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T

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
 
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
 
Hi there,

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


 
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!
 
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.
 
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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
 
The timer output can be used to complete the control circuit of the contactor/s(which pulls in the contactor/s contacts)
This will be a small current and can be fed off a 6 amp mcb


With a ring you feed the contactors main incoming contacts all off the ring mcb, you then have the timer doing its bit with 2x 2 pole contactors with the coils wired in series,
The load side of these contactors can then be via their own mcb or fuse,which can give overcurrent protection to the individual heaters wired as radials,much like a Grid switch system in a domestic kitchen
 
TB....
Some things to consider
1/ Before you do anything draw a circuit diagram of what you would like to happen
2/ Draw a wiring diagram showing the position of the time switch/s contactor/s and how you are going to make the physical connections with mcbs covering the control circuit and final heater circuits
3/ I personally would use radials fused separately to each heater.
4/ There are various ways of wiring the control circuits, but in this case, I would keep it as simple as possible. One time switch with one contactor.
5/ If you use a 4-pole contactor then the phase and neutrals will be balanced, so you will need to link/loop the phase contactor and neutral contactor inputs together. You can then run 4 circuits via 4 separate MCBs in pairs across the contactor output.

Don't take any notice of the ones marked in Red (avatars) they are members of the local Old Peoples home where they sit around watching TV and discussing the benefits of Wonga dot com
 
I've proberbly missed something but would not the timer control the contactor coil ( not input or output ) - thats what i thought the op said

Im waitin for the flack!
 
Your correct Bugsy the only flack you will get is you haven't read through this thread this mis-phrasing of what the O/P intended has been brought up already and OP was relating to timer energising coil on contactor. :)
 

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