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System Description
General Overview
The PC-Series pool conditioner is a pool room dehumidifi-
er, that cools and dehumidifies pool room air whenever it is run-
ning. This is an energy-efficient alternative to the traditional
method of controlling pool room humidity, which involves ex-
hausting moist air and introducing fresh outside air that must
then be heated or cooled to the correct temperature.
The vapour compression refrigeration cycle used to cool
the air (similar to that that used in air conditioners or refrigera-
tors) produces excess heat, equal to the amount of electrical
energy put in to run the compressor.
This heat can be put into one of three places: back into the
pool room air, into the pool water, or sent to the outdoor air via
an optional outdoor condenser. There are therefore three oper-
ating modes. The operating mode is determined according to
the inputs from the supplied communicating room air thermostat
that measures the room temperature and humidity, and an inter-
nal routine or external aquastat that measures pool water tem-
perature. The air thermostat also has a user interface that al-
lows changing the air temperature and humidity setpoints.
Air coils are e-coated for corrosion protection, and pool
water heat exchanger is titanium/PVC for a corrosion resistance
that is much superior to steel, copper, or CuNi. The cabinet is
powder coated galvanized sheet metal, which achieves com-
plete coverage and has a corrosion protection that is superior to
stainless steel due to the potential for impurities in stainless
material. Control is overseen by the Nordic GEN2 programma-
ble control board, which has many advanced features like laptop
connectivity via the free PC App software, data logging & gra-
phing, and electronic temperature & pressure sensors. An elec-
trically commutated (ECM) blower motor with adjustable airflow
is standard.
An optional AC2-Series outdoor condenser is available as
an accessory, which enables Heat Rejection Mode (see below).
1. Air Reheat Mode
In this mode, air is cooled and dehumidified by the PC's
internal refrigerant-to-air evaporator coil. Air is then reheated
with the PC's internal refrigerant-to-air condenser coil. There is
a net heating effect on the air, equal to compressor power input.
The air emerges drier and warmer than it went in.
2. Pool Water Heat Mode
In this mode, air is cooled and dehumidified by the PC's
internal refrigerant-to-air evaporator coil. Heat is rejected to
pool water, some portion of which is circulated through the
PC's internal refrigerant-to-water condenser coil by the pool
pump. The air emerges drier and cooler than it went in, and
water emerges warmer than it went in.
Unlike in firmware prior to v3.60, priority is now always
pool water heating, since the previously available air heat priori-
ty setting resulted in excessive compressor cycling and mode
switching. Therefore if there is demand for both air and pool
water heating, the pool water heating demand will be satisfied
first.
Typically, while performing dehumidification the PC-
Series unit will provide all of the pool water heating re-
quired for an indoor pool, with no auxiliary pool water heat-
ing required. Auxiliary heat will be required for the pool
room air during colder weather.
ISSUE 03: 1-Oct-2021
3. Heat Rejection Mode
(AC2-Series Outdoor Unit)
In this mode, air is cooled and dehumidified by the PC's
internal refrigerant-to-air evaporator coil. Heat is rejected to an
optional outdoor condenser unit (AC2-Series), which is
available as an accessory from Maritime Geothermal Ltd., and
is often only necessary in warmer climates or in buildings with a
high solar gain. There is automatic detection of the outdoor
condenser by the PC unit. If not present, either air reheat mode
or pool water heat mode will be engaged instead, according to a
user setting accessible through the PC App software.
There are two sizes of outdoor unit, one for PC sizes
45/55 and one for PC sizes 65/75/80. The AC2 contains only
the outdoor refrigerant-to-air heat exchanger (air coil), and an
ECM hub motor axial fan. The hub motor fan is speed con-
trolled by the PC's GEN2 control board based on refrigerant
discharge pressure. This results in maximum airflow when
needed, while allowing reduced airflow at other times for noise
and power savings.
Because the outdoor unit is only used for heat rejection,
there is no outdoor expansion valve (EEV) or defrost cycle logic
necessary. Although the NORDIC AC2 and ACE outdoor units
look similar, the AC2 is used with the Nordic PC series, and the
ACE (which includes the outdoor EEV and defrost logic) is used
with Nordic air source heat pumps like the ATW, ATA, and ATF
series.
Open loop (well water or other cold water loop) may be
used in place of an outdoor unit for heat rejection; see
chapter.
Auxiliary Air Heat
While PC is operating in any mode, auxiliary heat (usually
an electric plenum heater) will also be engaged if the air temper-
ature drops below the air heat Auxiliary setpoint.
The first function of the plenum heater is to act as an auxil-
iary heat source for the pool room air. It will provide additional
air heating on cold days when the pool water requires all or
most of the unit's heat output.
The second function of the plenum heater is to provide
emergency heat should a problem occur that causes the PC unit
to be locked out on a safety control. The control board automat-
ically controls the auxiliary heat, allowing the plenum heater to
function even if the PC compressor is locked out and not opera-
tional.
Electric plenum heaters are available as accessories in 5,
7, 10, 15 and 20kW sizes. See the Sizing, Wiring, and
work
sections. These heaters are installed in the air dis-
charge ductwork outside the PC unit.
Other types of air heat (gas, hydronics from a water-to-
water geothermal system) can be used, and should be con-
trolled by the 2 stages of dry contacts marked "Plenum Heater"
on the terminal strip in the PC unit.
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