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I need a higher amperage timer

I have a water heating element that draws about 14 amps @ 120V.

I want to put it on a timer so it shuts off after a certain number of hours. I have several of these timers that are commonly sold for turning lamps on and off. One of digital, the others are manual. Most are rated at a maximum of 8 amps. some a little less.

I imagine there are timers rated for the amperage I need, but buying a timer like that is likely costly, because it's probably a commercial item.

I have seen a lot of relays on ebay that are inexpensive. I'm thinking of just finding a relay that has a 120v input, and the output can handle at least 15A @ 120v. I can mount the relay in one of those cheap plastic electrical boxes and use the timer to flip that relay ON while the timer is ON, and Turn OFF the relay when the timer shuts off.

Will this work? Do I need a relay rated MORE than 15A on it's output side for a 14 amp heating element? I know that some loads need heavier contacts.

This heater draws a continuous 14A when it's operating.

Reply to
oldschool
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You don't want some consumer product. You want what the electrical power folks use.

So, very similar or even the same as a transfer switch. You make a panel specifically for that load where your low voltage timer switch actuates a higher amperage capable relay.

Or you make an inline or tank mounted add-on yourself.

You must remember you are switching very high current capable AC line voltage.

I would have the timer fire a solid state relay or two if you want to open both sides of the line.

Off the shelf product will be expensive breaker panel installed item.

Otherwise, one you fashion yourself will be more reliable and enable use of the design for other applications as well.

Something you could sell as a consumer product for a niche not yet filled.

Reply to
Long Hair

It is probably not worth the effort - you should be able to buy a 24/7 timer immersion heater rated for at least 16A & 240v ac for under $20.

How does the US do electric immersion heaters? 14A @ 120V sounds distinctly under powered to me. Do they not work across a phase pair like the aircon does? UK immersion heater is 15A @ 240v (or more).

It might draw very slightly more when cold so 16A rating should be fine

- it is a resistive load so relatively benign.

--
Regards, 
Martin Brown
Reply to
Martin Brown

Amazon will sell you a 20 amp twist timer for $13.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin

Buy a timer that's designed specifically for this purpose. Hacking something together out of junk you find on fleabay might just kill you.

Reply to
krw

Did you try searching

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? Do a search for "water heater timer".

If you want to DIY, you could probably use any time source, and then wire its output up to a "definite purpose contactor".

Also, check this site:

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According to my project notes that last time I did something very similar to what you described, I got most of the parts from here. And that was a low-budget project. Maybe you'll get lucky on prices, availability, etc.. for whatever you decide to do.

Reply to
mpm

of course it works, if you wire it up right. And you'd only need 14A contac ts. But if you can get something capable cheaply, why bother. I don't know about US products, but here many 13A timers only barely manage 13A, and deg rade over time. 10-13A Cylinder water heaters are not meant to go on 13A el ectrical accessories for this reason, so it may be wiser to get something a t least 20A rated, and not something of borderline quality.

Our immersions (UK) are normally 3kW, but 1.75 is fine really.

NT

Reply to
tabbypurr

You can buy a timer for the purpose. If you put something together for yourself you might run into insurance problems if you get a fire. And it might be a code violation in your jurisdiction.

Bill

Reply to
Bill Gill

On Feb 10, 2018, snipped-for-privacy@tubes.com wrote (in article):

Such things are commercially available, used to ensure that hot tub heaters

there are plenty of sources.

Joe Gwinn

Reply to
Joseph Gwinn

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