Sterlco 4300 Series Stainless Steel Condensate Pumps - Manual (Page 2)

Page 2 of 10
Sterlco ® Condensate Pumps
Operation and Installation Instructions
Tel (262) 641-3808 • Fax (262) 641-8625 • www.steamcontrolproducts.com • Bulletin: SCP1-600.3 • Effective: July 1, 2008 • Supersedes: August 23, 2005
Selection of Discharge Piping
In selecting condensate pumps and making proper piping
connections, the friction in the discharge line from the pump to
the boiler is very important. The pressure drop due to friction is
sometimes much greater than the boiler pressure. In some
cases, using larger discharge piping will make it possible to use
a less expensive pump with a lower pressure rating. In all cases,
adequate discharge piping will mean longer life and better
service from your pump.
The pressure drop due to friction should always be estimated
carefully, using the gallons-per-minute rating of the pump as a
basis and referring to any standard pipe-friction tables or charts
(be sure to make extra allowance for elbows, valves, etc.). The
discharge pipe size and pump pressure rating should be selected
so that the pump pressure rating will provide a generous margin
of safety over and above the friction pressure drop plus the lift
from pump to boiler water level (not to water inlet to boiler)
plus the maximum pressure at which the boiler will operate.
Usually, the best discharge pipe size will be at least one size
– sometimes two sizes – larger than the pump outlet tapping.
If possible, piping from the condensate pump outlet to the boiler
inlet should be graded upward for the entire distance. In a
downward run, or an ‘up-and-down’ run, air may be entrapped,
restricting the flow of condensate. If an ‘up-and-down’ run
cannot be avoided, it should be vented at the highest point.
Float Switch Settings
When condensate pumps are tested in our factory, float
switches are set according to the capacity rating. At the time of
installation, the float switch should be checked to see that
settings have not been disturbed during shipment and that they
are correct for the particular job.
The travel of the float switch between the upper (ON) position
and the lower (OFF) position determines the amount of
condensate delivered to the boiler each time the pump operates.
At our test, the float switch is set so that the amount is equal to
or a little less than the GPM rating of the pump. For example,
if the pump is rated 4000 sq. ft. EDR, 6 GPM, the switch is set
to deliver about 4-6 gallons at each cycle. Depending upon the
water capacity of the boiler and the other characteristics of the
heating system, this float switch setting may require
modification for best results.
If the float switch travel is too short for the job, only a small
amount of condensate will be discharged each time the pump
operates and consequently the motor will have to start and stop
too frequently. In normal operation, it is usually undesirable
for a condensate pump to start and stop more than once every
three minutes.
If the float switch travel is too long for the job, too much water
will be discharged at each cycle. In this case, the boiler water
level may fall too low before the pump starts. Then the boiler
low-water cutoff will operate unnecessarily, or if there is a
boiler-feed device it will supply make-up water unnecessarily
and the heating system will become water-logged.
If the lower (OFF) position of the float switch is too low, the
pump may continue running until it loses its prime and the
rotary seal may be damaged by running dry. When starting up
a new pump, always check the lower float switch position to be
sure that the inlet from the tank to the pump is covered with
water at all times.
Any condensate pump can be used for a smaller capacity than
its nameplate rating by decreasing the travel of the float switch.
In addition, in the case of Sterlco
®
4100, 4200, and 4300 series
pumps, all units of the same horsepower are identical except for
float switch settings. Therefore, many of these units can be
used for larger capacities than the nameplate ratings by
increasing the float switch travel. The table below shows
standard float switch settings for 4100, 4200, and 4300 series
Sterlco
®
pumps.
Capacity
Sq. Ft.
E.D.R.
G.P.M.
Rating
Pump
Number
Approx.
Inches
Travel
1/3 H.P. Pump
8 Gal. steel tank or
6 Gal CI tank or
8 Gal stainless steel tank
8,000 12
4028
4222
4028-GS
3”
2,000 3
4132
4232
4332
3”
4,000 6
4124
4224
4324
5”
6,000 9
4126
4226
4326
7”
1/3 H.P. Pump
15 Gal. steel tank or
13.5 Gal. C.I. tank or
15 Gal. stainless steel tank
8,000 12
4128
4228
4328
8”
10,000 15
41210
42210
43210
7” 1/2 H.P. pump
30 Gal. steel tank or
24 Gal. C.I. tank or
30 Gal. stainless steel tank
15,000 22.5
41215
42215
43215
10”
The “travel” as listed is the vertical displacement between the
water levels at the “On” and “Off” positions of the switch. The
method of adjustment is indicated in the float switch instruction
sheet or card that accompanies the pump. The “travel” distance
can be checked by inserting a yardstick into the vent opening at
the top of the tank.
Operation & Installation