Rickard IN-LINE DUCT HEATER User manual

INTRODUCTION
Rickard’s VAV diffusers are designed to modulate the volume of
warm or cold air to meet the zones demand. In some cases, typically
in particularly cold zones, the warm supply air is insufficient to heat
the zone adequately. To satisfy this shortfall, Rickard has developed a
range of in-line top-up duct heaters.
FORM FACTOR
These heaters have been designed to be fitted to the take-off of the
main duct, upstream of the diffuser. By positioning the heater be-
tween the main duct and the diffuser flex, the heater is able to meet
the building codes that are required for some markets.
Any Rickard MLM diffuser supplied with a round duct can be fitted
with an in-line duct heater and controlled. This applies to ceiling
diffuser types VCD1, VSD1, CCD3, CSD3, VSW1 and CSW3’s. A 2m
ribbon cable is supplied to connect the in-line heaters triac to the
diffusers main controls.
If used correctly, electric duct heating in VAV diffusers can be consid-
ered an energy saving device. By using them in offices that are typi-
cally colder than the building average allows the central plant to
produce less heating in winter than is otherwise possible.
The most efficient scenario in heating is for the central plant to sup-
ply sufficient heated air to allow most of the zones to be in control
when the diffusers damper is close to minimum position. Zones that
are colder are controlled by the diffuser opening further. Zones that
cannot be satisfied by the diffuser supplying warm air at full volume
are toped up with supplementary heating.
The most efficient scenario in cooling is for the central plant to sup-
ply sufficient cool air to allow most of the zones to be in control
when the diffuser dampers are close to minimum position. Zones
that are warmer can be controlled by the diffuser opening further.
Zones that cannot be warmed sufficiently by reducing the cold air
supply can be controlled by heating this reduced volume of air.
If the room temperature were to fall by 0.5°C below set point, the
Triac Controller will commence energizing the heater proportionally
and will fully energize the heater when the room temperature is ap-
proximately 1.5°C below set point.
Integration of the Rickard VAV diffuser system with the central plant
BMS is possible by using our MLM Interoperable BMS Compatible
Controls.
PROPORTIONAL HEATING
For accurate control of room temperature, the electric re-heater is
controlled on a step-less, proportional basis. In addition to having a
proportional output signal for cooling control, the temperature con-
troller also has a proportional output signal for heating.
This is done by means of a triac switching set (current valve) which
varies the heater output capacity by cycling the power supply to the
heater on and off –Pulse Width Modulation (PWM). This switching
takes place over a cycle of approximately 2 seconds and always oc-
curs at zero voltage to avoid radio frequency interference and volt-
age spikes. The “on” and “off” periods are varied in proportion to
the amount of heating required, i.e. a required heating capacity of
75% will result in an “on” period of 1.5 seconds and an “off” period
of 0.5 seconds.
CONTROLS
In a situation where multiple diffusers are controlled from a single
controller, each diffuser will be fitted with its own triac that will re-
ceive a heating signal from the Master controller. The heating signal
transmitted by the controller is a 9 Volt DC signal.
From the table “Maximum Recommended Heater Output (Watts)”, it
will be noted that for each neck total pressure there is a specific
heater output quoted and for each diffuser size a standard heater
capacity is referenced. For example, in the case of a VCD 250 diffus-
er, the re-heater sleeve would be factory fitted with a 1500 watt
heater, which by utilizing the RICKARD MLM or MLM Interoperable
BMS Compatible Controls, can be electronically set for any output
from as little as 100 watts to 1500 watts to match the design engi-
neer’s requirements for minimum cooling mode supply air flow and
desired leaving air temperature. Therefore, if the diffuser neck total
pressure were to be set at 50Pa and the minimum desired air flow
was 30% of maximum with 15°C air temperature rise, the heater
output for a VCD 250 should be set to 1300 watts. Kindly refer to the
help section in the MLM software program for more detailed infor-
mation.
IMPORTANT ELECTRICAL INFORMATION: Electrical reticulation
should be designed to have the capacity to manage the heaters full
capacity e.g. when a heater is set to 50%, the heater element draws
the same current as it would when set to 100% but it is drawn for
50% of the time.
Bypass Damper
Face Damper
In-line Heater
Diffuser
AHU
Return Air
SAMPLE DUCT LAYOUT

SELECTION GUIDELINES
When calculating heater capacities for VAV diffusers, please keep in
mind that heating in the cooling mode takes place when the diffuser
is supplying minimum air flow and care must therefore be taken to
ensure that an excessive temperature rise in the diffuser is avoided.
