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  #1  
Old 10-27-2007
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Greywater Blues

I've got a grey water pump out problem and it all seems to boil down to this circuit board. I need to draw up a schematic for it but I'm hoping until then someone can help me out with a few questions.

In my grey water tank I've got 2 float switches, an upper and a lower.
The lower level float switch is usually in the up position until the upper float switch is triggered. The pump then runs until the lower float switch is open. Usually about 3 minutes.
What is telling this pump to run for 3 minutes once the upper float switch is open?


I'll walk you around the board.

1. 24vac incoming on the 2 yellow leads.
2. Rectified... to 32vdc. upper right hand corner.
3. Green/Black wires go to lower float switch.
4. White/Black wires go to upper float switch.
5. Power out to a 24vdc/120/vac relay to trigger pump.


I've replaced the float switches, rectifier, the 2200uF 50V Cap and the diodes with no change.
I've jumped from the red on the relay to bypass the MOV and resistor that goes to Green wire (I have no power to the green) Doing this I do get the pump to turn on at the upper float switch trigger, but it only runs until it falls back down, maybe 20-30 seconds.
So maybe it's gotta be that MOV causing a problem? Among other things...

The biggest head scratcher for me is where is the timing coming from?

Thanks in advance for your help!
Oz
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In an industrial setting a cct like that will trigger on the upper switch and run until the lower switch takes it out (when that switch contact changes state) There's no "timing" per se, but it should pump until the level drops to and triggers the bottom switch.

This usually involves a relay(s) to latch the power so that the switch doesn't stop the instant the upper switch opens... which is what it sounds like your set up is now doing.

It sounds like the latch is not working..... A relay contact failed, perhaps?

Last edited by Faster; 10-27-2007 at 12:51 PM.
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Thanks Faster, that's what I initially thought as well, but checking on the specs of that relay made me look in other directions. That Zettler relay is supposed to have 10 million mechanical and 1 million electrical operations...

Incidentally the Red/Black wires and Hasco relay are part of a high-level alarm not used now.
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Old 10-27-2007
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Quote:
Originally Posted by oz_hole View Post


I've replaced the float switches, rectifier, the 2200uF 50V Cap and the diodes with no change.
I've jumped from the red on the relay to bypass the MOV and resistor that goes to Green wire (I have no power to the green) Doing this I do get the pump to turn on at the upper float switch trigger, but it only runs until it falls back down, maybe 20-30 seconds.
So maybe it's gotta be that MOV causing a problem? Among other things...
I don't see anything that looks like an MOV. I see diodes, capacitors, LEDs, relays, but nothing like an MOV. Are you sure there is an MOV? I can't imagine what it would be for.

Have you tested the contacts on the lower float switch? This is what would release the latching circuit on the relay, and if it is buggered, the latch will release immediately.

I was really impressed with the neat installation, not too crowded, wires neatly arranged, ..... until I saw the bottom of the circuit board. Egads!
I used to make stuff like that when I was in high school.

BTW what is a grey water holding tank for? Especially one with an automatic dumping circuit?
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I was told by the local electronic components store that the blue jobbies were the MOV's. There is absolutely nothing written on them.
The one inline from the switch to the green wire seems to be blocking the current, I can steal the other from the alarm side.
The floats were tested and the lower replaced.

Why would I get 32vdc after the rectifier?

Unfortunately I can't take the credit for the design (or the assembly!)
But this is my first step in troubleshooting a circuit board and seeing the price difference between repairing this at $40 compared to $1100 at Headhunter for a new tank monitoring setup...
The other alternative is to ditch everything and get a timer relay @ $100.

Grey water is the waste water from showers/sinks.
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Quote:
Originally Posted by oz_hole View Post

Why would I get 32vdc after the rectifier?


Grey water is the waste water from showers/sinks.

The 32V is not unusual. You are rectifying a 28VAC RMS sine wave [where does the AC come from on your boat?] whose peak value is 1.4x28V, and if the load on the other side of the rectifier is light, you could see up to the peak of the sine wave. That big capacitor charges up to the peak value if there is not sufficient load to bring it down within one cycle of the AC.

I know what grey water is, I just wanted to understand why you have a reservoir for it. I could only imagine that you are in an area where you are not allowed to discharge grey water. In that case, why the automatic purging system? Wouldn't that kick in while you are in a no dumping area?
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My apologies if I offended you, we've got a tank so as to cut down on the thru-hulls.
AC's coming from shorepower/genie/inverter.
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Quote:
Originally Posted by oz_hole View Post
I was told by the local electronic components store that the blue jobbies were the MOV's. ... the one inline from the switch to the green wire seems to be blocking the current....
As I understand them, a MOV (Metal oxide Varistor? IIRC) is an over-voltage protection device that will act as an open until a certain voltage is applied, after which it conducts and protects the rest of the cct. It is usually in parallel with the cct or device it is to protect.

I'd take another look at that control relay.. since you've replaced the float switches and nothing has changed, and its acting like the latching cct is not working for you, that points back to the relay itself (or the "latch" contact)
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I'm planning on trying that; the relay was, of course, the part not in-stock when I went to pick up the other pieces.
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Here's a simple 12 Vdc circuit that you could put in place of what you have that would do the same job. You need a straightforward 12 V relay and your two float switches. You could probably put it in the same enclosure. This may be similar to what you have... you can see that if the relay fails the pump will cycle with the high level switch.

Feel free to PM me if you have any questions.
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