Operating instructions

4
maintained as low as comfortably possible.
The type of floor covering and the spacing of the pipe in the
floor have the greatest effect on operating fluid
temperature. Table 1 gives a rough estimate of expected
operating temperatures for specific floor coverings:
Table 1 – Expected Operating Floor Temps
Floor Covering
Temp (
o
F)
Carpeting
115
Tile/Linoleum/Hard Wood
100
Concrete/Quarry Tile - Residential
85
Concrete/Quarry Tile - Commercial
70
Enertech designs its ECONAR hydronic heat pumps using a
115
o
F leaving water temperature (LWT) design point. This
LWT is the ideal maximum fluid temperature for radiant
floor systems. Higher operating temperatures would result
in an uncomfortable hot feeling in the conditioned space. In
fact, boilers connected to radiant floor heating systems must
be restricted to a 115
o
F maximum temperature by mixing
valves or other control devices.
Suppliers of radiant floor heat exchanger tubing can help
size the length of pipe and fluid temperature required for
specific radiant floor heat exchanger applications. Be sure
to include two inches of polystyrene insulation under the
slab and two to four inches around the perimeter down to a
four-foot depth.
This insulation reduces the heat loss to the ground and
decreases the response time of the heating system.
Insulation is as important in radiant floor heating as it is in
other methods of heating. Poorly insulated buildings can
result in higher floor temperatures needed to heat the
building, which could exceed the level of human comfort.
Night setback controls are not recommended on radiant
floor systems due to the slow response time of the slab.
Radiant floor systems are not usually recommended for
cooling, since poor dehumidification and cold/clammy
floors may result. To provide cooling to a radiant floor
heating installation, the installation of an ECONAR FC fan
coil unit is recommended..
B. Fan Coils
Fan coils, such as the ECONAR FC series, can be used with
ECONAR 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, and the rate of
dehumidification can be adjusted by selection of the fan
coil operating temperature.
Many different sizes and configurations of fan coils are
available, making them very flexible to each particular
application. Valence heating and cooling systems, which
use natural convection to move air, can also be very
versatile.
Important – Fan coil units for cooling must have a
condensate pan; and if accidental water discharge could
cause property damage, there must also be a drained drain
pan under the unit.
Fan coils are sized for capacity at specific water flow rate
and temperature combinations. Sizing also depends 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 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.
C. Baseboard Heating
Another application of hydronic heating is finned tube
baseboard heating. This is the same tubing used with boilers
with the major difference being that the discharge
temperature of a geothermal heat pump is much lower than
a boiler. The heat pump system must be sized at 115
o
F
maximum hydronic LWT to maintain efficiency. Standard
3/4" finned tube baseboard conductors have approximately
200 Btuh/ft at 115
o
F hydronic LWT. There have been
successful installations using baseboard as supplemental
heating, and many other factors must be considered, such as
sufficient perimeter area in the conditioned space to allow
for the required amount of baseboard. Suppliers of
baseboard radiators can help size the amount of baseboard
and fluid temperature required for specific applications.
Cast iron radiators have been used successfully. When rated
for an output of 70 Btuh/square inch at a 115ºF hydronic
LWT, they work well with geothermal systems. Although
the radiator may be rated at 130
o
F, the system could still
operate at the maximum 115
o
F LWT of the water-to-water
heat pump.
D. Other Applications
Open loop applications such as outdoor swimming pools,
hot tubs, whirlpools, tank heating, etc. are easily sized
based on heat exchanger operating temperature and flow. In
many instances, sizing the heat pump to these applications
comes down to recovery time. A larger heat pump (within
reason to avoid short cycling) will provide faster system
recovery.
Important – An intermediate nickel/stainless plate heat
exchanger (as shown in Figure 1) between the heat pump