DOL starter and switches

[munga42]

Hi,

I have a Dol starter which i would like to use for my single phase irrigation pump. The Coil on the contactor is 240v. there are 3 lines in L1 L2 L3. It is connected to a 17 - 25 amp overload. I know that I have to link the wires together some how, T1 to L3?? There is a start button on the top but its not connected to anything, 13 & 14 N/O?

The idea would be to link in a pressure switch to stop pump when the travel sprinkler comes to the end of its run. Also within the water tank I would like a float switch that would cutout the pump when the water is low. I would like a solenoid water valve to be activated when the float switch stops the pump and allows fill up of tank then shut off when the float switch starts the pump again when the tank is full. Its only in my head at the moment and not sure on how to carry all this out!! Any help would be appreciated.

Jim

 

[geoffa]

not being funny but if you don't know what the N/O contact is for maybe you should get an electrician who knows what he's doing to carry out the work for you.
are you a qualified electrician?

 

[munga42]

I'm just asking for advice on my setup,. I haven't done much with contactors before so advice was all I was looking for Geoffa. I do know what N/O is. The question mark was to emphasize that I need help in wiring the contactor correctly and not N/O?

Jim

 

[johnboy6083]

i know exactly what you want, but i cant translate it onto paper. IMO, you dont want a sol valve, they can be more hassle than they are worth. a ball cock is more than adequate. you can buy sump pumps with float switches for your pump protection.

with single phase loads on 3 pole contactors its considered good practice to use all of the poles. you do this by looping the live from t1 to l2 and then you take your outgoing feed from t2, your neutral goes straight through l3 and t3.

for the pressure switch, you may want to consider using a small relay that interupts the coil to the main contactor.
as i cannot see exactly what gear you have ect, its difficult for me to help any more, and also im crap at translating what im thinking into words that are legible to any normal man! lol

 

[munga42]

Thanks. The reason i'm looking at using solenoid valve is cos i'm linking more than one tank together, therefore I need the solenoid to let water in to all tanks. The float switch would only be on one tank but as they would fill at the same rate. Not sure how I go about getting them to work together As one closes, the other opens and also starting pump . Is it best practice to use a relay or can I link them in series in to the contactor. Therefore kinda making the start button obsolite. Does that make sense?

Jim

 

[johnboy6083]

can you draw a small shematic of your system? the i and others may be able to suggest something. how many pumps are there? are you using multiple tanks to feed one pump? how big is your water main? ect

 

[munga42]

I have one 3KW vertical multistage pump with a return flow pipe to the tanks , one pressure switch on the outlet side, 5 IBC tanks linked together with 1 float switch and looking to get solenoid valve for tanks top up. The travel sprinkler I am using has a auto cut off when it has finished its run, that's where the pressure switch comes in. Thanks all for your help.

Jim

 

[Marvo]

Consider it as three separate electrical systems. First you have a high liquid level system to control the water going into the reservoir tanks, this could be a solenoid with probes/float switch or a good old ball float valve like in a toilet. Second you have a low level safety system to stop your pump from dry running when the tanks become empty. This could also be probes and liquid level control or a float switch which interrupts the power to the contactor coil. Third you have a pressure switch or prescontrol on the discharge side of the pump to swicth it on when there's demand. Now all you need to do is figure out the best way to integrate the three systems. I'd offer a suggestion but I'm confused about the line in your OP where you say 'when the travel sprinkler comes to the end of its run.'

 

[munga42]

The travel sprinkler i have has a mechanical cut off valve on the sprinkler which shuts off the water flow to the sprinkler head. The pump needs to have the pressure switch as the flow from the pump to the sprinkler is still on until in reaches the desired pressure to cut out.
I did toy with the idea of ball floats but i would have to install in each tank which adds to the cost. 1 solenoid i thought might be the answer but if I go and use the ball float solution I guess it makes the system alot easier.

Jim

 

[Marvo]

Cant you just link your tanks together below ground with a 50mm LDPE pipe and a few insert fittings? That way the tankswill find their own level and act as a single larger tank.

 

[munga42]

still left with how to stop the water top up though

 

[Marvo]

Here's a schematic. The two probe sets obviously have associated liquid level controllers.

