EMM-3U UNIVERSAL ELECTRONIC MINIZONE™ PANEL
15 68-0237-2
TROUBLESHOOTING
The primary diagnostic tools are the System and Zone damper status LEDs and BOOT and PURGE OVERRIDE buttons. See
Fig. 20 and 21 for troubleshooting flowcharts.
Fig. 20. Thermostat is calling for cooling but the Cool LED is not turning green to show a cool call.
Ye s
Ye s
Is the
thermostat calling
for cool?
Ye s
No
Thermostat may be in a
5 min delay in cooling.
Make sure thermostat is
calling for cooling.
Ye s
No
Is there
24 vac at R and C on
the transformer
contacts?
Ye s
No
Check the transformer
for 24 vac.
No
The
thermal fuse has
tripped because of a high amp
draw. Remove the R wire on
the transformer contacts from the board
for 5 minutes and allow the board to reset. Take
the thermostat and damper wires off from
each zone before you re-attach the
transformer R wire. Is there
voltage at R-C on all
of the zones?
Re-attach each zone thermostat wire. Attach
each zone separately, checking after each
zone is attached if the thermal fuse
has tripped by checking voltage across R
and C on that zone. After attaching the
thermostat wires, attach each zone motor
wires, again checking the thermal fuse to
see if it trips. This step-by-step process
should help you identify what is tripping the
thermal fuse on the board.
Is there
24 vac on all the zones
at R-C?
The board may have been damaged.
Take the transformer R wire off again
for 10 minutes. After 10 minutes re-
attach that R wire and press the BOOT
button. Check voltage at R-C on all
the zones. If no voltage at R-C then
call Honeywell Zoning hotline,
800-828-8367.
Start
No
It could be a bad wire. If you have voltage
on the panel at R-Y1 (and R-O/B if there is a
wire on O/B) but not at the thermostat, it is a bad
wire. Check for voltage at R-W or W1, G on the
thermostat. If there is voltage there then it
is a bad Y or Y1 (or O/B if you are using O/B) wire.
If no voltage at R-any other terminal on the
thermostat then it is a bad R wire.
Jumper the R wire to the Y or Y1 (and O/B if you have
a wire on O/B) wire on the thermostat. If the
COOL light comes on, you have a bad
thermostat. Replace thermostat. If you
jumper R-Y or Y1 on the thermostat and the COOL
light does not come on, you may have a bad wire.
Try another set of wires or check continuity.
Check for
24 vac at Y1-C on
the zone calling for cooling.
You should have
24 vac?
No
Is
24 vac at R-Y or Y1
and R-O/B on the
thermostat?
Ye s
Are you
using heat pump
or conventional
thermostats?
Conventional
Ye s
Do you
have the correct volt
reading at O/B-C on
the board?
Ye s
No
Check for 24 vac at Y1-C on the zone that is calling for
cooling. Check for 24 vac at the O/B-C on that zone.
Are you using O or B on the thermostat? If you are
using O on the thermostat, you need to place the
shunt jumper across the two pins. If you are using B,
you need to place that jumper on just one of the
pins or completely off. If you are using O then you will
have 24 vac at O/B-C. If you are using B on the
thermostat, you will not have 24 vac at O/B-C.
Heat pump
Is there
continuity at Rc-Y1 and
Rc-O on the equipment
contacts of the EMM-3U
board?
Ye s
No
Do you have
a DATS sensor hooked
to the board?
The cooling equipment should be
on. Seems like the board is
working but the COOL light is not
coming on. Call Honeywell
Zoning hotline, 800-828-8367.
Remove all wires from the board except R and C (power from the transformer)
Reboot the board. Jumper R-Y1 (and R-O/B if you are using O from
the thermostat) on one of the zones. If the COOL light does not come on,
call Honeywell Zoning hotline, 800-828-8367.
Remove the DATS wires from
the board. Reboot the board.
Return to "Is the thermostat
calling for COOL" part of the
flowchart and begin
troubleshooting from that point.
No
Ye s
END
M14827A
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