Daikin Rebel DPS Series Installation And Maintenance Manual page 50

Auxiliary Limit Switch Function
The auxiliary limit switch is a manually resetable switch and is
designed to trip in the event of a supply fan failure. It should not
trip during any other conditions. In the event of a blockage to the
return or discharge air, the primary limit, which is an automatic-
reset type, is designed to trip.
Should there be a fan failure which results in the tripping of the
auxiliary limit, the limit must be manually reset to resume function
of the unit.
On the Rebel A cabinet (3-6 ton), the auxiliary limit resides in
the fan compartment between the furnace heat exchanger and
the fan. To access the switch, the fan compartment door must
be opened. Be sure all power to the unit is disconnected before
opening the fan compartment door.
Once the fan compartment door is opened the auxiliary limit
switch can be found behind the supply fan on a bracket mounted
to the cabinet wall.
Depressing the red button on the auxiliary limit will reset the limit
and allow the furnace to be powered. The furnace should now
respond to a call for heat.
Figure 52: 3–6 Ton—Auxiliary Limit Switch
Figure 53: 7–15 Ton—Auxiliary Limit Switch
Figure 54: 016–028 Auxiliary Switch
The auxiliary limit The auxiliary limit
on the C cabinet on the C cabinet
(17-28 ton) is in (17-28 ton) is in
the compressor the compressor
compartment above compartment above
the furnace vestibule . the furnace vestibule .
The red button of The red button of
auxiliary limit switch auxiliary limit switch
must be depressed in must be depressed in
order to reset the limit order to reset the limit
and allow the furnace and allow the furnace
to be powered . to be powered .
IM-1125-13 • REBEL ROOFTOPS
View of supply fan
with aux limit behind,
mounted on a bracket
off the cabinet wall
The auxiliary limit on the
B cabinet (7-15 ton) is in
the furnace compartment
(vestibule) above the furnace
DPS Modulating Burner Setup for VB1200 Burner
Controllers.
DPS have two variations of burners 5-1 and 10-1. 10-1 burners
have a split manifold where one side is modulating and the
other side is single stage. 5-1 burners have a single manifold
with a modulating gas valve. Both burners are manufactured by
Beckett or Heatco but their respective burner controllers vary in
programming. When replacing a VB1200 board make sure to
compare the tag on the original board to make sure the correct
one is installed in the unit. If an incorrect board gets installed,
an alarm for bad ID plug will occur.
When performing startup, even though it is not on the current
startup forms, be sure to verify and usually adjust low fire rate
accordingly.
Inlet natural gas pressures should be between name plate
ranges of 5"-14"
Low fire should be between 0.25"-0.3"
Best Suggested adjustment from testing is 0.28"
At the ON/OFF regulator outlet, gas pressure should be 3.5"w.c
This is done by backing the screw out to decrease manifold
pressure and screwing in to increase pressure.
Adjustments of these burners are done through the MANUAL
CONTROL menu at the Microtech III controller. Low fire is set
with 20% heating capacity, generating a 2 VDC output from
Microtech. There will be a slight increase in pressure at each
voltage increase from 2VDC to 10VDC. See air/gas graph
below. Fine tune adjustments on gas pressure are done on the
Maxitrol EXA modulator valve. The adjustments are done with
the two electronic push buttons under the blue cover. Refer to
the directions below on how to use these buttons.
Once a good stable flame is verified at low fire, adjust the
burner to 100% heating capacity from the Microtech controller
and check for high fire.
High Fire should be at 3.5"w.c
Best suggested adjustment is 3.5"w.c
At the ON/OFF regulator outlet, High fire should still maintain
3.5"w.c. This is done by backing the screw out to decrease
manifold pressure and screwing in to increase pressure.
On the 10-1 burners, the single stage burner needs to output
3.5"w.c at all times when heating capacity is above 60%. Below
60% this section on the manifold does not get energized.
50
Optional Gas Heat
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