Bypassing a fridge thermostat?

[homebrewdude]

I have a industrial type SS fridge.
I think this can either be a fridge or a freezer, but the thermostat is
the limit.

I am currently running a Johnson digital control on it.
I would like to bypass the internal thermostat and have it turn off and
on based on the johnson control.

Can I just jumper the thermostat? Or is this more complex?

[Dick Adams]

homebrewdude <homebre...@ATyahooDOT.com> wrote:

Take this question to alt.home.repairs.
Great newsgroup for home projects.

Have you measured the limits on the thermostat?
My experience is that the lower limit can be as
low as 42F and the upper limit as high as 65F.

How old is it? I went through three fridges and
two freezers I got for free. Finally I bought
new "energy efficient" ones - my electric bill
dropped $120 in one year.

Dick

[Wayne]

No need to bypass or jumper the thermostat at all. Just turn the fridge
to its lowest setting and plug it in to the Johnson control. The
Johnson unit will keep it an any temp you want that is at or above the
minimum temp the internal thermostat will keep the fridge.

Wayne
Bugeater Brewing Company

[homebrewdude]

I want to see if I can use the fridge to freeze also.

This is an industrial "true" bramd SS unit.

[Bob F]

"homebrewdude" <homebre...@ATyahooDOT.com> wrote in message
news:c_ydnQ3S1-txTErb...@comcast.com...

If you want to go colder, you need to find the connections to the thermostat and
connect the controller in parrallel to the contact connections there. Disconnect
the wires from the internal thermostat and connect to the controller for full
range operation. You may find that the unit will not perform well as a freezer.

Bob

[MDixon]

homebrewdude wrote:
> I want to see if I can use the fridge to freeze also.
>
> This is an industrial "true" bramd SS unit.

Try the settings on the thermostat that came with the unit first. My
back bar bottle cooler would freeze just fine and yours may do the same.
The thermostat that came with the unit would go from 0F to 65F...but of
course I had to put a thermometer in the thing to set the desired temp.

Cheers,
Mike

[wayne edgin]

I picked up a Beverage Air zero degree freezer and took the variable
resistor out and jumped the wires together. Then pluged the unit into my
external controler and pluged the controler into the wall. Now the freezer
goes on and off at what the controler is set for. You'll see a knob for
cooler/warmer or numbers. Take that unit out and connect the two wires
together. It will run forever like that or until you plug the unit into the
controler.
Takes about 10 minutes.

"MDixon" <m...@privacy.net> wrote in message
news:5jr4v8...@mid.individual.net...

[guiller...@elire.com]

Hi Everyone,
Any ideas on how to bypass a digital thermostat? I'm also trying to bypass the thermostat; unfortunately mine is digital (Magic Chef HMBC58ST)
Thanks!

[Joerg]

Looks like their can cooler:

https://www.homedepot.com/p/Magic-Chef-Beverage-23-4-in-154-12-oz-Can-Cooler-Stainless-Steel-HMBC58ST/300509606

For fermentation I am using a wine fridge from Vinotemp and this had the
same problem, a high-falutin LED deal with micro controller and all
that. The only way to handle those from a brewer's perspective is to
find out what this controller does.

In most cases (and also in mine) this kind of fridge simply issues a
control voltage when it demands cooling. That voltage engages a relay
(a.k.a. contactor) which turns on the compressor and the fan. If I
wanted to simply bypass all this I'd jumper the relay contacts shut and
then control from an outside box.

I ended up not doing that but added in my own electronics and kept the
LED display and some other stuff. Now my homemade electronics board
controls the compressor/fan relay and it also has a heating function for
winter which it didn't have before. Since September 2016 there hasn't
been a single day where there wasn't something fermenting in it.

http://www.analogconsultants.com/ng/brew/chamber1.JPG

Heater module, controlled via the former light relay:

http://www.analogconsultants.com/ng/brew/chamber2.JPG

Be careful, don't probe around in it with the power cord plugged in.
Happens easily.

--
Skol, Joerg

http://www.analogconsultants.com/

[guiller...@elire.com]

Hi Joerg,

Thank you for your prompt response, I really appreciate the help.

In this case, I want to just bypass the thermostat and control from an outside box to get the can cooler to reach a couple of degrees colder. Should I do it at the PTC Starter Relay? Or should I do it at the thermostat level?

What email address can I use to send you the pics of the PTC Starter Relay and the electronics board that has the thermostat?

