Set Water Flow Rate; Pump Modification/Trimming - Carrier AQUASNAP 30RB060-390 Installation Instructions Manual

SET WATER FLOW RATE Once the system is cleaned,
pressurized, and tilled, the flow rate through the chiller
needs to be established. On units with the hydronic package,
this can be accomplished by using the balancing valve.
Follow the manufacturer's recommendations for setting the
balancing valve. Local codes may prohibit restricting the
amount of water using the balancing valve for a given motor
horsepower. In this case, use the method listed in the Pump
Modification/Trimming section. See Table 7 for the type of
combination valve in 30RB units with the optional hydronic
package.
Table 7 -- Combination Valve Details
30RB UNIT I SINGLE/DUAL PUMP
060-130 I FTV-4 in.
150-190 FTV-6 in.
NOTE: Carrier recolrnnends a differemial pressure gage when
measuring pressures across the pumps or balancing valves.
This provides for _eater accuracy and reduces error build-up
that often occurs when subtracting pressures made by different
gages.
A rough estimate of ,a_aterflow can also be obtained fiom
the pressure gages across the 30RB heat exchanger.
Figures 36-38 show the relationship between gpm and heat
exchanger pressure drop. It should be noted that these curves
are for fiesh water and "clean" heat exchangers; they do not
apply to heat exchangers with fouling. To read the chart,
subtract the readings of the two pressure gages on the hydronic
kit. This number is the pressure drop across the heat exchanger.
Adjust the thctory-instatled balancing valve or external balanc-
ing valve (in units without hydronic package) until the correct
pressure drop is obtained for the required gpm.
PUMP MODIFICATION/TRIMMING Since the pumps
are constant speed, the only way to obtain _eater flow with a
given pump/impeller is to decrease system head. This will
allow the pump to "ride" its curve to the right, resuhing in
increased flo,a: If _eater flow is necessary, consider opening
the combination vane. Also, verii_ that the strainer is dean,
and that no unnecessary system resistance is present, such as
partially closed isolation valves.
Once the combination valve is set, note the stem position. If
later service work requires the valve to be closed, it will be easier
to re-balance the system, if the original balance point is known.
Increasing system resistance by closing the balanchlg vane
will force the pump to "ride" its cula,e to the left, resuhing in
less flow. Although this does reduce power consumption
slightly, it may not be the desirable method of reducing the
flo,a; especially ira large reduction is needed.
The other method for reducing flow on a constant speed
pump is impeller trilrnning. The impellers in the pumps provid-
ed in the 30RB hydronic kit can be easily removed for this
purpose. Refer to the vendor literature packet supplied with the
hydronic package information on Seal Replacement in the
Smqce Section, and follow instructions for impeller removal
and trimming. See Fig. 39-46 for pmnp envelope curve ilRbr-
mation. Trilrnning should only be done by a qualified machine
shop that has experience in this operation. Contact your local
Carrier representative tbr a recommeMed machine shop.
After trilrnning, the impeller MUST be balanced. Failure to
balance trilrnned impellers can result in excessive vibra-
tion, noise, and premature bearing failure.
Impeller trilrnning has the added benefit of maximum bhp
(brake horsepower) savings, which can recover the cost
incurred by perfonnthg the impeller trilrnning.
80
(179.4kPaZ
30RB060-130
50 080, O_.3, 100
(149.5kPa' 060, 07(
(119.6kPa Z
30 / / _11C 120,130
%: / yY"
1o
(29.TkPa' _
0
0 100 200 300 400 500 800 700
GPM
6.3 12.6 18.9 25.2 31.5
Us
Fig. 36 -- 30RB060-130
Cooler Pressure Drop Curves
37.6 44.2
30RB210-300
/
,/
/
/
..j'J
/
J
o
loo 3oo 93o 7oo 900 11oo 13oo
GPM
15OO
63 189 315 442 568 694 82 946
Us
Fig. 37 -- 30RB210-300
Cooler Pressure Drop Curve
30RB150-190 and 30RB315A,B; 330A, B; 345A,B; 360A,B; 390A, B
/
.Y
J
/-
J
0 200 400 600 800
GPM
12.6 25.2 37.8 50.5
Us
1000
63.1
Fig. 38 -- 30RB150-190 and 30RB315A, B; 345A, B;
360A, B; 390A, B Cooler Pressure Drop Curve
38