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Domestic Hot Water
The EcoULTRA tank is equipped with an optional internal Heat Exchanger (HX) for domestic hot water
production. This consists of 200 feet of 1/2” copper piping. Based on 120 F water tank temperatures this
200 ft of ½”OD cooper pipe 26.2 sq/ft surface area and has a volume of 1.5 total gallons.
Based on 50 F entering water temp with a tank temp of 120 F the internal HX
has the performance variable based on flow rate.
At 2.5usgpm: the DHW outlet temp. shall get to around 115F
At 5.0 usgpm: the DHW outlet temp. shall get to around 100F
Pressure Drop versus Flow Rate
Because the efficiency of the heat pump is better at lower water temperatures, we recommend using the
internal domestic hot water coil in a pre-heat arrangement. In this diagram the cold water enters the coil
from the bottom and exists at about 95% of the tank setting temperature. Following this the warm water
then goes to the primary tank or an on-demand water tank where it is topped up a few degrees to reach
120 F or more depending on the application.
When sizing a heat pump with domestic hot water load please add about 10,000 BTU per person to the
daily load. So a house with 4 persons would need an extra 40,000 BTU per day. On an hourly bases this
would be 1,667 BTU/hour over 24 hours.
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