Double-R
Well-Known Member
www.duralite.com/store/scripts/prodView.asp?idproduct=83
plus this
www.duralite.com/store/scripts/prodView.asp?idproduct=87So for about 60$. I could control a 5500W 240v Element with no SSR. Would it work
How about This
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Sawdustguy
Well-Known Member
You don't really give enough information to answer but I will try to lay it out. If you are trying to control your mash temperature this is not a good solution because your controller reads our in percentage. If you are controlling your mash temperature $70 will do it for an SSR, PID and sensor and be much, much more accurate. If you are simply controlling the boil, this will work but a SSR and PID (no sensor needed) will be slightly cheaper.
If you insist on using that for boil, you might want to check the cycling frequency. IIRC, the Auber is adjustable, a they recommend a 0.5Hz cycle for an SSR. If the frequency of the control kit is something like a minute, I don't think it'll work.
As was mentioned, it would be the same price to get an Auber PID with manual mode and an SSR+heatsink, so you aren't saving any money here.
But, even if your two items were significantly less expensive, they will not work the way you are thinking.
Infinite switches are mechanical devices that use bimetallic strips inside of them. One side of the strip is made of one kind of metal. The other side of the strip is made of a different kind of metal.
When current flows through the strip, it begins to heat up. When it heats up, the bimetallic strip starts to curve (one metal expands more than the other as they get hot).
It's this bending of the bimetallic strip that forms the switch for the device. When you turn the dial, you are moving a contact point along the length of that strip.
So, with the knob set to low, it takes a very small bend to break the contact and cause the juice to shut off. With the knob turned the other way, it takes a much larger bend to break the contact.
Once the contact is broken, the strip starts to cool off and will bend back in the other direction, which will cause the switch to close again and begin to heat up.
That's how they work, in a nutshell. The important part is that the heating up of the switch is caused by having electric current run through the thing.
The switch you linked to us meant for directly powering a pretty good sized heating element, which means lots of current will be flowing through it, and that causes the strip to heat up at a good rate.
The relay you linked to has a coil that is just 4 volt-amps, which is pretty much 4 watts. 4 watts, on 240V, draws only .016 amps. Nothing near the 15A that that infinite switch is capable of handling.
With only 0.016 amps flowing through the infinite switch, it is going to take a LOOOOOONG time for the strip to heat up enough to break the contact.... if it ever even DOES heat up enough.
edit: someone please correct me if I am wrong here on how infinite switches work. I looked them up one time when I was considering one for my BK control and read about them, but I might be wrong.
Oh... and you can get a pulse width modulator and an SSR to control the boil kettle. That would only cost you about $20.
Junkster
Well-Known Member
Hmmm..... I thought (from what I've read about those switches) that they have an internal heater that causes the bimetal strip to deflect and are totally independent of the load which they're switching. Their rating in amps is the max current that the contacts are designed to carry - like any other switch. I don't have a link off hand to reference at this time, but could probably find it.
Can anyone explain why the relay is necessary? The installation instructions on the infinite switch seem to say to hook it directly to the heater, no?
Here's the link to the installation instructions
Here's the link to the installation instructions
Junkster
Well-Known Member
That's for direct control of a heater which is within the rating of the switch.
"Switch Electrical Ratings:
120 Volt- 15 Amp- 1800 watt
240 Volt- 15 Amp- 3600 watt"
It states further: "To control higher wattage heating loads, it can be used with KILN RELAY, 30 AMP (DURAG001) type relays."
"Switch Electrical Ratings:
120 Volt- 15 Amp- 1800 watt
240 Volt- 15 Amp- 3600 watt"
It states further: "To control higher wattage heating loads, it can be used with KILN RELAY, 30 AMP (DURAG001) type relays."
Ok, that would make sense if they used an internal current path to heat the strip. It would be a much better design for sure and means that it could be used with any kind of load.
Though, I still don't know if it would work for boil strength control on a kettle, and is more expensive.
I think the cheapest solution is the pulse width modulator and SSR.
Junkster
Well-Known Member
I think the infinite control + relay would work to modulate the power for the boil just fine, but it would be a relay or contactor banging on / off with the pulses. The PWM / SSR solution would, IMHO, be the better, more elegant (and cheaper) approach. Plus, it eliminates mechanical components which would probably require maintenance in the long run.
I'm not so sure it would work well.
On a range top, it works because even when the heat shuts off, there is a lot of trapped heat in the element to continue the boiling action. With an electric element mounted inside of a kettle, the heat transfer from the element to the liquid is extremely efficient. There is no heat left hanging around when the element shuts off.
Unless that infinite switch cycles VERY rapidly (every 3 seconds or less), then you are going to end up with a pulsing boil.
BOIL
stop
BOIL
stop
I am speaking from experience here. I use a DIY pulse modulator to control my boil strength, and I made the cycle time a little longer than I should have. If I drop it down to 75% power or so, it visibly pulses.
Junkster
Well-Known Member
That's interesting! I don't know what the frequency or duty cycle of those infinite switches is - maybe someone else will chime in here. It seems like I read somewhere that someone had one rigged in the boil kettle & it worked ok. I suppose these things may vary somewhat depending on the manufacturer. Also, it might vary too depending on the liquid volume / mass in the kettle?
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