Cheap Chinese 2-stage Temp Controller

[johnfoster]

from the spec sheet

Relay contact capacity (Heating): 10A (max) 250 V
Relay contact capacity (Cooling):10 A (max) 250 V

remember your OHMS law: E * I = P
in other words Volts * Amps = Watts

therefore 250V * 10A = 2500W. that last number is the PEAK watts that this thing can supply. we really don't care about the other two numbers so much as they are relative to what is driving it and because the controller works on a range from nothing to lots. so if you run that in the US the max volts is 110. so we can figure out the MAX amps in reverse.

thus running it at 2500W / 110V = 22A which is 2 amps over a normal home circuit. for a typical chest freezer or fridge it is recommended to be hooked up to a 15A circuit. this is well within the range of this device.

also it appears that this using a physical relay that is doing the on/off not a digital circuit. meaning with the rating as shown it's a fairly stout device even though it say "mini" in the name.

[ajdelange]

... therefore 250V * 10A = 2500W. that last number is the PEAK watts that this thing can supply.

This is probably just a knee jerk reaction from the old EE in me but electrical equipment is nearly always specified in terms of rms voltages and currents so that 2500 would be the average (heating) power handling capacity of the device at 250 V. I think what you are trying to say is that 2500 watts is the maximum heating power the unit can handle (at 250).

...running it at 2500W / 110V = 22A ...

rms which would trip a 20 amp breaker but also be beyond the device's contact rating. At 110 V (rms) the max. the thing can handle is still 10 amps (rms) for 1100 watts average.

[Edit]:Also E*I = P isn't Ohms law but rather a combination of Ohm's Law (I = E/R) and Joule's law (Q =R* I^2*t) with the latter being significant because Joule did all his work in a laboratory which was part of his father's brewery.

[Kbar]

For the savings, I think I'll pick one up and put a little celcius to fahrenheit conversion chart next to it. Thanks for the info though... that is really helpful to know. I'd be really sorry if I did my first brew and set it for 69 C.

How long did it take for it to get to you?

PS: your cart is looking BADASS!

Do better than I did Anderson. Check and see if Ebay or this supplier have a DegF option. I may have just gotten the "rest of the world" version. There are a lot of suppliers on Ebay with these goods!

[TheDarkSide]

I've never used a dual stage but I'm about to pull the trigger on this thing. I have a question:

Do I need 2 probes? How do you get extras if I do need them?

No...just one probe. I bought mine prewired so it had 2 plugs. One for the freezer and the other for my fermwarp. Mylo posting the formula for setting the temps in this forum post:

http://www.thebrewingnetwork.com/forum/viewtopic.php?f=19&t=14746&hilit=ranco+2+stage

I wrote it on my chest freezer so I'd always remember.

[andersonimes]

Do better than I did Anderson. Check and see if Ebay or this supplier have a DegF option. I may have just gotten the "rest of the world" version. There are a lot of suppliers on Ebay with these goods!

I actually did contact them after I read your post. They said they didn't make a degrees f version, unfortunately. I have been searching for a dual stage like this for a while. A lot of times I've seen the Ranco on eBay for around $60 (prewired, which is nice) but that's the best I've seen.

I'm not even sure I'd be able to build one myself for this price. I'm willing to give it a shot for $20. The Celsius really doesn't bother me, honestly.

[Kbar]

Do better than I did Anderson. Check and see if Ebay or this supplier have a DegF option. I may have just gotten the "rest of the world" version. There are a lot of suppliers on Ebay with these goods!

I actually did contact them after I read your post. They said they didn't make a degrees f version, unfortunately. I have been searching for a dual stage like this for a while. A lot of times I've seen the Ranco on eBay for around $60 (prewired, which is nice) but that's the best I've seen.

I'm not even sure I'd be able to build one myself for this price. I'm willing to give it a shot for $20. The Celsius really doesn't bother me, honestly.

I agree. That is why I bought one. Damn Chinese

[Luthierzan]

It only took 11 days to receive it in Canada. When I get stuff shipped from the States to Canada it takes longer than that!

The device works great, but the instructions are horrible almost non existant. It took me a while to get it figured out.

It's a good buy IMO

David Oh

[Kbar]

It only took 11 days to receive it in Canada. When I get stuff shipped from the States to Canada it takes longer than that!

The device works great, but the instructions are horrible almost non existant. It took me a while to get it figured out.

It's a good buy IMO

David Oh

Yes, took me only 9 days to get mine. I hooked it up in 2 minutes and it seems to work well. Good luck guys!