Current Draw Of Domestic Undercounter Fridges

I'm trying to design a circuit for 3 standard domestic under-counter fridges but for the life of me, I cannot find the current draw of any of them. Tried even sites like Currys in case it's in their specs, but they only seem to show annual power consumption which isn't helpful.

I've checked my Fridge / freezer at home and it's only 87W, so that's tiny, but do any of you have any ideas?

Customer isn't forthcoming with brand / model, so trying to get ahead of them.

Thanks,

Si

Are they all going on one circuit or 3 separate circuits?

Power consumption is tiny, but they do have quite a high start up surge when the compressor comes on.

but I'm sure a 16A radial would do those just fine.

1 circuit. So long as Earth Leakage doesn't mount up!

ProDave said:

Power consumption is tiny, but they do have quite a high start up surge when the compressor comes on.

but I'm sure a 16A radial would do those just fine.

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That's the rating of the existing where they want to put them on, but I just wanted to be sure.

Start-up surge would also be useful to know - can be up to 10x can't it sometimes?

I wouldn't stress, 16 Amp will be more than adequate for 3 x small domestic fridges, start current is way too short in duration to trip a B or C curve MCB on thermal and too low to trip on it's mag. Cumulative earth leakage shouldn't be a problem either unless they're faulty.

mr.si said:

I'm trying to design a circuit for 3 standard domestic under-counter fridges but for the life of me, I cannot find the current draw of any of them. Tried even sites like Currys in case it's in their specs, but they only seem to show annual power consumption which isn't helpful.

I've checked my Fridge / freezer at home and it's only 87W, so that's tiny, but do any of you have any ideas?

Customer isn't forthcoming with brand / model, so trying to get ahead of them.

Thanks,

Si

Click to expand...

Erm????

am I missing something here? or is this a joke???

Supposedly we can design circuits....   But basic power calculations are "Not Helpful"...

consider:-

a)  A 1.0kw electric fire switched on for 1 hour would consume 1kWh..

if its on all day it would be 24kWhrs.. 

and its it is left on all year it would be (24x365)  8760kWhrs...

b) Now a fridge is normally on 24/7 365 days per year..

So if you have the annual consuption....

Its not too difficult. (or shouldn't be) to back calculate how much power per day / per hour..

and thus also get the current!!!

I just had a random look at a Curry's fridge  150kWh annually..

150/365 = 0.41kWh per day

0.41/24 = 0.017kW per hour..

or  17watt..

17watts/230v = 0.073amps!

Remember a 500w floodlight is only taking 2.17amps!!

SPECIAL LOCATION said:

b) Now a fridge is normally on 24/7 365 days per year..

So if you have the annual consuption....

Its not too difficult. (or shouldn't be) to back calculate how much power per day / per hour..

and thus also get the current!!!

Click to expand...

 This isn't possible. You can't work back from an annual energy consumption figure to a run current. Even if you assume it's plugged in 24/7 you don't know the running time because of the thermostatic control; you can't go from kWh to kW without knowing the exact hours.  

SPECIAL LOCATION said:

I just had a random look at a Curry's fridge  150kWh annually..

150/365 = 0.41kWh per day

0.41/24 = 0.017kW per hour..

or  17watt..

17watts/230v = 0.073amps!

Click to expand...

The smallest generally available refrigeration compressor is 1/12hp. Looking at the easiest three makes to find on the internet the Embraco is 72watts, the Techumseh is 76w and the electrolux(ACC) is 70watts. Obviously if the compressor runs 25% of the time because of the thermostat then you get the 0.4kWh per day you mentioned above but your run current will be 0.3Amps and not the 0.073A you calculated.I would say the only certain methods of finding the run current is either by accurate measurement or the info plate on the appliance or in the manual.

All domestic fridges i can remember have 5A fuses in the plug. As 5A is not a  recognised 'normal' size ( couldn't think of a better description before anyone jumps on me) i assume they draw just over 3A.

I have a American style side by side fridge, but of a smaller design. Its 10 years old now & wired on its own radial circuit. When the compressor kicks in i notice a dip in the lights. I checked all the connections at the mains in case of a loose connection & found nothing wrong. 

The 5A fuse is probably due to the compressor  start current though, not the running.

Marvo said:

This isn't possible. You can't work back from an annual energy consumption figure to a run current. Even if you assume it's plugged in 24/7 you don't know the running time because of the thermostatic control; you can't go from kWh to kW without knowing the exact hours.  The smallest generally available refrigeration compressor is 1/12hp. Looking at the easiest three makes to find on the internet the Embraco is 72watts, the Techumseh is 76w and the electrolux(ACC) is 70watts. Obviously if the compressor runs 25% of the time because of the thermostat then you get the 0.4kWh per day you mentioned above but your run current will be 0.3Amps and not the 0.073A you calculated.

