Mammoth 800 to 5500 CFM: Dedicated Outdoor Air System with Enthalpy Wheels (VHC) - Manual (Page 12)

MAMM-VHC-IOM-1A (JANUARY 2013) 12
Free Cooling
Power connected, unit ventilating, free cooling call. Wheel
stops rotating.
Variable Speed Setpoint Free Cooling
Power connected, unit ventilating. Wheel modulates to
keep discharge temperature air at setpoint.
Unit Fault
An external unit fault can be initiated by removing the
dry contact jumper to the field wire terminal in the control
panel. This contact is normally closed and requires an
open contact to initiate a fault and shut down the unit.
Dirty Filter Sensor
The VHCs can be equipped with dirty filter sensors which
monitor the pressure across the filters and close the con-
tacts when the filters become restricted with dirt. Field
wired connections can be made to the terminal interface
for both the supply and exhaust filter sensors (electro-me-
chanical controls [EMC] units only).
Remote Fan Control
Remote fan control can be achieved by connecting dry
contacts to the terminal interface (during occupied or un-
occupied recirculation). These controls could also be the
following: SPDT switch, dehumidistat, CO2 sensor, light sen-
sor, heat sensor, timer, Building Management System, etc.
CO
2
Ventilation Control
VHCs can be directly controlled by a CO
2
controller (acces-
sory or field supplied) that can be connected to the supply
and exhaust high speed contact terminals (VFD units only).
As the CO
2
levels exceed acceptable limits, dry contacts
close raising high speed fan ventilation. See Appendix F,
CO
2
Ventilation Control . Alternatively a field supplied CO
2
controller output can be connected to the BMS which can
then be connected to the supply and exhaust fan modu-
lating signal input terminals (VFD units only). As the CO
2
placed across terminals, heat wheel stops,
defrost recirculation damper opens, outside
and exhaust air dampers (if equipped) begin to
close and supply blower starts.
c. Occupied recirculation (Or) (DDC control pack-
age only): With the occupied recirculation
contact closed or a jumper placed across termi-
nals, heat wheel starts (not in free cooling), de-
frost recirculation damper closes (if equipped),
outside air damper (if equipped) opens. After
outside air damper opens supply blower starts,
exhaust air damper (if equipped) opens; after
exhaust air damper opens, exhaust blower
starts, occupied recirculation damper opens,
outside and exhaust air dampers modulate to
the damper minimum setpoints.
5. Check that dampers are operating properly.
6. Check that blowers and heat wheel are rotating in the
correct direction.
7. For occupied recirculation scheduling mode the out-
side air and exhaust air dampers must be adjusted
during start-up to achieve the required outside and ex-
haust air volumes. See Airflow Balancing for further
information.
8. Re-check the voltage at the disconnect switch against
the nameplate and against phase-to-phase read-
ings on three-phase with all blowers operating. If the
voltage is not within 10% of rated or 2% of phase-to-
phase have the condition corrected before continuing
start-up.
9. Check amperage draw to each motor on each
phase against motor nameplate FLA. If significantly
different, check ductwork static and/or take correc-
tive action.
10. Before activating the compressor on WSHP units, are
water shut-off valves open and is water circulating
through the water-to-refrigerant heat exchanger.
11. Enable cooling and check if the sound of the compres-
sor is normal or if there is excessive vibration.
12. Check all field and factory refrigerant and water piping
connections for leaks and correct.
13. Enable heating options, see start-up and check out in-
structions in Appendix J for electric coil and complete.
14. Check the operation of the control options provided
on the unit. A functional description is provided below
and in the VHC-36, 42 and 50 DDC Control Package
Manual.
15. Check the setpoints on the DDC Points Reference,
adjust and record changes as required.
16. When unit has achieved steady state take measure-
ments and complete the readings section of the start-
up report in Appendix H and send copy of the start-up
report to Mammoth to validate warranty. Maintain a
copy of the report at the unit for future reference.
Optional Controls and Accessory Sequence and Interlocks