Pumps and thermal cut outs

[jpadie]

Hi

i have a well pump about 23m down a well. It's under a quarter ton manhole cover ...

at certain times of year the pump cuts out, needing a manual reset. the reset is on the low pressure head at the top of the well - but under the manhole cover.

there is no scope (budget wise) for reboring the well to a greater depth. and no room to drop the pump further into the well.

My question is whether anyone knows how the thermal cut outs work and what would be needed to be build a remote reset device (I am ok with electronics). I've tried turning on/off the power supply to the pump but that does not reset the thermal cut out. There is frequently no one around able to get the man-hole cover off; and even if there is, that person has to lean quite a distance into the well to turn press the reset button (quite a lot of force is required on the button for the reset).

The pump controller is this one if it helps;

http://aquajulien.com/PressControl-...he-automatique-manque-d-eau-pompe-12899.html.

But I have tried a number of alternatives too.

thanks in advance for advice and suggestions
Justin

 

[Artisi]

Are you saying the pump controller is under a quarter ton manhole cover?
Think about what is triggering the shut down at certain times of the year, is it low water level in the well during the dry period?
There is probably a good reason for the shut-down, making it auto-reset could lead to a problem.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[jpadie]

yes - it is low water. the water table drops radically when the farmers over water during july and august.
i'm happy for the pump to cut out. but i want to be able to reset it sensibly, without taking the man-hole cover off each time. and yes, the reset button on the pump controller (essentially just a low-pressure valve) is under the manhole cover. it is feasible in the future that I can move this to a more accessible location but for that I'd need a mini digger. at the moment I'm looking for an electronic solution for a remote reset (which would be needed wherever the thing is).

even at the worst times, the well refills enough to give a few minutes of irrigation water every hour. so the plan would be to reset remotely then fire irrigation. if the pump re-tripped then so be it. at the moment i have to employ someone to come check the system every day that I'm not there.

 

[Artisi]

During the dry period, reduce the pump output by throttling a discharge valve until you achieve a steady flow that doesn't overpump the inflow.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[jpadie]

Thanks.

And whilst I appreciate the practicality of your post (and i already do something similar) it is not an answer to my question. Which relates to remote resets of thermal cut outs.

 

[LittleInch]

It's not clear what that unit is actually doing or what a"failure" is. A thermal cutout is usually on the motor itself and often just a simple bimetallic strip which resets once the motor has cooled down. Without the circuit diagram you can't possibly see if there is a route to somehow bypass this relay which is latching out some other relay inside the unit.

Unless there is an RTD or some other temperature sensor wire from the motor to this unit it isn't a thermal lockout.

I can only suggest you buy this unit which comes ready made with a remote reset connection or get the circuit diagram.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[jpadie]

thanks. that would be my response to a typical electronics question too. However these well pump tops are so common that I felt sure that someone in this forum would know about them. They are sold everywhere in France so I assume that is the case elsewhere.

good point on the thermal cut out being 'difficult' without a sensor! there is none - just three wires (including the earth). So it must be using a current sensor and detecting under-load, I guess.

It is possible that this is a latching relay (whatever the triggering sensor), I hadn't considered such an over-engineered solution. That would be easy to circumvent however; so let's hope it is the case.

 

[rotw]

think the cooling of the pump's motor is function of the annular section that is between the pump diameter and the borehole diameter. When the borehole diameter is bigger than the recommendation, the flow velocity reduces (mass flow conservation) and the cooling of the motor reduces which could explain the thermal cut-off.

 

[Artisi]

jpadie, fully understand your question, however just thinking a bit further ahead, why does it trip and what is the effect on continually resting - burnt-out motor?
Not sure if undercurrent is the trigger, more likely flow sensing, hence my suggestion to increase head and reduce flow.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[jpadie]

Artisi
it doesn't matter what mechanism causes the trip, sod's law dictates that it will need resetting from time to time and almost certainly when I am not around to do it. So there is still a paramount need for a remote reset.

@rotw
The diameter of the borehole is 100cm. I don't recall anything in the datasheet for the pump that specified a maximum diameter.

 

[LittleInch]

However you have a device on your system that you don't know what it does or what cause it to trip or how it resets. Is it a switch or a physical reset?

