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stuey

Do Fridges Work Better On Gas?

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Hi,

Just had my fridge repaired(new electric heater element) and checked on the gas side. Still not working well on the gas(doesnt seem to be cooling the main compartment)The engineer & a second opinion assured me they work better on gas. Mine is a dometic in a 4 yr old bailey senator & apparantly dometic are pretty good,any ideas anyone before i hear back from the service guy

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There was a thread on the Swift forum about the Thetford caravan fridge and the guy from Thetford certainly gave that impression, especially about bringing the temperature down to the correct level.

 

David

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I was forced to run mine on gas this year on holiday, as the mains element failed.

I found it was nowhere near as cold on gas as it had been on mains.

Mine is a Dometic fridge .

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All the gas appliances in a van work better on Gas, as that is their primary fuel source.

Electric was only added to fires and fridges to satisfy customer demand with the introduction of electric hook ups.

 

As for the fridge, as long as the burner is serviced regularly and kept clean, and preferably run on Propane, it should be better than electric for efficiency.

 

The problem is, many owners fail to get their fridge burner serviced as often as it should be.

 

It does not take very much to reduce the efficiency of the gas burner by debris falling down the flue, or corrosion in the burner.

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As for the fridge, as long as the burner is serviced regularly and kept clean, and preferably run on Propane, it should be better than electric for efficiency.

Not when you have already paid for your electric hookup

Brian

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Quote "Not when you have already paid for your electric hookup"

 

And that comment is exactly why a lot of gas appliances fail to work effectively,,,,,,,because they are not used enough and deteriorate.

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far colder on gas in our van. in fact we used gas through the day while in france as the 240v couldnt keep it cool enough. annoying when you`ve paid for a hook up but still better than chucking grub away

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far colder on gas in our van. in fact we used gas through the day while in france as the 240v couldnt keep it cool enough. annoying when you`ve paid for a hook up but still better than chucking grub away

 

Probably cos u get 220v at best on French sites and with long leads and shared connections often a lot less. I've had the led on my Thetford flashing on mains, indicating that the voltage has fallen below 190.

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Anyone explain the logic behind gas being more efficient?

 

The fridge works by heating a fluid in a pipe.

 

Heating can be mains or 12volt element or a gas flame.

 

Mains and gas are controlled by a thermostat setting the fridge temperature.

 

The mains cuts in and out when operating so, presumably, is supplying the correct amount of heat demanded by the system.

 

Similarly, the gas heating is controlled according to demand.

 

How can there be any difference in performance?

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Beejay

I agree. I have never noticed any difference in cooling the fridge whether on mains electric or gas.

However, the elements are rated at 230v, so in the UK at nominally 240v, there should not be a problem, but in Europe at 220v on a hot day performance could be marginal.

Brian

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Beejay

I agree. I have never noticed any difference in cooling the fridge whether on mains electric or gas.

However, the elements are rated at 230v, so in the UK at nominally 240v, there should not be a problem, but in Europe at 220v on a hot day performance could be marginal.

Brian

 

In theory, all of the EU countries should have the same voltage and frequency, as the nominal European declared voltage is now 230V 50 Hz (formerly 240V in UK, 220V in the rest of Europe) but this does not mean there has been a real change in the supply.

 

The original "harmonised voltage limits" in Europe were: 230V -10% +6% (i. e. 207. 0 V-243. 8 V) in most of Europe (the former 220V nominal countries), and 230V -6% +10% (i. e. 216. 2 V - 253. 0 V) in UK (former 240V nominal).

 

This was really a fudge and means there was no real change of supply voltage, only a change in the "label", with no incentive for electricity supply companies to actually change the supply voltage. In other words, simply more reams of 'bumf' from the overpaid bureaucrats in Brussels!

 

To cope with both sets of limits, electrical equipment therefore needs to cover 230V +/-10% i. e. 207-253V. This actually became the official limit for the whole of the EU in 2003.

 

Variations should still be anticipated in some areas as the voltage will drop during periods of heavy demand and rise during periods of low demand. Further, the wiring in some of the older French caravan sites "leaves more than a little to be desired"! Voltages as low as 190v are not un-common on some pitches that are situated distant from the main voltage distribution point, so under circumstances such as this, gas could well give better/quicker cooling than 'mains' electricity.

 

Regards,

David

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Most 230v fridge elements are around 125w which is quite small, therefore gas will deliever much more heat faster to the heating chamber than electric and therefore cool faster and react to themostatic variance more swiftly.

 

If temperatures are extreme, on gas the fridge has a much better chance to respond. Caravan fridges started off as gas appliances only (1960. 70's) with electric elements being added later in the design in order to respond to the demand after widespread installation of EHU during the 1990's.

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Looking at it another way, assuming the element is rated at 125w at 230v.