 

[johnboy6083]

The idea of balance lines to link your tanks is a good one, but in the past weve had problems sizing this line. We found that the balance lines had to be oversized so that the last tank in the line is filing up at the same rate as the one receiving the water main.
As marvo said liquid level controllers could be used, and are relatively easy to wire. You would need one for your water make up and one for your pump protection. I can't remember the ones that we used, so I can't link to one. I don't get your pressure switch? We would need to know how your sprinkler system is set up to know that. I've used rainbird in the past, and that was straight forward.

 

[munga42]

I am trying to use what I have available to me with out spending to much. I have the float switch, the pressure switch,the pump , 5 ibc tanks and starter. The pressure switch is being used to protect pump, as the pressure rises after sprinkler has finished its run the pressure switch will cut in at say 8 bar. When the travel sprinkler has been set up for another run, the pressure switch will cut out and so on. It sounds a bit crude the setup. but with a solenoid valve on the water inlet I thought might be the answer? The flaw with ballcocks is the tanks will fill up constantly as the level drops where as with a sole valve they would almost empty before refill.

 

[johnboy6083]

that isnt a flaw with the ball cocks, its probably their best feature. also they rarely fail.. in your idea of using a sol valve, your tanks will havwe to be sized to take the full amount of water t5hat the system will use. with a ball cock, as the water will constantly be topping up, you have more capacity.

 

[Marvo]

I am trying to use what I have available to me with out spending to much. I have the float switch, the pressure switch,the pump , 5 ibc tanks and starter.

The sketch I gave you is just a rough schematic. You can use float switches instead of the probe system I showed and you can use 5 tanks instead of the two on the sketch. I'm not sure what 'ibc tanks' are mind you.

The pressure switch is being used to protect pump, as the pressure rises after sprinkler has finished its run the pressure switch will cut in at say 8 bar. When the travel sprinkler has been set up for another run, the pressure switch will cut out and so on.

You'll still need a small diaphragm tank to give some differential otherwise the pump will rapidly cycle on/off with even a very small leak.

It sounds a bit crude the setup. but with a solenoid valve on the water inlet I thought might be the answer? The flaw with ballcocks is the tanks will fill up constantly as the level drops where as with a sole valve they would almost empty before refill.

The fill solenoid on the sketch is controlled by the short probes in the RHS tank so refill would start after a small drop in the tank water levels. You can use a ball float valve but they tend to be more restrictive and a lot slower filling than a solenoid unless you use a larger commercial one which may well be more expensive than a solenoid. Float valves also don't always like brackish or river water, the particulates can cause problems with the seat, most half decent irrigation solenoid valves are designed to work with impure water.

 

[munga42]

I think ill go with ballcocks for a start. I have an old booster pump with a 24l diaphram tank so I could use that. Going on to the pressure switch and float switch, how do you guys think I should wire them in to the system? The pressure switch is 240v as is the float switch.

Jim

 

[Marvo]

The live of the supply to the pump will be via the low level float to prevent dry run and via the pressure switch normally closed contact assuming it's a 'break on rise' switch and assuming both components are AC3 rated to take the full run current. If not then use a contactor. Should be easy peasy japanesey. Does your booster pump have built-in overload protection?

 

[munga42]

Are you saying to use another contactor other than the one in the starter? I dont think booster has overload

Jim

 

[geoffa]

................

 

[munga42]

your input and help is greatly received geoffa!

 

[geoffa]

there's no need to be like that munga42.
the reason i deleted the post was because i had spent a considerable time describing to you exactly how to wire the system up and what additional equipment you would need for the system to operate as you wish.
To write all that was taking a long time and as i was 3/4 of the way through it i pressed the save button accidentally.
I didn't have the time then to edit it without the post being read and it was incorrect as it was and would've been confusing or just obviously wrong depending on who was reading it.
So i decided it was better to delete it save it edit it and re-post when i had time.
If i had a way of drawing the circuit for you to see i would do that as it would be quicker.
What i will say is that i believe you need 2 float switches both having N/O and N/C contacts to gain control over the solenoid switching on and off to re-fill and the pump switching off and on as necessary. you will also need an additional relay to operate the solenoid.
Supply phase conductor connects to the N/C contacts on the stop button, overload, pressure switch and Low level float switch connect in series prior to the start button, retaining contact of the contactor, and the N/O contact of the High level float switch which all connect in parallel and feed the coil of the contactor.
Supply phase conductor connects to the N/C contact of the High level float switch then to the N/O contact of the Low level float switch and the N/O retaining contact of the control relay which are both connected in parallel which then feeds the coil of the control relay and and the coil of the solenoid.
Supply phase conductor connects to L1 of the contactor through the overload to the T1 terminal then back to the L2 terminal through the overload to the T2 terminal then to the pump. N conductor connects to L3 through the overload to T3 terminal and to the pump.
Reason for looping the L through the contactor twice is to get balanced current flowing through all 3 overload elements.

