Stimmen - 4, Durchschnittliche Bewertung: 3.5 ( )

Hersteller: Amtrol Dateigröße: 272.82 kb Dateiname: Unterrichtssprache:

We now must select a pressure range (min. to max.) to establish pressurized delivery of water to the system and that we overcome elevation (static height) and friction loss of the piping. We must select a minimum pressure at the Well- X-Trol® location that will insure enough pressure to keep water flow under pressure at the top of the system…overcoming both the static height and the resistance to flow through the piping. We’ll do this by pre-charging the Well-X-Trol® to a pressure (P1) equal to the minimum pressure required at the Well-X-Trol® location. In addition, we’ll select a pump cut-in pressure (P2) which is at the same pressure to start the pump whenever system pressure drops to this point. We’ll assume that a minimum system pressure at the Well-X-Trol® location of (30) PSIG. This pressure will be adequate to insure system pressurization to overcome elevation and friction loss and provide adequate pressure at the fixture. To find this pump cut-in point on the pump curve, we’ll have to convert (30) PSIG to feet of head. To convert PSIG to feet of head, we must multiply PSIG by (2.31). 30 PSIG x 2.31 = 69.3 or 70 feet of head To locate this point on the pump curve, we must add 70 feet of head…the pump head required to pressurize the system to 30 PSIG…to the feet of head required to lift the water to the surface: Minimum System Pressure = 70 Ft. of Head Plus Lift = 240 Ft. of Head * Pump cut-in point on curve = 310 Ft. of Head We have selected the point on the curve which will be the pump cut-in setting (P2) of 30 PSIG on the pump switch, and we will pre-charge the Well-X- Trol® to 30 PSIG (P1). Now we will select the maximum pump cut-out point on the curve which will allow the widest possible pressure range without impairing pump performance and efficiency. We will do this by moving up the curve to find a point that: Is just before the curve begins to “flatten” out And is still within the upper limits of best efficiency range of the pump In this example, that point would be at the intersection on the curve of the horizontal line indicating (410) or (420) feet of head… let’s say (420) feet. This is the point on the curve which will be the maximum pump cut-out for this particular pump. -3 Subtracting the feet of head required for lift (240.) we can convert this point to PSIG: Maximum pump cut-out = 420 feet Less lift = 240 feet Maximum pressure = 180 feet To convert feet of head to PSIG, we divide by (2.31) (there is (2.31) feet of head for each PSI): 180 . 2.31 = 77.9 or 78 PSIG. Or pump cut-out pressure (P3) is 78 PSIG. 700 600 500 Even though the pump may be rated as a (85) GPM pump (as in our example) the actual capacity in GPM will vary as the pump operates throughout its pressure range from pump cut-in (30 PSIG) and pump cut-out (78 PSIG). So, we’ll go back to our curve and determine what capacity in GPM the pump will deliver at its cut-in point, and what capacity in GPM it will deliver at its pump cut-out point. Then, we’ll average these two capacities by adding them together and dividing by two. Reading the curve, we can find the point that indicates pump cut-in. We already know that this is: 30 PSIG x 2.31 = 70 Ft. of Head Plus “Lift” = 240 Ft. of Head Point on Curve = 310 Ft. of Head TOTAL HEAD IN FEET 700 80 600 EFF. 20 40 60 80 100 120 140 60 EFFICIENCY % TOTAL HEAD IN FEET 500 400 300 60 40 20 EFFICIENCY % EFF. 200 40 CAPACITY IN GPM 100 20 0 20 40 60 80 CAPACITY IN GPM 100 120 140 To Summarize: We have used actual pump performance as shown on the pump curve for the pump selected, to complete Reading down to capacity we can determine that, at step one in utilizing maximum capacity of the full (310) feet of head, the pump will deliver (106) GPM. acceptance Well-X-Trol® models, Series 420 and 450. We then read the curve to determine the capacity at pump cut-out: In this step we have determined: 78 PSIG x 2.31 = 180 Ft. of Head System minimum pressure of 30 PSIG. To Plus “Lift” = 240 Ft. of Head establish the Well-X-Trol® precharge pressure. Point on Curve = 420 Ft. of Head (P1) Pump cut-in pressure (P2) of 30 PSIG. Capacity at (420) Feet of Head = 90 GPM Pump cut-out pressure (P3) of 78 PSIG. Determine ESP Volume: Being a large pump, we will want to have a mini- Step Two – Determine, ESP volume mum run time of at least (2) minutes on the pump: required to control pump cycling. Average Capacity Average Capacity Determine average capacity in GPM: With larger pumps, capacity, or flow of the pump will at P2: 106 98 GPM x 2 = 196 ESP Volume vary depending upon the pressure or feet of head at at P3: + 90 which it is operating. 196 . 2 = 98 -4 Step Three: Calculate Acceptance Factor (AF) Remember our formula for calculating the acceptance factor (AF) for diaphragm tanks? 30 + 14.7 AF = 1 78 + 14.7 AF = .518 Step Four: Maximum Acceptance Factor Verification After calculating the acceptance factor (AF), we must compare the value to the maximum acceptance factors shown in Table 1. In the case of our ex...

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