At 240v, it will give 136w

At 220v, it will give 114w

 

So thats 19% more heat in the UK than on the continent, even if you actually get 220v.

 

Quite a difference

 

Brian

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That's presuming you get 240V in the UK.

When I am calibrating our test meters, I never get more than 232V and sometime 226V, so it looks like we have a 230V supply around here.

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Looking at it another way, assuming the element is rated at 125w at 230v.

At 240v, it will give 136w

At 220v, it will give 114w

 

So thats 19% more heat in the UK than on the continent, even if you actually get 220v.

 

Quite a difference

 

Brian

 

Agreed that a drop in voltage will reduce the wattage available but that is assuming the element is rated for 240v or 230v. As the fridges are made in Germany it may be that they have a nominal design voltage of 220v.

 

Measuring the element resistance will provide the answer as to what voltage provides the nominal wattage.

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That's presuming you get 240V in the UK.

When I am calibrating our test meters, I never get more than 232V and sometime 226V, so it looks like we have a 230V supply around here.

 

My plug in meter is currently showing 234 volts which is the usual figure.

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Curiously, I just checked the spec for our RM4271 - it gives 125w for 230v nominal, 120w for 12v nominal and 232w "input" for gas - so unless the gas is less than 54% efficiency then the gas will work better.

 

Perversely, 12v nominal is normally running at 14. 8v so should be able to outperform mains electric but few have noticed that!

Edited by RogerL

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Agreed that a drop in voltage will reduce the wattage available but that is assuming the element is rated for 240v or 230v. As the fridges are made in Germany it may be that they have a nominal design voltage of 220v.

 

Measuring the element resistance will provide the answer as to what voltage provides the nominal wattage.

All electrical appliances sold in the EU have to be rated at 230v and have been for some years. This is EU harmonisation at work, the idea being that they will work on both 220v and 240v nominal systems. Have a look at the rating plate on your domestic kettle. The benefit in the UK is that we get a few extra watts at home, the downside is that if you actually get more than 230v in your caravan, you will pull slightly more amps than you might have thought, but should not normally be a problem.

Brian

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Curiously, I just checked the spec for our RM4271 - it gives 125w for 230v nominal, 120w for 12v nominal and 232w "input" for gas - so unless the gas is less than 54% efficiency then the gas will work better.

 

Perversely, 12v nominal is normally running at 14. 8v so should be able to outperform mains electric but few have noticed that!

 

Doesn't gas water heating have a 50% loss via the flue so is that the difference between input watts and output watts? If the heat required to make the fridge work is 120/125 watts via electric elements why would gas require more wattage unless it's to compensate for losses in the system?

 

It's true that voltage drop with either 230v or 12v reduces the wattage available at the element. The 12 volt wiring in most cars and caravans is far below the specification that Dometic require of 6mm² cable to reduce voltage drop. If you are getting 14. 8 v at the fridge heater element your system must be up to scratch of which I have doubt. Mains voltage in the U. K. will generally be acceptable and wiring is not an issue. A plug in meter showing voltage enables a continual check and a switch to gas if necessary.

With high ambient temperatures in Europe another problem can be the limit of TN rated fridges to a maximum 35°C drop below ambient temperature which many fridges will not achieve because of poor performance. On a hot summer day at 30°C ambient many fridges will not maintain the 5°C required in the fridge.

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Doesn't gas water heating have a 50% loss via the flue so is that the difference between input watts and output watts? If the heat required to make the fridge work is 120/125 watts via electric elements why would gas require more wattage unless it's to compensate for losses in the system?

 

It's true that voltage drop with either 230v or 12v reduces the wattage available at the element. The 12 volt wiring in most cars and caravans is far below the specification that Dometic require of 6mm² cable to reduce voltage drop. If you are getting 14. 8 v at the fridge heater element your system must be up to scratch of which I have doubt. Mains voltage in the U. K. will generally be acceptable and wiring is not an issue. A plug in meter showing voltage enables a continual check and a switch to gas if necessary.

With high ambient temperatures in Europe another problem can be the limit of TN rated fridges to a maximum 35°C drop below ambient temperature which many fridges will not achieve because of poor performance. On a hot summer day at 30°C ambient many fridges will not maintain the 5°C required in the fridge.

I've no idea what the loss % between input and output is for caravan appliances - our old domestic boiler is 79% but very different in design.

 

You may be right to doubt voltage at the fridge - mine's only 14. 4v at the fridge due to the drop in the caravan cabling - I used 8awg for the car though ;)

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Does it really matter as long as the fridge is working safely and the beers are cold !!

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Anything more than 12v at the fridge will give you more than the nominal rating, so provided you have a minimum of 12v it should work as designed. 2. 5mm2 cable is the recommended size.

Brian

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