Question about cycle sensor from CSV

[erkme73]

I just lost water pressure. Going to pressure tank/switch, I saw my cycle sensor pump monitor blinking rcyc...

I've had that happen once before, about a month ago, and found the air pressure in my tank had bled down to about half of what it should be. I recharged it (it's < 1 year old) and tightened the Schroeder valve.

Today, the pressure in the tank is still 41 PSI. I have the cut-on pressure set to 43. So that appears to be correct.

The rapid cycle timer is set to 30 seconds, and I watched it cycle a few times to make sure the problem didn't immediately repeat - it did not.

So, my question (to @valveman or anyone else) is, what else could cause that rcycl lockout to occur?

I just recently replaced the rusted steel barbed nipple between the pump's check valve and poly tubing, and all appears to be functioning as expected.

 

[Reach4]

I've had that happen once before, about a month ago, and found the air pressure in my tank had bled down to about half of what it should be. I recharged it (it's < 1 year old) and tightened the Schroeder valve.

One thing... put a tire valve cap on that valve. From what I read, the valves themselves can leak a bit-- at least more than a sealed tire valve cap.

So, my question (to @valveman or anyone else) is, what else could cause that rcycl lockout to occur?

One possibility is the low precharge made the diaphragm pretty much up against an internal dome in the WX tank. That kept the tank from accepting much water, and that would cause cycling.

 

[Sponsor]

 

[erkme73]

Yes, undoubtedly, that's what caused it the first time - but this time, the tank pressure is right where it should be. That's the head-scratching part. I can't reason out what else would cause short-cycling of the pump. Unless maybe the pressure switch has drifted?

ETA: I just timed the refill rate for the tank. From cut-on to cut-off take 48 seconds. Timer is set to 30 seconds. So, if I understand correctly how the sensor works, only if my pump was running for less than 30 seconds, would the rcyc lockout happen. Is the correct?

ETA2: After reviewing the general info on cycle stop website:

"Rapid cycling can be caused by water logged or improperly sized tanks, improper pressure switch settings, control malfunctions, broken check valves, and chattering contacts. "

So, assuming my tank is properly sized (20 gallon), tank is pressurized to 2 psig less than cut-on pressure, and the pressure switch isn't chattering (it is <1 year old), the only thing left is the check valve. And, even if that were to fail, given that there are no other CV's in my system, the tank would have to bleed down to 41 psig before the pump comes on - which would not shorten the tank refill time.

I'm stumped.

 

[Valveman]

I am afraid the tank maybe bad. The loss of air the first time could be because you need a better sealing cap. But most of the time it is because the diaphragm has sprung a leak. It can even be the same or higher pressure at the Schrader, but it could be from water pressure in the air chamber. I here people say the air chamber pressure increased on it own, which means there is water in the air chamber. Take the tank off and see how much it weighs or let all the air out and see if any water comes out. With the Schrader on the bottom water will come right out, but with the Schrader on top you have to let all the air out before you see water.

If the tank checks good just set the rapid cycle in the Cycle Sensor for 20 seconds instead of 30.

 

[erkme73]

Thanks Cary. So you're saying that if the system pressure is at zero - all water drained from the tank, spigots open, pump off - the pressure I'm seeing at the Schrader valve may still be partly due to water stuck above the diaphragm? I'm at zero water pressure, and 41 in at the Shrader, and assumed that was true air pressure.

It's a bear getting that tank off even when it is really empty. I'm incline to just lower the time to 20 seconds and see what happens. Worst case, if the diaphragm is leaking, at some point I'll have no air left, and very fast cycling, correct? So no harm in lowering the cycle time? Can you tell I'm lazy?

Edit: I will let all the air out with water pressure at normal levels (between 43 and 63) and see if I get water. If not, I can move on to just shortening the time...?

 

[Valveman]

Yes that could be water pressure you are seeing. It will drain quicker with water pressure pushing it out the Schrader while holding down the valve stem. But make sure the pump is off. Any lower than 20 seconds and you will need to replace the tank. Sorry.

 

[LLigetfa]

A drawdown test could be used to gauge the performance of the tank. If there is water on the air side of the diaphragm, the drawdown will be less.