 

[silva.foxx]

Helpful post by Geoffa... diagram to supplement.

(disclaimer: not the finished article as to what Geoffa stated, but offers some visual)

.

 

[geoffa]

agree silva what you've represented so far is the same as i described. The only bit i find a bit confusing are the states of the float switches and that maybe it would've been better to show them assuming the water was midway in the tank so the Low level float would be shown as a N/C contact and the High level float shown as a N/O contact as they would be in reality.
If i had a scanner i'd attach the ladder diagram i've drawn for the control circuit. Can't afford the time to draw it with CAD.

The only problems i can see with the circuit i described is that the pump will not re-start until the tank is recognised as being full, this can be overcome by including a timer contact in parallel with the start button. (whether this would be necessary would depend on the output from the pump compared to the input of water through the solenoid valve and user preference. If the fill rate was greater than the drain rate then a timer contact would be ok to parallel across the Low level float contact and start button combined for the duration that Low level float took to return back to the N/C state)

The other problem is that if the tank was full and the pump was running it wouldn't be possible to switch the pump off until the High level float had dropped so that the contact in parallel with the start button had returned to the N/O state. There would be no way of dropping the retainer out otherwise.
The way around this is to have a D.O.L. starter with a twist to release mechanism, essentially an emergency stop button.

 

[geoffa]

it would be far better to abandon the D.O.L. starter altogether and build a small control panel for the job as there are other control components required.
That way it would be possible to have a control contactor operated in a D.O.L configuration which would then supply power to the circuit you have drawn so far.
It's far from ideal having a pump automatically starting up as soon as an emergency button is released.
A start button should be pressed to begin any control system from a safety point of view.
Maybe there's a simpler way to get the desired result.

 

[geoffa]

i'm interested to know munga42, if you are a qualified electrician, a plumber or a diy'er.
you didn't answer the question i posted in reply to your original post, and seem very defensive and attacking in response.
my point was that you are asking people how to do something which appears to be putting you out of your depth with capability, so, as i said before maybe it would be better / safer for you and anyone else in the environment of your proposed system, (assuming it's for personal use rather than a client as it sounded) to employ somebody who knows what they are doing to handle the elecrtrical control side.
i think that's a fair comment.

regardless of your apparent irritation with being suggested of this, i have spent some considerable time helping you although i doubt it will be understandable to you.

 

[munga42]

Geoffa, forgive me for sounding a bit off as your first 2 posts seemed a bit off. Apologies and i'm grateful for your input and thought in to my system.
You are correct that im not an electrician but I have done many different projects which I have been more than capable of carrying out with no issues. This is a more complex situation hence coming on this forum for expert advice. The advice I have had so far is invaluable! When it comes to wiring the system up I will probably ask a competent electrician to do the install. As this forum has shown me, everyone has a slightly different opinion on the setup. Thanks again. Jim

 

[geoffa]

no prob's
geoff

 

[geoffa]

Also munga42,
you say the overload is rated 17-25A
I suspect the motor on the pump is only a few Amps, so if i'm right that would need to be changed.
It's good practice to have a separate fuse for the power circuit and another fuse for the control circuit; as different currents are likely to be used. It would be better to have an anti-surge fuse protecting the motor, wheras a quick blow fuse for the control circuit would be safer.

 

[munga42]

the pump motor is 3kw with max 17 amps, I was told by an electrician to look for a contactor with a 17 to 25 amp rated overload.

 

[geoffa]

that be right then. big pump
definetly need separate protection for power and control to prevent fire in control panel e.g. coil on contactor overheating.