Installation and Operation Manual
●
Fan Coil Controller – EZstat
EC-EZstat
Date: 9-2014
Supersedes: NEW
Engineered Comfort reserves the right to change any information concerning product or specification without notice or obligation.
Page 29 of 36
Modulating valves Cont.
•
Normal — The valve is fully closed when the output signal is 0 volts and fully open when the output is 10 volts DC.
•
Reverse —The valve is fully closed when the output signal is 10 volts and fully open when the output is 0 volts DC.
Two-pipe water supply temperature evaluation
For two‑pipe fan coil units, the EZstat uses the WST sensor to determine if chilled or hot water is being supplied to
the unit. The water type is determined by comparing the value of the WST input to the room temperature. The EZstat
programming then determines that the water temperature is one of the following:
•
Chilled—the water temperature is 10° F below room temperature. Hot—the water temperature is 10° F above room
temperature.
•
None—the water temperature is within 7° F of room temperature.
If the water temperature is evaluated as None, the EZstat runs the water evaluation program every six hours. During a
water evaluation, the EZstat opens the valve until a water type is determined or for five minutes, whichever is reached
first. If a water evaluation is not being performed, the valve remains closed.
The supply water type is stored in multistate variable Water Available.
Two-pipe with electric heat
For EZstat fan coil models that support both on/off and modulating valves, electric heat can be added to two‑pipe systems.
Typically this heat is a duct or baseboard resistance heater controlled by a relay.
When the supply water type is chilled water and there is a call for heat, the EZstat controls the heating element through
output terminal BO5. The output turns on when the heating loop is equal or greater than 40%. The output is turned off
when the loop falls below 40%. If the supply water type is hot water, only the water valve output is used to satisfy a call
for heat.
7.9 Fan operation for fan coils
The EZstat supports both modulating fans and fans with one, two, or three speeds. Speed for either type of fan is
determined directly off room temperate and the fan is controlled by the PID loops. Fan speed control is set up from the
user interface by a user with Password 2
.
7.10 One, two, and three speed fans
For one, two, and three speed fans, the EZstat controls the fan speed with terminals FAN‑L, FAN‑M, and FAN‑H. This
feature applies to Fan Speed, located in System menu.
The user selects on the interface the Fan selection ‑ Auto, and then in the SYSTEM menu select Fan Speed. See in
Enter the
Commissioning Mode
.
•
Single speed fans use terminal FAN‑L only
•
Two speed fans are controlled with terminals FAN‑L and FAN‑H
•
Thee speed fans use terminals FAN‑L, FAN‑M, and FAN‑H
The fan output terminals are energized as the cooling or heating loop varies from 0‑100%. Terminal activation is shown in
the following table. The values listed below correspond to loop percentages.
Table 7-1
Terminal Activation (Auto Mode)
Fan L terminal
Fan M terminal
Fan H terminal
Fan speed
On
Off
On
Off
On
Off
One
*0%
5%
n/a
n/a
n/a
n/a
Two
*0%
5%
n/a
n/a
95%
80%
Three
*0%
5%
65%
50%
95%
80%
Fan minimum is enabled at dead band sequence, and loop percentage not applicable.
NOTE
