35
Model VSU Make-Up Air
®
Control Center LayoutDirty Filter Switch
Reference
13 22
26 28
27
20
15
21
4178
29
3
5
16
23
17
18
1914
25
10
12
11
6
24
1. Supply Motor Starter — 24 volt magnetic
contacts for starting supply motor.
2. Supply Overload — provides electronic overload
protection to supply motor.
3. Low Voltage Transformer — provides low
voltage to fan/heat/cooling enable controls.
4. Control Terminal Block — provides wiring
access to controls.
5. Fan Relay — allows power to pass to energize
motor starter.
6. High Voltage Enclosure — provides protection
from high voltage circuits.
7. Auxiliary Contact (optional) — provides one
normally closed and one normally open contact for
other equipment.
8. Exhaust Motor Starter (optional) — 24 volt
magnetic contacts for starting exhaust motor.
9. Exhaust Overload (optional) — provides
electronic overload protection to exhaust motor.
10. Transformer Fuse (optional) — provides proper
fusing for cooling transformer.
11. Terminal Block — provides wiring access to high
voltage circuits.
12. Exhaust Fuses (optional) — provides proper
fusing for exhaust fan motor(s).
13. Dirty Filter Switch (optional) — monitors filter
pressure drop, turns on indicating light when
pressure drop is above field adjustable set point.
14. Inlet Air Sensor (optional) — outdoor air stat
that automatically controls the heating and/or
cooling based on outdoor air temperature.
15. Remote Temperature Selector (optional) —
allows for remote temperature set point.
16. Heat Relay — allows power to pass to heating
controls.
17. Heating Terminal Block — provides wiring
access to heating controls.
18. Flame Safeguard/Spark Generator (Direct
Spark) — monitors flame, shuts down unit when
unsafe conditions are detected.
19. High Limit — prevents unit from discharging air
above a set point.
20. Low Voltage Transformer — reduces voltage to
Maxitrol system.
21. Amplifier — controls modulating valve, assures
the desired temperature is delivered.
22. Transformer (optional) — provides voltage to
optional evaporative cooling pump.
23. Cooling Relay (optional) — allows power to
pass to cooling controls.
24. Cooling Terminal Block (optional) — provides
wiring access to cooling controls.
25. Low Voltage Transformer (optional) — reduces
voltage to cooling controls.
26. Reset Timer (optional) — resets cooling system
to run a time interval.
27. Auto Drain Relay (optional) — assures supply
pump does not operate during drain interval.
Allows pump to operate in cooling mode.
28. Cooling Timer (optional) — allows for automatic
draining of the evaporative cooling system based
on time schedule.
Negative Pressure
after the filters
Common
Normally Open
Normally Closed
CCW to Decrease Trip Point
CW to Increase Trip Point
Positive Pressure
before the filters