Solar and electrical wiring to fridge connection question (1 Viewer)

[Cliffdale]

On the hand over, I was told the fridge has to be switched manually between 240v, gas supply or motor 12v battery. Also the 12v does not really cool things down but maintains a temperature.

Is the following possible?

To save gas, I have 300W of solar and a good inverter. How can I connect the 240v inverted power to the fridge but keep the fridge isolated from the rest of the motor home. I'm thinking of 2 * 3pin plugs, one plug directly from the inverted power supply and the second plug connects back to the normal motor home 240 supply.

Would it work, just switch the plugs when wilding during the day and revert to gas over night, and when back on EHU plug back into the mains.

The inverter has no Earth, will this nacker the system?

 

[SandraL]

Be aware that with a male to male 13amp plug lead if you remove the fridge end first and touch the pins you will get a rather nice tingling feeling, or maybe worse as you touch the exposed 240 v ac pins. Sometimes these leads are called suicide leads......
There have been threads on here about changeover circuits from ehu to inverter. Also need to use an rcd when on inverter.
Later fridges use 12 volt via solar, but they are auto selection fridges.

 

[Bart]

I don't think you will get enough power from you solar to run a 3 way fridge .

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[tonyidle]

The fridge 12v element is the same power as the mains element: the limitation of cooling power is due to voltage drop on the long 12v lead from the front of the van. To bring 12v cooling in line with mains cooling simply increase the size of this lead. Having said that I absolutely agree with Bart: your panels would need to supply a pretty constant 10 amps. Gas is simpler & works.

 

[Lenny HB]

You don't say what model fridge so the draw at 12v either straight or via inverter is going to between 10-15amp as it is an absorption fridge it will be constant. To do what you want to do you would probably need at least 500a/h of batteries and probably 500-600 watts of solar then it might work in southern Spain for a couple of months in the summer.
Much better to use gas, 3 way fridges work better on gas and they don't use much.

 

[funflair]

if you want your fridge on 240v from the inverter why not set up the inverter to power all the motorhome electrics with an automatic changeover that would prioritise 240v hook up.

I have run our fridge on 240v this way in Spain but I would not go out for the day and leave it in case the sun goes in, you would have to switch the fridge to the desired power source manually.

Martin

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[denisejoe]

The fridge hardly uses any gas as it's it's just a pilot light so you won't save a lot of gas a bottle will last a very long time

Joe

 

[Cliffdale]

sound like good advice everyone, Ill give it a miss!

 

[DanielFord]

It might be silly, but I've often wondered the same. The fridge goes to 12v when the engine is running. It would be great if it also went to 12v when there was sufficient sunlight. Surely it must be possible?

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[funflair]

It might be silly, but I've often wondered the same. The fridge goes to 12v when the engine is running. It would be great if it also went to 12v when there was sufficient sunlight. Surely it must be possible?

It is and has been covered on here several times, our fridge runs on solar 12volts when there is enough spare, you need a modern AES fridge with S+ or an older D+ equipped AES fridge and a strategically placed diode and a suitable solar regulator with AES out, ours is a Votronic.

Martin

 

[sallylillian]

It is and has been covered on here several times, our fridge runs on solar 12volts when there is enough spare, you need a modern AES fridge with S+ or an older D+ equipped AES fridge and a strategically placed diode and a suitable solar regulator with AES out, ours is a Votronic.

Martin

As Martin says you can connect your fridge to one of the latest solar regulators which will auto switch to 12v I have done just that and here in Spain in good sun it auto switches, even when on EHU.

 

[PeteH]

Interesting, What would be needed is an "intelligent" switching module, that which would monitor the Solar output, switch to solar when sufficient was available, and then Auto switch back to gas when the Output Dropped?. And prioritising the Batteries when necessary.? Getting 10+ Amps on a Murky UK day would be the biggest drawback!. Having said that, My frig; ONLY fires up when required anyway, the pilot (flame) does not run ALL the time, only when the thermostat "calls" for it?. When "off grid" you can hear the igniter "clicking" from time to time, as it relights the flame.

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[scotjimland]

Fridge Gas consumption

80lt model
Gas use in grams in 24 hours approx 270 gm

therefore, 1.89kg per week, 7.56kg per month

31 lt model 140gm per day

Electric power usage
Example
RM 8400

Electrical
Input voltage (AC 230-240 V
Input frequency 50/60 Hz
Rated input power (AC) 135 W
Rated input power (DC) 130 W
Rated input current (AC) 0.6 A
Rated input current (DC) 11 A
Input voltage (DC) 12 V

as I understand, all new models have thermostats on all three energy sources, so on 12v it is not a constant load of 11A

Dometic have energy consumption on all new models,

 

[Lenny HB]

It is and has been covered on here several times, our fridge runs on solar 12volts when there is enough spare, you need a modern AES fridge with S+ or an older D+ equipped AES fridge and a strategically placed diode and a suitable solar regulator with AES out, ours is a Votronic.

