cudaaar

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Has anyone used a line voltage controller (the cheap bimetallic type) for fermentation control? I've read that they are inaccurate, but that can be calibrated so long as a given knob setting corresponds to some average temperature. I've also read that they swing the temperature quite a bit, but with five gallons of beer I don't expect that to be a problem.

Jaybird

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They dont work that well on refrigeration, Mainly because the compressor needs to run full voltage. Your way better off with a relay type like a Rancho or Johnson, both work well and are fairly cheep.

Also it dosent really matter if its five gallons or five hundred gallons, Temp control is one of the most important aspects of creating consistant results in brewing.
JJ

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aa8jzdial

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I am not sure what you mean by line voltage controller.
Bimetallic strip must refer to the temperture sensor.
Do you have a better description / link?
r

cudaaar

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Jaybird:

I intend to use it to control a small heat lamp. I have an insulated upper compartment in my refrigerator dedicated to to fermenting two carboys (serving temp in lower compartment). I just need to raise the temp in there by about 15F-- it maintains temp quite well once heated.

When I say that large fluctuations don't matter, I mean that I am assuming that the temperature of a 5 gallon carboy will not see the same fluctuations as the air in the compartment, though it will depend on the duty cycle ultimately...

aa8jzdial:

have a look at this one: http://www.grainger.com/Grainger/items/2E158 It has a temperature differential of 2-4 degrees. A 40watt lamp at 120V would draw 1/3 amps.

I'm just looking for a cheaper solution to temperature control. If someone can tell me why an LVC will not work, I can avoid wasting $20. Anyone try one?

Shakespeare

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cudaaar, Your topic caught my eye. This is my first post and I joined here to learn a thing or two about beer brewing. I'm in the controls and automation business so I can comment on your concept, however how this plays into the process of fermentation I won't be able to help as I'm a stark naked brewing newbie.

The LVC's are inexpensive and perhaps not the most accurate device to maintain even temperature. The two degree differential that the controller you linked to at Graingers essentially means that the unit will turn on at one setting and two degrees later it will cut off. After a two degree cool down it will cut back on. If you could only maintain temperature within 2 degrees then that would be a good thing. The issue is the actual temperature swing will be more than the controller differential during cool down and heating periods due to latency. That's the nature of on/off control. The temperature looks like a sine wave basically. I would suspect that your brew won't see those temperature swings since there's quite a mass of liquid in the fermenter and hopefully its temperature will average out. So to answer your question, if your brew can tolerate those temperature swings on the outside, then the concept should work. You may have to play with the wattage of the bulb so that the temperature swings aren't too erratic... a lower wattage bulb being better because it takes longer to heat up the environment and the overshoot will be minimized.

I hope this helps.

Mike C.

cudaaar

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Thanks Mike. Is "latency" in this case the extra time needed to raise the temperature of the bimetallic strip? On the Grainger site I see "Differential (Deg. F) 2h/4c". Do you know what 2h/4c means?

Shakespeare

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Latency means that when the instrument cuts power to your lamp that doesn't necessarily mean it's done heating as the lamp has residual heat that it gives off and the environment that it is in will continue absorbing that heat. Similar to the way a brick patio stays warm after the sun goes down. The opposite is true during the "off" period. The temperature is falling and even though the lamp kicked on at some point, it has to overcome the declining heat loss in order to catch back up. So what you end up with is a temperature swing that's +/- a degree or two beyond the controller differential. Keep in mind that this is all theory talk. Until you actually put the instrument into use and start sampling the temperature and doing some sort of analysis you won't know how severe this anomaly is. The point is there is some validity to what you hear about LVC's being a little sloppy in controlling the temperature. Oh, I thought of another good example. If you've ever been in a house with baseboard heating then you've experienced first hand the amount of temperature swing that the room has while waiting on the unit to satisfy the temperature.

The 2h/4c thing means 2 degrees differential in heating mode and 4 degrees differential in cooling mode.

Mike C.

dcunitedfan

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An interesting aspect to using temperature controllers for brewing is where exactly the probe goes. If you leave it open to the air inside your fridge, then the temp of the beer is likely to stay bounded as the air temp rises and falls around it...but also since fermentation is exothermic, it may be higher than you expect. To deal with this, some people (Jamil) advocate attaching the probe to the side of the carboy with something like bubble wrap so that it picks up the temp of the glass (which should be very close to that of the beer) and is insulated from the air somewhat. So that way you should be able to keep the beer temp closely tied to the target temp, albeit still cycling between a high and low value.

Any thoughts on this issue Mike?