12
Operational Overview
Heat Pump Water Heater Operation:
Heat pump water heaters remove heat from
surrounding air and use that heat to heat water.
By doing so, heat pump water heaters can operate
much more ef
fi
ciently and at signi
fi
cantly lower costs
compared to standard electric water heaters.
This heat pump water heater has four (4) operating
modes for maximum
fl
exibility in meeting hot water
needs under a variety of conditions. Available modes
are: Ef
fi
ciency, Hybrid, Electric and Vacation.
Operating Mode Descriptions:
Ef
fi
ciency Mode
provides the highest ef
fi
ciency and
lowest cost operation by using only the heat pump to
heat water. Recovery time and ef
fi
ciency will vary with
ambient temperature and relative humidity. Ef
fi
ciency
will be greatest when both are high and recovery time
will be shortest. At lower temperatures and relative
humidity levels, ef
fi
ciency will be lower and recovery
will take longer. Heat pump operation is allowed
from 45°F to 109°F ambient temperature. At ambient
temperatures lower that 45°F and greater than 109°F
the heat pump will not operate. Similarly, if the water
temperature in the tank is less than 59°F, the heat
pump will not operate. The unit will operate in electric
mode until ambient and water temperatures return to
the safe operating range of the heat pump.
Hybrid mode
provides the best combination of
energy ef
fi
ciency and hot water delivery. The heat
pump will be used to heat water after moderate hot
water use. When a large quantity of hot water is used,
the upper electric heating element will heat water in
order to speed up recovery. Once the upper portion of
the tank reaches set point, the element will shut off and
the heat pump will heat water until the average tank
temperature reaches set point. Hybrid mode provides
the highest
fi
rst hour hot water delivery with excellent
economy.
Electric mode
allows operation like a standard
electric water heater, using the upper and lower
heating elements to heat water. The heat pump is not
used in this mode. The key advantage of using this
mode is that it eliminates the cool air exhausted from
the heat pump. During cold weather months, this may
be desirable. Hot water delivery and operating costs
are comparable to a standard electric water heater with
similar tank capacity.
Vacation mode
should be used when hot water will
not be needed for a period of time greater than three
(3) days. In vacation mode electric elements are used
to heat water and set point is a non-adjustable 60°F.
Minimal electricity will be used and maintaining 60°F
minimizes the risk of the water heater freezing in cold
weather.
User Interface Module Overview:
The User Interface Module (UIM) is used to control
the heat pump water heater. It displays useful
information about the operating status of the water
heater, the selected mode of operation and the set
point temperature. Fault information will be displayed
should a malfunction occur with one of the components
or sub-systems. The UIM also is used to set the water
heater to the desired set point temperature, mode of
operation, temperature units (°F or °C) and to check
the operating condition of the heat pump through the
maintenance display, see “Accessing the Maintenance
Display”(p. 21).
Initial Start Up:
When powered up for the
fi
rst time (or when power
is re-applied after a power outage or service work is
performed), the control will run the dry
fi
re check to
establish that the tank is completely
fi
lled with water,
see “Dry Fire Element Protection” (p.8). The UIM will
display “Dry Fire” during this operation, which will take
about four (4) minutes. After eight (8) minutes have
elapsed, the fan should come on; after an aditional
thirty (30) seconds, the heat pump compressor should
turn on. Note that during the initial start up, the heat
pump will come on regardless of operation mode
selected. This is intended to allow for evaluation of
the heat pump to ensure that it is operating properly.
The heat pump will heat water until the set point
temperature is reached in the tank; it will then shut
off. After this initial start up is complete, the water
heater will operate per operational mode setting,
ambient air and tank water tamperatures, and set point
temperature.
