York D1SV300 Installation Instructions Manual page 13

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It is recommended that the control band be set as shown:
8°F for D SV300
7°F for D .SV360
L
6°F for D. SV480
The controller has a built in feature which provides a 4 min-
ute off cycle and a 4 minute on cycle to prevent compressor
rapid cycling.
When power fails, the W7100 shuts off all stages of mechan-
ical cooling. When power ~esumes,the economizer will first
be modulated open, prowded enthalpy of the outside air is
suitable. Once the economizer is open, mechanical coofing
is sequenced back on with a minimum of 4 minutes between
succeeding stages, If outside air enthalpy is not suitable, econ-
omizer modulation is bypassed, allowing mechanical cooling
to begin sequencing after 4 minutes, with a minimum of 4
minutes between stages.
When the D. SV does not have economizer option, a 510
ohm, ]/4 watt,
570
resistor is placed between termina]s 9
and Y on the W7100 to eliminate the economizer delay and
energize mechanical cooling immediately.
COOLING
When the discharge temperature has deviated 1'F above(or
below) the control band, additional stages of cooling will be
turned on (or off) at four minute intervals until either the
discharge temperature drops (or rises) to within one degree
of the control band, or the discharge temperature falls (or
b
rises) at a sufficient rate that will insure that discharge temp-
erature will soon be within the control band (about 10 mm-
utes). The rate feature prevents needless cycling caused by
changesin load. The last stage to be turned on or off is re-
ferred to as cycfrngstage.
D- SV units have nominal cooling capacities of 25, 30 and
40 tons. The D SV300 has two stages of capacity achieved
by unloading a single compressor. The D. SV360 has three
sttigesof'capacity achieved by two unloading solenoids on
one compressor. The D SV480 has four stages of capacity
achieved by two compressors each with an unloader.
All systems are completely factory assembled, refrigerant
piped, refrigerant charged and leak tested. A strainer drier
and a tno]sture indicator are installed in each liquid line. A
h]gh pressure cutout is located in each system( ' s) on the
compressor before the discharge valveand will de-energiie
the compressor control circuit should the system('s) dis-
charge pressure exceed 395 psig. The pressure cutout wil[
remain de-energizeduntil the system('s) pressure returns to
310 ps]g.The opening of the high pressure cutout wdl en-
ergize the kwkout circuit. The control
circuit must
be
open-
ed and closed to reset the
lockout circuit,
AntLcycletltning
is part of the compressor protection module. This prevents
the compressor from lapid short cycling. A low pressule
cutout 1slocated in each system('s) on the compressor be-
fore the suctmn valveand will de-energl/e the c(~n]pl cssor
L
cent
rol circu]t should the
system( ' s) pressure drop t~~ 7
psig. This control will automa[ ically rese[ when the suetl<)n
pressure rises to 22 psig. The operung of the low p[essute
cutout will energwe the Iociout CII w it.
The control circuit must be opened and closed to reset the
lockout circuit.
Normal sequence of operation is as follows:
1. Power is supplied to the unit through the disconnect
switch. The switch can be field-installed or factory-
installed as an option.
2. As soon as power is supplied to the unit, the compres-
sor crankcase heaters ITH (and 2TH) will be energized,
CAUTIOIV:Do not attempt to start the compressors wirh-
out at least 8 hours of crankcaseheat or com-
pressor damage will occur.
3. If the unit is not equipped with a morning warmup ther-
mostat or a day-night switch the 7R relay coil will be
energized. The 7R contact closes energizing the 3M coil.
3M contacts close, starting the supply air fan motor. Af-
ter an adequate air flow is established, 5 LP closes to en-
ergize 6R coil, 6R contact closesin the compressor con-
trol circuit. If the unit has a day-night switch the switch
must be in the day position. If the unit has a morning
warmup thermostat it must be sat]sfied or the above fan
and unit operation will not occur.
4. If the D. SV unit does not have an economizer cycle or
if the outdoor enthalpy is too high, on demand , the dis-
charge air sensor will signal the logic panel to close the
"Cool 1" contacts and energize IR coil.
5. 1R contact closes and energizes IM coil, which starts the
(No. 1) compressor ]n an unloaded condition. At the same
time. 4M is energized to start the condenser fans.
6. If the discharge air temperature is not within 1°F of the
control band the logic panel will energize the following
stages.
a. "Cool 2" contacts will energize. On the D- SV300 this
energizes the 2R relay. The 2R contacts close de-ener-
gizing the compressor urdoadlng solenoid which loads
the compressor. On the D. SV360 t}us energizes the
~R re]uy, The 2R contacts close de-energii.ingthe com-
pressor unloading solenoid which loads the compressor
to 2/3 or full capacity. On the D. SV480 this de-ener-
gi/es the compressor unloading solenoid which loads
t}leNo. 1 compressor.
b.
"COO1 3" contacts will energize. On the D..SV36Othis
de-energizesthe compressor unloading solenoid which
Iodds the compressor to full cap~ctty. On the D .SV480
this enclgizes the 2R relay. The 2R conlacts close and
energize 2M COII w hich starts the No. 2 c~~mpressor i n
an unk}. ided condition.
c, "COO!4" contacts will energize. On the D. SV480 this
de-energues the ct~mpressorunloadlng solenold winch
l(xidsthe No 2 compressor.
7, The u(~mpressor s hort cycle time and low vt)ltage p]otec-
tmn ISp~rt of [he solid stdte compressor prot ec~lon m[~d-
ule. It plevents J compress(~[fr(~mstarting unless It has
Central Environmental Systems
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