Made a sewage pump controller to alternate two ejection pumps

Pictures here:
http://www.machinerymoverschicago.com/blog/Sewage-Pump-Controller/
What this does is makes sure that only one pump runs at a given
time. Running them together may blow a breaker, that is located in a building that I do not own.
i
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On Wed, 04 Jun 2014 10:13:59 -0500, Ignoramus13687

Looks like you found a good solution to a shitty deal (pun intended)

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It was very shitty and extremely frustrating.
i
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message

What does it do if a pump fails or the breaker trips anyway? jsw
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If the breaker trips, everything stops. If a pump fails, depends on what pump fails. If The forward pump fails, the rear will run constantly. (as it would without this controller).
If the rear fails, the forward pump will work fine, but the system would not be useful.
i
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message

I asked after trying to think of a cheap, simple and reliable way to indicate malfunctions using the float switches and motor current sensors. One would be to detect either float switch being closed for longer than perhaps 10 minutes, with a time delay relay powered from your breaker instead of the pumps'. jsw
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This controller is located inside a sewage manhole away from everything, it is hard to make it signal anything.
i
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Ignoramus13687 wrote:

There are plenty of cheap wireless link modules available, even WiFi.
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if you ever find a good one, let me know. I gave up on a low temp alarm for the greenhouse.
Karl
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200+ feet away, from an unerground manhole... I am doubtful
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message

Please take this discussion as an interesting design exercise rather than a suggestion to rip out and redo what you have. It sounds like your consequences of failure aren't as bad as an overflow in someone's home.
I incorporated a 4-channel priority encoder into a dynamic RAM memory controller custom IC. It was more difficult to understand and fully specify the operation than to design the logic circuit to implement it. My boss forgot to ask for a buffer enable signal from the channel that had been granted priority so after all that work we couldn't use it. At least I could add ASIC design to my resume. -jsw
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Right.
What happens when the pumps fail, usually, is bad, but not catastrophic. Sewage somewhat rises in the system an I can see it rise in one of the floor drains, but it does not overflow into my building. Toilets become harder to flush. No sewage flood occurs, however.

This was nice.
i
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message wrote:

From your description I could assume that the first, upstream pump runs independently and the second can start only if the first is off. Will the second pump shut off when the first one starts?
As an old ladder-logic designer I'm trying to see how few relays I could do this with. One mechanical relay controlled by the first pump's float switch would run the first pump through its NO contacts when energized and send power to the second pump through the NC contacts when off, but that doesn't work with SSRs and may not last long in 100% humidity plus ammonia from urine and cleaning compounds.
Of course a surplus dealer or hobbyist might modify the circuit to use whatever they already have instead of buying new parts for the most logically elegant solution. -jsw
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It is the opposite. The downstream pump runs independently.
The upstream pump is allowed to run, only when the downstream pump is not running.

The pumps have their own float switches, as always.
The controller is in the upstream well, where electric power comes in.
The main part of the controller is a current sensor relay. This is what detects that the downstream pump is running. The current sensor relay switches a solid state repay, which in turns turns on the power relay that enables the upstream pump.
i
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message wrote:

OK. I don't know (or care) the relative storage capacities of the wells and pipes and had to make an assumption. This problem of dividing a limited resource like the AC power between competing demands can become very complex and subjective, a task for Generals. I guessed that you would want the well furthest from your property to overflow first. jsw
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These demands are not competing, but complementing. Both of these pumps work together to remove sewage from my building.
i
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message wrote:

They cooperate as long as it's convenient, while the flow is less than 50% of their pumping rates. If flow + groundwater infiltration (etc) raises the duty cycle of the distant pump above that you back up.
I don't mean to pick on you so here are different examples of the 'general' problem: http://www.qmfound.com/pol.htm Patton needed to be supplied with 350,000 gallons of gas per day. As his supply line lengthened the trucks carrying it came to consume 300,000 gallons themselves per day. Once they left the supply depot the gasoline they carried became the limited resource to be shared between themselves and Patton.
Tanker trucks can deliver only the excess above what they need to drive out and back. Rommel found the practical limit to be around 700 miles from base.
An extreme case, like a multi-stage rocket: http://en.wikipedia.org/wiki/Operation_Black_Buck
It's rumored that SAC bombers headed for the USSR needed to take -all- the fuel from their tankers, which would then go down in the Arctic Ocean.
-jsw
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That is impossible for a mostly sewage system..
I liked the SAC discussion.
i
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I hasten to add, that the controller runs them according to a certain logic, made to ensure optimum pumping. Described on the above webpage.
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On 6/4/2014 11:13 AM, Ignoramus13687 wrote:

The simplest approach is to use a current relay picked by the downstream pump running to prevent the upstream pump running (priority to downstream pump). I.e., the upstream pump can only run if the downstream pump is not running. The downstream pump can run whenever it needs to.
Your description of a relay for each pump implies that the downstream pump cannot start if the upstream one is running. What made you decide to do it like that?
Bob
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