Frost-Free Freezer: Use compressor for cooling, defrost heater for heat?

[zman_]

I have two ~14 cubic foot Frigidaire upright frost-free freezers that I want to turn into fermentation chambers. Cooling is obviously in their wheelhouse, but I was reading and it turns out that part of being frost-free is the incorporation of a couple hundred watt heater by the cooling coils to prevent ice build up/etc. This got me wondering if I could perhaps wire in a temp controller (like the ITC-1000 or STC-1000) to cool the chamber with the compressor and heat the chamber with the built-in defrost heater?

I was wondering if anyone had experience doing something similar? Right now, I have a ITC308/50watt reptile heating cord for one of the chambers, but don't have anything for the second one - so this would be an interesting project/possibility.

I will be getting pictures of the wiring diagrams for each freezer once I get home which will hopefully inform as to how the compressor/defrost heater/other internals are wired and could tell me if this is feasible/possible.

 

[Stealthcruiser]

Don't over think it!

Have your read the plethora of ferm chamber builds in the forum?

 

[zman_]

Don't over think it!

Have your read the plethora of ferm chamber builds in the forum?

I have, and I've successfully been using one of them... Just wondering if there is any consensus on if this is a good idea or no. I can always grab an itc-308, another heating cord and ferment away. But it would be nice to use the available components in the freezer

 

[Stealthcruiser]

So your scheme involves relocating the defrost heater, from the "jacket" to inside the cooling compartment where you can utilize it?

As in secure it to a vessel that needs some heatin' ?

 

[zman_]

So your scheme involves relocating the defrost heater, from the "jacket" to inside the cooling compartment where you can utilize it?

As in secure it to a vessel that needs some heatin' ?

From my understanding, the heater is set around the cooling coils within the freezer. It normally serves to defrost the coils, but wondering if it should be possible to use that to heat the chamber/fermenting beer. Don't need to move anything, I think, just rewire things.

 

[Stealthcruiser]

So without relocating the heater, you'll "ambient" heat the whole chamber, and allow the vessel to heat by convection, instead of conduction?

If you rewire the heater for this purpose, how will you still facilitate the defrosting of the coils when needed?

The refrigerator already knows when it needs it, unless someone starts shufflin' wires around.......

Watchin'!

 

[zman_]

Coils don't need defrosting since I don't ferment below freezing . Ice formation shouldn't be a problem.

This is the wiring diagram, so if I can identify the appropriate wires it should be pretty easy to bypass the internal controls and set up heating on the defrost heater and cooling on the fan/compressor by just cutting/jumping some wires. Now the next challenge will be to make the fan run whenever the system is heating or cooling... Not sure how to achieve that.

 

[Stealthcruiser]

Run the fan all the time?

You need the warm moving, and you need the cool moving.....

 

[zman_]

Run the fan all the time?

You need the warm moving, and you need the cool moving.....

That was my first thought. Would be easy enough to do and might end up going with that. Probably not worth doing something more elaborate

 

[ajdelange]

Get something like a Honeywell T775 with two relays and 1 temperature sensor. Run L through the heating relay to a 120V icecube relay (this is not one of the two relays mentioned earlier - those are in the T775) and use its SPDT contacts to connect the heater either to L (call for heat) or the controller (Terminal 4 as it is connected now - call for cooling). Connect the control terminal 2 and the thermistor to L through the cooling relay in the T775.

This says nothing about whether the heater can practically control the temperature inside the box. It just lets you turn it on or off according as to whether you want heating or normal operation as a defrost coil. It also says nothing about the ability of the heater to raise the temperature of the coil to the point where it may burst (what refrigerant is in the thing?) if the T775 leaves it on too long which, presumably, the unit's own controller wouldn't do.

[EDIT] #8 raises a very important point WRT the last paragraph above. Use a second SPDT pair on the icecube relay to switch the fan between controller and L. Thus when heat is called for the fan always runs. In cool mode it runs when the controller wants it to which is, apparently, whenever the compressor runs.

 

[zman_]

Those controllers seems a bit expensive for what I'm looking to do. I would just get an additional heat source for that price. I was thinking of using something like the auber mini power relay (http://www.auberins.com/index.php?main_page=product_info&products_id=250) to switch power to the fan. Set it up so the NC connection is drawing from the heating relay of a temp controller, and then NO from L or the cooling relay. Have it switched by the cooling relay of the temp controller.

Haven't looked too carefully at it, but initially that seems like it should work to have the fan run when heating and cooling.

 

[ajdelange]

I only mentioned the T775 because I have used them to control freezer temperature for years and I am putting one in my heat pump control system. Anything with two relays, one for heating and one for cooling will do. The circuit is what's important.

 

[zman_]

So, I've been doing some poking around in the freezer. So far, I've verified that there is indeed a defrost heater, compressor, etc and they are wired as decribed. There are a few more wire colors than described on the wiring diagram so I have to do a bit more tracing/figuring out exactly what is connected to what. Thankfully, there are built in places to disconnect/isolate certain parts of the wiring so it should be easy to splice into the already existing wiring to make my own modification.

I have attached the wiring plan that I have. This should work for using the compressor to cool, heater to heat, and ensuring good air circulation with the fan running whenever either temperature control circuit is engaged. Thoughts?\

Just ordered the ITC-1000 for this build, gotta get the relay (will likely order in a few weeks/a month when I get the rest of my RIMS setup parts from auber). Hopefully by then I will have identified exactly what I need cut/re-wire to make this work.