ironman said:

    The Knight is capable of accepting 3 thermostat (heat demand) inputs. Each can have its ODR curve programmed differently.

    That's an awesome feature!

    But, what happens when more than one t-stat is calling for heat and both zones have different ORD curves? Say it's 30F outdoors and one zone calls for 120F SWT and the other zone calls for 135F SWT.
    The boiler can't supply two or more different SWT's can it?
  • Leon82
    Leon82 Member Posts: 684
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    > @NY_Rob said:
    > The Knight is capable of accepting 3 thermostat (heat demand) inputs. Each can have its ODR curve programmed differently.
    >
    > That's an awesome feature!
    >
    > But, what happens when more than one t-stat is calling for heat and both zones have different ORD curves? Say it's 30F outdoors and one zone calls for 120F SWT and the other zone calls for 135F SWT.
    > The boiler can't supply two or more different SWT's can it?

    The highest temp is used
  • russiand
    russiand Member Posts: 73
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    I love the idea of connecting another zone controller to the DHW terminals. I will do exactly that, that's exactly what I need. Thank you so much for all the suggestions!!!
  • Rich_49
    Rich_49 Member Posts: 2,766
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    What is connected to the zone you want to ignore ODR on ? Why are you interested in doing this ?
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    732-751-1560
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • NY_Rob
    NY_Rob Member Posts: 1,370
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    @Leon82...

    Thanks for your reply!
  • Boon
    Boon Member Posts: 260
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    I may not be interpreting what is going on here exactly but I think I’m reading that a space heat call will run through a zone controller and land on the DHW terminals at the boiler. Is that right?

    That would avoid the ODR but it would be subject to the DHW anti-cycling parameters.
    DIY'er ... ripped out a perfectly good forced-air furnace and replaced it with hot water & radiators.
  • NY_Rob
    NY_Rob Member Posts: 1,370
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    Most ODR "sensors" are just NTC (Negative Temperature Coefficient) thermistors.
    You could run one of the thermistor leads to the NC terminal of a SPDT micro relay, bridge that to a high value (68K Ohms maybe) resistor connected to NO relay terminal. Connect the common terminal back to the thermistor lead that runs to the boiler. Wire the relay coil to the t-stat hot lead. When the t-stat is calling for heat, the relay coil energizes and you add 68K ohms to the thermistor value which would fool the boiler into thinking it's -5F outside. Once that zone is satisfied, the relay coil releases and the thermistor value is normal again.

    Total cost would be under $20 if that much.
    Ironman
  • Ironman
    Ironman Member Posts: 7,379
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    Boon said:

    I may not be interpreting what is going on here exactly but I think I’m reading that a space heat call will run through a zone controller and land on the DHW terminals at the boiler. Is that right?



    That would avoid the ODR but it would be subject to the DHW anti-cycling parameters.

    I think what Dave is proposing is using a 2 zone pump control like an SR502 and running both the DHW circ and the High temp zone into it. Then use the "X X" terminals on it to signal the DHW terminals on the boiler. The "Priority Zone" on the SR502 or 503 would have the indirect connected to it. It's a sound idea.

    The only holdback that I see would be if the HIGH temp zone requires a sustained heat, then the priority function in the BOILER would have to be set to a very minimum time depending upon the likelihood of this.

    A similar issue is there if you setup one temp zone on the boiler to override the ODR: that will cause the boiler to go to the highest SWT calling and that would send 180* to every zone that's calling until the High temp zone is satisfied. A mixing valve(s) would then be necessary for the other zones to prevent over heating. Lochinvar has an add on module to do this, but it also requires motorized valves on the zones. Not cheap.

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.