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  1. #1
    Join Date
    Jul 2008
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    9

    Driving dual fuel Carrier Infinity from a standby generator

    Back in 2008 I had 2 Carrier Infinity systems installed in my house, and since that was the year of high oil prices I had them install it as a dual fuel system - about 35-40 degrees it uses a heat pump and below that uses oil hydronic heat. It's worked great since then.

    But now in the Northeast we've had entirely too many week long power outages so I'm looking to install a permanent backup generator. The generator people are asking me to find out if the Infinity systems can be configured to skip the heat pump stage and go right to oil heat in the event that the system is being driven by the generator - this would greatly reduce the size of the generator required and save me a lot of money.

    I'm a little afraid that since this question is off the beaten trail that it might be over my local installers head, but Carrier won't talk directly to me. I'm not trying to do this work myself, just trying to find out for sure what the correct answer is and steer my installers in the right direction.

    Does anyone have any info on this?

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,048
    A carrier guy can confirm. but don't you have the ability to set the controller to emergency heat, or to raise the lock out temp to above what ever the temps are during the time your on the generator.
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  3. #3
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
    Posts
    1,481
    On the Infinity UI, you can hold the red (heat) button for approx. 10 seconds. You will then have the option for emergency heat only. With emergency heat, this will engage your oil furnace only and disable the heat pump.

    Are you wanting to do this automatically when the generator starts? This will be near to impossible with this communicating systems. If you had a standard systems, we could accomplish this with a few relays.

  4. #4
    Join Date
    Jul 2008
    Posts
    9
    Thanks for the reply. I did just see the red button for 10 seconds option to pick a heat source and that gets me closer, but I'd really like this to happen automatically - if it isn't automatic and the power fails then I'd be trying to overload the generator until someone manually set the controls to bypass the heat pump. Probably not a good thing.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,048
    Not if you don't connect the condenser to the generator.
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  6. #6
    Join Date
    Jul 2008
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    9
    I think we're getting there. So if the condenser is not powered and the rest of the system (thermostat and air handler) is, then even if no settings change is made at the thermostat and heat is needed, will the Infinity system just try to use the heat pump for maybe 10-15 minutes, have it not be enough and then move on to the hydronic heat without manual intervention? And will this not damage anything and simply go back to normal once the full power is restored? If that's the answer then I'm all set.

  7. #7
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
    Posts
    3,185
    so, this backup generator you are installing, is not going to be large enough to handle the compressor startup loads... so... in the summer time when power demand is at it's highest, and you need a/c, you will not have it?
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  8. #8
    Join Date
    Jul 2008
    Posts
    9
    The house has 2 Carrier Infinity systems (one for each floor) and one oil burner. Supporting power for everything would require a move from a 20kw air cooled unit to a 30kw water cooled unit which is $10k more expensive. And we have a woodburning fireplace which is sufficient for heat in the commonly occupied parts of the first floor. So the compromise we're planning to make is that the first floor compressor will not be powered, but the second floor will - that way we'll have A/C in the bedrooms in the summer and oil heat.

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,048
    Smart move.
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  10. #10
    Join Date
    Apr 2011
    Location
    SE Washington
    Posts
    533
    no way for you to configure this so it knows what the power source is,
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  11. #11
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    5,520
    Quote Originally Posted by isuredo View Post
    no way for you to configure this so it knows what the power source is,

    Sort of. I believe you can setup the controller to accept and external input to the "G" terminal that you can use to disable either jsut 1st stage of both stages of the compressor. I think it can also be probrammed ot force hte unit into a particular stage for soning applications usign a 3rd party zone controller. The compressor lock-out feature I think is primarily intended for Utility load shedding programs with smart meters. I'm not sure if it works in heat mode. Hwoever, it might not be a bad idea to have a switch wired in to enable that feature when using the generator so the upstairs only runs on 1st stage and saves you some operating costs. 1st stage is much more efficient than 2nd in cooling. About a wash in heating for most units I think.

  12. #12
    Join Date
    Aug 2001
    Location
    Pavilion, NY
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    2,139
    I am not familiar with the specific unit jut I assume the unit will shift to emergency heat below your balance point of x degrees. I also assume that the control uses an outdoor sensor to achieve this. Perhaps a resistor can be installed in parallel through a relay powered by the 12volts from the transfer switch? It will think it is zero degrees outside when the generator runs... Just a thought
    ...

  13. #13
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    Newer infinity controllers use the temp sensor on the outdoor unit. If you tried to fool it you could affect the defrost logic. Mine displasys coil temp and outdoor temp..but it just cooling only. I wish I had gone dual fuel.

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