Discharge temperatures in excess of 32°C are likely to cause stratifi-
cation within the room. As a guide-line, the temperature of the air
leaving the diffuser should not be more than 10°C above actual
room temperature. Kindly refer to the appropriate products table
giving the “Maximum Recommended Heater Output (Watts)” on
page 3 for each diffuser size. These heater output ratings have been
computed on the basis that minimum air flow is 30% of maximum
and the maximum capacity of the fitted re-heater are set electroni-
cally for an air temperature rise of no more than 15°C, a standard
feature of the RICKARD MLM and Interoperable BMS Compatible
Controls.
IMPORTANT: These maximum capacities do not take into account
limitations of the triac which are rated at 12A maximum. This reduces
the capacity of the triac at low voltage supply.
ELECTRICAL AND OVERHEAT SAFETIES
Every in-line Duct Heater Module is fitted with a coiled Electrical
Element inside a Mill Galvanised Sheet metal enclosure. The Heater
Elements are “black heat” having a heat density of 3.2W/cm² and are
constructed from an Incaloy material that does not glow red when
energised. This element is selected to reduce the risk of combustible
materials igniting should they come into contact with the heater
element itself. No combustible materials are used in the construction
of a Rickard in-line Heater Duct Module. The in-line Duct Heater
modules are fitted with their own Triac or Heater driver and receive a
proportional signal from the diffuser controls when additional heat-
ing is required to bring the room into control. The Triac receives its
power from a seperate power circuit. Dedicated plug tops can be
fitted to the heater module on request.
The in-line Duct Heater Modules Triacs are fitted with a number of
safeties to reduce the risk of failure. The Triac is fitted inside an elec-
trically grounded metal enclosure that is physically attached to the
Heater module Enclosure. This safety increases the electrical safety of
the device should a short circuit occur. A fuse offers additional pro-
tection against large current surges and shorts. A Transient suppres-
sor prevents the Triac from failing closed and therefore driving the
heater permanently after a voltage surge has occurred.
In all cases an auto-reset 65°±5°C (10 000 cycles) and power-reset
85°C±5°C (300 cycles) overheat safety cut-out is fitted as standard.
The reset temperatures indicate the air temperature inside the over-
heat safety cut-out casing at which it operates. Rickard heater mod-
ules are designed so that the overheat safety cut-outs trigger when
the neck Total pressure is 30Pa or below. The trigger point can vary
depending on a number of factors namely, excessively squashed or
bent flex, neck size, heater size and damper position. Rickard controls
do not activate its heaters below 20% flow damper position, thereby
reducing the likelihood of the overheat safeties not triggering in the
range described. The power reset cut-out is reset by turning the
power supply off momentarily. If a power reset is required, an inves-
tigation into the cause should be made. Push-button type manual
reset safeties are not recommended in conjunction with diffuser re-
heaters.
For additional safety, RICKARD offer an Airflow Switch to interrupt
power to the re-heater controls when there is insufficient airflow
across the heater element. The switch is calibrated to disable the
heater current valve below a static pressure of 12Pa (+/- 5Pa). The
switch operates as a dead man switch i.e. if the cable between the
switch and the heater controls is unplugged, the heater will not op-
erate.
TESTING
All electrical wiring associated with the re-heater is carried out in the
factory and all units carefully tested for correct operation.
OPTIONS
Heaters are available in various capacities, ranging from 0.5kW to
2.5kW.
An internally insulated option is available. (see page 3)
Lengths of 500 or 650mm are available depending on the building
code applicable. Special lengths may be available on request.
For additional safety, RICKARD offer an Airflow Switch to interrupt
power to the re-heater controls when there is insufficient airflow
across the heater element.
Power-reset
Cut-out
Auto-reset
Cut-out
Incaloy “Black
Heat” Element
Silicone
Insulation
Silicone Insulated
Wire
STANDARD SAFETIES FITTED TO ALL VAV DIFFUSER TYPES
(VCD1, VSD1, CCD3, CSD3, VSW1, WBD’s and VLN’s )

INSTALLATION GUIDELINES
The In-line Duct Heater is designed to be mounted directly to the
main or branch duct up stream of the flexible ducting and diffuser.
• Take note of the airflow direction label and mount
accordingly. The overheat safeties and airflow cut-out will not
work if mounted in the wrong direction.
• Make a hard connection between the upstream side of the
duct heater and the duct spigot (Rickard recommends the
heater driver box and overheat cut-out is mounted horizontal
or below horizontal.
• The downstream side can be connected to the flexible duct
using the included jubilee clamp.
• Connect the 2-5m (specify when ordering) ribbon cable
between the diffuser interface box and the heater driver box.
Ensure both latches are closed on either end.
• Plug the heater driver box into a 230VAC power outlet.
