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40 amp water heater timer.

Discussion in 'Growroom Design & Setup' started by Globel, Jan 2, 2011.

  1. Is it safe to run the 40 amp water heater timers at 40 amps 12 hours a day? Can i run 8 lights on them? or should i stick to 7.
  2. I wouldn't do that. Are you trying to plug a splitter into a single heater timer? No bueno, you are asking for trouble. What is the timer rated at?

    Get a cheap 40 amp light controller or look into some schematics to build one if you can't afford the $140.
  3. I was using 2 Intermatic 40A 240 digital water heater timers to run my 4k in lights. I use Galaxy electronic ballasts. I ended up melting the relay contacts inside on both of them. I had a good talk with the people there, and the story was that the inrush of current that happens when the ballasts first fire up is way in excess of the 40A that the contacts were rated for. It was truly just for a water heater. I would just use a regular digital timer (either plug in or hard wire) to trigger a lighting controller. I did the swap, and it works perfectly. Not too expensive either.


  4. Never max out your shittttttz. It wont work as long and probably cost you your crop if you dont moniter it often.
  5. I'm currently designing my led system, being powered off a 350w pc power supply. Along the way of researching, I came across some guides for converting a simple digital thermostat into a DC timer. The thermostat's only good for about 4 amps, but I'm adding some vdc relay switches. .. The same thing can be done for vac.. ie: hid lights.

    Thermostat was $15 at a liquidation store, and my 2 12v 10amp DPDT relay switches came to $14. I plan on tying poles on each of the relays to get 20amps out of them instead of 10.

    Same thing can be done for 40amps vac.. just get a higher rated relay switch. The thermostat usually runs on 24vac, but can also run on 2 AA batteries.. 3v - 3.3v. I powered mine directly to the 3.3v line of the psu I modified. You could use a simple 3v - 3.3v power adapter for under $20 new.

    It's a cheaper option to look at.........
  6. If you use a digital thermostat for a baseboard heater, a new 4000W at 240VAC unit can be bought for $50 at home depot.

    All that you need to do to modify the unit, is open it up, and replace the "thermistor" (thermal resistor) with a set valued resistor. 120K ohms made mine a solid 41F. Then to use it as a timer, you have your source wires going into it, and the target wires on the "heater" connection. You then set the thermostat for the highest temp it allows.. mine is 91F. The thermostat had 4 schedules per day, and a total of 7 days.. not the 5+1+1.. those are limited on weekend schedules. I then set the 1st 2 settings as "heater 91F, fan on", and the last 2 settings as "40F, fan on". Since my set resistor gives a constant 41F, when schedule starts, it reads 41, and "tries" to raise to 91F.. but never does. Instead, it passes the voltage needed for your custom set-up. Then come the 3rd and 4th schedules, it switches the target temperature to 40F.. and since it's a constant 41F, it shuts off the power until the temperature falls below 40F.. which will never happen of course. :)

    And I put "fan on" in the schedules, rather than "fan auto". If set for "fan auto", the thermostat takes 10 to 15 seconds to kick in.. reads the temperature first. If set as "fan on" in the schedules, it kicks in right on time. You hear the clicks of the heater 10 seconds in, and a few times throughout the schedule, but that's normal.. does it on your wall as well, when actually hooked up to the heater.

    So.. for $50 + tax, and $1 for resistor if you don't already have.. and you have your 4000W 240V digital timer. :)

    You can always get a higher rated thermostat as well. Just make sure it's the "baseboard" type, and it's programmable.. a few of them aren't.