Fermentation chiller

[Bilf]

Hello!
I'm not allowed to upload pics or links yet, sorry for the wordy post!

I brew ale at home, and have always wanted to temp control the fermenter.

There's 2 routes - cheapest is putting the fermenter in a fridge with a temp controller, expensive option is a glycol chiller, circulating through a stainless steel coil in the fermenter.

These rigs are expensive - $250 usd for the coil, pump and fittings, $999 usd for a 1/3hp glycol chiller.

Anyhow, I already have a 5 meter 3/8 stainless steel coil used for chilling beer (£10, thank you eBay), a stc 1000 temp controller (£11, thank you China) and compression fittings to fit the coil to the fermenter lid. I also have a 4m head pump (same spec as the commercial one).

So far so good.

To the point: I saw and purchased on a whim a water chiller unit from eBay that had been salvaged from a vending machine. It was too cheap to miss.

The compressor is a GD40AA@ 325 btu/h.

During testing it cooled 5 litres of water 10c in 20 mins. (29c to 19c) (1kcal / litre / 1c = 50kcal = 198.3 btu’s removed over 20 mins).

I calculate I need a cooling capacity of 12btu/hour for my fermenter (using an online brewing chiller sizing calculation), so the chiller has ample capacity.

In reality, I'm looking to bring 25l down from 21c to 19c, and, be prepared for summer weather (when brewing during a heat wave is a risk of getting to warm - more than 22c.

The plan is to chill/recirculate a 15litre reservoir of water in a cool box via the steel coil located in the fermenter, using the temp controller to maintain temp at 19c. When temp exceeds this, the controller will turn the chiller and pump on until the temp has dropped again.

Anyhow, the fan over the condenser is loud. It doesn’t sound like the bearings are gone, just a loud fan, high rpm and wind noise. I don’t think noise limitation was a design factor as the unit is from a commercial vending machine…

I’d like to swap the fan unit out with something quieter – although am wary of making a potential fire hazard / ruining the compressor. The fan is an axial fan, the same size as a pc psu cooling fan and am thinking of getting a “silent” pc fan and retrofitting it.

I guess is comes down to airflow – if the airflow of the new fan is not adequate I think run the risk of the compressor over heating and seizing up.

I’m thinking that, as my cooling needs are far less than the unit is capable of, a smaller fan will mean the unit is running longer to cool the same volume of liquid.

I think the unit will only run for ten mins / hour, and max temp output during fermentation is over 72 hours, then tapers off.

The existing fan doesn't have any serial number so I don't know what it's airflow is, so I'm unsure how to size the replacement.

I'm also curious / concerned that if the coil in the fermenter doesn't exchange heat quickly enough my reservoir could freeze, however I understand a glycol mix can be used.

What do you think of my plan?

Can anyone help regarding suggestions for replacing the fan? I don't want to make a fire hazard or cause the compressor to overheat and fail.

Is using a commercial water chilling unit in this way (recirculating and cooling a reservoir of water / glycol) a good idea? I know it's not as the device was intended to be used.

I really appreciate any thoughts / concerns / input you can provide.

I'll upload pics if/when people are interested and I have enough posts.

[Cimerian]

When I brewed beer I found that a cheap small used chest freezer was the easiest option. I just added in a temp controller so i could adjust temps from 70F down to 32F. I wouldn't think a coil you submerge in the beer would be a good option because of the chances of contamination. Beer is very picky about being kept clean or it will be ruined. Any extra equipment or utensils you add to the process increases the chances of contamination.

Sent from my SM-G900P using Tapatalk

[BBeerme]

I built an insulated closet in my garage with refrigeration. Controlled, of course, by a thermostat.

Fermented in five gallon glass bottles with an air lock.

[Bilf]

I don't want to go down the chest freezer route, mainly for space reasons, as well as logistics. I don't fancy moving full fermenters when my current setup doesn't require this. I like the idea of the chiller from a "boys and toys" perspective.

Sterilisation of the coil isn't an issue - it'll be fitted to the inside of a stainless steel fermenter - this is both chemical and heat sterilised before use.

My main concerns are not causing a fire or compromising the unit replacing the fan for something that doesn't sound as loud.

[Cimerian]

I'm not seeing how the space would be an issue. I went with a small chest freezer that barely held a 5 gallon carboy. If it is just the fan noise you are worried about you get a smaller fan and add in a water pan to assist it. A small coil in a bucket of water should easily make up for the loss of air flow.

Sent from my SM-G900P using Tapatalk

[trippintl0]

You need to get together with this guy http://hvac-talk.com/vbb/showthread....-mini-split-AC and buy his 1/3hp unit from him LOL

[BBeerme]

[trippintl0]

Regarding installing a quieter condenser fan motor, I think the easiest test is just to measure the temperature of "liquid line" coming out of the condenser coil. Usually this line is lukewarm to warm. If the liquid line gets hot - like difficult to hold onto with your hand - then the new fan is probably not moving enough air across the coil.

