Advice needed on a sewage pump

[lennox]

Hi all

go easy on me now!

Basically at this factory Iv started to do some maintenance for we have got a 3 phase sewage pump,with two float switches and a alarm float switch.

this is a new install as such, an electrician prior to me has run the cables for the pump and float/alarm

On the incoming end we have an adaptable box with a 3phase 240v 20a contractor in and a auto+ hand switch

The previous electrician hadn't made off each end so it's down to me.

the alarm side is in a separate adaptable box and isn't a problem.

basicaly I'm struggling to see how it can work using both float switches switching the contactor,through one contactor as I can get it to work with the two float switches through out but not auto and hand?

Please could ups anyone point me in the right direction as not had much experience with this sort of thing really!

Will add photos shortly

 

[lennox]

 

[telectrix]

photo is no good

 

[ian.settle1]

Think of a normal stop start circuit and replace the push buttons with the float switches for auto position and when in hand you just energise the coil

 

[Pete999]

Obviously the alarm float sounds some sort of alarm what do the other two control? is it low and high level? as in on and off

 

[lennox]

Sorry yes, on and off. Struggling to get the photos on here to show!

 

[ian.settle1]

Obviously the alarm float sounds some sort of alarm what do the other two control? is it low and high level? as in on and off

Bottom float makes when the tank starts to fill then the top float makes as the contents rises and brings in the contactor starting the pump which pumps out the tank until it reaches the bottom float when the contactor drops out as this is in series with the hold on contact for the contactor just like a stop button.

 

[lennox]

Yes I understand that but then how can I have it so can Manually have it on without the use of the floats (hand) or am I being a **** and missing something!?


thanks for all the comments

 

[Marvo]

Sorry yes, on and off. Struggling to get the photos on here to show!

I've given you full member permissions so if you 'Go Advanced' in the reply box you should be able to see the attachment options if you scroll down. Other option is upload the pics to photobucket or a similar service and paste the links here.

 

[ian.settle1]

Yes I understand that but then how can I have it so can Manually have it on without the use of the floats (hand) or am I being a **** and missing something!?


thanks for all the comments

Your control supply goes via the auto/hand switch (another name for a two way switch) when you switch it to auto you control the contactor via the floats when you put it to hand you put the supply directly on to the contactor thus energising it

 

[Bobster]

Why are you using 240V control external to the panel on a new install?

Unless i've miss read.

 

[lennox]

Thanks for all the comments and sorry for the late reply. Went well once I took a minute to think about it!!

Rob as mentioned a previous electrician began the works and for what ever reason never finished it

 

[Jack of all]

You should have a control circuit on low voltage with a small transformer in the enclosure...
If I was wanting some distance between the start & stop then I'd use a Radar float switch, very easy to set up, with 2 floats on a piece of string & no electrical devices in the liquid.

 

[lennox]

Like previously stated jack of all, my job was to connect what was there. In an ideal world yes it would be low voltage

 

[Darkwood]

What you need to be saying here is did the previous Electrician make a pigs ear of it and do I have to correct his work - now the question you need to ask yourself here is 'does the work I finished off comply?' .... this is your job to know not to pass the book saying the previous guy wired it this way.

Ask for advice by all means but please don't use that as an excuse when a question is posed to you, it reflects your somewhat out of your depth here and shouldn't have taken the work on until you were confident about any regulations you needed to comply to...

PS ... Im not saying what you did was correct or not, I just reflecting on you replies.

 

[lennox]

Dark wood I'm not passing the blame but as its compliant and I didn't design the job I don't see the problem, when it's down to personal preference.but yes I would rather the control circuit to be low voltage but it's compliant and safe.

my point would be that as the submersible pump is 400v and if that seal fails then it's not going to be pretty either...

 

[Bobster]

Please don't take this like I'm having a pop.

How do you know it's complient?

 

[lennox]

As its not in a special location so doesn't have to be extra low voltage and manufacturers instructions (being 230v rated) and probably being double insulated also.

 

[davesparks]

As its not in a special location so doesn't have to be extra low voltage and manufacturers instructions (being 230v rated) and probably being double insulated also.

I believe you may have just opened the floodgates (pun intended)

 

[Darkwood]

The control set-up you have wired up has been done by yourself and not by the sounds of it as part of a control system supplied with the pump (unless you tell us otherwise). In wiring it up you become the designer and installer as the previous has buggered off, it is a motor with a control and very little of this set-up would fall under the scope of the BS7671 except maybe cable sizing and install methods hence the comment made about knowing if its compliant.... if your wiring this using just your knowledge of the BS7671 only then you cannot know if what you have done is compliant.

Whenever anyone with experience and competence working under the BS7671 only moves into any kind of control system design be it for a motor like a pump or a machine then they are subject to a very different set of regulations and from experience they are probably ignorant of them as they think the BYB covers all this work but in reality they couldn't be further from the truth.

We are not trying to trip you up here we are asking if you know the regulations that would govern an install of this nature? If it was just a plug and play kit then it would mostly fall under the BS7671 with the manufacturers having the responsibility for the design aspects, as you have taken over a job and had to work out how to wire it then you have designed a control system for a sewage pump and been the designer and how ever simple the circuit was to do, you are subject to a different set of regulations.

We are not telling you its right or wrong what you have done, I need alot more info for that but we are just telling you to heed caution on jobs like this as you may be breaching regulations you are not even aware of.

Take a look at the pig feeder thread for an insight to what could be a simple task ends up been a heated debate on the separate regulations that govern control systems.

http://www.electriciansforums.co.uk...lectrical-forum/100591-pig-feeder-system.html

 

[SheffSimon]

BS EN 60204-1:2006+A1:2009


Safety of machinery. Electrical equipment of machines. General requirements

BS EN ISO 13849-1:2008

Safety of machinery. Safety-related parts of control systems. General principles for design

would apply here.

Is the sewage tank a hazardous area, any potentially explosive gases where these float switches are, where the pump/motor are? If so, ATEX regs also apply.

It might look simple on the face of it, and it generally is when you know what you're doing, and when you know that it might not be as simple as it appears....

 

[courtwba1]

Totally correct sheff simon , the pump should be ex rated, the float swithes should be connected to IS barriers in the control panel and also any ducts should be sealed with an ex rated compund.

 

[Knobhead]

Totally correct sheff simon , the pump should be ex rated, the float swithes should be connected to IS barriers in the control panel and also any ducts should be sealed with an ex rated compund.

Do you know the location or circumstances?

Have you worked on sewage plants?

How can you give a blanket recommendation about the equipment to be installed?