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ClimaDry Whole House Dehumidication - ClimateMaster Geothermal Heat Pumps - Rev.: 18 April, 2008B
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Overview
ClimaDry™ Whole House Dehumidication Overview
Indoor Air Quality (IAQ) and Relative Humidity (RH)
are increasingly becoming design issues that must be
addressed by selecting heating and cooling equipment
with advanced capabilities. The ClimateMaster
ClimaDry™ reheat option (patent pending) offers unique
features unlike anything currently available today.
ClimateMaster’s ClimaDry reheat option is an innovative
means of providing modulating reheat without the
complication of refrigeration controls. ClimaDry is Hot
Gas Generated Reheat, which utilizes one of the biggest
advantages of a water source heat pump (WSHP), the
transfer of energy through the loop piping system.
ClimaDry simply diverts condenser water through a
water-to-air coil that is placed after the evaporator coil.
If condenser water is not warm enough, the internal
“run-around” loop increases the water temperature with
each pass through the condenser coil.
ClimaDry Benets
ClimaDry is like no other reheat option on the market.
Proportional reheat is controlled to the desired leaving
air temperature set point (factory set point of 72°F,
[22°C}), no matter what the loop temperature is. Since
dehumidication operation will occur under less than full
load cooling conditions a good percentage of the time,
it is important to have a reheat function that provides
100% reheat in the spring and fall when the loop is cool.
Supply air temperature is eld adjustable to +/- 3°F
[+/- 1.7°C] for even greater exibility with an optional
potentiometer.
Competitors without ClimaDry typically use an on/off
(non-modulating) refrigeration based reheat circuit,
typically referred to as “Hot gas reheat” (HGR). HGR
needs higher condensing temperatures to work well,
typically 85°F [29°C] entering water temperature (EWT).
With HGR, cooler water temperatures produce cooler
supply air temperatures, which could overcool the
space, requiring additional space heating from another
source or a special auto-change-over relay to allow
the unit to switch back and forth between reheat and
heating. Rarely does HGR provide 100% reheat, like
ClimaDry.
A key benet to ClimaDry is a simple and easy to
troubleshoot refrigerant circuit. No switching valves or
hard to diagnose leaky check valves are utilized. No
unusual refrigerant pressures occur during the reheat
mode. The ClimaDry refrigerant circuit is like every other
ClimateMaster unit (without reheat), so everything the
technician already knows applies to troubleshooting
the ClimaDry refrigeration circuit. Plus, the water loop
portion of the ClimaDry option is easy to understand
and diagnose.
Features Include:
• Modulating reheat for precise control of supply
air temperatures
• 100% reheat (operates as a whole house
dehumidier)
• “Neutral” supply air temperature even at part load
(non-design) conditions
• Supply air temperature adjustment, +/- 3°F
[+/-1.7°C] from 72°F [22°C] factory setpoint with
optional potentiometer
• Integrated factory supplied reheat controls – simply
attach a humidistat or dehumidistat
• Microprocessor (DXM) controls standard
• Ultra simple refrigeration circuit
• All water system eliminates refrigeration circuit
modications (same refrigeration circuit as units
without ClimaDry)
• Stable refrigeration pressures, even at low EWTs
• All components located inside the cabinet
•
Moves heat of rejection from ground loop to supply
air stream
Availability
ClimaDry is currently available on ClimateMaster
residential Tranquility
27™ (TT) and Tranquility
20™ (TS)
series units (vertical and horizontal units only).
ClimaDry Applications
With the ClimaDry option, return air from the space is
conditioned by the air-to-refrigerant (evaporator) coil, then
reheated by the water-to-air (reheat) coil to dehumidify
the air, but maintain the same space temperature (thus
operating as a whole house dehumidier). The moisture
removal capability of the heat pump is determined by
the unit’s latent capacity rating. Latent Capacity (LC)
equals Total Capacity (TC) minus Sensible Capacity (SC).
For example, at 85°F [29°C] EWT, the moisture removal
capability (latent capacity) of a ClimateMaster size 036
heat pump is 9.6 MBtuh [2.8kW] as shown in gure 1.
Dividing the latent capacity by 1,069 BTU/LB of water
vapor at 80°F DB and 67°F WB [26.7°C DB and 19.4°C
WB] moist air enthalpy, converts the amount of moisture
removal to pounds per hour (multiply pounds per hour
by 0.4536 to obtain kg/hr). Calculations are shown
in gure 1. Most ClimateMaster heat pumps have a
sensible-to-total (S/T) ratio of 0.72 to 0.76. Therefore,
approximately, 25% of the cooling capacity is dedicated
to latent cooling capacity (moisture removal). When
selecting a unit with ClimaDry, the space sensible
and latent loads should be calculated. If the unit will
be used for space cooling, a unit with at least enough
capacity to satisfy the building sensible load should be
selected. If the latent cooling load is not satised by
the selection, a larger unit with enough latent capacity
will be required. The ClimaDry Option can be used for
the additional moisture load. If the unit will be used for
dehumidication purposes only, the latent capacity is