Ensure the power outlet is interlocked with an airflow cut-out
mounted in the main duct. This will ensure that the heaters
are not energised when there is now airflow.
Please note that the in-line heater’s airflow cut-out and overheat
safeties are secondary safeties and should not replace the airflow
interlock as the primary safety.
DIFFUSER TO HEATER CABLE OPTIONS
• Standard 1.5m ribbon cable
• Special length cable (1.5 to 5m). An adapter kit is required
that consists of:
• 2x legacy adapters
• 2x short ribbon cables
• 1x RJ45 (1.5-5m)
IN-LINE DUCT HEATER
Air flow Switch
Triac/current valve
Bypass Damper
Face Damper
In-line Heater
Diffuser
AHU
Return Air
SAMPLE DUCT LAYOUT
Short Ribbon Cables
RJ45 Cable (1.5 to 5m)
Legacy Adaptors
Triac
650mm
or
500mm
Nominal Size
less 5mm

To limit stratification in heating Rickard recommends that the heater outputs be limited to the values published in the tables above.
The calculated values will ensure that the heat rise is no more than 15°C in VAV diffusers. Please note that these values are a guide
and are calculated at 30% volume for VAV diffusers. By adjusting the diffuser damper position down, a smaller volume will create a
larger heat rise and therefore increase the likelihood of stratification. The Fit column indicates the maximum fitted heater size recom-
mended, the Adjust value indicates the maximum heater setting recommended to achieve a 15°C (VAV) heat rise and the Set column
is the MLM Heater Output % value required to achieve a 15°C (VAV) heat rise.
VCD
VSD
VRD
Recommended Heater sengs & sizing for a 15 Degree C Heat Rise @ 30% Open
Pa 20 30 40 50 60 70
Neck Size
(mm)
kW kW kW kW kW kW
Adjust Fit Set Adjust Fit Set Adjust Fit Set Adjust Fit Set Adjust Fit Set Adjust Fit Set
150 0.35 0.50 70% 0.34 0.50 68% 0.50 0.50 100% 0.50 0.50 100% 0.60 0.75 80% 0.65 0.75 87%
200 0.60 0.75 80% 0.70 0,75 93% 0.75 0.75 100% 0.90 1.00 90% 1.00 1.00 100% 1.00 1.00 100%
250 0.85 1.00 85% 1.00 1.00 100% 1.15 1.25 92% 1.30 1.50 87% 1.40 1.50 93% 1.50 1.50 100%
300 1.00 1.00 100% 1.25 1.25 100% 1.50 1.50 100% 1.65 2.00 83% 1.75 2.00 88% 2.00 2.00 100%
350 1.30 1.50 87% 1.50 1.50 100% 1.85 2.00 93% 1.85 2.00 93% 2.25 2.50 90% 2.50 2.50 100%
VSW
VRW
Recommended Heater sengs & sizing for a 15 Degree C Heat Rise @ 30% Open
Pa 30 40 50 60 70
Neck Size
(mm)
kW kW kW kW kW
Adjust Fit Set Adjust Fit Set Adjust Fit Set Adjust Fit Set Adjust Fit Set
150 0,35 0,5 70% 0,4 0,5 80% 0,45 0,5 90% 0,5 0,5 100% 0,55 0,75 73%
200 0,6 0,75 80% 0,7 0,75 93% 0,8 180% 0,85 185% 0,9 190%
250 0,85 185% 11,25 80% 1,1 1,5 73% 1,2 1,25 96% 1,3 1,5 87%
300 11100% 1,2 1,5 80% 1,35 1,5 90% 1,5 1,5 100% 1,6 280%
VLN1
2 Slot
Paern
C
Recommended Heater sengs & sizing for a 15 Degree C Heat Rise @ 30% Open
Pa 30 40 50 60 70
Length (mm) kW kW kW kW kW
Adjust Fit Set Adjust Fit Set Adjust Fit Set Adjust Fit Set Adjust Fit Set
600 0,3 0,5 60% 0,35 0,5 70% 0,35 0,5 70% 0,4 0,5 80% 0,45 0,5 90%
900 0,45 0,5 90% 0,55 0,55 100% 0,6 0,75 80% 0,65 0,75 87% 0,7 0,75 93%
1200 0,65 0,75 87% 0,75 0,75 100% 0,8 180% 0,9 0,9 100% 11100%
1500 0,85 0,85 100% 11100% 1,1 1,25 88% 1,2 1,2 100% 1,3 1,5 87%
Duct Heater Sizing
Diuser Nominal
Neck Size (mm)
In-line Duct Heater
Outer Diameter (mm)
150 148
200 195
250 244
300 290
350 338
350 338