Brew-fridge Tube Heater Power?

[morethanworts]

Hi

I've just (FINALLY!) managed to acquire a 5ft tall fridge ready to convert. I have an STC1000 box already built and working, but I need to know a good tube heater to buy.

Would 50W be enough to reach right up to saison temperatures inside the fridge (say 25C) even in the depths of winter in my shed, or should I go for more Watts?

It seems best not to go stupidly over-powered, to encourage a slightly more gradual heat release, but I need to know there's enough.

Thanks

 

[pittsy]

It's a fridge which is an excellent insulated box so a small amount of heat will easily be retained in it and a tube heater is designed for a greenhouse so a 50w is enough , i have a 60w and have no problems .

 

[morethanworts]

OK, thanks Pittsy.

By the way, is there generally a best place to drill to get the power cable through, to miss the most likely places where the fridge will have 'vital organs'?

 

[PD]

The cable can just be trapped in the door seal, no need to drill.
Or you and feed up the drain hole.
Only safe place to drill is the door if you need to

 

[morethanworts]

OK, thanks for the help. So I'm set on a 30cm 50W tubular heater for the fridge.

Same theme, different question: I want to buy something similar to keep the shed (brewhouse!) a bit drier this winter. It's a double-fronted, double-size-shed, drafty and poorly insulated affair, which got very damp last winter and needed a total scrub-out. Any idea roughly how much power I would need just to keep some of the damp away? Doesn't need to feel warm as such.

I'd save a bit on postage if I ordered it at the same time as my brew fridge heater.

 

[Touchstone]

If you buy a greenhouse type fan heater with thermostatic control you can select the optimum heat level. Maybe to insulate the shed too.

 

[graysalchemy]

They are not accurate enough Touchstone and really you need to be able to cool as well as heat as fermentation is exothermic. :thumb:

 

[morethanworts]

They are not accurate enough Touchstone and really you need to be able to cool as well as heat as fermentation is exothermic. :thumb:

Just to be clear, the second heater I referred to in my last post is just to help with damp in the shed. Nothing to do with brewing, which will all be going on in the fridge with the first heater and control box. :thumb:

So maybe a greenhouse fan heater with thermostat, rather than a tube then. Running costs will be a big factor. :hmm:

 

[graysalchemy]

:thumb: :thumb:

Didn't read it properly.

 

[joe1002]

The back of my fridge has a 'box' and all that is behind it is the compressor etc. I carefully drilled through it and put the heater power cable through there. I used the drain hole to feed the STC sensor through.

You can just about see the wire i the bottom right of this picture:

 

[graysalchemy]

Is your stc probe in a container of water?

If so it may not give a true reflection of the temp of the fermenting wort as fermentation is exothemic and the temp inside the fermenter could be a degree or two above that outside. I use my sensor in the wort. :thumb:

 

[morethanworts]

Is your stc probe in a container of water?

That's so interesting!

I was thinking of experimenting with putting the probe in different quantities of water, like you appear to have done, to simulate some of the lag that the wort will show in responding to the heating/cooling.

In deciding where to put the probe, these are my thoughts so far, from what I can gather. Please read them as ongoing thoughts, rather than firm conclusions:

-Although the fermentation is exothermic and the wort may get warmer than the air around, putting the probe in the wort itself would create a massive lag in response to both the heater and the fridge. Although the control box would know the proper wort temperature, by the time each dose of heating or cooling had reached the probe, there would be such a build up of cool or warm air around the FV, that it would then overheat/overcool way beyond the intended temperature, every cycle, widening the high-low swings. This effect may be reduced by at least having the probe in the outer edges of the wort, perhaps. [Then there's the slight increase in risk from nasties on the probe infecting the beer.]

- Having the probe mid air means a much quicker response to the heating/cooling, but then opens up all the opposite concerns to those above, ie - not enough lag; swings back before the wort has had chance to catch up. But, in theory, if the air inside the fridge is kept at the right temperature, it reduces the room for error to just that which is caused by the exothermic reaction - and it's maybe easier to guesstimate an adjustment for that over the first three days or so of each fermentation than it is for an ongoing lag from a probe within the FV. :hmm:

I'm going to do tests, obviously, though they will be with (unfermenting) water. But when I've used a water bath and aquarium heaters, I've found the vertical gradient to be more pronounced than the effect of the exothermic reaction, which was never more than a degree C or so in the admittedly few readings I took, at the same height, inside and outside the FV.

 

[graysalchemy]

I use a maxi chiller and a tube heater in an insulated cabinet and I keep my temps spot on. They never over shoot and may only drop 1c below my target which isn't a problem. As long as the beer stays constant it doesn't matter what the temp outside is. If your glass of water is reading 21c but 21c equates to 22-23 in the beer then you have a problem, better the beer is with in range albeit fluctuating than being over temp.

 

[orlando]

The only method I have ever tried is taping the sensor to the outside of the plastic fermentor about 1/2 way up the wort, insulated with some bubble wrap it stays within .5 of a degree for the whole of the fermentation. I keep a daily log of what the STC is set at, what the wort temp is and what the SG is, as I keep an attenuation chart for each yeast used in order to understand its profile and whether there is a problem. This has convinced me this works very well and avoids a few issues on the way. I don't think there is one perfect method but this one is pretty close.

 

[morethanworts]

Thanks guys. I can see merit in all three methods. Time for some experimentation. :thumb:

 

[Wezzel]

+1 for attaching to the outside of the fermenter. I don't even tape mine I just put a big wad of bubble wrap on top and hold it in place with a bungy cord.

 

[Doingatun]

I've a larder fridge with a 45w tube heater, both controlled by a ATC 800, wired with a 230mm long stainless steel sensor/probe that I push through an airlock grommet in the fv lid, immersed in the wort.

 

[joe1002]

Is your stc probe in a container of water?

It was for my first brew in the fermentation fridge GA, but I now put it about half way up the FV with some bubble wrap to insulate it against the air temp in the fridge :thumb:

I have thought about putting the probe directly into the wort but haven't done it as yet. Some interesting thoughts here :thumb:

 

[anthonyUK]

One thing for sure is the probe needs to have some thermal mass to stop the see-sawing.

I've nearly finished my RasPi temp logger and can see the benefits of this.
I have two types of logging sensors which show roughly the same result of Fridge1. Fridge 2 only has one type of logging sensor so is only shown on the top image.
Both Fridges are STC-1000 controlled. Fridge 1 the sensor is attached to the FV and the logging sensor is in liquid.
Fridge2 the STC-1000 sensor is just in air as is the logging sensor.
The variance in Fridge2 is due to the differential value (F2) which looks to be set at 1.0°c.

 

[Wezzel]

As per my earlier post my temperature probe is simply held against the side of the FV with a wodge of bubble wrap and a bungy cord.

I have just checked and the STC reads 19.2 degrees while the measured temp in the wort is 19.0 degrees. That's good enough for me and means there is one thing less to sanitise that comes into contact with the wort. :-)