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IRS
04-17-2007, 12:14 AM
I have taken over maintenance on a system that has a 5 H.P cent pump pulling out of
a lake, 2" discharge, 2" swing check valve, 60/40 pressure switch,galv pressure
tank 240' away 20' up the hill. Problem is this; when pump reaches cut off point
switch keeps going on & off like the tank is waterlogged or full of water but it's not, any ideas?

Midlo Snow Maker
04-17-2007, 12:22 AM
I have taken over maintenance on a system that has a 5 H.P cent pump pulling out of
a lake, 2" discharge, 2" swing check valve, 60/40 pressure switch,galv pressure
tank 240' away 20' up the hill. Problem is this; when pump reaches cut off point
switch keeps going on & off like the tank is waterlogged or full of water but it's not, any ideas?

you have got to spread the 60/ 40 out to like 80/40 or even 90/40

jerryrwm
04-17-2007, 05:44 AM
You might be better off in raising the setting to 70/50 or up. If you don't know what you are doing by changing the differential setting you can really mess things up.

bicmudpuppy
04-17-2007, 07:10 AM
if the switch is "bouncing", then it isn't set at 60/40, your just giving us the factory settings. If you don't know how to adjust it, I would take jerrys very good advice and leave it alone and call a pump guy.

speedbump
04-17-2007, 10:53 AM
I would take jerrys very good advice and leave it alone and call a pump guy.

The above would be a wise move.

First of all centrifugals don't work well with pressure switches. The other thing is, the pressure switch needs to be with the tank not the pump. While it's doing this, it's doing real damage to the motor.

bob...

bicmudpuppy
04-17-2007, 03:07 PM
The above would be a wise move.

First of all centrifugals don't work well with pressure switches. The other thing is, the pressure switch needs to be with the tank not the pump. While it's doing this, it's doing real damage to the motor.

bob...

I've run lots of pressure switches at the pump w/o problems. A pressure tank is just storage and location isn't that important. The garage or shed on the other side of the property works just fine. BUT, the switch has to be set properly and work properly, or your gonna be buying a brand spanking new pump.

Dirty Water
04-17-2007, 04:19 PM
The way I look at is that any line between the pressure tank and the pump is simply just adding capacity to the pressure tank.

How many GPM is this pump rated for, how many GPM of water is actually being used. This is the real question.

Bigred350
04-17-2007, 09:47 PM
Why dont you take the pressure switch and tank off. ANd install a pump start relay and let the timer turn the pump on. Thats how we do it on a centrifical pump.

Dirty Water
04-17-2007, 10:18 PM
Why dont you take the pressure switch and tank off. ANd install a pump start relay and let the timer turn the pump on. Thats how we do it on a centrifical pump.


Perhaps the mainline has quick connects or hydrants on it?

Midlo Snow Maker
04-17-2007, 11:17 PM
You might be better off in raising the setting to 70/50 or up. If you don't know what you are doing by changing the differential setting you can really mess things up.

same problem different setting you need a bigger spread.

IRS
04-17-2007, 11:51 PM
Talked with a well driller/pumpman today he said to try a small expanison tank
or a "snubber valve" I have ordered the snubber valve and will see what kind
or results I get. We just got 4" of rain so I'll have some time to get this fixed.
would rather remove tank and put in pump start relay but if snubber works
it will save customer $$$ Stay tuned for results

speedbump
04-18-2007, 09:42 AM
What the hell is a snubber?

Wet_Boots
04-18-2007, 09:49 AM
A snubber (http://www.differentialpressure.com/snubbers.html) dampens the response of a gauge or a pressure switch

speedbump
04-18-2007, 01:30 PM
I have put many of these little plastic devices on piston pumps many years ago, but never heard them called snubbers before.

I've run lots of pressure switches at the pump w/o problems. A pressure tank is just storage and location isn't that important.

Don't call this guy to work on your pump if you want it to last very long.

bob...

Dirty Water
04-18-2007, 03:59 PM
Don't call this guy to work on your pump if you want it to last very long.

bob...

Explain. A pressure tank's bladder system is designed to store pressure and reduce the need for pump to cycle on in the case of small demand (Take a house, when someone opens just one tap).