I would say the only certain methods of finding the run current is either by accurate measurement or the info plate on the appliance or in the manual.

Click to expand...

However....

When designing circuits we take into account diversity...

Not just the peak load for a small percentage of the time...

On average over the course of a 24hr period the current drawn by a single fridge will be as per my rough back calculations ...

Just as when we design for a ring or radial circuit, we do not assume ALL appliances are going to be running full load current 24/7..

Or lighting circuits we do not assume all lights are on together...

The total load averages out over the 24hr period..

even though as we all know circuits can quite happily take higher currents than both the cable and protective device are rated at for short periods...

The question was about 3x under counter fridges, I doubt 3x fridges will all be drawing the max full load simultaneously for the bulk of the 24hour period..   It will be averaged out..

Same principle as how many houses cope quite easily with 60A main fuse & 16mm2 tails..

when the apparent max load could appear to be 100A+ if you just look at all the circuit breakers and all of the appliances and loads connected...

Diversity..  Pg 109 onward OSG 

or

pg 81 & 177 onward GN1 

By your own calcs the compressor may only be running 25% of the time..

so 3x fridges probably only 75% between them..

so 25% of the day the cable is carrying naff all !..

With something like domestic under counter fridges..

I can't see you will be to far off calculating an average (over 24hrs) for a single item and multiplying by 3 fridges....

What are you going to do if you do know the exact max load running current?

add em all together as if they are all running full load 100% 24/7  ??

:C

SPECIAL LOCATION said:

What are you going to do if you do know the exact max load running current?

add em all together as if they are all running full load 100% 24/7  ??

:C

Click to expand...

I know the UK regs have recommended diversity calcs in there but I have no idea what they suggest about individual radial circuits. I'd suggest caution applying 'across the board' diversity formulas to a radial cct in this application. Even at 25% running time it's a reasonable assumption that all 3 appliances would on some occasions be running simultaneously for long enough to cause an MCB to trip on thermal if the sum of the run currents exceeds the MCB In rating by a significant margin.In this scenario it's mostly academic, as you say the fridges are drawing next to nothing and even a 10Amp radial would probably be more than sufficient.

In this scenario it's mostly academic, as you say the fridges are drawing next to nothing and even a 10Amp radial would probably be more than sufficient.

Click to expand...

That is precisely the point I was trying to make with my posts...

the actual figures for these "domestic fridges" are that small that even a basic 2.5mm radial with a 16A will be no issue...

But the OP...

Apparently designing a circuit couldn't even do a bit of basic maths to work out a rough daily consumption from the yearly running figures!

Which TBH does worry me when electricians struggle to design simple things... 

What happens if we were designing a circuit for a kitchen with...

12A Washing machine

13A Tumble drier

10A Kettle

12A Toaster

3A Bread machine

5A Microwave

10A Dishwasher..

+ loads of other <2A hand held appliances..

Are we going to install cables for 65A+ ????

Its not about using standard diversity calculations...

its just bog standard common sense diversity based on a few simple calcs for some Domestic appliances..

It  shouldn't be too complex to grasp should it??.

I mean we are not talking about a whole bunch of industrial grade equipment are we?

p.s.

our fridge came with a 13A fuse in the plug!

SPECIAL LOCATION said:

However....

When designing circuits we take into account diversity...

Not just the peak load for a small percentage of the time...

On average over the course of a 24hr period the current drawn by a single fridge will be as per my rough back calculations ...

Just as when we design for a ring or radial circuit, we do not assume ALL appliances are going to be running full load current 24/7..

Or lighting circuits we do not assume all lights are on together...

The total load averages out over the 24hr period..

even though as we all know circuits can quite happily take higher currents than both the cable and protective device are rated at for short periods...

The question was about 3x under counter fridges, I doubt 3x fridges will all be drawing the max full load simultaneously for the bulk of the 24hour period..   It will be averaged out..

Same principle as how many houses cope quite easily with 60A main fuse & 16mm2 tails..

when the apparent max load could appear to be 100A+ if you just look at all the circuit breakers and all of the appliances and loads connected...

Diversity..  Pg 109 onward OSG 

or

pg 81 & 177 onward GN1 

By your own calcs the compressor may only be running 25% of the time..

so 3x fridges probably only 75% between them..

so 25% of the day the cable is carrying naff all !..

With something like domestic under counter fridges..

I can't see you will be to far off calculating an average (over 24hrs) for a single item and multiplying by 3 fridges....

What are you going to do if you do know the exact max load running current?

add em all together as if they are all running full load 100% 24/7  ??

:C

Click to expand...

you're not married, are you?  :|

:slap

SPECIAL LOCATION said:

Erm????

am I missing something here? or is this a joke???

Supposedly we can design circuits....   But basic power calculations are "Not Helpful"...

