Johnson Controls YORK YPC Series, Installation Manual

Page: 24 / 114

JOHNSON CONTROLS
24
SECTION 6 – UNIT WATER PIPING AND HOOK-UP
FORM 155.17-N1
ISSUE DATE: 4/1/2013
FLOW SWITCHES
The unit inlet and outlet nozzle con nec tions are iden-
ti fied by yellow labels placed adjacent to each noz-
zle. An evaporator water flow switch is sup plied by
Johnson Controls as a ship loose item. This water flow
switch must be in stalled in either the evaporator sup-
ply or re turn wa ter circuit, as close to the unit as possi-
ble. It may be advantageous to mount the flow switch
on the outlet side of the bundle, to ensure flow is go-
ing through the bundle. (See Figure 9 on page 25 .)
Johnson Controls highly recommends mount ing the
flow switches in a horizontal length of pipe, with the
switch in a vertical position at the top of the pipe. It is
not rec om mend ed to mount the flow switch in a ver ti-
cal pipe with an upward flow, due to the fact that min-
i mum water flow may not be substantial enough to lift
the switch’s paddle.
A condenser and/or a hot water switch is shipped only
as an extra order option. However, these switches must
be used in each in stal la tion. See unit shipping papers
if these switch es are sup plied. Foreign objects which
could lodge in or block flow through the cooler, hot
water heat ex chang er, and ab sorb er tubes must be
cleaned or flushed before being connected to the chill-
er pumps or other equip ment.
PRESSURE DIFFERENTIAL SWITCHES
Johnson Controls factory can supply differential
switches in lieu of flow switches as a special order
option. Differential switches serve the same function
as flow switches – to ensure that flow is es tab lished
for chiller operation. This is accomplished by de ter-
min ing a difference in pressure between two sam ple
points in the chiller piping, usually at the inlet and out-
let of a heat exchanger bundle. It is very im por tant that
the pres sure dif fer en tial switch be installed as close
to the heat ex chang er bun dle as pos si ble so that only
the pres sure dif fer ence across the bundle is sensed. Do
not put the pres sure dif fer en tial switch across the suc-
tion and dis charge of a heat exchanger pump. Doing
so may not ab so lute ly en sure flow across the chiller
bundle due to valves that could be closed.
Another important aspect to remember when using a
pres sure differential switch is to ensure both the sam-
ple points are on the same elevation with other. If one
connection is higher than the other, then static pressure
becomes a factor into the total differential across the
switch. The switch could be reading a differential un-
der this con di tion even when there is no flow.
STRAINERS
Permanent strainers (supplied by others) are required
in all the absorption unit’s water circuits to pro tect the
tubes, coils, and controls. The strainer should be a #10
mesh and be installed in the entering water line, direct-
ly upstream of the chiller. Water piping circuits should
be arranged so that the pumps discharge to main tain es-
sentially constant chilled, tower and hot (if applicable)
water flows through the unit at all load conditions. If
pumps discharge through the chiller, the strainer may
be located upstream from the pumps to protect both
pump and chiller (piping between strainer, pump and
chiller must be very carefully cleaned before start-up).
If pumps are remotely installed from chiller, strainers
should be located directly upstream of the chiller.
ABSORBER AND CONDENSER WATER
PIPING
The ab sorb er and condenser water piping should be in
accordance with the drawings for the specific system.
The tower water must be piped into the inlet absorber
nozzle and out of the con dens er nozzle. A factory in-
stalled well is located in the absorber inlet nozzle on
the absorber inlet water box. This nozzle should also
have a yellow inlet sticker at tached at the top or side
of the nozzle to help the installer identify which nozzle
is the inlet.
TOWER WATER CROSS-OVER LINE
On some units it is nec es sary to field fabricate the
tower water cross-over line from the absorber outlet
nozzle to the condenser in let noz zle. All material must
be field supplied for fab ri ca tion of this line. The cross-
over line must be fab ri cat ed so that the pressure drop
is kept to a min i mum! This should only be 1 or 2 psi
at the extreme!
Tips to help accomplish this when fabricating the
cross-over line:
1. Use only butt-weld ed connections. Do not use
victaulic connections other than those at the unit
nozzles.
2. If the absorber and condenser nozzles are not the
same size, use a gradual reducer. Do not go from
one size to another abruptly!
3. Use long radius elbows if possible.
4. Make the cross-over line as short as possible.
5. Use the couplings on the absorber outlet box and
condenser inlet box to check the pres sure drop
across the line.