Pressure drop at pressure switch cut-in; switch does not engage

[RobertV]

Hi folks,

Thanks in advance for your help. I've used the forum before and gotten good advice.

I put together a new system to my cabin recently. Here are the details...

Well is 242' deep.
1hp Tuhorse pump with control box; 10 gpm
Check valves set at 25' above pump, 150' above pump and one at the pressure tank
32 gallon pressure tank, with 28lbs pressure (I set this)
30/50 switch that cuts in at 28 and out at about 49lbs

All parts are brand new.

Problem:
When I fired up the system, it pressurized to 50lbs and shut off normally.
I checked the system by hooking up a hose to the drain at the T and allowed it to drain the tank.
When the pressure gets down to 28lbs, the pressure switch kicks in for a fraction of a second (the contacts briefly touch with an arc flash and then the contacts go back to their resting position)...when this happens, the pressure on the gauge goes to zero.
The pressure switch has the manual start toggle lever on the side, so I can then engage the swich by hand. When I do so, the pump starts up and pressurizes the tank to 50 lbs no problem and then the switch cuts out as expected.
Draining the system again produces the same result. At 28lbs where you'd expect the switch to engage and start the pump, the switch makes contact briefly and stops and the pressure on the gauge goes to zero.

Any ideas? Thanks again in advance.

 

[Valveman]

You have too many check valves. You need a good check valve right on the pump. Any other check valves in the system can cause water hammer on pump start, which will bounce your pressure switch. Also if the pump starts at 28, make sure there is 26 or less air in the tank.

A 32 gallon size tank only holds 8 gallons of water. That tank is not big enough for a 10 GPM pump. However, with a Cycle Stop Valve to control the pump that tank is plenty large as a 4.5 gallon size tank would have been sufficient.

 

[Sponsor]

 

[Reach4]

A couple additional points. You could try setting your precharge to 27 or 26. Your air gauge and water pressure gauge may be a little different.

The extra topside check valve could contribute to the delayed water, but do dry reducing the air precharge a tad.

 

[RobertV]

Okeydoke, thanks much. I put the check valves in the vertical section of pipe because local well guy here in NH told me it's a good idea to have one every 100' you come up the well.

So you're saying that if I pull the pump and remove those check valves in the vertical pipe (leaving only the check valve at the presure tank), that should fix the problem?

I'll also adjust the pressure tank to 26-27lbs when I am out there this weekend.

 

[Craigpump]

There is NO logical reason to have multiple check valves in the drop pipe. We always install our systems with one at the tank and the one in the pump.

 

[Valveman]

The only check valve you need is the one on the pump at the bottom of the well. Any extra check valves can cause water hammer and the switch to bounce. A check valve at the tank won't cause a problem right away, but eventually it will. I probably have to tell 5 people a day to remove the above ground check valve to stop the water hammer on pump start. A check valve above ground is also illegal in many states like Michigan because it creates a negative pressure in the underground line which can draw in contamination.

 

[LLigetfa]

I agree with Cary, that there should only be one checkvalve (at the pump) but the jury is still out whether that is the cause for the switch to open. What I believe is happening is that you have too much air precharge so the tank is completely empty when the pump comes on and not having any reserve in the tank, it continues to fall below the low pressure cutoff. I don't think water hammer is bouncing the switch but I would need to be there to know for sure.

It is possible that the extra checkvales are also contributing. Checkvalves hold best when they have pressure against them. The topside checkvalve prevents the others from having pressure hold them tight and they will leak down. That causes the water column to fall creating a vacuum in the line. When the pump starts, there can be a delay while it refills that vacuum. As that vacuum is being filled, the column of water will be racing at full speed toward the last holding checkvalve which causes the water hammer that Cary mentioned.

The reason that the extra checkvalve is illegal is that the vacuum it creates can suck in contaminated surface ground water if a leak forms.

Rather than letting air out of the tank, I would readjust the switch to kick in and out at a higher pressure.

 

[RobertV]

Thanks for all the responses gents.

I'll post an update here for anyone still monitoring this thread. Sorry...I had to get up to the cabin and pull the pump, do the repairs and then re-drop it...took a bit of time.

I did the things suggested above in this thread. Removed the check valves except for the one at the pump and the one at the pressure tank. While I had the pump out I double checked the wiring...seems solid, secure and watertight.

I reset the pump, then fired up the system. It worked as expected. Releasing water from system has the pressure drop to about 28lbs, then the pressure switch connects and begins filling the tank immediately. And shuts off at just under 50lbs.

NEW PROBLEM: the trip switch on the pump control box keeps kicking while filling the tank. For example, pressure drops to 28lbs, the switch engages and begins filling the tank, when the tank gets in the 40-45lb range the trip switch kicks out and stops the system. After a minute or so I will hear a click in the control box and I'll push the trip back in resetting it and the tank will fill the remainder of the way.

This happens every time. My understanding is that the trip is a failsafe to keep the pump from overheating. But not sure the pump can possibly be overheating in 30-40 seconds that it takes to fill the pressure tank to 40 lbs or so, especially given that the water down there is so cold and the pump is brand new.

Another thread in this forum suggested making sure that the voltage was correct to the control box. It calls for 230v...I used my multimeter to check it and it is a little above 230v, so no problems there.

I can call Tuhorse and wait to talk to one of their tech folks but thought I'd try this forum first.

Any suggestions?

 

[Valveman]

Overload is tripping either because the motor is drawing high amps, or the overeload could just be bad or weak. You will need a clip around amp meter to see if the motor is pulling more than the 9 amps a 1HP is suppose to draw.