Keeping fridge in a cupboard - good or bad energy?

[Richard Marx]

Hi, I have recently moved and have a large kitchen cupboard designed to take a fridge, with a full-height wooden door on it (almost like entering another room or broom cupboard). Is keeping the fridge in there with the door shut a good thing or a bad thing, energy-consumption-wise?

I.e. does the fridge's heat not dissipate so well, heating the cupboard, causing the fridge interior to warm up faster so its thermostat clicks in more often; or does it keep the cool in by double-insulating the fridge making it more energy efficient?

I don't notice any particular cold or hot air when I open the door, but it certainly keeps the noise in with the door shut!

Thanks for any advice.

[Ophelia]

I had a big fridge die after I put it in a cupboard. Of course I have no proof that was the reason.

[Huge]

Built-in appliances have extensive ventilation to avoid the overheating problem, so I would say that, Yes, your frig will likely use more energy if sealed in a box.

(Isn't this one of Andy Hall's thermodynamics questions?)

[mcbrien410]

We put our smallish deep freezer into out larder a few years back and it did make the larder a lot warmer. We were not keen on this heat as the larder was just nice and cool before so we put the freezer back where it started.

Chris.

[Lobster]

The former. The fridge cools its interior by, in effect, pumping the heat to the exterior; if you prevent that from dissipating, it will overheat. (I would imagine the inside of your cupboard must be a *bit* warmer than the room as a result of the fridge being in there, so there's a bigger temperature gradient overcome between the fridge interior and exterior than if it sat in the kitchen). But I imagine if you can't detect any increased temperature in the cupboard, it's probably big enough a volume inside for it not to be a problem for the fridge.

David

[dave]

If the cupboard was really designed for a fridge properly there would be some ventilation built in, either to the outside world or into the room containing the cupboard.

You really can't win. In winter venting the cupboard to the outside world would be the best solution for energy consumption of the fridge, but not neccesarily the house heating. In Summer your house might be cooler than the outside world on average depending on construction, so venting into the house would be best. The whole story needs to consider the heating/ cooling energy requirements of your whole house. Its impossible to say without knowing exact energy balance details for your house with regard to heating and ventilation and temperaures, when a change over point would give you the least energy consumption overall. So I would say forget it and put the fridge where it pleases you most. You won't make much difference to your bills or Ozone layer either way.

Dave

[Richard Marx]

Thanks everyone.

Would just taking the door off the cupboard (which is recessed into the kitchen wall anyway be a better idea, and just leave the fridge recessed in there, but open to the kitchen instead of enclosed?

[john]

My fridge is in a tight location and I have thought of fitting a small fan somewhere to create a draught - something like the fan in the back of a PC but a bit bigger.

Any thoughts?

[Stickems.]

Yes.

| > You really can't win. In winter venting the cupboard to the outside world | > would be the best solution for energy consumption of the fridge, but not | > neccesarily the house heating. In Summer your house might be cooler than | > the outside world on average depending on construction, so venting into | > the house would be best. The whole story needs to consider the heating/ | > cooling energy requirements of your whole house. Its impossible to say | > without knowing exact energy balance details for your house with regard to | > heating and ventilation and temperaures, when a change over point would | > give you the least energy consumption overall. So I would say forget it | > and put the fridge where it pleases you most. You won't make much | > difference to your bills or Ozone layer either way. | >

| > Dave | >

| >> I.e. does the fridge's heat not dissipate so well, heating the cupboard, | >> causing the fridge interior to warm up faster so its thermostat clicks in | >> more often; or does it keep the cool in by double-insulating the fridge | >> making it more energy efficient? | >>

| >> I don't notice any particular cold or hot air when I open the door, but | >> it certainly keeps the noise in with the door shut! | >>

| >> Thanks for any advice. | >>

| >

| >

| |

[Dorothy Bradbury]

You need to ventilate the cupboard or larder... o Vents

---- one in the front bottom of the dooor (intake)

---- one in the front top of the door (exhaust, by convection) o Door left 2" ajar

---- you will find the cupboard slightly warmer when you walk in

---- however hot air will exit, drawing in cooler air near the floor

Cooling appliances work by... o Compressor uses gas-liquid phase change to pump heat out of a box

---- compressor does not run continually (it would soon fail)

---- compressor cycles on & off based on an internal thermostat o Appliance sits in its own ambient temperature

---- appliance in a cupboard will heat ambient quite considerably

---- so the compressor will cycle more often & use more power

In a cupboard you may want to set the appliance so it tilts backwards. o So the door naturally swings closed if someone doesn't shut it properly o This is particularly important for freezers where food can go off fast

No it does not "double insulate" the fridge... o Fridge is a heat pump removing heat from inside the fridge

---- insulation stops the heat from outside the fridge getting in quickly o Higher temperatures outside the fridge

---- reduce effectiveness of the insulation (higher temp delta)

---- reduce effectiveness of the fridge coils to dump heat (lower temp delta)

---- increase the amount of energy the fridge will use

Modern fridges/freezers do seem to dissipate a lot less heat than some of 20yrs ago - which results in lower thermal input into the surroundings. However the same applies, and energy does add up over a long time.

Personally I would simply not shut the cupboard door, stick a fridge thermostat inside and glance at it every time you open the fridge.

