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| TECH
TALK 61 |
.friction
Loss in pvc plumbing.....
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The AES Technical
Department set up this actual pumping system (shown at left) six different
times using our SQ3 pump. Two elbow types and three pipe sizes
were used to illustrate the importance of correct plumbing.
Study the
results below to understand these principles:
- Elbows vs. Sweeps
- Flow vs. Pipe
Size
- Vertical Head
vs. Total Dynamic Head (TDH)
- Pumping Cost
vs. TDH
NOTE: Centrifugal
Pumps (not self priming) perform best with flooded suction (pumps filled
by gravity) as shown. The suction pipe should be nonrestrictive. To
control pump’s output, put a valve on the discharge side.
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Pipe
Size
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EII
Style
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Vertical
Head
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Measured
TDH
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GPM
Pumped
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Running
Amps. @ 115 V
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kwh
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Pumping
Time Per 100,000 Gal.
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Pumping
Cost
Per 100,000 Gal.
@ $ .08 kWh
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1
1/4"
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90°
El
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4'
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20.5
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16.5
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2.2
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0.22
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100
hours
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.$
1.81
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1
1/4"
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Sweep
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4'
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20..
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20.8
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2.3
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0.23
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...80
hours
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.$
1.50
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1
1/2"
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EI
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4'
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18..
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33.5
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2.5
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0.26
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...50
hours
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$
1.03
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1
1/2"
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Sweep
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4'
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15..
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46.2
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2.7
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0.28
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...36
hours
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.$
. .82
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2"....
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EI
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4'
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11..
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57.8
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2.8
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0.29
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...29
hours
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$..
.68
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2"....
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Sweep
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4'
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..9...
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62.6
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2.8
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0.30
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...27
hours
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$....63
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| All
PVC was Schedule 40, elbows were 90° short, sweeps were flexible PVC.
Cost is based on $.08 per KWH. |
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vertical head was only 4 feet. IMPORTANT: Vertical head is always measured
from the water surface (as shown), not from the pump. |
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Plastic
Pipe Selection Chart
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Friction
Loss in PVC Pipe |
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Feet
of Head Loss per 100' at Diameter (inches)
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1. |
From
the chart at left, using gpm and pipe size, find the friction loss per
100' of pipe. |
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Flow
(GPM)
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1/2"
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3/4"
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1"
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1
1/4"
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1
1/2"
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2"
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2
1/2"
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.0.5
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0.3
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----
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----
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----
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----
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----
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----
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....1
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1.1
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----
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----
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----
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----
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----
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----
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....2
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4.1
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1.0
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.03
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----
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----
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----
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----
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....3
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8.6
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2.2
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.07
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----
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----
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----
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----
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....4
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14.8
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3.7
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1.1
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.03
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----
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----
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----
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....5
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22.2
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5.7
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1.7
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0.5
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----
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----
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----
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..10
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80.5
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20.4
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6.3
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1.7
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0.8
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0.2
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----
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..15
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----
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43.3
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13.4
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3.5
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1.6
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0.5
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----
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..20
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----
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73.5
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22.8
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6.0
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2.8
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.08
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.03
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..30
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----
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----
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48.1
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12.7
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6.0
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1.9
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.07
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..40
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----
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----
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82.0
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21.6
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10.2
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3.0
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1.3
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..50
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----
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----
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----
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32.6
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15.4
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4.6
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1.9
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..60
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----
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----
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----
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45.6
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21.6
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6.4
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2.7
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..70
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----
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----
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----
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----
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28.7
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8.5
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3.6
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..80
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----
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----
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----
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----
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36.8
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10.9
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4.6
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..90
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----
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----
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----
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----
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45.7
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13.6
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5.7
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100
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----
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----
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----
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----
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56.6
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16.5
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6.9
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150
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----
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----
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----
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----
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----
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35.0
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14.7
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200
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----
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----
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----
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----
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----
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59.4
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25.0
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Example:
40 gpm in a 11/2" pipe = 10' loss per 100' of pipe.
40' then causes about 4' of head loss. |
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2. |
Next
find the friction loss caused by the fittings. Please note that the friction
loss depends on the fitting diameter. A standard 1.5" elbow is equal
to about 4' of pipe; long elbows, sweeps, and 45° elbows are equal
to about 2' of pipe; straight through a "T", about 3' of pipe;
and a 90° turn through a "T", about 9' of pipe. |
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Example:
40 gpm through 5 standard 1.5" elbows = 20' of pipe, which equals
2' of head loss. Add this to the pipe’s head loss and the actual
vertical head height in feet to get Total Dynamic Head (TDH).
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All
pumps sold by AES are performance tested. It is up to you to determine
which pump to purchase and how to plumb it correctly. If you need help,
send us a sketch and we’ll size the pipe for you – at no charge.
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NOTE:
The electric energy required for a centrifugal pump usually goes down
as the head pressure goes up. It is the opposite of an air compressor. |
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| TECH
TALK 10 |
Water
pump working too hard?......
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You will only know
by measuring the pump motor amp draw at the motor. If it is drawing
more amps than the Full Load Amps (FLA) rating on the motor label, there
is a serious risk of burning out the motor. To reduce the amp draw,do
one of three things: (1) Get full voltage to the motor by using heavier
wiring; (2) Restrict the pump discharge; or (3) Trim the impeller.
(1) .Check
the voltage at both the pump and the source. If it is less than 5V (or
more) at the pump, a heavier gauge wire will reduce the voltage drop
and, thus, the amp draw.
(2)
.Pump discharge can be restricted by using a valve, but there
is a risk of someone opening the valve later. In place of a valve, use
a permanent restriction, such as a reducer fitting in the discharge
pipe.
uch as a reducer fitting in the discharge pipe
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(3) .To
trim the impeller, remove the pump case (volute) and very carefully
trim 1/8” off the impeller diameter. In some cases, this can be
done by very carefully holding a file to the impeller while the pump
is on. Put the pump back together and test the amp draw again. Repeat
the trimming procedure until the desired amp draw is achieved. Remember
that trimming reduces the gpm.
To be absolutely
certain that motors won’t fail due to excessive amp draw, do the
following: In many places with 110-120V service, a voltage variation
from 105 to 126 may occur. A motor’s amp draw will be the highest
when the voltage is the lowest, so check the full load amps when the
facility’s voltage is lowest and while all other equipment on that
circuit is in use. Always check volts and amps at the motor while the
pump is running at full load.
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| Taken
from AQUATIC ECO SYSTEMS,INC. Pg. 400 (2004 Master Catalog) |
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