Witch, t's basic math. If you have a 10 gallon void to fill and your filling it at 10 gallons per minute, how long do you think it will take to fill?
Sorry Sammy, I read that wrong. I thought it said a 1 minute rest between running. You are absolutely correct that a tank with a usable capacity of 10 gallons will give a 1 minute run for a 10 gpm pump.
The key (and what I got confused) is that it appears to be one minute RUN TIME, not one minute between runs. Sammy said from on to off, not from off to on. I the cooling would take place because of the water passing through the pump the motor. This assumes that the start causes excessive heat.
This is kind of non-intuitive for me. I would have thought that the heat that needed to be dispersed would be the accumulation from the run mode that had been trapped by losing the water flow at the end of the run cycle. Sammy's post implies the opposite.
It is, I believe generally accepted, that short cycling the pump is a bad thing. This is generally solved by a pressure tank big enough to insure that action. The cvs thing, if I understand correctly, runs the pump at full speed when there is demand, but throttles a pressure regulated flow to match the load. This means that (effectively) as long as water is being drawn, the pump runs all the time. That is why a small tank is OK. It is not as efficient a process as using traditional tanks and a free flowing pump but I believe it provides more constant pressure to the user.
i think you are confusing yourself. The motors starting mechanism needs a minimum of one minute of run time from start to stop to provide proper cooling. It doesn't take much demand for the pump to start at it's cut in pressure.
If the pressure in the system is just about at its low turn on pressure, someone gets a glass of water, the pump turns on, that person shuts off the faucet,the pump fills the tank. From there it needs a minimum of one minute of run time. If you still don't get the concept of that, i don't know what else or any other way of explaining it
Sammy... you had it right to start with, 60 seconds off between starts for proper cooling of the motor. That's for up to 1.5 hp motors.
The other guys are right about the pump with average sized tanks coming on in less than 60 seconds depending on demand.
Also, a 10 gpm pump will put out more than10 gpm in most wells unless the pump is set at the pumping level that only allows 10 gpm from the depth of the pump.
The CSV allows the pump to run from the time the switch closes until the water use stops, then the pump fills the tank. Pump motors are rated for continuous use and the number of starts determines how long the motor will last; the fewer starts the longer the life of the motor.
The OP stated the incoming pipe is in a laundry closet & that space is limited . That's why I suggested a small tank & a CSV . He seems leary of using a small tank . What do you guys think of a horizontal tank strapped to the ceiling if space allows ?
Last edited by WV Hillbilly; 01-14-2009 at 05:29 AM.
Hi Everyone. My computer has been down a few days. These are good questions about on and off times for the motor. The inrush current from starting a motor creates heat in the core of the motor. It takes about a minute of run time for this heat to transfer to the skin of the motor and be dissipated to the water. Then when the pump shuts off, the motor is still warm, and it takes about a minute for the motor to cool down where it is safe to restart. So a minute on and a minute off has always been the minimum rule of thumb. Two minutes on and two minutes off is just that much better for the motor.
With the old conventional pressure tank method, the pressure tank fills at the rate the pump can produce, less the amount of water being used at the time. So if you have a 10 GPM pump and a tank with 10 gallons of draw down, the tank will fill in 1 minute if no one is using water. If there is an 8 GPM hose running, then the tank will fill at 2 GPM and give 5 minutes of run time to fill the tank. Then because there is still an 8 GPM hose running, the tank will be empty in 1.25 minutes and the pump will be restarted. This is 5 on and 1.25 off or 230 cycles per day.
If you only have a 2 GPM hose running, the tank will fill at 8 GPM in 1.25 minutes, and be off for 5 minutes. That is 1.25 on and 5 off, which is still 230 cycles per day. Either way you are just barely getting the 1 minute on or the 1 minute off that the motor needs. Doubling the size of the tank to 20 gallons of draw down will also double the run and off times but, is still 115 cycles per day. The less cycling, the longer the pump will last.
With a CSV the process is a little different. As long as there is at least 1 GPM being used, the CSV will keep the pump running continuously. This means absolutely no cycling for systems that use more than 1 GPM for 24 hours a day, such as with heat pumps. When there is no water being used, the CSV then fills the pressure tank at 1 GPM, from the pressure setting of the CSV to the off setting of the pressure switch.
A 4.4 gallon size pressure tank only holds 1 gallon of water. Every time you use more than 1 gallon of water the pump must start. So the pump does not usually need to start while you are rinsing your toothbrush or the ice maker is filling. However, the pump will start when a toilet is flushed or the shower is running. With a 40/60 pressure switch and the CSV set at 50 PSI, that is only 30 seconds of run time to fill the tank. However, when you flush a toilet, it takes about 30 seconds for the toilet to refill, then the CSV refills the pressure tank for another 30 seconds, and this gives you the required 1 minute run time. When a shower is running, the pump will continue to run as long as the shower is on, then when the shower is turned off, the CSV will refill the pressure tank in another 30 seconds and shut off the pump. This will always be more than 1 minute of run time.
