Operating instructions

7
into the heat pump.
Filling and purging a loop system are very important steps
to ensure proper heat pump operation. Each loop must be
purged with enough flow to ensure two feet per second flow
rate in each circuit in the loop. This normally requires a 1½
to 3 HP high-head pump to circulate fluid through the loop
to remove all the air out of the loop. Allow the pump to run
10 to 15 minutes after the last air bubbles have been
removed. After purging is completed, add the calculated
proper amount of antifreeze to give a 12
o
F to 15
o
F freeze
protection. After antifreeze has been installed and
thoroughly circulated, it should be measured with a
hydrometer, refractometer or any other device to determine
the actual freezing point of the solution.
The purge pump can be used to pressurize the system for a
final static pressure of 30-40 psig after the loop pipe has
had enough time to stretch. In order to achieve the 30 to 40
psig final pressure, the loop may need to be initially
pressurized to 60-65 psig. This static pressure may vary 10
psig from heating to cooling season, but the pressure should
always remain above 20 psig, so circulation pumps do not
cavitate or pull air into the system.
Contact your local
installer, distributor or factory representative for more
information.
VII. HYDRONIC-SIDE SYSTEM
DESIGN
This section deals with some common practices used when
coupling the ECONAR Ultra hydronic heat pumps to the
space conditioning heat exchanger. There are so many
possible applications for hydronic systems that they cannot
all be covered in this text. Hopefully these ideas can help in
many of your system designs.
Note – Actual systems
must be constructed to all appropriate codes and according
to accepted plumbing practices.
Caution – Always use copper pipe on the hydronic side
of the system.
Important – Pressure/Temperature port fittings must be
installed in the entering and leaving hydronic lines of the
heat pump.
A. Storage Tanks
Important – The heat pump must be coupled to the
space conditioning system through a water storage tank.
Important – The guideline for the active amount of fluid
circulating between the heat pump and the storage tank is
10 gallons of fluid for each ton of hydronic heat pump
capacity (Example, 50 gallons minimum for a 5-ton unit. If
the fluid only circulates through half of the storage tank,
then that half of the storage tank must contain the minimum
10 gallons per ton.). A properly sized storage tank
eliminates many problems with multiple zone hydronic
systems. These problems include excessive leaving water
temperature if a single zone cannot dissipate heat quickly
enough and hydronic flow reduction through the heat pump
when only one zone is calling. This may occur because the
hydronic circulating pump is normally sized to provide the
heat pump’s required flow with all zones calling. In
applications that use multiple smaller zones, storage tanks
absorb the relatively large amount of energy supplied by the
heat pump in order to provide longer run times and less
compressor cycling for the heat pump. Storage tanks also
serve to dispense energy in small amounts so that the
conditioned zones have time to absorb heat without
requiring high discharge water temperatures. (The only
instance where a storage tanks is not required is when the
heat pump is coupled to a large heat exchanger containing
the recommended amount of fluid capable of absorbing the
entire capacity of the heat pump.)
Insulated water heaters are commonly used for storage
tanks.
Note – Always check local codes to ensure water
heaters can be used as storage tanks. Using the electric
elements in the tank as a secondary heat source to the heat
pump is appealing in some applications, but special Listing
Agency Certifications may be required by many local
codes. Specially listed water heaters are available. While all
hot water tanks are insulated on the top and sides, many do
not have insulation on the bottom. An insulated pad beneath
uninsulated tanks will reduce energy loss to the floor.
Important – The hydronic flow into the storage tank
(particularly a water heater)
must not be restricted. If the
water heater has an internal diffuser “dip tube,” cut it off at
approximately 12 inches into the tank.
The tank temperature can be controlled with a simple
Aquastat or a setpoint controller. The setpoint controller
senses tank water temperature and outside air temperature
to increase the tank temperature as the outside air becomes
colder. This control scheme provides the highest heating
efficiencies by requiring the lowest possible water
temperature to heat the space. Setting the optimal design
temperatures in the controller is difficult, and the simple
Aquastat does have its advantages. To help in setpoint
control, the following equation can be used:
Reset Ratio = Design Water Temp – Indoor Design Temp
Indoor Design Temp – Outdoor Design Temp
B. Hydronic Side Circulators
Hydronic circulator pumps transfer the energy supplied by
ECONAR hydronic heat pumps to the water storage tank.
Select a quiet operating pump with the ability to supply the
required flow rate at the system pressure drop. The
circulator supplying the heat pump
must be placed in the
water supply line
into the unit to provide the best pump
performance. Individual zone circulators
must also be
placed in the supply lines of the heat exchangers they serve.
These pumps are often used as the on/off control
mechanism for the zone they supply as shown in Figure 4.
Zone valves are also commonly used for this purpose using
a common pump as shown in Figure 5.
Note – Select a common pump at the total flow of all the
zones and the highest pressure drop of any one parallel