Operating instructions

7
Night setback thermostats are not recommended on
radiant floor systems due to the response time of the slab.
Radiant floor systems are not usually recommended for
cooling, since cold, clammy floors and poor
dehumidification may result. To provide cooling to a
radiant floor heating installation, the installation of a fan
coil unit is recommended. Another alternative is a
GeoSource 2000 combination heat pump.
B. Fan Coils
Fan coils can be used with ECONAR's hydronic heat
pumps in the heating and cooling mode. In many cases,
radiant floor heating and fan coil cooling are used
together. Fan coils also provide dehumidification in the
cooling mode. The rate of dehumidification can be
adjusted by varying the fan coil operating temperature.
Fan coils are available in many different sizes and
configurations, making them very flexible to your
particular application. Valence heating and cooling
systems, which use natural convection to move air, can
also be very versatile.
)Note: When selecting fan coil units for cooling use,
make sure they include condensate pans.
Fan coils are sized for capacity at specific water
temperature and flow rate combinations. Their sizing is
also based on air temperatures, air flow rates (which
remain constant based on fan speed selection and static
pressure differential), and humidity conditions. The fan
coils are then matched to the heat pump at a common
system flow rate and operating temperature to provide the
overall system capacity to a space load.
High static pressure fan coils have recently come onto the
market, which work well with ECONAR's hydronic heat
pumps. These systems provide heating and cooling for
houses without ductwork. They use a high static pressure
blower to supply air through small tubes, which run
through chaseways to the living space. The blower passes
air though a water-to-air coil that is coupled to a hydronic
heat pump to provide heating and cooling. These systems
work nicely on retrofit applications where ductwork isn't
available or wanted. Fan coil data is available in Table 5.
C. Baseboard Heating
Another application of hydronic heating is finned tube
baseboard heating. This is the same tubing used with
boilers with one major difference. The discharge
temperature of a boiler is much higher than geothermal
heat pumps. The heat pump system should be sized at
115
o
F hydronic leaving water temperature to maintain
efficiency. At a 125
o
F hydronic leaving water
temperature, the heat pump is at a maximum operating
temperature and may start to trip off on high head
pressures. Standard 3/4" finned tube baseboard
conductors have an average output of 230 Btuh/ft at
120
o
F hydronic leaving water temperature. In most cases
there is not enough perimeter area in the conditioned
space to allow for the required length of tubing to handle
the entire heating load. There have been successful
installations using baseboard as supplemental heating but
many factors must be considered.
Cast iron radiators have been used successfully. If these
radiators are rated for an output of 70 Btuh/square inch at
a 130
o
F hydronic leaving water temperature, they work
well with geothermal systems. Although the radiator may
be rated at 130
o
F, the system should still operate at the
standard 115
o
F leaving water temperature of the water-to-
water heat pump.
D. Other Applications
Additional open loop hydronic applications such as
outdoor swimming pools, hot tubs, whirlpools, tank
heating, etc. are easily sized based on heat exchanger
operating temperature and flow. The worksheet in
Appendix 1 was taken from the ASHRAE 95
Applications Manual and can be used for outdoor
swimming pool sizing. In many instances, sizing a heat
pump to these applications comes down to recovery time.
The larger the heat pump (within reason to avoid short
cycling) the faster the system recovery time will be.
)Note: Installing a plate heat exchanger (see Figure 6
for an example) between the heat pump and an open
system is required when corrosive fluid is used in the
open loop, especially on swimming pools where pH
imbalance can damage the heat pump. )Note: Expect
the maximum operating temperature of an indirect
coupled application to be 10
o
F below the maximum
operating temperature of the heat pump.
Other forms of closed loop systems such as indoor
swimming pools, pretreated fresh air systems, snow melt
systems, and valance heating/cooling systems are also
very common with hydronic heat pumps. The sizing of
the heat pump to these systems is more precise and
information from the system manufacturer is required.
V. APPLICATIONS OF
HYDRONIC HEAT
EXCHANGERS
This section deals with some common practices used
when coupling the ECONAR GeoSource 2000 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.