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Can I run 1500 Watts Electric heater with a BT136 TRIAC? Answered

I wish to make a preset timer switch that can carry loads > 1000 watts. I plan on using a 555 timer preset to a certain value then connecting it to a BT136 TRIAC through an opto-isolator. Is it feasible? If not what are the other options I have?

Thanks in advance!



3 years ago

when I worked on welding machines, they would switch 600 amps using banks of trials in parellel. Each triac rated for 25 A and each bank controlled by a transistor.

The bt136 is rated for 4A so maybe 4 bt136 in parellel can do the job. I don't know about using the 555 for timing. I have found them to be unstable with heat and not good for welding.

The BT136 isn't rated to handle 14A (1500W @110V), or even 6.5A (1500W@230V)

Unless you are switching fairly quickly, a 555 is a lousy way to get long times, unless you take special measures.

On state 4 amps surge 25 amps I think you are right Steve but he could use it to run a relay.

The Triac Q6040K7 has a surge ability of over 300 Amps.

On state current is 4 amps you will need to connect it to a relay for current above that but yes it can be done.


4 years ago

So I wrote out a wonderful answer on the use of relays, but all of the text disappeared when I posted it, so simply put, use a relay not a semiconductor, for these long duration operations. Here is one with a huge margin of error for your wattage http://www.ebay.com/itm/like/290700438965?lpid=82

Its UNDERrated for a 110V load, and its conceivable the O/P is after low noise, zero voltage switching - only a triac and a zero crossing Opto can do that.

Any serious electrical water heater runs 240V (yes, even in the USA, just like dryers and ovens). 2000 watts @ 240 volts is only 8.3 amps, this relay would handle 10, so a total of 2400 watts. As for all that other stuff, there are plenty of comments on those alternatives. I just felt I should offer a more robust and easy option, there was no reason for you to try to discredit me and say my answer is completely wrong. A relay is a perfectly viable option for switching a water heater.

You seem to have come here with your own opinions and questions and rather than offer any benefit, you seem to have just told every commenter they are wrong. The writer of this original post didn't say he wanted zero voltage switching, he didn't say he wanted low noise. Maybe, he just wants his water heater off when he is at work!!! How crazy is that, and if he does wan't that, he can either look for some ungodly expensive retail timer with those high ratings, or he can use a cheap relay off ebay.

From what was asked, I see using a sainsmart (cheap unofficial arduino) nano, a relay, and a simple MOSFET for triggering the relay as the best option. This could be upgraded to all kinds of gimmicky things like wifi control via phone using a super simple server and wifi shield.

You seem to know what the OP wants. And you know what country he's from and you know what kind of load he wants to switch - since he already knows he wants to use an optocoupler to the triac, its seems a fair bet he know about zero voltage switching too.

Why not use a commercial plug in timer?


4 years ago

Yes it can be done but you don't need even need the transistor to make it work. The 555 timer circuit can be used by itself to trigger the opto coupler. Just make sure the opto coupler can handle the power draw of the heater.

No optocoupler I know can handle 10A. You CAN use them to trigger a triac though