Electric Heat Pump Water Heaters
Chelan Home Inspections
I think we will see more and more of these Heat Pump Water Heaters (HPWH) as the energy code requires to achieve a certain amount of energy credits based on structure size.
With the Wenatchee and Chelan areas being cold during several months of the year planning on the Heat Pump Water heater discharge will need to be considered. These unit discharge cold air as part of the process of extracting heat energy from the surrounding air, just like a heat pump, air conditioner or refrigerator will.
Here is a study that was done in Richland Washington on energy consumption of ducted and unducted HPWH. From the study- “HPWH are a promising technology for substantially reducing water heating-related energy use. However, concerns have been raised regarding the impact of HPWHs on space conditioning energy when installed in conditioned space in northern climates. Modeling studies have suggested that installing exhaust ducting on HPWHs may mitigate some of this impact.” For many of these HPWHs you may need an adapter kit to install ducting.
Study Link- https://aceee.org/files/proceedings/2014/data/papers/1-1203.pdf
These HPWH have a slightly more complicated set up than your standard electric water heater because you have to plan on condensate discharge just like a AC/Heat Pump.
Your typical cold water inlet is also at the bottom of the unit versus the top like conventional water heaters.
These water heaters should have an unrestricted airflow and require a minimum installation space of 750 cubic feet.
From AO Smith- “To ensure optimal performance and efficiency a minimum clearance of six (6) inches from the back, left and right sides of the water heater must be maintained. A minimum of 12 inches from the front of the unit should be maintained for control access. Service clearances of three (3) feet from the left and right sides are recommended as a best installation practice.”
Another item these HPWH have is an air filter. It is recommended to clean the filter of the HPWH every month.
Another difference is that your heat pump water heater will come with several modes on how the HPWH will operate.
Heat Pump Mode-
This mode will heat with Heat Pump operation and will not use electric heat during typical heating and demand cycles. This mode has a low recovery, but minimizes power consumption.
Energy Saver Mode- (typically factory set mode for shipping.)
This mode optimizes Heat Pump and electric heat that results in low power consumption and High recovery.
This Mode will heat with the electric resistance elements. This mode should only be used during filter and condensate drain maintenance periods. This mode will result in maximum power consumption.
This mode will allow duration setting between 1 and 28 days or set indefinitely with the "Hold" setting. Tank temperature will be maintained at about 65º F.
It is my feeling that with proper planning of ducting of the HPWH you can take advantage of this cold discharge in the summertime to provide some additional cooling BTU’s and by using conditioned heated air from the conditioned space in wintertime to improve efficiency during the heating months.
Links to a few Manufacturer documents-
“The first principle is that you must not fool yourself... and you are the easiest person to fool.”
If you find any errors or have additional information that would expand on any code, building standards or manufacturer requirements please let me know.
NCW Home Inspections, LLC is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…
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