Enviro 170S5FG manual Application Considerations Mql, Constant volume applications

APPLICATION CONSIDERATIONS • MQL

Application Considerations Model MQL blower coil units offer a wide range of application flex- ibility, while maintaining a simple, easy to install unit design. These units are intended to provide comfort cooling and heating within a small footprint. They may be applied in many types of building structures including schools, office buildings, hospi- tals, condominiums, assisted liv- ing facilities, apartments or stores. Applications can be constant or variable volume.

There are many applications in which the MQL product can be utilized. Some examples include:

Constant volume applications

•Two-pipe hydronic system for cooling and/or heating

•Two-pipe hydronic cooling system with electric heat

•Four-pipe system with dedi- cated heating and cooling coils

•Direct Expansion (DX) split systems with hydronic heat

•Direct Expansion (DX) split systems with electric heat

Variable volume applications

•Two-pipe hydronic system for cooling and/or heating.

•Two-pipe hydronic cooling system with electric heat.

•Four-pipe system with dedi- cated heating and cooling coils.

Acoustics

Control of noise within both occu- pied and unoccupied spaces has become increasingly important to designers and building own- ers/occupants. Proper considera- tion must be given to placement of indoor air conditioning units, particularly in the occupied space.

Inherent flexibility of the fan and coil combination in the vertical configuration allows application in sound-sensitive areas. In such instances, a fan running at low speed with a high capacity coil normally yields satisfactory results. It also may be desirable to select a larger nominal capacity unit and operate it at a less than nominal airflow for further acoustic benefit.

Three phase motors are recom- mended for sound-sensitive appli- cations to avoid potential single phase motor hum. Unit operation in the stall region of the fan curve is not recommended since it may cause unsatisfactory noise levels and excessive unit vibration.

Installation

These floor mounted or ceiling hung units can be installed on a base rail or hanger rods at the cor- ner points. All units have internally isolated fan decks; therefore, flex connections are not required, which will reduce installation costs. One of the most important and basic IAQ issues is condensate management. The first step to ensure trouble-free operation is proper installation. It is very important that the unit be mounted high enough so that the condensate drain from the unit may be properly trapped. Please refer to the MQL IOM Manual at www.enviro-tec.com for specifics on this issue. As with all HVAC sys- tems, these units should be installed according to all applica- ble ASHRAE standards, SMACNA and local code requirements.

Operating Limitations

Units must not be operated above maximum fan speed or unit air- flow as listed in the Fan Performance section of this cata- log. Unit operation at greater than maximum fan speed could drastically reduce bearing life and may result in a catastrophic fail- ure. Operating at greater than the maximum allowable airflow in the cooling mode may result in unsatisfactory operation due to moisture carry over from the coil. In addition, it is often not eco- nomical to operate a unit at its maximum fan speed due to the greater motor power require- ments.

Units with electric heat should not be operated with leaving air tem- perature greater than 104°F, to prevent excessive leaving air tem- peratures and electric heat limit trips. A hydronic (or steam) coil and electric heat should not be operated simultaneously to pre- vent excessive leaving air tem- peratures and limit trips. Electric heat units are equipped with a lockout switch that disables the electric heater if the temperature of the hydronic (or steam) coil is greater than 104°F (40°C).

Water coils must not be operated above a fluid velocity of 8 ft./sec. to reduce the possibility of veloc- ity induced erosion and flow noise. Water coils must not be operated below a fluid velocity of 1 ft./sec. to prevent degraded coil performance caused by laminar flow. These high or low fluid flow rates may not be included in the ARI coil certification.

ENVIRO-TEC 5