Controller for Submersible pump in well.

[Mrdjc]

Looking at a Grundfos SP3-50
(Single phase, 1.5Kw Max, 6A, 10Bar Max)

I can't for the life of me seem to find a decent controller to go with it for a reasonable price.

I'm looking for something like this:
http://www.italtecnica.com/index.php?ip=4&cat=1&prd=42

Basically it will be 8m down in a well, pumping up to a fairly "large" pressure vessel of around 150L, at 6-8 Bar, 4m above ground level in a loft, with a pressure reducer for the house's water supply at 2.5-3 bar.

I want a controller to be able to adjust that if the pressure in the tank falls below 3 bar it starts pumping back up and pressurising the vessel until it reaches 6-8 bar again, and stops pumping.

A mechanical on/off switch is all fine and well but there will also be a boiler in the same room running off gas, so unless its galvanically isolated i'd rather not go down that route.
Plus I believe you can't adjust them so well to say at which pressure they should come on or off.

The electronic version has other benefits such as being able to detect excessive current drawn (motor not turning) or very low current (No load on motor) as well as other nifty functions.

Can anyone point me to a decent controller that doesn't cost more than the darned pump itself? I'm looking at around £1-£250 for a controller.
A mechanical one can be had for £50,-

Cheers.

 

[Norcon]

How much did the pump cost?

They sell packaged pump sets here complete with pressure vessel, pressure switch etc for about £500 quid.
You just fit a foot valve in the well. Job done.

 

[matt1e]

A mechanical on/off switch is all fine and well but there will also be a boiler in the same room running off gas, so unless its galvanically isolated i'd rather not go down that route.

care to explain better?

Plus I believe you can't adjust them so well to say at which pressure they should come on or off.

they adjust well enough,
as long as the vessels precharge is set correctly and the PRV is set lower than the cut in pressure than it will be fine

The electronic version has other benefits such as being able to detect excessive current drawn (motor not turning) or very low current (No load on motor) as well as other nifty functions.

Can anyone point me to a decent controller that doesn't cost more than the darned pump itself? I'm looking at around £1-£250 for a controller.
A mechanical one can be had for £50,-

with all the bells and whistles you req, its doubtful

Matt

 

[Boilerman2]

Allen Bradley or Danfoss make suitable pressure switches - make sure you purchase a switch suitable for a steam boiler as they are UL approved and are far more robust and reliable, they are not hard to set the cut -in cut out set points and will give Years of service
try Western automation or Spartan Controls for a supply

 

[SPWiddy]

Here is a photo I took of an installation in a large villa I maintain.

This has a mechanical pressure switch as you can see.
A boiler is also wall mounted above the EV just out of the photo.
The sub well pump is 200m down a bore hole.

Untitled

• SPWiddy
• 14 Jun 2012
• 1

Runs 6 bed villa 4 bathrooms.

controller 9 euro.

 

[Mrdjc]

care to explain better?

If for whatever reason all safety precautions fail with the gas supply and there is a gas leak, having a switch which makes fairly intense sparks when operating (the mechanical ones tend to do this) and its not sealed so the combustible gasses mix around it, things could potentially go boom.

The pictures of mechanical ones I've seen there is a simple plastic cover protecting the user from touching the terminals, but there is nothing to effectively "seal" the live parts from air.

they adjust well enough,
as long as the vessels precharge is set correctly and the PRV is set lower than the cut in pressure than it will be fine

Could you please name some makes/models so I can see what exactly is available?

with all the bells and whistles you req, its doubtful
Matt

I could *make* a system which does everything I require for under £100,- myself but it won't be approved in any way shape or form.

Pump will be around £400,-
Expansion vessel around £300,-

But there is nothing listed that you can directly control when the pump comes on and switches off again.
You can buy a fancy box from Grundfos that makes sure the pump doesn't get cooked, at a price tag of £400,- but that still doesn't control when it switches on and off.
You can buy a "Pressure Manager" from Grundfos but it only goes up to 3.5Bar and its for maintaining a constant pressure in a system without the use of a expansion vessel.

I just want a simple product that I can set the kick-in pressure and switch off pressure.

Any extra's functions which will protect the pump from burning itself out due to lack of water or not being able to turn the impeller are welcome, but I'm not counting on it

 

[SPWiddy]

Must admit, I dont fit mechanical pressure switch's any more, only as direct replacements which is rare.

What I think your looking for is an Inverter control, fully programmable. Like this one http://www.cswaterpumps.it/articolo.asp?l=UK&c=23.

Nearly all electronic controllers protect the pump from itself due to no water or over load even the 40 euro ones.

The last inverter I was quoted for was 280 euro trade so if possible extend your budget.

also be aware that power problems from the grid can kill electronic controllers as in southern Europe our electricity supply is far less stable than the uk, I keep a stock of controller pcb's on the van as blown boards are common and rarely covered by warranty.

 

[Agile]

If for whatever reason all safety precautions fail with the gas supply and there is a gas leak, having a switch which makes fairly intense sparks when operating (the mechanical ones tend to do this) and its not sealed so the combustible gasses mix around it, things could potentially go boom.

I suppose NASA needs to have intrinsically safe controllers but luckily in the uK its not normal for domestic properties.

We just use the correct materials and installation techniques and dont expect any gas leaks.

As far as protecting the motor against overcurrents a standard thermal current limited contactor would be a cheap solution.

Tony

 

[Mrdjc]

The inverter ones as I understand it only control the speed of the pump, if the pressure is low they step it up by increasing the speed of the pump.

If someone closes the tap it senses the sudden rise in pressure and switches the pump off.

If the tap is opened half it runs the pump at half speed to keep up with demand.

If the tap is opened fully it runs the pump at full speed to keep up with demand.

It's really for systems without a pressure vessel from what I gather, keeping the system at a certain pressure at all times.


Looking at a "oil" Pressure sensor 0-10Bar, High current 5V operated sealed relay and a Arduino microcontroller along with a temperature sensor and LCD display with buttons and CT sensor (Current Transformer)

I recon its do-able.. Would definitely be a fun project.

 

[SimonH2]

For independent adjustment of high and low pressure points, two pressure switches and a relay will do it. When low pressure switch closes, it pulls in a relay - one contact runs the pump, another holds in the relay until ... the high pressure switch opens (similar to the stop-start buttons on a motor starter/contactor).

If you build you own, then build a spare - and package it so that's it's replaceable as a unit with just normal screw terminals or connectors, and do some documentation. The WAF of a failed DIY unit when you aren't around to replace is is "rather low" ! If you have a spare, then at least someone else can swap it out.

 

[matt1e]

For independent adjustment of high and low pressure points, two pressure switches and a relay will do it.

One pressure switch will do it, they have adjustable hysteresis
all though you use two with differing set points if you have two pumps
Matt

 

[Boilerman2]

If you are worried about explosive atmosheres look at the Allen Bradley (Square D) range of pressure switches