Which Generator / Power Source For Large Freezer?

[Maja]

Hello all,

 

Please forgive me not introducing myself but it is very late and I have been trying to solve my latest boat-conundrum for many hours!

 

I have a narrow boat powered by a BMC 1.5 diesel engine. I sell ice creams and have just fitted a medium size freezer (like you would find in a shop or cafe), the problem is that it drains the leisure batteries very quickly and I need to find a better solution for running it.

 

I believe the freezer is 1.9kw (per 24 hours) and assumed that a 2.2kva or 2.5kva generator would be big enough to power it. Now I have been told that the compressor uses twice as much power than the average running of the freezer (but have also been told that, while this may be true, the maximum load cannot be too high or it would be blowing the 13 amp plug fuse.

 

My question: what is the best way to power my freezer? It is a standard commercial slide top freezer, plugged into a 240v supply (as in a building) although it is linked to the leisure batteries too which will power it for up to 4 hours.

 

a. a generator .... but if so, what size. I have been looking at the Hyundai 3000 (2.5kva)

b. installing a larger alternator ... but this will involve running the engine whenever I am selling (an engine that is a bit poorly at the moment)

c. installing solar panels

d. ... your recommendations??

 

I appreciate that most of you will have much smaller appliances but I hope that the principles are the same and I hope that your knowledge will shed some light on a very confusing situation.

 

Thank you

[bigste]

The freezer spec doesn't sound right. What is the make and model.

[Scholar Gypsy]

A quick google of Which came up with some chest freezers (rated A+ energy consumption) that consume about 300 kWh a year, 1kWh a day, so if the number you have is correct then that's 1.9kWh each day.

 

That gives you an average power consumption of about 0.1 kW - same as a 100W light bulb. That will take an average current of 10 amps out of your batteries. 4 hours = 40 AH which again sounds about right (depending on how many batteries you have in your leisure bank).

 

Another approach is to use the generator to charge the batteries - say running it for one hour in four? That will surely be cheaper than running the generator all the time?

 

These are average loads - as you say the compressor does not run all the time. And they usually draw a larger current when starting up.

[Arthur Brown]

The issue must also include the inrush current to the motor of the freezer. This will need an inverter or generator of at least three times the steady running consumption of the freezer.

 

Yet another case for measuring the actual current drawn and estimating the time proportion for which the freezer is actually drawing power, and the expected number of motor starts per day.

[Neil Smith]

If your inverter runs it OK which I assume it does hence running battery bank fast, then your batteries may be on there way out or to small, so either get new ones or fit a bigger bank.

 

Neil

[Arthur Brown]

Realistically without hard numbers there is little but guesswork that we can help with. You need to measure the freezer running current or read it from the rating plate (or owner's booklet). You also need to work out he proportion of time the motor is actually running.

 

A LARGE solar array will help.

 

Tell us please, how old are the batteries and what was their original capacity rating.

[ditchcrawler]

Remember if the OP is selling icecreams he/she will be opening it quite often to remove the icecream and letting warm air in. I would have thought if the 4 batteries are FULLY charged at the start of the day they should last for 18hrs if they are in good condition but then it will probably take the other 6 hours to recharge them again from the mains via a good charger. This assumes that the boat goes back to a mooring with mains electricity every night. If the OP is trying to recharge from his/her engine I would say they have no chance. A good solar installation would go a long way towards it working on the basis that sales, hence opening the freezer is higher when the sun shines producing more charge.

[Maja]

Hello all,

 

Thank you so much for your answers and advice. I am two hours away from my boat / marina so it is hard for me to answer each query immediately but it seems that the freezer is probably only 1.5kw so there is no reason that we can see that it wont run off a smaller generator. I like the idea of using a small generator to recharge / top-up the batteries while I run the freezer off them. I will also look into Solar Panels for installation on the roof as it is a free resource over the longer term.

 

Thank you again, I hope to keep you informed of my progress

[smileypete]

Maybe solar for sunny days, plus some genny for uber hot or cloudy days, or when the freezer is loaded.

 

Bimble solar have 2nd user panels that work out cheap if buying a few, plus try Ebay, look for the more efficient mono[crystalline] panels if roof space is tight. Tracer MPPTs controllers have a decent reputation, avoid the really cheapo controllers.

 

Some good priced gennys at 'thepowersite', maybe worth phoning em up, the bloke from there has been on here and sounds like he'd give a frank opinion of what's OK or not.

 

A cheap plug in power meter will give the running current of the freezer, would have thought the startup surge is up to 10x this.

 

cheers, Pete.

~smpt~

Edited June 21, 2015 by smileypete

[Scholar Gypsy]

NB the difference between kW and kWh - I would suspect your freezer uses 1.5 kWh of energy each day, which is 1500/24 = 60W of power.

 

It's similar to the difference between Amps and Amp-hours - the former is a flow (charge used per unit of time) and the latter is a stock (total charge stored).

[DHutch]

NB the difference between kW and kWh .

... it seems that the freezer is probably only 1.5kw so there is no reason that we can see that it wont run off a smaller generator.

If its pulling 1.5kW (equivalent to a decent hair dryer/kettle) even on a 50% duty cycle, good luck.

 

I would suggest a plug in power meter would be a good start, if better data is not available.

 

 

Daniel

[ditchcrawler]

many years ago I had a chest freezer and I fitted a 5 amp fuse in the plug top, this blew on startup. Looking at the Whirlpool range of chest freezers they are rated at 100W so the start up inrush is quite high.