Toshiba TRANQUILITY 20 ClimaDry Benefits, Features Include, Availability, ClimaDry Applications

Overview

ClimaDry™ Whole House Dehumidification 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 Benefits

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 dehumidification 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 field adjustable to +/- 3°F [+/- 1.7°C] for even greater flexibility 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 benefit 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 dehumidifier)

•“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 modifications (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 dehumidifier). 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 figure 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 figure 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 satisfied 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 dehumidification purposes only, the latent capacity is

ClimaDry Whole House Dehumidification - ClimateMaster Geothermal Heat Pumps - Rev.: 18 April, 2008B