The off time required by the motor is also figured a little differently with the CSV. Since the CSV keeps the pump running as long as you are using at least 1 GPM, the pump only shuts off when you are no longer using water. Since you are no longer using any water, when the pump shuts off, it stays off until you start using water again. This gives you much longer than 1 minute of off time. The only way you could make the pump come back on in less than 1 minute, is to shut off all water use, sit and wait 30 seconds for the pump to go off, then quickly open a faucet that uses more than 2 GPM. This will still give you more than 30 seconds of off time. In reality, if you shut off all water use, then start using water again in less than 30 seconds, the pump has never shut off and does not cycle. If you shut off all water use, then restart using water 1 minute later, the motor has already had it's 1 minute to cool down. Only if you start using more than 2 GPM, between 30 and 60 seconds after the last water outlet was closed, can you make the pump stay off less than 1 minute. This may happen on a rare occasion but, it is not something that can be repeated, or can even happen often enough to cause any damage to the motor.
With the CSV and a tank that holds 1 gallon of water, the pump must start every time a toilet is flushed. As long as you flush again within 30 seconds of the toilet refilling, the pump does not cycle again even for multiple flushes. With the CSV and a tank that holds 1 gallon of water, the pump must start every time the shower is on. However, the pump will stay on for the entire time the shower is running, instead of cycling on and off 4 or 5 times during a shower, as with a standard tank system. With a CSV and a tank that holds 1 gallon of water, the pump must start every time the sprinklers or heat pump is running. However, the pump will stay on the entire time the sprinklers or heat pump is running, instead of cycling hundreds of times per day as it would with a standard pressure tank system.
The pump must start every time a toilet is first flushed. However, the CSV eliminates so many cycles during showers, heat pump or sprinkler zones, and other long term uses of water, that even though the pump cycles every time a toilet is flushed, it is still cycling hundreds of times per day less than a regular pressure tank system with a large tank.
A CSV with a 4.4 gallon size tank (1 gal draw down) will cause the pump to cycle about 40 times per day on the average house. Using the CSV with a 20 gallon tank (5 gallons of draw down) will cause the pump to cycle about 20 times per day on the average house. In most cases, this is not enough difference to justify the use of any larger than a 4.4 gallon tank. The way the CSV controls the pump system, there is really no justification in using a larger tank. Then if you consider the cost and space needed, there is even less justification for using a larger tank.
I hope this helps explain it better.
Guys, assuming a 10 gpm pump sized and set correctly, it will deliver more than 10 gpm at the pressure tank. That's unless the pump is pumping from the depth on the pump chart that corresponds to 10 gpm; right?
And running water out a 1/2" or 3/4" boiler drain valve on a 1" tank tee with 1" or 1.25" line from the pump, and getting 10 gpm is not going to give you the gpm the pump is actually delivering when water is being used in the building. That pump will be delivery more than 10 gpm.
Don't we all agree that the system has to at least meet and hopefully exceed the maximum peak demand gpm of the house? Today we have 2-3 showers going at once with the laundry washer and a toilet being flushed - you can't do that with only 10 gpm. Many of my water treatment customers have 3.5 to 5.5 bathrooms with 2 person showers with up to 6 body sprays and large tubs being used every night or 2-4 times a week, with other water use at the same time. You need one hellova large expensive and heavy tank to get the pump to cool for at least a minute between starts because they also have much larger pumps because they need much higher than 10 gpm.
So the only way to come close to the gpm the pump is delivering is to pull the pump a few feet out of the well and turn it on and measure the gpm at the average of the pressure switch settings (30/50 is 40 psi). The gpm figure will be slightly high due to the pressure loss between the well and the pressure tank.
A 10 GPM, 1 HP submersible will produce 12 GPM from a pumping level of 168' when the pump comes on a t 40 PSI. If the pumping level stays at 168', this pump will only produce 10 GPM as the pressure reaches 60 PSI before the pump shuts off. If the pumping level drops below 168', this pump will produce less than 10 GPM before the pump shuts off at 60 PSI. The lower the pressure required, and the higher the pumping level in the well, the more GPM the pump will produce. It is very important that the pump be able to produce the volume of water needed for peak demands. For the purposes of seeing how the pump functions with the pressure tank, it might be easier to just say the pump is producing an average of 11 GPM.
thanks for the info. I understand the cvs and small tank now. I guess with the pump starting less would us less evergy just running? From what I read the csv and small tank is the best system with less starts, also your saying the presure would be the same both way with pump giving the 10 gpm either set up. Maybe one of you guys could tell me the price of a csv and a 4.4 gallon tank?
Everyone had great input and advise but valveman explained the CSV in detail.
I suggest you eliminate the in ground tank and install the CSV Pside-Kick. Your family will enjoy the constant pressure.
However keep in mind that if the driller made a hole in the drop pipe (pipe in the well) it needs to be plugged for the Pside-kick to work properly. Perhaps you should clarify this with valveman!
Well yes you did Sammy, and I corrected the myth that a submersible pump will only deliver the gpm it is rated at and Valveman proved it. Along with nailing down that to correctly size a pressure tank, you have to use the length of time the pump is off between starts. Now all you need is to learn why you shouldn't use an arrestor... and that DIYers don't need an electrician to run their power cable for a submersible pump.
Yeah Gary, no one else seems to be backing you on this whole torque arrestor thing but maybe people should learn why you have been kicked off like 6 other forums in the past. I don't look for trouble but i do speak up when you give bogus advice. Like telling people to test their water from Lowes so you can make a quick sale or that whole smelling bacteria thing that you came up with that got you kicked off of water technology bulletin board. I think you need to get out of that mobile home that is probably in some McDonalds parking lot and get some fresh air. I have no idea how you run a business out of a mobile home but i don't do service calls in a Winnebago.
If i told someone to get an electrician to run a power line it was probably because the guy was a hack and was going to hurt himself.