I suppose you could also measure discharge line temperature (6" away from compressor, before line goes into condenser) with a thermometer. Compare before and after temps with new fan. Put a rag or somethibg around thermometer to insulate it from the condenser airflow. Good temp ranges are 150f - 190f. Much hotter than that and the compressor oil starts breaking down (225f I think is where POE oil breaks down, and you lose some heat on discharge line measurement do to airflow across the discharge line, so a measurement of 200f might really be 225f inside compressor, others on this forum will know better that me and probably chime in exact discharge temperature "safe" ranges). A discharge line that is too hot means a compressor that will fail prematurely - though likely not a "fire hazard" as you said. Fire hazard would be more likely due to poor electrical work, so make sure you have somebody who is good with electrical look it over if you're not confident.

Just so you know, changing a consenser fan motor can affect the way the whole unit runs - if the new fan is quiet but moves more air, the unit may need more refrigerant charge and may actually respond like it is low on refrigerant and not cool well at all.

Sent from my SAMSUNG-SM-G890A using Tapatalk

[trippintl0]

One thing you may find with the water chiller - though you say it's oversized for your application - the btu per hour rate is not based on the minimal temp rise you care to see. It is based on the temp difference from fermenter temp vs chilled water temp. I'm guessing 40f water going through 60f or 70f product. You might find that the water chiller warms up FAST and basically runs in a fully loaded, hot pull down type of condition for hours. This may very well put the chiller out of its design temperature range, resulting in premature failure, or frequent cycling of the compressor by thermal overload - in other words, it may not work like you expect. The only way to regulate it would be a way to vary how fast the circulation pumps run. I'm picturing a variable speed DC circulation pump coupled with some kind of speed controller rated for that type of pump.

Sent from my SAMSUNG-SM-G890A using Tapatalk

[Bilf]

trippintl0: That's a really helpful set of things to check. I guess I'm only going to know if it will work by trying. Measuring the temp of the liquid line before and after fan replacement sounds like the best thing I can do to assess any impact on performance, and again during fermentation to see if it can handle the generated heat.

I'm not aiming to bring the temp down much, only 21c (70f) to 19c (66f) for 25litres (6.6 US / 5.5 imperial gallons), using a 15 litre (4 US / 3.3 imperial gallon) reservoir in a igloo coolbox. Most of the generated heat is over the first 72 hours of fermentation, then it really calms down. I'm thinking if putting a fermenter in a fridge won't overload it's compressor, the chiller and temp buffer the reservoir will provide should also work.

However, I'm not a hvac engineer and value your input on the subject.

On an academic note, can you explain why an increased airflow over the condenser could result in decreased cooling efficiency?

BBeerme: like the cupboard! What rating / btu chiller do you use, how many fermenters do you have on the go simultaneously and what's your ambient air temp?

[trippintl0]

Increased airflow could cause too much liquid refrigerant to stack up in the condenser coil, decreasing hi side pressure, resulting in less liquid refrigrrant in the drier. The lack of liquid wil boil off into a vapor to "fill the void", so to speak, before it hits the cap tube. Vapor bubbles won't flow through the cap tube, so you end up with a shortage of refrigerant in the evaporator (starving evaporator). If you ever have gauges on a cap tube system, splash some water on the condenser and watch suction pressure drop and pull into a vacuum due to the liquid refrigerant stacking up in the condenser coil.

Sent from my SAMSUNG-SM-G890A using Tapatalk

[jim147]

Only a few little freezers use a fan. It was an add on in really hot locations but shouldn't be needed in a normal hot wall set up doing those temps.

[BBeerme]

I haven't brewed for several years now, but did brew for a few decades. The idea is to always have something in a carboy so when one of the [five gallon] kegs gets empty, you can fill it right up. So I'd always have something waiting. Used to like having each of the four taps with something different.

Ambient in the garage can get pretty hot in the summer. Have to go look at the compressor to see the capacity, everything was scavenged off of one job or another. Just put it all together and made it work.

trippintl0: That's a really helpful set of things to check. I guess I'm only going to know if it will work by trying. Measuring the temp of the liquid line before and after fan replacement sounds like the best thing I can do to assess any impact on performance, and again during fermentation to see if it can handle the generated heat.

I'm not aiming to bring the temp down much, only 21c (70f) to 19c (66f) for 25litres (6.6 US / 5.5 imperial gallons), using a 15 litre (4 US / 3.3 imperial gallon) reservoir in a igloo coolbox. Most of the generated heat is over the first 72 hours of fermentation, then it really calms down. I'm thinking if putting a fermenter in a fridge won't overload it's compressor, the chiller and temp buffer the reservoir will provide should also work.

However, I'm not a hvac engineer and value your input on the subject.

On an academic note, can you explain why an increased airflow over the condenser could result in decreased cooling efficiency?

BBeerme: like the cupboard! What rating / btu chiller do you use, how many fermenters do you have on the go simultaneously and what's your ambient air temp?