Thanks again for the help!!!
Best regards
Guillermo

[Joerg]

Hello Guillermo,

The one in my header is valid, I got your email (and just responded).

Long story short, for others that might want to do this: Most such
fridges have NTC thermistors as temperature sensing elements mounted
somewhere in the back of the box. To fool the controller into thinking
the temperature is higher than it actually is you can parallel a
resistor to that. If you want to stretch the upper range and fool it
into thinking it is colder than it really is you can connect a resistor
in series. The temp display will then no longer be correct and also
become non-linear but one can place another thermometer inside. Or
calibrate it and use a look-up table.

The other alternative is to wire the compressor relay contacts shut as
long as that also controls the condenser fan with yours does, then
control from an external device. The internal controller now becomes
fairly useless. In your case you'd then also likely have to disconnect
the heater.

I have explained it in a bit more detail in my email to you but that's
more geared towards your particular fridge model.

--
Regards, Joerg

http://www.analogconsultants.com/

[baloonon]

Joerg <ne...@analogconsultants.com> wrote

> I have explained it in a bit more detail in my email to you but that's
> more geared towards your particular fridge model.

I've also seen references to people connecting a temperature probe to a
Raspberry Pi that then turns the fridge on or off, although I have no idea
of the relative merits of different approaches.

[Joerg]

You can use a Raspi but that's a lot more work. Before I scored a used
wine fridge I worked with this controller:

https://www.amazon.com/WILLHI-Temperature-Controller-Thermostat-Improved/dp/B00V4TJR00

Much easier because someone else already did all the programming of the
micro controller in there, it contains the relay, an enclosure and, best
of all, a wide range power capability. The latter was important to me
because our Bosch fridge is from Germany so needs 230V. I have an older
version Willhi controller which still has an IEC power input so I could
plug in a standard German Schuko cable. Its output accepts an English
plug for which I had made a travel adapter, so that was plug-and-play as
well.

Now I have the wine fridge which I stripped, installed sturdy shelves
and built some electronics to adapt it so it can also heat in winter. It
can hold two primary and three secondary fermenters. Occasionally when I
have a really long resting beer such as Belgian Quadrupel I run over and
then the old Bosch fridge connected via the Willhi controller has to
crank into action.

[trevor....@gmail.com]

I too could use some help here. I recently got a wine/beer cooler RCA RMIS 2434 is the model number. This cooler has been ok so far cooling the way it needs to. The problem is the lowest setting is 41 and I'd like to get the cooler colder for my beverages.

I've read up on a couple things, bypass the thermostat by wiring the two wires into the thermostat together and also heard of getting a johnson controller that goes into the wall. I'm curious as to if I can get some help on what I should do and how I should go about it.

thanks

[Joerg]

Looking at a picture it seems that your cooler has digital control:

https://images-na.ssl-images-amazon.com/images/I/61wL9hTxOEL._SL1000_.jpg

There are several ways to handle this. One is to find the relay that
turns on the compressor and bridge its contacts from mains to compressor
motor (and coil fan, which is often hooked up in parallel). Now the
cooler compressor would run all the time. You can connect the cooler to
mains via an external controller that has a sensor which goes inside the
cooler and this would cycle the whole thing on and off.

The other way is to hack the innards. Find out where the sensor is,
mostly this will be an NTC or PTC resistor on a cable from the
electronics towards the back. You could fool the unit into a "wrong"
temperature by adding a resistor there.

Lastly, you could install another internal thermostat and let that
control the low voltage relay line.

However, be aware of caveats such as these:

1. Going below 41F can cause occasional local ice build-up and the unit
may not have means to deal with that It could potentially become damaged.

2. The external controller must have short-cycle protection. For
example, after a very brief power outage while the compressor was
running it must wait some time before turning it back on. On an older
fridge I am using a Chinese Willhi external controller which has
short-cycle protection. You also need to set a sufficiently high
hysteresis to avoid short-cycling. I set mine to +/-1F.

3. In the summer months the compressor could run flat-out all the time
and barely get it to your desired lower temperature. The compressor
might not be tough enough to withstand such a high duty-cycle use.

This is my fermentation set-up with temp control mods (except now I have
stainless fermenters in there):

http://www.analogconsultants.com/ng/brew/Blowoff.JPG

Here is our old Bosch fridge from 1956 in a carbonation setup when it
was way too hot outside:

http://analogconsultants.com/ng/brew/Fridge_1.jpg

Sometimes I use the Bosch to ferment if I run out of space.