Bryant FA4A - Manual (Page 28)

AUG/14/2008/THU 03:52 PM UTC TECH PUB
FAX No, 31 7 240 5662 P, 028
R Checking Sequencer Operation
To check for operation of power circuit of ¡sequencer, place
voltmstsr leads across sequencer teroiinal 1 of sequencer 1 and
terminal 4 of limit switch 3. The reading should be 208/230v, and
heater should be energized.
If 20S/230v is not observed at teritiinals specified, check the
following:
• Are fuses FU3 and FU4 good?
* Is limit switch LS3 Open? If so, check fan coil air filter or air
distribution system for blocking or restriction that might
reduce airflow pud cause limit switch to open.
Operation of heaters can be confirmed^fiiither by using a clamp-on
ammeter in circuit shown to verify current is flowing through
heaters. Amperage readings will depend, on size of heater. The
procedure fOr checking other sequencers in
system is identical to
that just described,
G. Emergency Heat
Emergency heat mode requires that room thermostat be placed in
EMERGENCY HEAT position. This locks, out and prevents
operation of heat pump outdoor unit. In tlits mode, heat is provided
exclusively by electrical heaters in fan qoil.
In this mode, room thermostat, at 1, provides'an enaergency heat
input signal to smart cdntrol at teiminaj WZT, If jumper JWl, at 2,
has not been cut and an outdoor .thermostat installed to control
electric heat stages, that samc input signal is applied to tcmiinakJ>
W3. For this example, assume that jumper JWl has not been cut-
Evcntually, the total number of heaters is cycled on. In emergency
heat mode, LED iijdicator signals 7 flashes.
The amount of emergency heat available depends on whether
jumper JWl is cut and the nupiber of heatiji^ elements. Table 10 -
illustrates results under various conditions. The heaters cycle on
every 5 minutes until maximum level is reached.
TABLE 10—EFFECT OF JW1 ON EMERGENCY HEAT
jWi cut*
4 elements 3 elements
50% 66.7%
JW1 not cut
4 elements 3 elements
100^ 100%
Outdoor thermostat opens
With cut, an-outdoor thermostat (if closc^) could cycle on
additional heaters and system would perform as if JWl was not
cut. In effect, closed Outdoor thermostat replaces cut jumper,
H. Defrost
In defrost mode, LED indicator signals 6 flashes. Defrost is
initiated by heat pump and is signalled to smart control by an input
to W2D terminal During defrost, outdoor unit switches to cooling
mode, making it necessary to cycle on electric heaters to temper
indoor air.
If electric heaters were not energized prior to defrost, smart control
energizes ’sufficient elements to temper air. If heaters were
energized prior‘to defrost, additional heaters may ОГ may not be
cycled on to provide additional heat-
Л defrost initiation signal can be confirmed by attaching voltmeter
leads ac/oss low-vcjltage terminals W2D and C. If 24v is not
observed, check the following;
* Is 24v available across R and C? See Ready-To-Start section
for items to check if 24v is not available,
* Is there continuity in thermostat leads between heat pump
and smart control?
* Is defrost control in heat pump operating properly?
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