Contactor, Timer Circuit Design HELP!

[tennis ball]

I have a question.

Basically I have been asked to install electrical heaters in a large area and the customer wants them timed and on thermostatic controls. Which is fine you can just buy the plug in's right?

Bloody hell their expensive!

I haven't played with contactors and din rail timers before and I was considering putting the entire circuit on a timer as the heaters have built in thermostats. But I noticed the DIN Rail timers all have low current ratings up to 16A. Each heater is 2 KW and so can draw around 8amps and theres four of them!

So is it possible to wire a timer to output to a contacter and would the timer be able to turn the contactor on and off? Thats the simple question really as I don't have a clue about the design and workings of contactors and timers.

Any help much appreciated

Dan

 

[Des 56]

Yes,you can either get a timer and 4 pole contactor to mount in a distribution board, din rail mounted, or others for external use
I cant post a link,its not permited,but have a look at the TLC site and there are many sizes available to suit

 

[tennis ball]

Hi there,

Thanks very much, i'll give TLC a call now and see what can be done! many thanks.

 

[Darkwood]

My first question is 1ph or 3ph supply?

 

[ackbarthestar]

So is it possible to wire a timer to output to a contacter and would the timer be able to turn the contactor on and off? Thats the simple question really as I don't have a clue about the design and workings of contactors and timers.

No point in putting the timer in the output lines of the contactors since you will need a switching device to close the contactor switch terminals.

Put the timers in the control/coil circuits. The time switches then will not have to carry the full load supplied to the heaters.

You could switch the heaters all together from one contactor, Or you could have separate timers controlling each heater.

BTW, You will need to protect the time switches in the coil circuit and also protect the individual heater circuits

 

[Darkwood]

No point in putting the timer in the output lines of the contactors since you will need a switching device to close the contactor switch terminals.

Put the timers in the control/coil circuits. The time switches then will not have to carry the full load supplied to the heaters.

You could switch the heaters all together from one contactor, Or you could have separate timers controlling each heater.

BTW, You will need to protect the time switches in the coil circuit and also protect the individual heater circuits

I think you misread the O/P he said 'to wire a timer to output to a contactor' not wire a timer on the output of a contactor.

 

[ackbarthestar]

I think you misread the O/P he said 'to wire a timer to output to a contactor' not wire a timer on the output of a contactor.

Lol, thank for the adjustment. But you never know what he may be thinking

 

[Des 56]

So is it possible to wire a timer to output to a contacter ?

No point in putting the timer in the output lines of the contactors

My own reply assumed he was refering to control :dozey:
"To output "and "in the output" being different statements :yes:

 

[tennis ball]

My first question is 1ph or 3ph supply?

Hi its single phase supply

 

[Darkwood]

Yes Des you read O/P as i did, my correction wasn't aimed at you but ackbarthestar to which he has already acknowledged, O/P isn't used to contactors/timers etc so his terminology/phrasing is a little out there and easily mis-interpreted if read quickly.
To O/P do you have 3ph available????

 

[tennis ball]

Hi guys thanks for the replies.

Ok so I would want to switch all 4 heaters together. As ackbarthestar says I need to protect the circuit and I was wondering how to get around this. The circuit was originally going to be on a ring, 32amp breaker but the timer is 16 amps.

Can you get a contactor with built in overcurrent protection? If not I guess you would have to output again to an mcb.

Here is my basic understanding of a contactor please help me if I am wrong. A current passes through some part of the contactor and creates a magnetic field which "pulls" in some other part of the contactor and closing the circuit. I am struggling to see how that can be wired to operate on and off because to turn it off then the current has to be broken somehow and I can't understand how the timer can fulfill that function?

 

[tennis ball]

Hi, No three phase available!

 

[tennis ball]

Yes Des you read O/P as i did, my correction wasn't aimed at you but ackbarthestar to which he has already acknowledged, O/P isn't used to contactors/timers etc so his terminology/phrasing is a little out there and easily mis-interpreted if read quickly.
To O/P do you have 3ph available????

No three phase available!

 

[Darkwood]

Soz tennis ball was writing when you replied to that.... never mind just a thought would have been better over 3ph but in this case just supply a timer and set it to energise and de-energise the coil on a contactor, if getting a 4pole contactor as suggested i would clarify the 4th pole is rated as this is usually there for the retaining contact and isn't always rated the same as L1,L2,L3...(phone call to tech' support may be needed) also you need to state the coil voltage when buying (230v in your case), you could save a few pennies and use a 3pole and just use L1 and L2 each doing 2 heaters each.
This way you could have 2 x 20amp circuits running through contactor, note if more than 1 circuit is used mark the enclosure up that it has more than 1 isolation point then list the mcb designations including the control timer circuit if it differs.

 

[tennis ball]

Many thanks for all your replies. At the very least I can go forward knowing that it can be done! When I get round to the task if its possible I will put some pictures up. I want to get this right not just because my reputation is on the line but because its new experience and its one of the site visit jobs for the NICEIC! Cheers, Dan