These things look so cheap I can't imagine they are anything special.

This actually has a manual in English

http://www.allpumpsdirect.co.uk/watertech-presscontrol-electronic-pressure-switch-230v

Shows its a mixture of low pressure and low flow protection but unless you break into the control board no mention of a remote electrical reset.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

LI, they look cheap but many many used thru-out-the-world by various pump companies and supplied by various manufacturers, they are very reliable, simple, effective and serve the purpose well in domestic situations. I think the no-flow isolation is simply an electronic switch that needs a physical(finger)re-set, although some units have auto-reset that can be time controlled.
Unable to open the link posted but Brio 2000 and Grundfos are 2 links you can view.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[jpadie]

@LittleInch

they are nothing special, no. I am on my fourth in fifteen years (they don't survive the winter very well). essentially they are low pressure switches. you turn a tap on, the machine senses a pressure drop and kick starts the well pump motor.

I know that
[ul]
[li]I have the box on top of the well piping[/li]
[li]the box has some form of pump-protection system in it[/li]
[li]the pump-protection system triggers when there is not enough water[/li]
[li]there are no float switches[/li]
[li]there are no temperature sensors[/li]
[li]the box is under 250kg of man hole cover[/li]
[li]it doesn't have a remote reset[/li]
[li]to reset you have to make contact with a membrane button on the device with positive force (i.e. it depresses).[/li]
[/ul]
What I am asking is whether anyone is familiar with this class of device (and its pump protection system) and can suggest a strategy for remote reset. I'm assuming by the responses that there is no familiarity. In which case there is little to do save butcher the controller to see what is what.

 

[LittleInch]

Attached is the actual manual of the device you seem to have.

Just to be clear here - what you have is a device which measures flow and pressure and switches off under certain conditions which indicate no flow. It is not a motor or pump protection system per se, but one which acts like one.

Note page 6 where it states that the device works by means of a microswitch (opened and closed by relays)

So if you can get to the microswitch which is under the reset button then you're away by wiring a switch in parallel.

Or type in "well pump pressure switch and flow switch remote reset" and other similarly priced options appear which offer either remote or auto reset.

A lot cheaper than taking one apart I think.

LI



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[jpadie]

yes - possible that I could sense whether there is a connection to the relay and then implement my own relay providing power to the pump. But that bypasses the cut-out device, rather than allows a reset. Big difference.

the well will partially refill continuously. so if I fire the pump every couple of hours, I will get some water from time to time, without burning out the pump.

I really am looking for a solution for a remote reset. If I get any insight from butchering the controller then I will post back.

 

[LittleInch]

I meant parralel the reset switch.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

Change controller to one that has timed auto reset.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[georgeverghese]

Try re posting this problem in the measurement and controls instrumentation forum..

 

[Valvecrazy]

Those devices are found all over France and many pump companies offer them because they ensure planned obsolescence (short life)for the pump. When offered a device that will really protect the pump and make it last longer, pump manufacturers want nothing to do with it. If it is in fact an overload condition, continually resetting the overload means you will be replacing the pump very soon. Those devices, under the names Presscontrol, Masscontrol, Burcam and many others will keep the pump running as long as .6 lpm is being used or leaking. .6 lpm is not enough to keep a submersible motor cool. These devices will also cycle the pump rapidly if less than .6 lpm is leaking or being used. Either of these conditions will trip the overload. It is a good thing it is not an overload with an automatic reset, or the pump/motor would be toast before you knew there was a problem.

A good pump protector will shut the pump off on low amps (dry run) or rapid cycle long before an overload condition appears. Most dry well protection devices look for low amps to shut the pump off. Most have a timed reset that can be adjusted to restart the pump automatically in a set amount of time, so the well has time to recover, and you don't have to manually punch a reset button. These type devices are not attached to the plumbing and do not need to be installed in an upright position under the well cover.

There are much better ways to protect a pump and eliminate cycling, but you won't find any pump company promoting these devices, as their goal is to sell replacement pumps as often as possible.

 

[Artisi]

Valvecrazy, think your comments are a bit over the top re planned obsolescence, do you really think that selling pumps that fail early is good marketing?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)