Martin

As Martin says you can connect your fridge to one of the latest solar regulators which will auto switch to 12v I have done just that and here in Spain in good sun it auto switches, even when on EHU.

I looked into this recently and I wouldn't recommend going this route if you have Gel batteries, OK with wet cells but Gel's need to be held at 14.2-14.4 volts for at least 8 hours (latest mains charges hold at 14.4v for 16 hours) to achieve a full charge. So if when the voltage gets to 14.2 and the fridge kicks in pulling 10-15 amps the voltage will drop and the batteries will never get a full charge.
I may be wrong and a good solar regulator may not trigger the fridge until the battery output has been at 14.2v for 8 hours but the sun will have gone down by then.

as I understand, all new models have thermostats on all three energy sources, so on 12v it is not a constant load of 11A

I'm a silly boy I for about allowing for the thermostat.

 

[sallylillian]

Lenny the regulator will only deliver the signal to the fridge to switch to DC IF there is excess solar energy. So I would assume it takes into account the demand for charging the battery and other DC draw?

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[Lenny HB]

Lenny the regulator will only deliver the signal to the fridge to switch to DC IF there is excess solar energy. So I would assume it takes into account the demand for charging the battery and other DC draw?

I just downloaded the Votronic manual and it doesn't give any parameters just says when sufficient solar is available. Although it would appear to work I can't see it working in practice with Gel batteries unless you have a very large solar array. The fridge kicking in at 14 amps is bound to drop the volts.
Although it would work I don't think the batteries would probably never get fully charged,
Only way to prove it is to monitor the battery voltage over a couple of hours with the fridge running off 12v and see if the voltage drops below 14.2v. Need to monitor constantly as the fridge will cut in and out on the thermostat.
Please prove me wrong it would be nice to know it works.

Edit:
The information in the manual is too sketchy to know how it works I'm now wondering if AES output is only triggered once the regulator has reduced the output to the 13.8v maintenance charge then providing the the solar output is cable of maintaining 13.8v with the fridge running it would work, if that is the case it would make the dribble I've written above irrelevant.
Even if that is the case I wouldn't want to try it with less than 400-500 watts of solar.

 

[funflair]

Hi @Lenny HB

Just been reading the EXIDE/Sonnenschein solar GEL charging instruction and read this,

Solar batteries have also to be operated at States-of-Charge (SOC) less than 100% due to seasonal and other conditions, for instance (acc. IEC 61427, /9/):

Summer: 80 to 100% SOC, Winter: down to 20% SOC.

Therefore, equalizing charges should be given every 3 to 12 months depending on the actual SOC values over a longer period.

So that suggests to me that not charging at 14.4v for 8 hours every day will not do them any harm as long as they get "fully charged" every now and again.

I dont see a problem with ours as 1/ I trust that the Votronic knows what its doing 2/ We have two solar controllers so if one has gone over to running the fridge the other one that had been in shut down as it had no work to do will wake up and hold the batteries at the desired 14.4v. 3/ Our batteries get a full charge when we go on hook up (if its paid for I use it) and if not the EFOY will do a full charge while its in the shed.

And apart from all of the above everything is working fine and has been for a few years, I check the battery volts before going to bed after having the TV on for 5 hours or more and it is usually showing around 13 volts so that is good enough for me (easily pleased).

Martin

 

[Lenny HB]

Hi @Lenny HB

Just been reading the EXIDE/Sonnenschein solar GEL charging instruction and read this,

Solar batteries have also to be operated at States-of-Charge (SOC) less than 100% due to seasonal and other conditions, for instance (acc. IEC 61427, /9/):

Summer: 80 to 100% SOC, Winter: down to 20% SOC.

Therefore, equalizing charges should be given every 3 to 12 months depending on the actual SOC values over a longer period.

So that suggests to me that not charging at 14.4v for 8 hours every day will not do them any harm as long as they get "fully charged" every now and again.

I dont see a problem with ours as 1/ I trust that the Votronic knows what its doing 2/ We have two solar controllers so if one has gone over to running the fridge the other one that had been in shut down as it had no work to do will wake up and hold the batteries at the desired 14.4v. 3/ Our batteries get a full charge when we go on hook up (if its paid for I use it) and if not the EFOY will do a full charge while its in the shed.

And apart from all of the above everything is working fine and has been for a few years, I check the battery volts before going to bed after having the TV on for 5 hours or more and it is usually showing around 13 volts so that is good enough for me (easily pleased).

Martin

I agree that Gel's cope well without fully charging them but my concern is on the average setup (yours is well above average) with Gel's only getting charged to 80% and you are wilding and get a few cloudy days you could end up low on battery power. For my own use, for the cost of running the fridge on LPG I'd rather ensure my batteries are fully charged. I'm a pauper, I only have 3 batteries and 200 watts of solar.

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