Mould Question - Dew Point Issue?

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Mould Question - Dew Point Issue?

Postby reee » Thu Dec 05, 2013 6:30 pm

I live in Sacramento, CA. Generally it's pretty mild here. Over the spring, summer and fall I am able to keep my RH at about 73% and temp at about 52 - in the curing chamber in my detatched garage. Something happens in the winter, however.

I have the same environment, nothing changes, same air circulation etc... But for some reason, everything in the chamber gets a little damp and I get wierd fuzzy, cottonball type mould appearing. Sometimes it gets gray. Could this be related to dew point issues? Any thoughts?

(All due respect, I dont need responses about what to do with the mould - I know what to do there. I'm interested in curing the issue due to some rather expensive stuff that's haning in the chamber and generally wanting to solve this problem.)

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Re: Mould Question - Dew Point Issue?

Postby reee » Thu Dec 05, 2013 6:33 pm

I should add, I'm using almost the exact setup as Jason over at Cured Meats. The only thing I dont have is the ceramic heater (or a light bulb for that matter). Perhaps that could be it. http://curedmeats.blogspot.com/2013/02/ ... hange.html
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Re: Mould Question - Dew Point Issue?

Postby herjac » Thu Dec 05, 2013 8:12 pm

You need to install a heater to raise the temp so that the frig cycles on. If the ambient temp is low, the frig will not turn on and the humidity will rise too high. The frig must be a frost free type and when it cycles on the moisture in the air will condense on the cooling coils and drip down out of the frig, lowering the humidity. Some people figured out schemes to make this work with non-frost free frig types but it is easier to use frost free types.

I'm in Canada and my curing frig is in the unheated garage so I'm familiar with your problem....... 8)
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Re: Mould Question - Dew Point Issue?

Postby reee » Thu Dec 05, 2013 9:01 pm

Perfect. Do you have pictures of how that is done? Or a brief description?
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Re: Mould Question - Dew Point Issue?

Postby reee » Thu Dec 05, 2013 9:23 pm

never mind. Got my answer. Thanks so much.
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Re: Mould Question - Dew Point Issue?

Postby herjac » Thu Dec 05, 2013 9:37 pm

A heat source can be a light bulb, length of heater cable, a heating pad or ceramic heater for a terrarium etc.. Depending on the size of the frig, 40 watts up should do. A temperature controller is required to turn the heater on below the frig low temp off point and off at a point where the frig just turns on. Some fiddling with these set points is required. I have separate controllers for frig temp, heater temp and humidity.
Image

I don't have a photo of my light bulb heat source but there are many examples on this site.
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Re: Mould Question - Dew Point Issue?

Postby reee » Thu Dec 05, 2013 10:00 pm

Okay, excellent. Nice setup btw. I was thinking of doing basically what Jason Mollinari did and put in a heat source (likely a heating pad for a reptile) and just leave it on on a low setting. I figure that would force the cycle a few times a day. And I would not have to get a different controller.
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Re: Mould Question - Dew Point Issue?

Postby reee » Mon Dec 09, 2013 7:18 pm

Update: I installed a reptile warming mat. It appears to be cycling as the temp has rizen in the chamber. Thanks. Let's hope this helps.
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Re: Mould Question - Dew Point Issue?

Postby bwalt822 » Mon Dec 09, 2013 7:42 pm

I actually have kind of the opposite problem in summer here in the pacific northwest. The warmer temps in my garage cause the fridge (not frost free) to cycle on more which jacks up the humidity. Various configurations of door cracking couldn't solve it and i lost a batch and a half.
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Re: Mould Question - Dew Point Issue?

Postby reee » Wed Dec 11, 2013 4:56 pm

Back at it - there's a little funky mould starting to pop up on my stuff. Going to hit it with vinegar and hope it was starting to grow before the refrigerator started to cycle again. Here's to hoping. I had the same issue last winter...but the heating pad, in theory, should work.
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Re: Mould Question - Dew Point Issue?

Postby herjac » Thu Dec 12, 2013 3:28 pm

reee wrote:Back at it - there's a little funky mould starting to pop up on my stuff. Going to hit it with vinegar and hope it was starting to grow before the refrigerator started to cycle again. Here's to hoping. I had the same issue last winter...but the heating pad, in theory, should work.


I assume that your frig is frost free and you have a humidistat controller operating a humidifier. How high is the RH between frig cycles with your new heater pad on? How often does the frig cycle on? If the frig doesn't cycle often enough then the RH might still be too high for too long between frig cycles. How often do you open the door? Some people have installed systems with a small fan on a timer to regularly introduce fresh air into the chamber.
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Re: Mould Question - Dew Point Issue?

Postby wheels » Thu Dec 12, 2013 4:16 pm

Be very careful, if you use a fan. Mine was a very small 25mm fan running at half-speed, but still resulted in case-hardening.

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Re: Mould Question - Dew Point Issue?

Postby reee » Fri Jan 17, 2014 12:46 am

Just saw these replies. The long and the short of it is I bought a reptile heating mat and it didnt do much at all. So I am now installing the same setup Jason Molinari uses and I'm hoping that will cycle the fridge more. The odd thing is my humity reading on the thermo-hygrometer is pretty steady. But I just think whatever moisture is in there is not being circulated with new air and it's getting stagnant.

Herjac, I have no idea how many times it is cycling. Is there a way to tell? I can say it's not much, because the temp outside is lower than the temp in the fridge (it's in a detatched garage). This is strictly a winter problem.

Thanks so much all.
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Re: Mould Question - Dew Point Issue?

Postby herjac » Sun Jan 19, 2014 2:24 pm

You need to cycle the frig on to reduce humidity in the frig. If you install a heat source in your frig you should be able to see the increase in temperature on the frig controller. When you used the reptile heating mat did you see an increase in temp enough to cycle the frig on? If the temp is raised sufficient to turn on the frig you can see and hear it come on. The heat source should be sized to allow around 4 - 6 cycles per hour. If the heat source is too great it can overpower the frig and the frig won't shut down or have it cycle too often. Not a good thing.... In this case the humidity will fall too much and you will need to add humidity to compensate. If the heat source is too small then it won't heat up the frig enough to cycle on. These systems need to be balanced so that they are not fighting against one another...

If you use a light bulb or a ceramic heater for a heat source it must be sized, watts, to work properly. A dimmer switch might be used to help to control this.
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