I do not disagree with Bryan at all. Location is not important at all, given the pipe running between the pump and pressure switch is of adequate size and you will get the same pressure readings at either end. Remember, the entire piping system itself becomes a pressure tank.

speedbump
04-18-2007, 04:19 PM
Pipe full of water is not a storage of pressure. It's just storage for water. Which means nothing really. When a pump starts or stops there is a water hammer that takes place that sends jolts down the pipes. These jolts can hammer a pressure switch to death unless there is something close by to absorb the hammer. This device is the tank. It can be galvanized or a bladder tank, but it has to have air to absorb the hammer. If not there is no pressure to store. Air compresses, water does not. Putting a tank more than 3 feet from the pressure switch will start to become a problem. Not all systems are exactly the same so this distance is not exact either, but to say you can put a tank on the other side of the property and adjust the switch on the pump is crazy.

I have taken over maintenance on a system that has a 5 H.P cent pump pulling out of
a lake, 2" discharge, 2" swing check valve, 60/40 pressure switch,galv pressure
tank 240' away 20' up the hill. Problem is this; when pump reaches cut off point
switch keeps going on & off like the tank is waterlogged or full of water but it's not, any ideas

This is what happens when you move the tank away from the switch. By the way, the swing check is another problem.

bob...

Wet_Boots
04-18-2007, 06:08 PM
Is the swing check on the suction or the discharge side of the pump? If it's on the discharge side, I'd install an expansion tank on the pump.

IRS
04-18-2007, 07:07 PM
The swing ckeck is on discharge side. I'am going with the snubber because it
will be more compact but may have to go with expansion tank if I don't get
results

bicmudpuppy
04-18-2007, 10:15 PM
Pipe full of water is not a storage of pressure. It's just storage for water. Which means nothing really. When a pump starts or stops there is a water hammer that takes place that sends jolts down the pipes. These jolts can hammer a pressure switch to death unless there is something close by to absorb the hammer. This device is the tank. It can be galvanized or a bladder tank, but it has to have air to absorb the hammer. If not there is no pressure to store. Air compresses, water does not. Putting a tank more than 3 feet from the pressure switch will start to become a problem. Not all systems are exactly the same so this distance is not exact either, but to say you can put a tank on the other side of the property and adjust the switch on the pump is crazy.



This is what happens when you move the tank away from the switch. By the way, the swing check is another problem.

bob...

If your getting significant water hammer from the pump cycling off, your pipe/pump isn't sized correctly in my poor humble opinion. Its called a pressure tank, not a surge tank. A surge tank is the same animal for different purpose. Yes, by and large pressure tanks are installed near the pump, but this is out of convienence not necessity. You are crediting a 5 hp pump with producing 20+psi of surge at startup? My 30hp pump doesn't create 20 psi of "surge" at startup. Granted, my switches have a lot more swing than 20psi, but even the guage on the filter doesn't jump more than 10 psi when the big pump starts.

Dirty Water
04-18-2007, 10:29 PM
SpeedBump: The concept that water does not compress is exactly why you can place a bladder tank anywhere.

And again, like Bryan, I've never witnessed a pump that is on properly sized pipe (Did you catch my mention of pipe sizing in my first post) to surge enough to kick off a pressure switch.

I still think that the issue is just a pisspoor match of pump output vrs water used and perhaps a very undersized pressure tank for a 5hp pump.

bicmudpuppy
04-18-2007, 10:59 PM
My money is on the switch. The spring that controls that 20psi spread is stuck or worn and isn't providing a 20psi spread. If you know how a pressure switch works, the adjustment takes a couple of minutes unless the switch has been adjusted before and just needs to be replaced. BTW, Jerry's fix of raising the cut off pressure works in a lot of situations for a number of great reasons.

PurpHaze
04-18-2007, 11:19 PM
I still think that the issue is just a pisspoor match of pump output vrs water used and perhaps a very undersized pressure tank for a 5hp pump.

We have one elementary school site that is experiencing "pump cycling" according to the electricians that are the ones that actually take care of our pumps. The head electrician was doing some work, turned on a test station and experienced the cycling which is bad for the pump and then makes an awful noise in the kindergarten classroom adjacent to the pump/well.

He sent us an email that we needed to coordinate our four controllers on site so that the pump continously runs when water is called for by the irrigation system. Fact is that the 4" main line is not big enough to sustain all four controllers being on at the same time because the zone draws would exceed the 5 ft/sec capacity. His pump would stay on all the time but none of the zones would work properly.

When this school was automated in 2002 I strongly suggested that the well/pump be brought up to newer standards and that any system put in would be subject to problems due to an unsatisfactory water supply. I was immediately ignored and the system put in anyway.

