Installation and Operating Instructions

Ample Power Models STC-12 and STC-24 March 8, 2004
Figure 1. SmartTemp Wiring Diagram

Mounting the SmartTemp
The SmartTemp is protected against ambient humidity, but must be mounted in a dry location free of moisture, dust, and other environmental insults. The unit will operate in temperatures to 60$^\circ $C (140$^\circ $F).

SmartTemp Orientation
All references to parts on the SmartTemp are given with the component side of the assembly up, and terminal blocks to the left.

Wiring Diagram
The wiring diagram above is the only way to wire the SmartTemp. Do not wire in any other way, such as combining ground wires or battery positive wires. For safety purposes, always use fuses where shown.

Signal Names and Functions
All voltages are given for 12-volt SmartTemps. Double the voltages given for 24-volt SmartTemps. There are two terminal blocks on the SmartTemp, TB1, a three-pin block and TB2, a six-pin block. See the wiring diagram for orientation ...TB2 is at the top left.

Terminal Block 1

Terminal Block 2

Determining the Mode of Operation
The SmartTemp operates in one of two modes described below.

Cooling Mode
In this mode the output drive will be active, (ground potential) whenever the measured temperature is greater than the setpoint potentiometer. This mode is normally used when the control device operates to cool the equipment. A typical application is a coolant circulating pump that runs whenever the temperature exceeds the setpoint. This mode is used on the Ample Power Genie to circulate hot coolant through an external water heater. The effect on the Genie engine is to cool it, however, it must not be overcooled.

Heating Mode
In this mode the output drive will be active, (ground potential) whenever the measured temperature is less than the setpoint potentiometer. This mode is normally used when the control device operates to heat the equipment. A typical application is a heater that maintains a specified temperature.

Configuring the SmartTemp
The SmartTemp is configured by setting switches on the DIP switch and adjusting a potentiometer, as explained below.

DIP Switch
An 8-position DIP switch is located near TB2, and is used to configure the SmartTemp.

Figure 2. DIP Switch

Setting the Mode of Operation
The mode is set using switch 1 shown in Table 1 below.

When switch 1 is on, (up), then the output drive will be active when ever the temperature is greater that the setpoint, (Cooling Mode).

The Heating Mode of operation occurs when switch 1 is off.

Setting the Update Rate
Switch 3 sets the rate at which changes may occur ...either 4 seconds, or 16 seconds. That is, the SmartTemp evaluates external conditions against the setpoints every 1 or 8 seconds, depending on the position of switch 3.

Update Rate Switch 3
1 seconds Off
8 seconds On

Setting the Offset Temperature
Switches 4 thru 8 set the offset temperature. The offset temperature is either added to or subtracted from the setting on the potentiometer to derive a second setpoint, (the potentiometer is the first setpoint).

The offset is used as hysteresis for the setpoint. Hysteresis is necessary to avoid rapid on/off switching at the setpoint. The wider the hysteresis, the less likely there will be chatter of the output drive signal.

For instance if Cooling Mode is being used, the output will switch to the active state when the potentiometer setpoint is exceeded. In this mode the offset is subtracted from the potentiometer setting. The output will switch back to the inactive state when temperature falls below the second setpoint, (potentiometer setpoint minus offset).

In Heating Mode, the offset is added. Thus the output goes active when the temperature is below the setpoint of the potentiometer, and inactive once temperature rises above the potentiometer setpoint plus the offset.

Offset temperature is done in Centigrade.

Offset S1
Temperature SW4 SW5 SW6 SW7 SW8
1 Off Off Off Off On
2 Off Off Off On Off
3 Off Off Off On On
4 Off Off On Off Off
5 Off Off On Off On
6 Off Off On On Off
7 Off Off On On On
8 Off On Off Off Off
9 Off On Off Off On
10 Off On Off On Off
11 Off On Off On On
12 Off On On Off Off
13 Off On On Off On
14 Off On On On Off
15 Off On On On On
16 On Off Off Off Off
17 On Off Off Off On
18 On Off Off On Off
19 On Off Off On On
20 On Off On Off Off
21 On Off On Off On
22 On Off On On Off
23 On Off On On On
24 On On Off Off Off
25 On On Off Off On
26 On On Off On Off
27 On On Off On On
28 On On On Off Off
29 On On On Off On
30 On On On On Off
31 On On On On On
32 Off Off Off Off Off

Setting the Potentiometer
The Potentiometer, R19, is located at the opposite end of the assembly from the terminal blocks. It is a 20-turn potentiometer which has a mechanism that allows the adjustment to be continuously turned in either direction without damaging it.

