Northern Heatpump NorthStar RD-WE-096 Installation & Operating Instructions Manual - page 23
08/19/2014
21
NI701
Buffer Tank Controller – HP-BTC or HP-BTC-24
This add-on optional Electro Industries controller is suggested to improve and easily take care of the buffer
tank, up to 6 zone pumps/valves, 4-wire stat for cooling, cooling fan coil pump, etc. In addition, a major feature
of this controller is the ability to operate the buffer tank temperature with outdoor reset concept. In its pricing
category, it is consider the most complete buffer tank controller available. The application drawings (HX101)
have nine suggested piping or usage configurations.
Forced Air Fan Coil
The water coil can be one zone from a buffer tank. When the zone controller is used, this is typically the
priority zone and with priority on the other hydronic zones are held off. The water coil should operate from the
tank’s highest temperature.
If cooling is desired or planned for the forced air water coil, the forced air room thermostat (1H/1C) will
control the Geo unit reversing valve as well as the call for heat/cool controls the air handler blower. The
buffer tank aquastat will need to function as a heat/cool device to activate the Geo unit.
Load Loop Temperature Operating Point Consideration
The efficiency of this water to water Geo unit directly relates to the load aquastat set point or operating water
temperature. Even though this unit is specified or rated at 110° (43° C) outlet temperature, the efficiency COP
can change as much as 0.8 or 1.0 from 110° F (43° C) to 90° F (32° C) (COP 2.4 versus COP 3.2). The higher
the load return water temperature, the higher the compressor discharge pressure and the higher compressor
motor current draw or watts.
Water Quality
It is very important to fill the hydronic system with good quality water to prevent bacteria or algae growth in the
antifreeze solution. This growth can cause a buildup on the heat exchanger surfaces, reducing efficiency,
capacity and cause lockouts. The water used to fill the system should have 100-PPM grains hardness or less.
There are different qualities of water, which are acceptable for use in these systems. Starting with the lowest to
the highest, softened water, bottled water, reverse osmosis (RO) water, and distilled water. NOTE: When using
reverse osmosis (RO) or distilled water you MUST use a glycol such as EnviroGard Ultra HD that contains
additional inhibitors for glycol concentrations below 35%. Using good quality water and adding 2 ounces of
household chlorine bleach for each 10 gallons of fluid, or boiler system conditioner can reduce the possibility
of a problem.