CONTACTORS - wiring confirmation sought please

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Pou Sto
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CONTACTORS - wiring confirmation sought please

Post by Pou Sto » Wed Nov 21, 2012 8:58 pm

G’d Evening Everyone

I am not an electrician and have never wired contactors before so at the risk of making a fool of myself in this my first post - even after having spent ages googling for info - I shall really appreciate if someone in the know can confirm whether or not what I am proposing to do is correct.

I am replacing the original 15 amp rated 1960’s thermostats which control electric under floor heating with Heatmiser thermostats Model PRT-E (13A resistive load, not the later 16A model which weren‘t available at the time when I bought them). Whilst most of the under floor heating circuits are about 2kW and can be connected directly to the thermostats, the lounge under floor heating circuit is 3.8kW and at 240V will exceed the thermostat’s 13A resistive load limit so it is for this circuit that I am planning to use a Hager ESC225 contactor module (situated in the attic in its own enclosure where hopefully it’ll not be heard).

I have a power supply coming from a 16A RCBO to the flush steel box in the lounge wall where I’m proposing to place the thermostat; in an adjacent flush metal box I have two cables which I plan to use between the contactors in the attic and the thermostat, one to extend the live and neutral from the under floor heating to the contactors, the other to receive the output from the thermostat to control the contactors. There is also a further power supply from a 16A RCBO to the contactors position in the attic.

So arriving at my question , can you please confirm that my wiring at the contactors should be:

Live/brown from thermostat to A1 (at top of contactor module), neutral/blue from thermostat to A2 (at bottom of contactor module) to energise the coil when thermostat wants the heating on.

Live/brown from consumer unit rcbo to terminal 1 (top of module)
Live/brown from under floor circuit to terminal 2 (bottom of module)

Neutral/blue from consumer unit rcbo to terminal 3 (top of module)
Neutral/blue from under floor heating circuit to terminal 4 (bottom of module).

And what should I do with the earths, connect them all up using a connection block and place in the enclosure?

Many thanks.

Rgds

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someone-else
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Re: CONTACTORS - wiring confirmation sought please

Post by someone-else » Wed Nov 21, 2012 9:42 pm

Link to your proposed contactor would help. (Found one, but not sure if its the one you want to use)
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Re: CONTACTORS - wiring confirmation sought please

Post by ericmark » Wed Nov 21, 2012 9:47 pm

The PDF listing does not give numbers but A1 and A2 are normally the coil so likely you are correct. Is it not marked on the side of the relay?

The use of LZ060 (heat dissipation inserts) between all contactors installed or between contactors and adjacent devices is required.

Hope you noted that.
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Re: CONTACTORS - wiring confirmation sought please

Post by Pou Sto » Thu Nov 22, 2012 4:07 am

someone-else wrote:Link to your proposed contactor would help. (Found one, but not sure if its the one you want to use)
the terminal numbers are just visible (when image clicked to enlarge)

http://www.tlc-direct.co.uk/Images/Prod ... ESC225.JPG
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Re: CONTACTORS - wiring confirmation sought please

Post by Pou Sto » Thu Nov 22, 2012 4:51 am

Thanks for the info. I am proposing to put the contactor module in its own 2 module enclosure in the attic, viz., there will NOT be any other module in it other than an adjacent blank so hopefully potential overheating will not be an issue. Yes, you are correct, there is a schematic diagram on the front but I am not an electrician and even on an electricians' forum I have noted disagreement as to its interpretation and whether the supply should enter the top or bottom! The terminal numbers appear to be the same whatever make of contactors are purchased with odd numbers at top and even numbers at bottom; it looks like that when the coil is activated terminal 1 will connect to terminal 2, terminal 3 to terminal 4.

the terminal numbers are just about visible here when the image is clicked to enlarge:

http://www.tlc-direct.co.uk/Images/Prod ... ESC225.JPG
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Re: CONTACTORS - wiring confirmation sought please

Post by warmadmax » Thu Nov 22, 2012 8:56 am

wouldn't it be easier to return / ebay the 13A thermostat and buy the 16A one now they're avalible? :dunno:
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Re: CONTACTORS - wiring confirmation sought please

Post by Pou Sto » Thu Nov 22, 2012 9:49 am

warmadmax wrote:wouldn't it be easier to return / ebay the 13A thermostat and buy the 16A one now they're avalible? :dunno:
yes, I agree, that'd certainly have been a much easier and cheaper solution and I was prepared to go down that path but the advice from Heatmiser is that even with a 16A rated thermostat they recommend using contactors for loads as high as 3.8 kW because the current would be so close to the thermostat's 16A limit (15.83A at 240V, 16.17A at 235V).
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