Variable Volume Linear Ceiling Diffusers (VLB1)
VAV COOLING AND HEATING
VAV COOLING AND HEATING WITH TERMINAL REHEAT
STAND ALONE OR BMS CONTROLS
When a buildings thermal efficiency is paramount, the ideal solution to limit thermal losses or gains through its exterior is required. The Rickard Variable Volume Linear Bar Diffuser (VLB) is an ideal solution to control a buildings internal perimeter zone or be an aesthetically attractive alternative to plate diffusers in internal zones. RICKARD Variable Volume Linear Bar Diffusers (VLB) are intended to heat or cool zones where load fluctuations vary. The Variable Volume Linear Bar Diffusers (VLB), as its name implies, automatically regulates the air volume entering the conditioned space and in turn controls the temperature.
The Rickard MLM controller automatically changes it’s control direction as supply temperatures switch from heating to cooling and vice versa. Please note that a changeover sensor should be fitted for this function to work. Top-up heaters are available if required. This is achieved by fitting a Rickard Neck Heater and Triac.
A VLB’s flow pattern can be adjusted to create a vertical curtain of conditioned air to act as a barrier to external thermal loads or a horizontal flow pattern that creates good mixing without drafts. Rickard VLB linear bars are designed to be joined end-to-end to create uninterrupted lengths of attractive linear bar.
NOTE: No onboard sensing is available: A remote wall thermostat is required in zones where top-up heating is fitted.
FLOW DIRECTION ADJUSTMENT
A useful feature of the RICKARD VLB is the ease with which the direction of airflow may be adjusted. Although airflow direction is not normally changed once the system is operational, it does simplify the ordering procedure. The choice of one-way (vertical) or two-way (horizontal blow) is easily implemented on site by simply shifting the flow directional plate left or right.
Air is generally directed vertically downwards for better room penetration, especially when the VLB is in the heating mode.
Remove both end plates from the ends you wish to join and connect using the alignment tabs fitted.
The first consideration when designing a system is to calculate the required supply air volume and temperature to satisfy room conditions at maximum heat loads. It is recommended that ducting is sized using static regain design principles. Supply air velocities in branch ducts should be between 3.5 and 7.5m/s (650 and 1500ft/min).
This is the distance from the centre of the diffuser to the point at which the supply air velocity has reduced to 0.25m/s (50ft/min) when measured 25mm (1 inch) below the ceiling. Coning occurs when two airstreams travelling in opposite directions meet and result in a downward moving cone of air (applies to horizontal flow). A similar effect is experienced should a diffuser be positioned at a distance from the wall that is less than its throw. The air will strike the wall and flow in a downward direction such that the point at which the air reaches a velocity of 0.25m/s (50ft/min), the sum of the horizontal and vertical travel of the air is equal to the diffuser throw.
NOISE LEVEL REQUIREMENTS
PLEASE CONTACT RICKARD FOR NOISE DATA.
DUCT STATIC PRESSURE
Diffuser performance has been established using diffuser neck TOTAL pressure, although that which is normally known or measured is duct STATIC pressure. What happens between the duct and the diffuser depends on the length and type of flexible duct being used. For simplicity, it can be assumed that the duct STATIC pressure is approximately equal to the diffuser neck total pressure. This is a valid assumption for systems where flexible duct lengths are not excessive and can be explained briefly as follows:
The static pressure loss due to friction in the flexible duct (±10Pa or 0.04ins Wg) would normally be about the same as the velocity pressure in the neck of the diffuser and since total pressure is the sum of static and velocity pressure. Although the tables reflect diffuser performance for neck total pressures ranging from 30-70Pa (0.12-0.28ins Wg), caution should be exercised when selecting diffuser outside the 30-50Pa (0.12-0.20ins Wg). At lower pressures air movement and induction may be insufficient and at higher pressures draughts and excessive noise may result. Best results are obtained when diffusers are selected at pressures of 30-40Pa (0.12-0.16ins Wg).
NECK SIZES & TRACK LENGTHS
LINEAR BAR TYPES
VLB Linear Bar Diffusers are only available with a single linear nozzle.
VLB’s are designed to fit Plastered Ceilings (Surface Mount) only.
VLB’s controls are mounted to the outside of the plenum on a removable access panel that gives access to the motor.
Rickard VLB Diffuser tracks are designed to be joined end-to-end to create uninterrupted lengths of attractive linear bar. The linear bar nozzles are finished in a high quality matt black epoxy powder coating as standard.
- Wired Wall Thermostat
- Wired Wall Thermostat with Occupancy Sensing
- Wired Wall CO2 Thermostat
- Wireless RF Wall Thermostat
- Wireless RF Pod Sensor