Pressure Tank and Pump Questions


  #1  
Old 05-17-04, 11:16 AM
sweet
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Pressure Tank and Pump Questions

Does the size of the tank reflect how much water you use in the household? The tank I have looks like a 10 gallon tank (half the size of a keg, or so) When the water is running (sink, shower) the pump cycles on and off every 15 - 20 seconds, is this normal? I know there is a cut in-cut out switch (30-50) , but where is this located. The pressure guage on the pump is at around 50, but the needle does not move when the pump cycles. I checked the valve on the tank and it reads around 32 psi. I know your supposed to empty the tank first to take a reading, but is that to low? Sorry for all the newbie questions, any help would be greatly appreciated. Thanks.
 
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Old 05-17-04, 11:53 AM
J
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The pressure gauge sounds like it is stuck. I would replace it.
Pump cycling every 15-20 seconds sounds a bit too often but the tank sounds a small also. The smaller the tank the more cyling you get.
The pressure in the tank should be at 28lbs if your pump switch is set to 30-50. To check it properly, measure the pressure with the pump shut off and the water pressure drained to zero. Open a tap and wait for the water to stop running with the pump off.
 
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Old 05-18-04, 06:22 AM
G
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The size of the tank is (should be) dictated by the pump run time but usually they are sized by price adn are undersized for the pump motor requirements. The rule of thumb is one minute off between starts for up to 2 hp motors (2 mins for larger) although that usually applies to submersible pumps. Your pump is a jet pump and they are air cooled so it's not as important as water cooled submersible pumps.

Your system may be (a) set up so the pump runs while water is used. That is done with a small tank to provide a gallon or so of water without the pump coming on but a larger/longer water use starts the pump and allows it to run until you shut off the water. Usually there is a throttle back valve (between the pump and pr. tank) that reduces the outflow from the pump to enable that to work.

The pressure switch is usually mounted on the motor of your style of jet pumps. It has the electrical wire/cable going to it. Usually a gray covered 3" x 5" x 3" box on the side of the motor. It will contain 120 or 240v. And if you don't know what you're doing, you can get things fairly far out of 'balance'.

Gary
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Last edited by Doug Aleshire; 03-11-05 at 05:38 PM.
  #4  
Old 05-18-04, 06:35 AM
sweet
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Obviously the guage not working would have something to do with the cycling of the pump, right? Would it not be easier on the hydro bill if the pump was to stay on during water use, instead of cycling on and off?
 
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Old 05-18-04, 08:01 AM
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Wink

I know your supposed to empty the tank first to take a reading, but is that to low? Sorry for all the newbie questions,
Did you check it with the tank empty????

ED
 
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Old 05-18-04, 08:09 AM
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The gauge is merely used to read the system pressure. It has nothing to do with actually controlling the pump. That's the function of the pressure switch.
The rule of thumb for sizing a pressure tank is this:
"One gallon of drawdown for each gallon of pump capacity".
In other words, if your pump has a capacity of 15 gpm, then the tank should have approx. a 15 gallon drawdown between cycles. This will usually give you the proper motor run time, as Gary Slusser alluded to.
The pump motor will run more efficiently (power wise) if the pressure tank is sized properly.
Telling us the horsepower and make of the pump would help in determining which tank you should use.
Ron
 
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Old 05-18-04, 11:08 AM
sweet
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Hey Ed: No I haven't checked the tank empty yet, trying to figure out how not to get to wet.

Pumpman: The pump is a 1/2 HP Franklin-Electric of Canada. In regards to the pressure switch, how are you to make sure the cuton/off (20/40) is set properly if there are no guages?
 
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Old 05-18-04, 05:59 PM
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Franklin Electric is a pump motor manufacturer, they don't make pumps but their motors are the most popular and are used by most pump manufacturers.

The pressure switch has two settings, on and off (cut-in and cut-out). To know what the settings of the switch are you or to adjust them you have to have a gauge on the system.

Most tanks (all should) have a drain valve you can attach a garden hose to. You drain the tank after shutting off the power to the pump. You check the air with an air pressure gauge that you check your car tires with. It has to be 1-2 psi less than the cut-in pressure setting. You can only check the air pressure when the tank is empty of water. You can shut off the water past the pressure tank before draining it so you don't drain the plumbing too.

Gary
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Last edited by Doug Aleshire; 03-11-05 at 05:38 PM.
 

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