New Refrigerator Question

We just purchased a new frig. We were advised not to put anything in it for 24 hours after plugging it in. Anyone have any idea why the delay? Thx in advance.

It takes some of the load off the compressor. This way you get the box cold, then when you load it, the compressor is just removing the heat from the items and not the items AND the air AND shelves etc.

Also, it should be noted that if you’re putting things in that are already cold, you can do it right away, in fact, it’ll make the compressor’s job easier.

Quick question. Did they say not to put anything in it for 24 hours after plugging it in, or not to plug it in for 24 hours after getting it in your house? It’s common to leave a fridge unplugged for at least a few hours after moving it (especially if it was on it’s side) so any oil that migrated out of the sump can drain back down.

It takes a long time for all that warm mass(the refrigerator) to cool down. Any fod inside during that time will be at prime bacteria growing temperatures.

After plugging it in.

Then, yeah, it’s just so the compressor isn’t trying to pull down the temp inside the box AND all the warm contents at the same time.

But, like I said, if the contents are already cold, like if you’re just moving them from the old fridge to the new one, that’s not going to be an issue. The only possible issue would be if, like running_coach mentioned, they get warm (for too long) before they get cold, but I don’t see that happening.

As a commercial refrigeration guy I’d give Joey_P one point for for saying that giving a unit 24 hours to let the oil settle is sound advice for the sake of the compressor if it had been other than vertical during shipping or being moved. The compressor itself is in fact not removing the heat load, the evaporator and condensing coils are. Are we to believe that one must somehow pre-cool anything we may wish to refrigerate?

The compressor doesn’t know how warm/cold the fridge is, it only knows how long it’s been running. Cheap oil-free air compressors don’t like to be run for a long time at high pressure without shutting down to cool off (i.e. use them to fill tires, not for sandblasting), but the compressor in a fridge is oil-lubed/cooled and operates at a preset output pressure; the load on the compressor is the same whether the fridge is hot or cold, and I would think it doesn’t care if it runs for 45 minutes to cool an empty fridge or 90 minutes to also cool a bunch of warm food.

Moreover, I can’t imagine circumstances where someone is filling a fridge (new or old) with warm food, unless they’re bringing home leftovers from a very poorly-attended pig roast. And if they are, then they have a need to get that stuff cooled ASAP.

Depending on the manufacturer, the advice is to let a recently installed fridge sit for 2-24 hours to let the oil settle back down into the sump, and then let it run for anywhere from 2-24 hours after that before putting food in it. The main reason cited for the latter spec is to give the fridge time to stabilize at the correct temperature, and to verify that it’s actually working properly. Allowing adequate time for the temperature to stabilize seems to be the main issue; this fridge manual (PDF) for example advises allowing 24 hours after any change in the temperature setting before trying to figure out if the new temperature is acceptable.

Other sources of info:

Overall, it’s not about protecting the compressor, it’s about protecting your family, i.e. food safety: keep cold food reliably cold, and chill warm food with adequate rapidity.

Technically, that’s true. But if you put an amp meter on the compressor, you’ll see it rise when the it’s extracting more heat. So, yes, the compressor doesn’t know how warm or cold the fridge is, but it has to work harder when it’s warmer.

Is that because warmer refrigerant vapor returning to the compressor leads to lower volumetric efficiency, or does the amount of heat in the vapor also affect condensing temperature/pressure? I understand that when the kitchen is warmer (or the condenser is dirty), the refrigerator will use more power because of the higher condensing temperature/pressure of the refrigerant, regardless of the load. In this case though we’re assuming a variable load with a consistent ambient temperature at the condenser.

Overall, the warmer vapor also means the compressor motor isn’t being cooled off as much as it normally would. That’s unlikely to be a problem with a brand new refrigerator with clean coils. Still, in order to maximize efficiency, the refrigeration systems are as small as possible, so as others have said above, the time required to cool down the whole box (which if delivered in the summer could also have a lot of heat trapped in the insulation) could lead to spoiled or melted food.

I’d think if it only meant the compressor had to make more revolutions to compress the same amount/mass of refrigerant, the amps wouldn’t increase. What would make sense, however, is that the vapor is coming back at a higher pressure and it’s going to be physically harder for the piston to compress it.

I remember learning this years ago. I was watching someone that was working on one of our big coolers at work. He turned the compressor back on, but the fans (inside) won’t turn on until the pipes get below a certain temp. Since he was up on a roof, he couldn’t see what was going on inside the box, but a meter on the compressor showed a spike in the amps when the evap fans turned on and started blowing warm air over the coils.

Also, just to be clear with everyone, I’m not arguing against that point. It 100% makes sense and is likely the reason for the warning. Taking the load of the compressor was just my initial thought based on my experience with small grocery store coolers/freezers.