McQuay PDHA Especificaciones descargar pdf (Pagina 40)

Catalog 1300-1 / Page 40 of 42

Engineering Guide Specications – PDAC/PDHP 16" × 42"

During The Heating Cycle:

Electric Resistance Heat – Control will call for electric heat when the space temperature is 1°F lower that the set

point. The control will cease its call when the space temperature is 3°F or higher than set point.

Only the indoor fan motor and electric resistance heater are energized. The outdoor condenser fan motor and

compressor shall not be energized. Heater shall be open wire type with quick response and high limit cutout. Heaters

shall be sized to meet heating requirements as shown on the schedule. Electric resistance heaters must be placed

behind the indoor evaporator coil and must not be visible through the indoor discharge grille. When the heater cuts out

the indoor fan continues to run for 15 seconds at the set speed, regardless of On or Off mode. After 15 seconds the fan

will stop running if unit is in Off mode, else the fan operation will depend on Fan Continuous or Fan Cycle setting.

Hydronic, Hot water or Steam, heat – Only the indoor fan motor, the (normally open) (normally closed) valve

and automatic fresh air damper shall be energized. The outdoor condenser fan motor and compressor shall not be

energized.

Hydronic Heat - Heat Fan Lock Out – When the control is in the heat mode and calling for heat, the indoor fan

shall not turn on until the HFLO sensor is above 115°F. If at any time while the unit is in heat mode the HFLO sensor

is below 95°F, the indoor fan shall turn off immediately. Control will check if the HFLO sensor temperature is above

115°F for 2 seconds before resuming indoor fan operation.

Hydronic with Intermediate Electric heat – Upon the call for heating and thereafter the HFLO sensor temperature

will be monitored. A trend in HFLO sensor Temperature shall determine which form of heat is to be used. If during

the 90 seconds that Hydronic is the heat source and the HFLO sensor is above 105°F and is increasing at 2°F per

minute then Hydronic is the heat source. If during this 90 seconds, the temperature of the HFLO sensor is above

105°F and is not increasing at 2°F per minute then Electric is the heat source. The hydronic valve is opened for 90

seconds. After 90 seconds whether Hydronic or Electric provides the heating is determined by the following:

If HFLO sensor temperature is less that 105°F, Electric provides the heat.

If HFLO sensor temperature is greater than 115°F, Hydronic provides the heat

Reverse Cycle Heat Pump with back-up electric heat – The reversing valve, the compressor, the outdoor air

condenser fan motor and the indoor fan motor shall be energized. Reverse cycle heating shall occur when the outdoor

coil temperature is 28°F and above. If outdoor coil temperature drops below 28°F or the Outdoor air temperature

drops to 35°F or less, Electric heat is the only source of heat. When the Outdoor coil temperature raises back to 40°F

and above, then the Compressor reverse cycle or Electric heater is used.

A temperature-sensing device shall be used to monitor the outdoor coil temperature to limit frost buildup. Defrosting

of the outdoor coil will be activated when outdoor coil temperature drops below 28°F of outdoor air temperature drops

to 35°F or less. Defrosting is terminated when outdoor coil temperature rises back to 40°F. During defrosting, both

compressor and the outdoor fan are turned off. The indoor fan will run at its set speed.

Condensation accumulated during reverse cycle heating must NOT be evaporated against the indoor coil so as

to prevent contamination of the indoor air with pollutants and odors. Condensation must be disposed of using a

(external) (internal) drain system as shown on plans.

Reverse Cycle Heat Pump without back-up electric heat – The reversing valve, the compressor, the outdoor

condenser fan motor and the indoor fan motor shall be energized. Reverse cycle heating shall occur when the outdoor

temperatures are 35°F and above. If outdoor coil temperature drops below 28°F or the Outdoor air temperature drops

to 35°F or less, the compressor stops and there is no source of heat. When the Outdoor coil temperature raises back to

40°F and above, then the compressor reverse cycle is the heat source.

A temperature-sensing device shall be used to monitor the outdoor coil temperature to limit frost buildup. Defrosting

of the outdoor coil will be activated when outdoor coil temperature drops below 28°F of outdoor air temperature drops

to 35°F or less. Defrosting is terminated when outdoor coil temperature rises back to 40°F. During defrosting, both

compressor and the outdoor fan are turned off.

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McQuay PDHA Especificaciones Pagina 40

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