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Inspecting Heat Pump Water Heaters
With the new hot water tank requirements, we will be
seeing more heat pump type hot water tanks. We will look at how they
work, then how to inspect them. First some background. Heat Pump Water
Heaters (HPWH) have been around for quite some time. Earlier units were
not integrated. They were added on to existing conventional hot water
tanks. They look like a large cube, next to a hot water tank. A heat
pump would pump water from a tank water heater, heat it and then return
it to the tank. The modern units are integrated into a single unit. A
heat pump basically moves heat from one place to another, no different
than a conventional air conditioning unit. A HPWH moves heat from your
basement or mechanical room into the hot water tank. This may also
reduce humidity and lower the temperature in the area where the unit is
installed. Auxiliary electric heating elements are installed to
compensate for large hot water demands. Most HPWH can normally heat 8
gallons of water per hour. In comparison, a conventional electric unit
can heat 20 gallons per hour. Most HPWH have different modes;
- “Hybrid” – uses both
electric heating elements and the heat pump. This is the
recommended setting and likely the default setting on many
units.
- “Heat Pump” – uses only
heat pump. Not a recommended setting as the hot water recovery
time is considerably diminished
- “Full Electric” – works
as a conventional electric hot water tank
Typical
Control Panel
What should a home inspector be looking for;
Inspecting Heat
Pump Water Heaters
·
Ambient air where the tank is installed should
be between 45°F and 100°F. If the temperature drops below 45°F, the unit will
switch to full electric mode
·
Ambient air in the area where the HPWH is
installed will be reduced by 2-4°F
·
It is recommended HPWH are installed in areas
where the temperature is between 50-55°F. The unit becomes less efficient as
the temperature decreases.
·
HPWH’s should be installed in areas with a
minimum volume of 750 cubic feet (room size -10’ x 10’ x 7’6” high) for 55
gallon tanks, 1000 cubic feet for 80 gallon tanks
·
The expected serviceability life is generally
the same as conventional tanks
·
Clearance requirements are as follows: Front –
2’, Rear- 8”, Top – 16”
·
The air entry and discharge at the top of the
tank must be free of obstruction to
allow air to flow freely
·
The unit should not be installed in obstructed
air space
·
The air filter, usually at the top of the unit,
should be clean. There may be a screw securing the filter panel to the unit
·
The evaporator coils should be clean and
undamaged
·
If installed in the living space, it may reduce
the temperature, causing the heating system to activate more often
·
It should not be installed near a thermostat
·
The unit will be much more noisy that a
conventional electric unit, similar to a window air conditioner
·
HPWH’s should not be installed in a kitchen;
oils can damage the unit
·
The condensate drain line should be undamaged,
and delivered to a proper drain. The use of a condensate pump may be required
·
It is recommended that the electric supply for
the condensate pump is directly from the unit, not from a separate GFCI
receptacle. This is to ensure that water does not accumulate around the unit if
the GFCI trips
·
It is recommended that a HPWH is slightly
elevated and installed in a catch pan
·
Any water in the catch pan or around the unit
indicates a leak or damaged condensate drain
·
The 240V electrical connection should be
inspected. Most units require 10 AWG with a 30 Amp double pole dedicated
circuit breaker
·
Temperature and Pressure relief valve should be
installed with an adequate discharge pipe to within 6” of the floor
·
A shut off valve should be installed on the cold
water inlet pipe
·
A thermal expansion tank should be installed
·
The tank temperature should be set at 120°F
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