Click to expand...

 

SPECIAL LOCATION said:

But the OP...

Apparently designing a circuit couldn't even do a bit of basic maths to work out a rough daily consumption from the yearly running figures!

Which TBH does worry me when electricians struggle to design simple things... 

What happens if we were designing a circuit for a kitchen with...

12A Washing machine

13A Tumble drier

10A Kettle

12A Toaster

3A Bread machine

5A Microwave

10A Dishwasher..

+ loads of other <2A hand held appliances..

Are we going to install cables for 65A+ ????

Its not about using standard diversity calculations...

its just bog standard common sense diversity based on a few simple calcs for some Domestic appliances..

It  shouldn't be too complex to grasp should it??.

I mean we are not talking about a whole bunch of industrial grade equipment are we?......

Click to expand...

I don't want an argument so I'm not going to post any further after this one but I think you're being a bit harsh on the OP to be honest. He asked about a possible load figure for the fridges because he was in the process of sizing a radial circuit. He'd already made some preliminary investigations and came here for further advice about the running currents. I'd agree the advertised annual energy consumption figures he found weren't sufficiently helpful and I'm not sure why it broke out in a diversity debate but from his posts so far I've no reason to suspect the basic calcs involved in the circuit design are beyond him or 'too complex to grasp' for him. I thought his questions were valid and fairly considered and I hope he feels he can still post with any further concerns if he still has any.

Marvo,

I do agree with your points,

but,

I feel that if someone cant grasp the fact that a radial circuit for 3x normal domestic fridges really needs a massive design doing then perhaps they are not that up to speed with much common sense.

3 x appliances that 'probably' run quite happily of a <3A fuse doesnt really demand much of the grey matter to design a circuit for,,,,,,,,

SPECIAL LOCATION said:

.

.

p.s.

our fridge came with a 13A fuse in the plug!

Click to expand...

Only 3 & 13A are recognised values now.  So since most fridges  come with a 5A fuse one has to assume 3A  does blow over time due to the compressor start up current. I suppose this means a 13A fuse is then acceptable ???

Marvo said:

 I don't want an argument so I'm not going to post any further after this one but I think you're being a bit harsh on the OP to be honest. He asked about a possible load figure for the fridges because he was in the process of sizing a radial circuit. He'd already made some preliminary investigations and came here for further advice about the running currents. I'd agree the advertised annual energy consumption figures he found weren't sufficiently helpful and I'm not sure why it broke out in a diversity debate but from his posts so far I've no reason to suspect the basic calcs involved in the circuit design are beyond him or 'too complex to grasp' for him. I thought his questions were valid and fairly considered and I hope he feels he can still post with any further concerns if he still has any.

Click to expand...

well thats the joys of a forum..  we are all free to disagree with whatever posts we like...

I don't agree fully with some of your points..

If the basic calcs were within his grasp he would not be asking here surely???

Re read the op's opening question..

{I'm trying to design a circuit for 3 standard domestic under-counter fridges}

In my mind Diversity is a significant consideration with any circuit design...

and the amount of current drawn over a time period is part of this consideration.. 

(thus an idea of the average daily consumption of the fridge is a relevant factor..

as I also tried to illustrate with my 65A+ kitchen supply..)

And as the OP has been a member since May 2011 I assume he's seen enough of the forum and typical post content and replies to be aware that comments on here are similar in content to out in the real world...

where sometimes a spade is called a spade...

and people who miss an obvious point are sometimes called a plonker!!

Or maybe everyone else on the forum has never heard any name calling or jibes to anyone when out on a site or in a factory or even in at a college..?  

Sometimes this forum gets too softly softly and tippy toe around all the answers in case someone gets the hump!

The question is not in the student area, so I assumed its not a college question...

But someone charging for their time to a paying customer who expects a competent person who is able to do the basic calcs while making a cup of tea and phoning the wholesaler at the same time..

No name calling... no bad langauge..

just a few suggested calcs to try and help the op understand how he can get some idea of the actual load his cable will be carrying each day...

and thats a bit harsh????

:coat  .

Why  was i descoobed for asking a question.

I didn't descoob but have re-scoobed to cancel whoever did

I agree with Spec and Step, this is a really something that should not need any train of thought.

I don't think anyone has been harsh, Spec's post was well put and detailed which would explain a lot to all the younger members on the forum.

Steve3948 said:

I agree with Spec and Step, this is a really something that should not need any train of thought.

I don't think anyone has been harsh, Spec's post was well put and detailed which would explain a lot to all the younger members on the forum.

Click to expand...

:Salute

Can I just say no bribery was involved with this post...............

But it is a sad sign of the dumbing down of this industry... :|

p.s.

did you want cheque or BACS transfer??

PM your payee details so I can do the biz..

:innocent

:slap   :slap   :slap

Guinness