Position of SCR

[Wozza]

OK, complete klutz as far as electricity goes. And I've done a fair amount of searching for an answer to this but a lot of the discussions simply go over my head. There was one thread that suggested what I'm going to ask might work but nobody said if it actually did. So...

I've got a boiler made from an old tea urn. 2.4kW element that has a controller on the side of the boiler running from 0 to 5. If it's set to 5 it will boil all day (well, a couple of hours at least when I've used it for brewing). If I set it to anything else, it will shunt off around any given temperature with a plus or minus range of about 2 or 3 degrees. And I want it to run continuously to give me a reasonably exact and constant temperature so I can run a reflux off it.

The controller and the element has wires coming and going every which way. There's earth, neutral and live on the element plus a couple of connections which are maybe the sensors for the temperature feedback to tbe controller (?). Anyway, I bought a 10000W scr for a few bucks. It's got three connections: IN, OUT and COM. It seems like you connect the live to the IN and then run the live from the OUT to...where you want it to go.

Rather than wire this directly to the element (I'd get an electrician buddy to do this if it's the way to go) can't I simply wire it in between the power and the element controller? Then I can set the controller to full on so it's telling the element to stay on, then adjust the power to the controller via the scr. If I feed 180V (I'm on 240V) to the controller then does the element receive 180V and give me 180/240 x 2.4kW equals 1.8kW? Or does it screw up my controller..?

I've got a spare element so I can try wiring that up directly without fart arsing about with the existing system. But thought I'd ask if the above set up would be the easiest way to go.

Thanks in advance.

[Setsumi]

the live goes in the In and out the Out, leave the Com. the problem with urns are they have a heat sensor between the element connections and element. i do not know how to bypass it. but if #5 does not switch of your plan will work. just put a fan on the SCR for extra heat management on the SCR.

last, you are correct that you want a continious setting. but it is not continious temprature. you want a continious power input to achieve a continious boil at a specific rate. and luckily that is just what the SCR does.

[Yummyrum]

Agree with setsumi .

If I feed 180V (I'm on 240V) to the controller then does the element receive 180V and give me 180/240 x 2.4kW equals 1.8kW?

Yes your kinda right but its not directly proportional .
You need a bit more math .Ohms law stuff .
First you need to know the resistance of your element . ( because it doesn’t change ).you can calculate that because you know its a 240V 2400W element .

R = V^2/P
=240x240/2400
=24ohms

So now you know the resistance of your element , you can calculate the power from the voltage.

P = V^2/R
=180x180/24
=1350watts.

[Demy]

Hi, I often use an electric plate so similar to your situation, I suggest you raise your original thermostat to 5 (I guess it is a bimetallic system) then connect the plug of this to a socket of the scr (yes, I recommend a socket) . This way it will work perfectly without changing anything, plus you can use your scr in different kettles or devices

[shadylane]

+1 Demy

[Wozza]

Hi, I often use an electric plate so similar to your situation, I suggest you raise your original thermostat to 5 (I guess it is a bimetallic system) then connect the plug of this to a socket of the scr (yes, I recommend a socket) . This way it will work perfectly without changing anything, plus you can use your scr in different kettles or devices

Thanks for the help guys. Much appreciated.

So Demmy, just to clarify this in my own mind...I'd wire a plug to one end of a cable then the other end to a socket via the scr. The scr would have just the live going in and out from it. So the socket would have the neutral and earth from the cable and the live from the scr.

Then I simply plug the scr into the mains and then plug the element into the scr's socket. Put the element thermostat to the max and control the power input via the scr.

I guess if I wanted to test this I could plug a lamp into the scr and see if it acts like a dimmer.

Sounds great to me. When I have it set up I'll report back on how it's working. Damn, can't wait to get that reflux up and running.

[subbrew]

I guess if I wanted to test this I could plug a lamp into the scr and see if it acts like a dimmer.

That will work if you can still find an incandescent bulb for your lamp, not an LED. Those are getting harder to find here in the US

[Setsumi]

I guess if I wanted to test this I could plug a lamp into the scr and see if it acts like a dimmer.

That will work if you can still find an incandescent bulb for your lamp, not an LED. Those are getting harder to find here in the US

rather test it with your electric kettle in the kitchen. just remember if you upscale the watts on your element a standard plug and socket only handles 16A... wel here in my woods.

[Demy]

Here on my little youtube channel there is an old video that I think will help (it is not specific for distillation but it is very similar)

[AlWorms]

Ebay etc have little power/Amp meters that read through a coil around the wire to your element.

If it's on the output of the SCR, you can see what the element is drawing/ or what the SCR is limiting it's draw to.

[Setsumi]

Ebay etc have little power/Amp meters that read through a coil around the wire to your element.

If it's on the output of the SCR, you can see what the element is drawing/ or what the SCR is limiting it's draw to.

+1. an Amp meter are your eyes on electric

[Wozza]

Thanks again to all who replied.

I wired the scr up and plugged in a lamp with an incandescent bulb. Worked well. Just as a dimmer would. So put some water in tbe boiler, plugged that in to the scr, turned the boiler control to full and the scr to about 8/10.

And...it appears to work as needed. It took the temp up to around 87 degrees and it dropped very slowly from there. But I think that was simply a function of low thermal inertia (I only had enough water to cover the element). But there was no shunting on and off. If I'd try to adjust the temp using the boiler controller then it would have fluctuated between say 85 and 89. Tried another couple of settings and all good.

Rock and roll! I've got some old sacrificial spirit that I saved last time I did a cleaning run so I'll run that through the reflux when I get the chance and get some experience on balancing power in, condenser flow and valve adjustment.