Garage Freezer thermostat controlled light

[Earthlark]

Trying to use modify my (Minnesota-based) garage refrigerator so that 1) the freezer freezes and 2) the fridge section does not freeze.

One way people overcome both of these problems is by repositioning the door light switch so that the light stays on at all times. This raises the temperature enough so that the compressor kicks in and cools down the freezer.

I thought I'd take this a step further and put in a thermostat to make the light turn on once the temp drops to a set point and then go off when it raises to a certain point. Is there an easy way I can wire in a thermostat to use the leads that power the light? I bought an inexpensive thermostat off Amazon but realized that the fridge is providing 138V AC at the light and the thermostat requires 12V DC.

I thought this would save electricity by not having heat from the light battling the fridge all the time... though I'm guessing this wouldn't save money. More about the principle and fun of it.

Anyone have any suggestions, e.g. other low-cost AC thermostat or a low-cost transformer or...? (p.s. I'm an amateur.)

 

[Pommie]

That's a very good way to increase your electricity bill.
Have you tried a full defrost? It could be either the thermostat or defrost timer are faulty.
If the defrost fixes it then it's probably the defrost timer.

Mike.

 

[gophert]

That's a very good way to increase your electricity bill.
Have you tried a full defrost? It could be either the thermostat or defrost timer are faulty.
If the defrost fixes it then it's probably the defrost timer.

Mike.

Pommie, I don't think you understand that Minnesota temperatures often drop to -20 to -40. Like me, our OP probably doesn't like to drink frozen beer. So, as you said, he IS looking for a way to raise his electric bill because he wants to warm his fridge.

 

[Earthlark]

Pommie Some refrigerators (like mine) have only one thermostat, located in the fridge portion, which when it kicks on, cools the freezer and sends air from the freezer into the fridge. This means that if the temp in the fridge doesn't get high enough, the compressor will never turn on and the freezer won't freeze. (Conversely, if the outside temp is below freezing eventually everything in the freezer and fridge will be frozen.) For a better explanation see this article from 3goodones.com or this video from Bill Newberry. Hence, alternatively to insulating the garage, a little light for warmth.

 

[rjenkinsgb]

A simple bimetal "frost thermostat" intended for central heating / HVAC freeze protection could work for the light.
eg.
https://heatingcontrols.honeywellhome.com/products/thermostats/frost-thermostats/T4360/

That's rated for up to 240V AC at a few amps on the contacts.

There are many makes and styles, just be sure it's a not a low-voltage or electronic version.

Another style, to attach to a pipe or surface:

Honeywell L641B1004 Low Limit Pipe Thermostat

Honeywell L641B1004 Low Limit Pipe Thermostat. Lowest price guaranteed. In stock: Delivery Next Day. Paypal Accepted. Trading Online Since 1999.

www.plumbnation.co.uk

You could fit a thermostat such as one of those outside the fridge, so it puts the light (or another small aux heater) on when the ambient temperature gets too low for the fridge to work normally.

Just be careful that any cable through the seal or casing has a perfect airtight seal on it to avoid condensation inside.
(And you don't hit any pipework)!

 

[Diver300]

You could fit the thermostat inside the freezer. If the freezer is too warm, heat the fridge. The appliance thermostat will then turn on the compressor.

You might also want to heat the fridge if it gets below freezing. You should make sure that the fridge temperature that causes the fridge heating to come on is at least a few degrees below the appliance's cut-off temperature. You don't want the heater and the compressor fighting unless it is to cool the freezer.

 

[Earthlark]

rjenkinsgb Thanks for the recommendations and links! Your recommendations inspired me to search a little more deeply. I found a few inexpensive used thermostats on Facebook Marketplace, but I also found this Bayite 110V 10A Temperature Controller and figured this one might be just as good for the same price and ease of ordering. This one should do the trick, right?

It's funny, the market was glutted with these dual-stage controllers for $15 that switch between hot and cold, but it took me ages to find a thermostat-like one. I suppose the popularity of brewing and incubating is the reason... None of these had a setting to allow for temp variance on one side though, e.g., setting the variance to 3° was +/-.

Diver300 Thanks for the reminder about dialing in the right temps so the heater and compressor aren't fighting. I'll have to do a little experimenting to figure out just what that temp is.

 

[rjenkinsgb]

This one should do the trick, right?

It should work fine, you can position the sensor a lot easier than an all-in-one thermostat, plus having an actual-temperature readout!

 

[debe]

I find a lot of Frost free fridge thermostats that are inside the fridge have a small heater taped to the thermostat.

 

[rjenkinsgb]

A lot of bimetal thermostats include a low power heater of some sort, switched by the thermostat contacts to reduce the hysteresis and improve accuracy.

 

[debe]

This is how an LG frost free fridge does it. The heater(resistor) is run contiously.

 

[rjenkinsgb]

Ahhh... In that case, I'd guess it may be to prevent condensation that could bridge the contacts or insulation?

This shows the resistor config I'm used to seeing:

https://heatingcontrols.honeywellhome.com/documents/All/pdf/1008.pdf