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Old 06-07-2014, 14:48   #1
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Pump Sensor Adjustment

I've been having trouble with my freshwater pump, namely it never fully shuts down and cycles on and off intermittently even with everything closed. This is a Jabsco Sensor Max 17, one of their variable speed pumps. Just running through everything it could be at the pump, the suggestion elsewhere is that its probably the sensor itself. I've pulled it apart and found no problem, but there is a screw at the top of the sensor assembly that changes the amount of pressure on the spring in the assembly. The manual is silent on adjustment, wondering if anyone here can say how its done? Tightening would make the pump shut off at lower pressure or higher?
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Old 06-07-2014, 15:12   #2
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Re: Pump Sensor Adjustment

Sorry, no idea on which way to make the adjustment, but I would think that the problem will remain, but with the system at a different pressure.
The pump is obsolete, but the service kits are still available and at a reasonable price (about $40 in the UK), so that might be worth a try.
Another point to consider is that if the FW system contains a hot water tank, then the problem could lie there, or with the expansion tank, and fittings (see http://www.jabscoshop.com/files/USIN...X%20doc550.pdf)

I take that you have checked all hoses and fittings and there are no leaks in the system.
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Old 07-07-2014, 07:25   #3
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Re: Pump Sensor Adjustment

Pump fails to turn off after all fixtures are closed:

• Empty water supply tank
Refill

• Air trapped in pump
Open faucet closest to pump

• Debris in pump
Remove upper housing and inspect

• Defective check valve assembly
Replace check valve assembly

• No battery in circuit
Install battery

• Punctured diaphragm (pump leaks)
Replace lower housing assembly

• Discharge line leak
Inspect plumbing and fixtures for leak

See ➥ http://www.pumpagents.com/pdf/Jabsco...31750-0000.pdf
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Old 07-07-2014, 08:29   #4
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Re: Pump Sensor Adjustment

In a situation like yours my first thought is that the valves in the pump are allowing water to leak back through the pump into the tank. No visible leaks yet the pressure in the line drops and the pump cycles on and off. The solution is to clean or replace the valves.
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Old 07-07-2014, 08:41   #5
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Re: Pump Sensor Adjustment

Same problem here with a new pump. I tracked it down to the system pressurising and then loosing back pressure through the pump. Fitting an accumulater tank reduces the cycle times, or swap it out with a surflo pump.

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Old 07-07-2014, 14:20   #6
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Re: Pump Sensor Adjustment

Simon, with a variable speed pump like the op has, you shouldn't use an accumulator tank. It confuses their little brain.
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Old 07-07-2014, 15:27   #7
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I'm fairly certain there's no leak. I can't hear one and an inspection at each of the junctions while the pump is on with the faucets all closed shows no moisture at any of them. I'm less certain about the tank side as, correct me if I'm wrong, there could still be a leak without the presence of dripping water. But that's something I'll have to wait to check after I run the tank dry again. I went back and tightened the clamps once more just to be sure, but the problem still exists.

Nigel's post was pretty illuminating. There's no expansion tank or non-return valve before my seaward heater. Just to check I took the heater out of the loop altogether, but that actually made the problem worse, causing the pump to just run continuously rather than intermittently with the faucets closed. The only thing is, the way the material reads the expansion tank and valve are only there to prevent the expansion valve on the tank from weeping when the water is hot, which it isn't at the moment. So I'm not sure if that's a likely problem or not.

I've actually ordered an instant on heater which I was planning to replace the seaward with. After my little test today it looks like that may be a problem as to some degree the seaward seems to be acting like an expansion tank itself. I'm not sure if Simon may actually be correct that I should put an accumulator in the mix, as outlined in the material above, to serve as an expansion tank.

I should also add that I'd disassembled this prior to posting and there aren't any problems with the internal components.
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Old 07-07-2014, 16:36   #8
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Re: Pump Sensor Adjustment

I take it back, there is a no return before the hw heater. Its this model: http://www.amazon.com/gp/aw/d/B000XB...ref=mp_s_a_1_3

One other thing I've noticed is some of the line expands under pressure. Is this preventing the pump from reaching the cutoff pressure?
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Old 07-07-2014, 20:46   #9
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Re: Pump Sensor Adjustment

The hoses after the pump could be expanding and thus act like an expansion tank. As someone else pointed out any expansion after the pump confuses the variable speed circuit.

Adjusting the pressure regulator screw might help. Turning the screw clockwise on most pumps increases the cutoff pressure. So I would start by turning it anti-clockwise a bit and see if that helps.
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Old 08-07-2014, 02:24   #10
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Re: Pump Sensor Adjustment

If you read the small print in the instructions you will see a piece about maximum hose run length. Once you exceed this the pump has problems. I had added 3.5 meters about 11 feet of hose for the cockpit shower and this is where my issue started. I blocked off the hose at the joint and presto no more cycling. So now I'm thinking copper lines where possible to eliminate the expansion under pressure.

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Old 08-07-2014, 06:47   #11
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Re: Pump Sensor Adjustment

Well I think its really just time to get a sureflo to replace this thing. Trying to figure this out I've read nothing but bad things about these pumps, and despite all the good advice I've gotten here I'm just left with more questions.
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