Testing the thermostat wiring – tekmar 521 Programmable Thermostat Installation User Manual

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A Watts Water Technologies Company

Testing the Thermostat Wiring

Testing the Power

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If the thermostat display turns on, this indicates that power is applied correctly. In the
event that the display is permanently off:

1. Remove the thermostat front.

2. Use an electrical meter to measure voltage between the R and C wiring terminals.

For AC power supplies the voltage should measure between 10 to 30 V (ac). For
DC power supplies the voltage should measure between 10 to 30 V (dc).

3. If the voltage on the R and C wire terminations is continuous and the thermostat

display is not on, the thermostat may have a fault. Contact your tekmar sales
representative for assistance.

If the thermostat display initially powers on but later shuts off intermittently, there may
be a short circuit from the W1, W2, Y or G wire to the power common or ground, or
the power supply is too small to power the load.

Testing the First Stage Heat Output Wiring

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1. Press the Mode button and set to Heat.

2. Press the

button and set the heating temperature above the current room

temperature. Make sure the display does not flash “Max” if using a floor sensor.

3. When the “Heat On” symbol appears on the display, use an electrical meter to check

for voltage on the W1 and C wires connected to the zone valve, wiring center, relay
or switching relay. The electrical meter should read 10 to 30 V (ac) or (dc).

4. If the W1 and C wires have voltage, check the zone valve, wiring center, relay or

pump to determine if the heat device is operating correctly.

Sensors

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Y/W2 Rc

Rh W1

S1 S2

Com

No Power

Indoor

Sensor

076, 077, 084

Outdoor

Sensor

070

Slab

Sensor

079

Indoor

Sensor

076, 077, 084

Slab

Sensor

079