Replies

1. 
   Mark_M | Jan 14, 2001 02:38am | #1

   *
   Although it is normally a better idea to use a single throw, double pole switch (timer) when working with 208 or 240v; I believe that if the timer is rated high enough in volts , amps, and wattage, then wire the timer into one leg. The other leg will be unswitched, and always hot.

1. 
   Phill_Giles | Jan 14, 2001 08:58am | #2

   *I supposed you read all the fine-print on the instructions that came with your timer; and: 1) it's rated for enough wattage (some are only 300W) 2) that the instructions don't preclude attachment to a high-resistance load, like a heater (a surprising number of these times can only handle incandesent lighting). 3) many electronic timers require a mini-current to pass through them all the time, that's why the timers can stop if they're attached to a light where the bulbs have all burned out: if the baseboard heater has a thermistat, well, then you don't have a permanent loop and the timer will not run once the backup batery has run down.

1. 
   p_m | Jan 15, 2001 02:25am | #3

   *Dennis, Please say it isn't so that you are using "the bare wire as the nuetral,". The neutral has to be a white [or gray] insulated wire. And the bare wire is only for ground. I don't know what kind of timer you have, but most common ones use 110 volts to run the timer motor. If you timer has two sets of contacts that open simultaneously and you feed it with 12-3 + ground, it could work. But interupting only one side of the 220 volt circuit would leave live 110 volts in your heater which is dangerous. My suggestion would be to use your timer to operate a properly sized relay.

1. 
   David_Thomas | Jan 15, 2001 05:48am | #4

   *Dennis: Do the ratings on the timer say something like 12 amps @ 120 volts / 6 amps @ 240 volts? Then I'd try interupting one of the hot wires (which means the contacts in the timers will see 240 volts when they make and break).Phill is right that a lot of these timers are only rated for about 300 watts. But I disagree with his statements in 2). A heater is actually a LOW-resistance load. Low resistance means high amps and high power. Also, the timer doesn't care if it is a heater or a bunch of incandscent lights, just the total wattage and amps. The timer DOES care if it is flourscent lighting or if an inductive load (an electric motor like a fridge) is switched. The timer must say that it will work specifically on such loads. There are timers that are rated at 1500 watts and are appropriate for switching air conditioners. They are about $15 (versus $6 for the 300 watt ones) and, if they can accomodate 240-volt wiring, a better choice for your application.I agree with PM that the bare wire should be ground not neutral. What does a 240-volt heater need with neutral anyway? Its chassis (that you can touch) should be grounded to the green or bare wires, not carrying current which the neutral does.PM: I've seen a lot of "240-volt electric baseboard" thermostats that only switch one side even though there are terminals for both legs. So I'd never work on a 240-volt heater with turning off the breaker (and checking for voltage). Now if someone is trying for a Darwin Award, they might not take those precautions, but that could happen with the timer approach or with a thermostat marketed for that purpose. I agree that a double pole switch (be it the timer, thermostat, or a relay) is the better way to go.When I typed your requirements into Honeywell's thermostat selection page: http://content.honeywell.com:80/Home/ptc-thermostats/Therm_Choose.htmI got the CT1950A (which I use in my house). It is a electronic programmable, 2-wire, 240-volt thermostat rated for min 500w max 3800w. Just program it for the desired temperature from 5:00-8:00 am and for 45F the rest of the time. Tight temperature control, off the rest of the time, designed for 240-volt baseboards - problem solved. The CT series is often special order maybe 7-10 days away. Here's the info on it. Print it out and take it to your local supply house: http://hcpretail.honeywell.com/HCP_Store/catalog/productdisplay.asp?subgroupnum=31

1. 
   Dennis_McCarthy | Jan 18, 2001 03:28am | #5

   *Thanks for the input. I checked and the timer is rated high enough. And it was my mistake - my message should have stated that the bare wire is the ground, not the nuetral. I appreciate the link to Honeywell, and will check on prices. Seems that a double pole switch or thermostat would be the way to go. I'm sure I can use the timer elsewhere on a 120v application.

2. 
   Dennis_McCarthy | Jan 18, 2001 03:28am | #6

   *
   I purchased a 500 watt 240V baseboard heater for a small bathroom. I only want the heat to turn on each morning from 5:00-8:00. So, I purchased a digital wall switch timer (Intermatic SS7C), which is capable of handling 12-277V. The wiring diagram for the switch only covers 120V applications, and has one pair of wires that go the line and load. Since the heater is 240V, it is currently running on 12/2 with the bare wire as the nuetral, and 120V on each of the black and white wires. My question: how can I wire this switch to work correctly?