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new Lochinvar NKC150N Noble combi and increased electricity usage

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BostonKGK
BostonKGK Member Posts: 10
in Gas Heating
A new Lochinvar NKC 150N GAS heating/hot water combi tankless unit was installed in October 2023. I noticed that the monthly electricity usage doubled from previous years. Previously I had a Rennai tankless unit (installed in 2012, gas). Does Lochnvar unit comsume more electricity? I notice the unit produces loud "engine" noise when I turned up the heat (from 50 degree to 60 degree in Boston winter) or use hot water. Thanks for your thoughts.

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  • Hot_water_fan
    Hot_water_fan Member Posts: 1,867
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    We need more details. Can you report this winter’s kWh vs pre combi? 

    In general, I think you’re noticing something else and attributing it to the wrong source. It’s possible for a boiler to use more electricity, but double the entire household? Unlikely. 
  • Jamie Hall
    Jamie Hall Member Posts: 23,358
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    And let's make sure we're talking about actual KWh of usage, and not the cost...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Hot_water_fanGroundUp
  • BostonKGK
    BostonKGK Member Posts: 10
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    Yes the usage increased from around 80kWh to around 160kWh monthly.
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,867
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    That’s for the entire house? That’s extremely low if so. 
  • BostonKGK
    BostonKGK Member Posts: 10
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  • BostonKGK
    BostonKGK Member Posts: 10
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    There was no change in the way that we used electricity- no additional appliances or lights, etc.
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,867
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    Hmm it’s possible. What are the circulator(s) programmed to do? Did that change? Was the Rinnai modulating? 

     That’s about $10/month in my area. 
  • Jamie Hall
    Jamie Hall Member Posts: 23,358
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    Quite possible that its a difference in pump or fan power -- particularly fan power. Your 80 KWh per month works out to a bit over100 watts consumption per hour, which isn't that much.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 22,189
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    Is it in the always hot mode?
    You can run most combis so they only fire and heat when hot water runs, or keep the boiler hot all the time , which shortens the wait time but uses more fuel and electricity 

    Get into the DHW parameter and see how it is set. The manual should explain the setting 
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • GroundUp
    GroundUp Member Posts: 1,918
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    Is the pre-heat enabled? Did anything else get changed when this was installed (pumps, zone valves, thermostats, etc)? The noise is just how the Noble is. They're loud, especially if the intake is drawing from indoors.
  • PRR
    PRR Member Posts: 151
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    60kWh/month is like one 75 Watt 24/7 load. Light in the attic?

    I wish I had 160kWh months.

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