tekmar 257 DHW Control - Manual (Page 5)

5 of 12 © 2009 D 257 - 03/09
This function rotates the firing sequence of the two boilers
based on the accumulated running hours of each stage. The
HEAT 1 and HEAT 2 items in the default menu display the
accumulated running hours of each stage. When one stage
has accumulated 48 hours more running hours than the
other stage, the operating sequence is rotated. The stage
with less running hours is rotated in the firing sequence to
turn on first, while the stage with more running hours will
turn on last. This function increases the quality and reliability
of the boiler plant by ensuring equal running times of both
boilers. When this item is set to off, HEAT 1 is always the
first stage to fire.
Forced Rotation:
If the difference in run times reaches 60 hours, then boiler
rotation takes place immediately. This could occur if the
DHW tank has a constant load causing one boiler to fire
for an extended period of time.
Relay Run Times
The control logs the number of run time hours for the HEAT
1 and HEAT 2 relay in the default menu. To reset back to
zero hours, press and hold the up and down buttons for
3 seconds.
1 2
500 Hours 452 Hours
Reset Rotation:
To reset the rotation sequence back to 1-2, clear both run
time hours in the default menu by pressing and holding the
up and down buttons. Next, switch the rotation dip switch
to the off position and then back to the on position. Both
stages now have 0 hours accumulated run time and the
firing sequence is 1-2.
Rotation
When P Staging Mode is selected, you are then able to
adjust the minimum stage delay between when stage
1 and stage 2 fires. This item is default at 30 seconds
and is adjustable between 0 seconds and 19 minutes 50
seconds.
When PID Staging Mode is selected, PID logic is able
to determine when to bring on stage 1 and stage 2.
The minimum stage delay now becomes the default 30
seconds.
Selecting a Delay Time:
For low mass boilers, select a shorter delay time.
For high mass boilers, select a longer delay time.
Stage
Delay
Stage 1
Contact Closes
Stage 2
Contact Closes
Stage 1
Stage 2
Time
•
•
Delay