My answer to my boss: (1) have Maintenance permanently fix the well/pump problems that have been persistent over the past 20+ years; (2) install a central control system that will insure that enough valves (= GPM) are opened on the four controllers to keep the pump running at whatever specs the electricians want but within our specs for the 4" main line. (I further told him that there was no way humanly possible for me to program four separate controllers precisely to alleviate the problem on our end); (3) get rid of the well/pump supply and hook into Cal Water with a 6" main line routed to a point I choose where the subsequent teeing off to the existing 4" main line would then be able to handle all watering in our narrow watering windows.

His response?: <gulp>

Dirty Water
04-18-2007, 11:44 PM
Do you have any QC's on this line? Perhaps this one is an ideal candidate to ditch the pressure switch and go with a relay.

PurpHaze
04-19-2007, 12:03 AM
Do you have any QC's on this line?

Yes... they need constant water/pressure.

Perhaps this one is an ideal candidate to ditch the pressure switch and go with a relay.

I'll let the "skilled trades" guys try and figure it out. They get paid the big bucks. I'm just a "sprinkler installer" according to the district. :)

speedbump
04-19-2007, 10:23 AM
SpeedBump: The concept that water does not compress is exactly why you can place a bladder tank anywhere.


Not to be a smart ***, but I've only been doing pumps and wells for 40 years or so. I'm not a sprinkler guy, I'm a pump guy. So you guys go on believing what ever makes you feel good. Or come to Terry loves forum and try your theory on some of the other pump guys.

bob...

Wet_Boots
04-19-2007, 10:56 AM
If you start working on 'concepts', then you can get into resonances in the piping, and other esoteric stuff. This install turns out to have a check valve interfering with 'communications' between pressure tank and pressure switch. Not sure why the check isn't located on the suction side of the pump. Strictly for the minimal-labor aspect, I'd be recommending a small pressure tank be added to the pump. Pull the priming plug and thread in a tee, and take it from there.

To be fair to the sprinkler guys, they do get some views of pump operation not immediately visible to the wells and pumps trades. (they can open a zone and see the total output of a pump, and can observe a change over time)

speedbump
04-19-2007, 11:32 AM
I agree Boots, but I would go a step further and replace that swing check with spring loaded check valve on the suction side, preferably at the end of the suction line. Talk about water hammer. A swing check will certainly cause that.

bob...

Wet_Boots
04-19-2007, 12:09 PM
I'm more inclined to go with a (spring-loaded) check at the pump, as a concession to the freezing temperatures in winter. Makes it easier to pull the inlet strainer and pipe, if the water drains from it. One could even go so far as to leave some strainers (on flexible suction hose) in place, and loosen the connection at the check valve, to let the water fall to lake level.

speedbump
04-19-2007, 12:40 PM
Sorry, being in Florida, I don't consider the freezing issue any more. The reason for the valve at the end of the suction line is to prevent loss of prime and nucleur meltdowns of the pump. And if it's possible to do, it makes for a whole lot less maintenance.

bob...

Wet_Boots
04-19-2007, 12:59 PM
There might be a limit to what height of suction lift can get by with no foot valve. I had someone inquire whether the water in an old dug well (complete with wishing well cover) could feed sprinklers, and without a foot valve on the suction hose, the (probably undersized) gasoline engine sounded like it was ready to throw a rod, when the lift was around twenty feet. The pump had a built-in suction check and had never made rude noises prior to this event. Adding a foot valve made for a happier engine.

IRS
04-22-2007, 10:04 AM
Installed the "snubber" on Sat it worked like magic pump went from bouncing
so much that it kicked the breaker,to just a simple stop like any pressure
switch on a regular well system. Cost of snubber $56.00 Customer (lawyer)was impressed when I told him of all the coments on this board and how I came up
with solution. Hope he is still happy when he gets the bill. Thanks for all you guy in put. Wise King Soloman said ' there is wisdom in the multitude of counselors.

PurpHaze
04-22-2007, 03:26 PM
Wise King Soloman said ' there is wisdom in the multitude of counselors.

Old axiom: "There's more than one way to skin a cat." :laugh:

IRS
04-29-2007, 10:18 PM
Snubber Valve info Ray Pressure Snubber Model 010B
Operating and Maintenance Spec Inc
Monroe N.C 1-888-SNUBBER

speedbump
04-30-2007, 09:24 AM
Have you given any thought to what will happen when this snubber plugs up with mineral?

bob...