[Dorothy Bradbury]

Duh, an obvious solution. o Remember the ?french? horizontal slatted doors used in various places? o They would be ideal for this application re allowing near free air ventilation

That avoids fitting vents into doors, although up to you. I would simply leave the door 2" ajar - that will be more than sufficient.

[Dorothy Bradbury]

No re the fan, it adds complexity re powering it & should it ever seize... o Most DC fans are designed for 72-200hrs locked rotor

---- eg, current limiting by power-cutout, timer, restart, repeat o However AC fans use thermal cutout for 24-72hrs, and get very hot

---- AC fan when not turning do not have current limiting

---- eg, they use bimetallic or other methods to prevent overheating

They are used in such applications, inside (-40oC rated) & outside. However for DIY use you can find a less complicated solution...

Simply use natural convection... o Most fridges only have adjustable feet at the front

---- at the rear they sit flat on the floor obstructing airflow

---- so convection is forced to use the side gaps, scavaging o Instead place the fridge on even slim floor spacers either side

---- so creating an air gap direct to the compressor & up over the rear

Fridges do not dissipate much heat (freezers do, particularly if they use a hot-gas auto-defrost system which can give a big heat spike).

[Jim Scott]

Bad idea. Fridges have to give out the heat they have taken from the food. They do it most efficiently in a cold room. That's why you have to turn them up in the summer.

[Blueyonder]

Some built-ins have a fan anyway, usually quite a large, but slow one at the front (to keep it quiet). It forces the air under the unit, around the back, and then back out through grills at the top of the fridge. I guess it allows smaller vents than otherwise to be used. The fan only comes on with the compressor though.

So yes, it is definately done in commercial units.

-- JJ

[john]

advice.

Why should you need to turn up a thermostat in a different season? It works by sensing the temperature inside the cabinet. A setting is the same all year round.

Do you turn up your room thermostat when it snows? Or your oven on a cold day?

[raden]

In message , john writes

The bit about working best in a cold room's also not necessarily true

as has been discussed numerous times in here

... not a post to take seriously

[Jim Scott]

Learn some basic physics then come back with a sensible answer.

[raden]

I have a degree in physics

and it was a sensible answer

and what I said was true - fridges can fail if the ambient temperature is too low, but since you don't seem to understand how a thermostat works, It's not really explaining anything more complicated to you

I think you should go away and learn some applied physics and come back when you have a clue

[Jim Scott]

Since I too have a degree in physics and 40 years teaching and examining it, it is obvious you don't have any knowledge at all about heat engines and thermodynamics laws. The question of the cupboard has little to do with the internal thermostat. It has everything to do with the temperature difference between the outer heat sink and the temperature of the surroundings.

[Palindr☻me]

ISTM that there are/were fridges didn't perform well in cold conditions.

They have a single thermostat in the fridge rather then the freezer section. If the ambient condtions are "too cold", then the fridge doesn't have to run much, if at all, to get the thermostat to operate. Great! Low electric bills! But it then doesn't run long enough to get the freezer section down to low enough to keep things frozen.

Having the thermostat in the freezer section can also cause problems:

This is a control system which can have big lags. Take the situation with the conventional situation of the thermostat being in the icebox. The heat pump runs and lowers the temperature to the point that the thermostat operates. These thermostats have hysteresis - so the temperature at the thermostat will have to rise a few degrees before the thermostat will operate again. Heat energy is being transferred into the body of the fridge from the environment, mostly by conduction through the case- the higher the temperature outside, the faster the inside will warm up. Inside the fridge, heat has to transfer to the icebox, and hence the thermostat, mostly by convection. Under certain circumstances, eg when the ambient temperatures are high and the fridge has poor insulation, the fridge section can rise to a relatively high temperature much more quickly than the heat can be transferred to the freezer section and raise that temperature to the point of operation of the thermostat. Thus the stuff in the body of the fridge can "go off", even though the stuff in the icebox is fine.

Turning the thermostat to a colder setting *will* help. Set low enough, the temperature in the fridge section doesn't rise to dangerous levels before the thermostat operates and the heat pumps starts again.

Putting the fridge in a cupboard can raise the ambient temperature. Which increases the rate of heat flow through the walls of the fridge into the main body. Which means the fridge section gets hotter faster. Which can mean it can get to unsafe temperatures before enough heat can be transferred bu convection inside the fridge to raise the freezer section enough to operate the thermostat.

The outer heat sink is a different matter. It too mostly loses heat energy through convection. In a restricted airflow situation, turning the thermostat to a lower setting will increase the temperature of the heatsink (simplifying things..) thus increasing the temperature differential between it and the ambient air. More heat energy will transfer. Which raises the ambient temperature - which increases the heat flow back into the fridge body...which makes the heatpump work more, which raises the heatsink temperature...

Thus the question of the internal thermostat has *everything* to do with being in a cupboard - if the fridge has relatively poor insulation.

The question of the cupboard has little to do with the temperature

*difference* between the outer heat sink and the temperature of the surroundings. It has a great deal to do with the actual temperature of the outer heat sink and hence the actual temperature of the surroundings, when hot air cannot escape to the infinite heatsink, known as my kitchen in Winter....