 

[erkme73]

Well, I think I did something I shouldn't have... I drained all the air out of the tank, with the pump ON. I felt the diaphragm bottom out on the valve stem... zero water came out. No popping sound (whew!). Let all the water back out and filled it back to the 41 PSI. Pretty sure there is no water in the air space. I'm guessing I took some life off the diaphragm by stretching it to the max....

 

[Reach4]

Pretty sure there is no water in the air space. I'm guessing I took some life off the diaphragm by stretching it to the max....

Which pressure tank do you have?

 

[erkme73]

AO Smith from Lowes. https://www.lowes.com/pd/A-O-Smith-20-Gallon-Vertical-Pressure-Tank/1000565619

I'm sure it's bottom of the barrel in terms of what's out there, but I needed one quick and it worked...

 

[LLigetfa]

Pretty sure there is no water in the air space.

Some tanks have an internal dome that keeps the diaphragm from being over-stretched. There can still be water in the space between this internal dome and the top of the tank.

 

[erkme73]

Interesting. I wonder why all of a sudden the valve stem froze in place. It was like something was jamming up a against it from the inside. I could not get it to depress just as the water pressure spiked and cut-out.

Oh well - as long as I'm not overlooking any other possible scenarios which could cause long term problems or damage, I'm just going to drop the timer down to 25 seconds (split the difference). If it does it again, I'll bite the bullet and pull the tank for weight/inverted inspection.

 

[Reach4]

Interesting. I wonder why all of a sudden the valve stem froze in place. It was like something was jamming up a against it from the inside. I could not get it to depress just as the water pressure spiked and cut-out.

That internal dome is a premium feature that your tank may not have.

Your tank does have a butyl diaphram, which is also a premium feature. https://www.aosmithatlowes.com/prod...ee-standing-20-gallon-vertical-pressure-tank/

 

[LLigetfa]

Picture of the tank shows a seam where the internal dome is welded.

 

[Reach4]

Good point. I think that is made by Goulds. Goulds calls that feature an internal shell. https://www.phoenixpumps.com/goulds-water-technology-diaphragm-bladder-tanks_8_1171_1077.html

 

[Valveman]

I didn't know you had a big 20 gallon size tank. With a 43/63 pressure switch setting and the CSV holding 53 while running a shower, you should get over a minute of run time to fill that size tank. I would do the draw down test as described and see if you get close to 5 gallons out of that tank as the pressure drops from 63 to 43? If so, the setting of the CSV maybe too high for that size tank.

 

[erkme73]

Just to wrap up this thread... After Cary's latest post, I decided to call him directly since I am too green to understand exactly what he meant. After some discussion, I think we've concluded that the pump fill time is where it should be (50 seconds) and thus it is likely not the cause for the rapid cycle.

We were unable to come up with any verifiable reason for the pump to run shorter than 50 seconds. Failed check valves, leaks, etc, all would have an effect on how long the pump would stay off, but not shorten the tank refill time.

If the pump is shutting off due to thermal overload within 30 seconds, the sensor will see that and lock out on rapid cycle. And, with the pressure tank in line, such a shut down would not produce any symptoms on the supply side.

Since I had just pulled the pump last week due to the leaking steel nipple, I noticed that the power cables were badly chaffed - to the extent that the copper conductor on the hot legs were bare/visible/corroded (green). So, the theory is, assuming the pump itself is mechanically and electrically sound, it is possible that some of the current is escaping to ground through the bare wire - thereby dropping the voltage to the pump (and reciprocally increasing the current at the motor). This could cause the pump to run hot, and trip out the thermal.

For now, I've left the cycle timer at 30 seconds. I'll source some of the THHN abrasion-resistant wire. If the problem happens again, I'll schedule friends/neighbors to help me pull the pump and replace the wire.

Anyone have any recommendations for suppliers? I'd need 250'...

 

[Reach4]

We were unable to come up with any verifiable reason for the pump to run shorter than 50 seconds. Failed check valves, leaks, etc, all would have an effect on how long the pump would stay off, but not shorten the tank refill time.

How about a photo that includes the pressure switch, pressure gauge, and the input to the pressure tank.

 

[erkme73]

Sure...

 

[Reach4]

Looks good, although you could replace the pressure switch in case that is doing something unexpected. Turning down the cycle timer makes sense.