tekmar 420 Boiler Reset Module User Manual

Page 11

11 of 24

D 420 - 08/07

Step 1

The primary pump turns on and remains on for
the rest of the test sequence.

Step 2

The boiler contact is closed to fire an on-off boiler
for 10 seconds or enable a modulating boiler.

Max Heat

The control has a function called Max Heat. In this mode,
the control turns on and operates the system up to the
maximum set temperatures as long as there is a demand
for heat. tN4 thermostats operate to meet the occupied
setting +5°F (3°C). The control operates in this mode for
up to 24 hours or until the Test button is pressed. Use this
mode to run the circulators during system start-up to purge
air from the piping.

To enable Max Heat:

Press and hold the Test button for more than 3 seconds
and less than 6 seconds.

If there is a demand for heat, the ‘TEST’ and ‘MAX’ segments
are displayed on screen and the control will turn on all
outputs for up to 24 hours.

If there is no demand for heat, the ‘TEST’ and ‘MAX’
segments are still displayed but no outputs are turned on
until there is a demand for heat present.

To Cancel Max Heat:

Press the test button to cancel Max Heat manually or wait
24 hours and the control will automatically leave the Max
Heat mode.

Zone Test

In Zone Test mode, each tN4 device is individually turned
on one at a time. The control tests each zone for up to 5
minutes of no button activity. Use this feature to purge air
out of each zone and assist in troubleshooting.

HAZARD

Access to the Test button requires the removal of the
front cover and exposes hazardous voltage while the
control is powered. Only trained, qualified and competent
personnel should operate the Test button.

Test

Press and Hold
for 1 second

Test

Press and Hold
for 3 seconds

HAZARD

Test

Press and Hold
for 6 seconds

IF the On-Off / Modulating DIP switch is set to Modulating
or the tekmar Stager / Off DIP switch is set to tekmar
Stager:

Step 3

When a demand is present, the modulation
output ramps up to 100%.

Step 4

When a demand is present, the modulation
output ramps down to 0%.

The boiler contact is opened and the boiler is
shut off.

Step 5

If DHW MODE is set to 1 or 2, the primary pump is
shut off and the DHW Pump contact is closed.

If DHW MODE is set to 3 or 4, the primary pump
stays on and the DHW Pump contact is closed.

The control exits the test sequence.

If a device fails to operate during the test sequence, refer
to the W 420 Wiring Brochure to check the operation
of the control. If the control works properly, refer to any
troubleshooting information supplied by the equipment
manufacturer.

To enable Zone Test:

Press and hold the Test button for more than 6 seconds.
The control displays ZN TEST OFF.

Press the Up button to change the display to ZN TEST
ON. After 3 seconds, the boiler, all pumps, and the
mixing valves are shut off.

The control operates stage one of the tN4 device with the
lowest address number. Device number one of the boiler
bus (b:01) has the lowest address number and device
24 of bus 3 (3:24) has the highest address number. All
other tN4 zones are shut off.

Pressing the Up button will turn off stage 1, and turn on
stage 2 of the same device (if that device has a second
stage) or turn on stage 1 of the device with the next
lowest address. The Down button can be pressed to
move to a device with a lower address number. The Up
and Down buttons will only move through devices on
the same bus.

Press the Item button to switch busses. The Up and
Down buttons can then be used to move through the
devices and the heating stages of each device on the
next bus.

To cancel the Zone Test, press the Test button. Once
the Zone Test ends or is cancelled, the control resumes
normal operation.