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PurpHaze
04-22-2007, 12:46 PM
While doing repairs at a site last week I had to do some reasearch on a system because we have no asbuilts from the installing contractor. Discovered that the booster pump was installed without a "flow cutoff", "hi/low" switch (various names). This system is only about three years old, is on one of our new elementary school sites and there are two other sites with the same set-up... domestic water source boosted for the large field sprinkler zones.

When the field controller comes on it also activates the booster pump through the pump start relay. Problem is... if there is no water going through the system due to someone shutting down a zone valve, an isolation valve or the backflow device the booster pump will still run the entire duration of the zone/system program without water going through it. This can lead to the booster pump motor burning up, requiring expensive repairs and/or replacement.

Even though the systems were designed by an irrigation consultant it's possible that the consultant is not up to speed on booster pumps. The info was turned over to the head district electrician who is looking into installing switches on each pump. Good thing is... there are two new school sites in the final design stages where a change order was initiated to insure that their booster pumps are installed with the switches.

Wet_Boots
04-22-2007, 12:57 PM
The info was turned over to the head district electrician who is looking into installing switches on each pump. Good thing is... there are two new school sites in the final design stages where a change order was initiated to insure that their booster pumps are installed with the switches.You mean paddle switches? For indicating a no-flow condition?

PurpHaze
04-22-2007, 01:04 PM
Basically... there's different types.

Dirty Water
04-22-2007, 01:08 PM
My ideal booster pump set up would be a PSR with a flow switch connected to the 24v line to the PSR.

bdb
04-23-2007, 12:16 AM
http://www.munrocompanies.com/content/view/29/84/

They make the Smart Box which has a pressure sensor that shuts off at low pressure. Also have a thermal sensor to shut off if there is no flow when the pump cavitates and gets too hot. Those are economical. They also make VFD controllers.....that is my ideal booster pump but it costs a bit more. In the long run you should have less problems. Any three phase pumps you can put a VFD control panel on.

Valveman
04-23-2007, 01:09 PM
Purphaze, the picture of the booster pump shows that the eccentric fitting on the suction side is upside down. This can cause air to build up at the high point. When the air bubble is big enough, it will be sucked through and the pump will loose prime.

Also, we have a lot of school and other type irrigation systems with booster pumps that use Cycle Stop Valves for the control. The CSV with a small tank and pressure switch, works better than VFD controls, flow switches, and pump start relays. See this link.

www.cyclestopvalves.com/video/pbs_2006-dsl.wmv



Thanks

PurpHaze
04-23-2007, 11:32 PM
Purphaze, the picture of the booster pump shows that the eccentric fitting on the suction side is upside down. This can cause air to build up at the high point. When the air bubble is big enough, it will be sucked through and the pump will loose prime.

I'll leave this to the "skilled trades" guys in our district since I'm just a "sprinkler jockey." :)

www.cyclestopvalves.com/video/pbs_2006-dsl.wmv

Very interesting video. Thanks.

PurpHaze
04-23-2007, 11:32 PM
Purphaze, the picture of the booster pump shows that the eccentric fitting on the suction side is upside down. This can cause air to build up at the high point. When the air bubble is big enough, it will be sucked through and the pump will loose prime.

I'll leave this to the "skilled trades" guys in our district since I'm just a "sprinkler jockey." :)

www.cyclestopvalves.com/video/pbs_2006-dsl.wmv

Very interesting video. Thanks.

bicmudpuppy
04-23-2007, 11:39 PM
Purphaze, the picture of the booster pump shows that the eccentric fitting on the suction side is upside down. This can cause air to build up at the high point. When the air bubble is big enough, it will be sucked through and the pump will loose prime.

Also, we have a lot of school and other type irrigation systems with booster pumps that use Cycle Stop Valves for the control. The CSV with a small tank and pressure switch, works better than VFD controls, flow switches, and pump start relays. See this link.

www.cyclestopvalves.com/video/pbs_2006-dsl.wmv



Thanks


Lose prime? on a city water booster pump?

Dirty Water
04-23-2007, 11:57 PM
Lose prime? on a city water booster pump?

Perhaps there is a LOT of air in the water :laugh:

I can see what Valveman is saying if there was no positive pressure on the pump...kinda, and I'm still doubtfull that a pump that large would lose prime from a small bubble like that. But when you have positive pressure coming in, then I'd be impressed if they could get that pump to lose prime :)

PurpHaze
04-24-2007, 12:03 AM
LOL... Bet I could get it to lose prime. (There's RW isolation valves in the ground nearby.)

Dirty Water
04-24-2007, 12:07 AM
Cheater.

Real men just sawzaw through the suction line.

PurpHaze
04-24-2007, 12:14 AM
LOL... Real men know where the isolation valves are and don't spend all that time with a sawzall. :laugh:

Valveman
04-24-2007, 09:36 AM
Even when boosting city pressure, air can still accumulate in the high spot and get sucked into the pump, which will then lose prime. Doesn't happen as much with pump start relays, because the pump is usually pumping a large amount of water. Purphaze has already described what happens when this pump start relay, starts the pump and no sprinklers zones open up. However, the pump and seal would be destroyed, not the motor. Switching to a variable flow system as with the Cycle Stop Valve or the VFD, the trapped air is more likely to cause a prime problem when small flows are being used.

Pump start relays can also cause a lot of water hammer when the pump is started at full flow into a system with 0 pressure. Keeping the system pressurized and starting the pump against an almost closed valve, as with the CSV, will eliminate water hammer. Variable Speed Drives on the other hand, can also cause water hammer from reacting too slow to start up or changes in demand.

The variable flow control system using the CSV, will also allow you to match the irrigation system to the field, not the pump. Zones no longer have to exactly match the maximum output of the pump. With the CSV, zones can vary from as little as 5 GPM to as much as the pump will produce. The pressure will remain constant, regardless of the size of zone.

Wet_Boots
04-24-2007, 09:58 AM
Yeah, but how much of the pressure boost will disappear in the specialty valve? Sort of a spinning of the wheels here. The flow switch would seem to be more useful here.

Valveman
04-24-2007, 10:23 AM
There is only 7 PSI friction loss in this size Cycle Stop Valve. The only time you will even see this friction loss is when the pump is at maximum capacity. If you match the irrigation to the field and not the pump, you may never use the maximum flow from the pump. Flow switches are fine if you want to continue to have water hammer, broken lines, and one size zones that always match the maximum output of the pump. Flow switches, pump start relays, and huge pressure tanks were the old way of controlling pump systems. Many people have been using the VFD systems for 20 years or more. Now the CSV is replacing the VFD for those who keep up with the benefits of new technology. Staying up with what the USDA is doing will help you keep up with new and beneficial technology.
See this link;

www.cyclestopvalves.com/techq_16.html