Build A Contactor/relay

[the d.o.c]

Normal household timers are not designed or rated to deal with the inductive power load used by horticultural lighting, There are 2 ways around this, you could go to your local Hydro shop and buy a contactor all built and ready to go along with a hefty price tag.

Or you can get yourself a suitable change over Contact Relay switch, this will only set you back a few £'s. A contact relay switch is required so that the timer turns on the contactor, which then turns the light on.

Almost all new growers will experience light failure. The reason for this is the contacts in these timers are not sufficient for the job. Household timers are rated for a RESISTIVE load, ballasts present an INDUCTIVE load, (a very large surge at switch on) this fuses the timer contacts together = Timer failure.

Q: What is a relay switch?

A: An electro mechanically operated switch.

What follows?

Complete instructions (including photos) on wiring a contact relay switch to replace your timer contacts in 6 easy steps

Q: What parts are needed and where can I buy them?

A: The following parts can be purchased at any good online electrical store i.e. maplin.co.uk rswww.com or a local electrical wholesalers such as City Electrical Factors

In my case I run 1 x 400w HPS, I know the INDUCTIVE load is 3.15 amps at switch on. Ask the manufacturers of your light for this info.

I have chosen a 230 volt, 10 amp contact relay switch from CEF (City Electrical Factor) reference number 6012-8230BP for the 2 pole 8 pin relay and 9020-BLKBP for the plug in base and is part of the MCG (Motor Control Gear) catalogues Finder range. This particular Relay switch has screw-terminals for easy wiring, and a push fit, easy mount base with numbered terminals.

You will also need a 3 way terminal block, 2 x 3 pin mains plugs, 1 x 3 pin female mains socket, 1.5 meter of 2 core mains wire, sharp wire cutters/blade, an electrical screwdriver, and a cross head screwdriver.

(optional:I housed my relay contactor in a waterproof ip65 housing at a cost of £12)

here is the tools and parts you will need

Edited January 22, 2005 by Vlad (the impala)

[the d.o.c]

How to wire a relay/contactor unit.

Note: mains voltage can kill you! So please exercise caution when wiring electronics of any kind!

1. Cut your 2-core wire into 4 measures the same length. Now pre-pair the wire ends, cut 2" from the outer sheath, then cut 1 cm off the inner sheath to expose wire. *Optional - solder all wire ends*

2. Fit mains plugs to 2 of the 4 pieces of wire, and then 1 of the remaining pieces of wire to the female mains socket.

[the d.o.c]

3. Select one of the pieces of cable terminated with a mains plug, and connect to the relay base as follows: - Connect the live wire (Brown) to terminal 7 on the relay base. Connect the Neutral wire (Blue) to terminal 2 on the relay base. These connections are used to energise the relay coil. Now label the mains plug “Timer” (Plug 1)

[the d.o.c]

4. Select the second piece of cable terminated with a mains plug, and connect to the terminal block as follows: - Connect the live wire (Brown) to terminal 1 on the terminal block (see diagram for terminal block numbering sequence). Connect the Neutral wire (Blue) to terminal 3 on the terminal block (see diagram). These connections are used to operate the grow room light (via the relay contacts). Now label the mains plug “Power” (Plug 2).

THIS DIAGRAM DOES NOT HAVE AN EARTH (EARTH CAN BE ADDED TO EACH OF THE PLUG ENDS BY USING THREE CORE ELECTRICAL CABLE INSTEAD OF TWO AND JOINING THESE TO EARTH CONNECTION IN THE WATER TIGHT UNIT TO INCREASE SAFETY)

[the d.o.c]

5. Select the third piece of cable terminated with a female mains socket, and connect to the terminal block as follows: - Connect the live wire (Brown) to terminal 2 on the terminal block. Connect the neutral wire (Blue) to terminal 3 on the terminal block.

6. Select the final piece of wire and proceed as follows: -Connect one end of the Brown wire to terminal 1 on the terminal block, connect the other end of this wire to terminal 8 on the relay base. Connect one end of the Blue wire to terminal 2 on the terminal block, connect the other end of this wire to terminal 6 on the relay base. Note: under operating conditions both of these wires become live.

Edited January 22, 2005 by Vlad (the impala)

[the d.o.c]

7. Now take the relay unit and plug into relay base. (Plug 1) plugs into the timer. (Plug 2) plugs into a separate power socket. The female mains socket will supply power to your grow room lights.

The Principle of operation

When the timer switches on it will provide power to the relay coil, this in turn closes the relay contacts and bridges the terminals 8 & 6 on the relay unit thus providing power to female mains socket.

Total cost =£12. Time taken = 30min.

Total cost with watertight housing=£24 (as good as purchased contactors)

Total saving =£25-30

Total saving with watertight housing=£13-18

i hope this will be of help to all

:peace: the d.o.c

Edited January 22, 2005 by Vlad (the impala)

[AurorA]

i followed this tutorial to make my relay, but i used the version on overgrow...... doc, are you skunkaroo on overgrow? (who did the tutorial there)

if you are, thanks, you saved me 20 quid, or a broken  timer

peace

~AurorA~

[the d.o.c]

no ,i also got the details from O.G and converted it to be applicable to a U.K audience

a similar version can be found on my homepage where i thank Skunkaroo because although it was american based and a nightmare to track down the bits and pieces here,it was a real crop saver

unfortunalty i dont have a digi cam yet (will have to borrow mates again) so i cant post my own pictures of how the U.K components look yet ,but as soon as i get the digi cam again i will be able to show the whole unit as it should look in the waterproof housing   :thumbs:

peace mate

the d.o.c

[MrBenn]

Thanks for that d.o.c. Nice one m8

[Guest THE PUFFER]

Very good thread d.o.c :thumbs:

Go on...build us one will ya...

[the d.o.c]

i thought i would post the pics of the U.K components and how it looks

and here is how it looks with the wiring in

peace

the d.o.c

[the d.o.c]

here is the whole thing ,ready to go

i would build them and send them as long as you buy the components and cover the postage (and £5 labour cost   )

hope this will help some new growers out there :thumbs:

:peace:   the d.o.c

[Guest THE PUFFER]

£5 per half hour.....you're doing alright ent'ya....

D.o.c.....I will be your first customer...I hope you work to the same HIGH standards I do  

PM me with the full price and I'll sort it.

[Orinoco_Womble]

Hi d.o.c. I was wondering ,would the same 10Amp relay work o.k for 1 -1000w hps?Ta Orinoco...............

[the d.o.c]

you would have to contact your manufacturer for the information related to the inductive load it produces at startup and buy a relay that comfortably will cope with the amps

as my light produces around 3.15 amps at startup (400w)

i reckon it would be touch and go ,

rough calculations would put the inductive load at around 9 amps plus with a 1000w on a 10 amp relay (and i like to have a few amps more than the light produces ,for peace of mind)

this is not by any means the real inductive startup load of your light and for safety and security i would contact the light manufacturers and ask the inductive load of the 1000watt light ,

i am sure you can buy relays with different capacitys and it wont be a problem finding a relay to fit

peace

the d.o.c