In both modes of operation, the potentiometer sets the temperature at which the output drive signal will become active.

To make adjustment easy, a testpoint is provided. The testpoint is a vertical pin adjacent to the potentiometer. By measuring the voltage on the testpoint with a digital meter, relative to ground, the potentiometer can be set at the desired temperature.

The voltage measured at the testpoint is related to the temperature in the following manner. A voltage of 2.98 Volts represents 25$^\circ $C. Every 10 millivolts difference, (0.01 Volts), represents a temperature difference of 1$^\circ $C. If a setpoint of 35$^\circ $C is desired, then the potentiometer should be set to 3.08 Volts. A temperature of 15$^\circ $C calls for a voltage on the test point of 2.88 Volts.

Determining the temperature in Centigrade when Voltage, V, is known can expressed mathematically as:

$Tc = 100 * (V - 2.73)$

Solving for V when a temperature setpoint is desired can be done using:

$V = (Tc / 100) + 2.73$

To convert between Centigrade and Fahrenheit use the following formulas where Tc is temperature in Centigrade and Tf is temperature in Fahrenheit.

$ Tf = Tc * 9 / 5 +32 $
$Tc = 5 /9 * (Tf - 32) $

Factory default settings are those used to control the hot water circulating pump for the Ample Power Genie. The voltage at the setpoint is 3.50 which represents $77^\circ$ C. An offset of 5$^\circ $ C is used

When the SmartTemp is first turned on, the Red LED will glow until the SmartTemp has been able to successfully deactivate the output.

Operational Indications
Once the SmartTemp is initialized, the Red LED extinguishes and the Green LED begins to report status. The Red LED will flash error codes if detected later.

Status Indicator
The Green LED shows the status of the SmartTemp. Status is shown by flashing the Green LED with On and Off time in seconds as shown below.

As shown, the Green LED merely shows the state of the output drive, and whether the state is the result of automatic operation or manual override.

Status On Off
Description seconds
Cooling Automatic Active 1 1
Cooling Automatic Inactive 3 3
Heating Automatic Active 1 3
Heating Automatic Inactive 3 1
Manually Active 6 1
Manually Inactive 1 6

Error Indicator
Abnormal conditions are reported with the Red LED. Errors are identified by On and Off times of the Red LED as shown below. If the Red LED is continuously illuminated, refer to the section on initialization.

Error On Off
Description seconds
Input Voltage High 3 3
Input Voltage Low 6 6
Missing Temperature Sensor 3 6
Mis-wired Temperature Sensor 6 3
Drive Error Positive 1 6
Drive Error Negative 6 1
Both On & Off 1 1
Setpoint too High 3 1
Setpoint too Low 1 3

Input voltage high error indicates a power supply input voltage greater than 17.5/35 Volts for the 12/24 Volt models.

Input voltage low indicates a power supply input voltage less than 10/20 Volts for the 12/24 Volt models.

The missing temperature sensor error occurs if the sensor is not wired, or the sensor is open circuited.

The mis-wired tmperature sensor error occurs if the sensor wired in reverse, or the sensor short circuited.

Drive signal positive error occurs if the output drive has low voltage on it when the output drive is inactive. That usually means that the control device does not have power wired to it.

The drive signal negative error is displayed if the drive signal line does not pull to ground properly when active. This can mean that the control device is drawing excessive current, or the internal drive transistor is defective.

The Both Open/Close error is presented if both the open and close manual inputs are asserted simultaneously.

The setpoint too high error is displayed if the setpoint pot is adjusted higher than about 4 Volts, equivalent to 127$^\circ C$.

The setpoint too low error occurs if the setpoint pot is adjusted below 1.98 Volts, equivalent to -75$^\circ C$.

Most problems with new installation are due to wiring faults. Look at the signal list above and make sure that all required wires are in place and properly connected.

If all required wires are proper, as verified by a multimeter on the SmartTemp connections, call your dealer or local installer with voltage readings for all the terminal block pins, and the activity of the LEDs.

Factory Troubleshooting Support
If your dealer or installer is unable to assist you, call the Ample Power service line at 206-789-4743. Additional information may be found on the Internet at

Ample Power products are manufactured by Ample Technology, 2442 NW Market St., #43, Seattle, WA 98107 - USA