AC Fridge In Campervan -.Power Consumption Test

[xsilvergs]

Well it is a saving

One of the unknowns is the impact on the unit of keep changing energy sources? Each time you ignite the gas on a burner, I understand something 'burns away'? miniscule effect maybe but it all adds up over time, so could igniting the gas on an hourly basis eat into the operational life of a gas appliance to any significant degree?
I really don't know but I am slightly wary about having the fridge not seeing a 'proper' AC supply when switched to it (i.e. when inverter is in ECO/AES mode) even though there are no apparent issues. I am a lot more wary about having the fridge restarted on Gas on such a frequent basis.
Personally, and on no basis other then my own feelings, I wouldn't set up the Stop/Start parameters so tightly

Regards reigniting:- I'm not using ECO mode. If the battery SoC is >=76% the igniter does not spark and it goes straight to 230V electric. Once the battery discharges to 75% the fridge switches to gas and the igniter does its thing as it would if just on gas. The fridge is unlikely to switch back to 230V in this ON cycle.

I don't think the gas would ever be ignited more than once in one ON cycle. I will monitor it and broaden the 1% gap if required but will be surprised if it needs it.

 

[wildebus]

Regards reigniting:- I'm not using ECO mode. If the battery SoC is >=76% the igniter does not spark and it goes straight to 230V electric. Once the battery discharges to 75% the fridge switches to gas and the igniter does its thing as it would if just on gas. The fridge is unlikely to switch back to 230V in this ON cycle.

I don't think the gas would ever be ignited more than once in one ON cycle. I will monitor it and broaden the 1% gap if required but will be surprised if it needs it.

This is what I mean - the gas ignites on each energy source change - and you are showing an on cycle and energy source change every hour at least. That is a lot more gas ignition activity than a typical user would see.
You say unlikely to switch back to gas on that cycle? Why? the SOC could increase by 1% within15 minutes or less with good solar? you bring in 20A from the solar and you could flip from 75% to 76% in just a few minutes with a 200Ah bank and you are back to AC again.
You said youself the day was fairly bad solar wise, so on a day with better harvesting the flipping would be even faster and frequent.


The ECO mode was not really relevant to the point about gas. It was just an observation that intermittant 12V might have strange affects on the AC side of the fridge. You said your Fridge didn't like ECO. Mine seems to not care about the equivalent AES - might be an inverter difference or a fridge difference, but kinda academic anyway.

 

[xsilvergs]

Surely, when the fridge temperature rises above x*C a cooling cycle is requested. So if the only source was gas every time the a request was made the igniter lights the gas and the burner stays alight until the temperature within the fridge drops below x*C. The next time the igniter lights the gas will be when the temperature rises above x*C.

Should the energy source be 230V the heating element does the same as the gas flame does and stays on until the temperature drops below x*C.

If the cooling cycle starts on 230V from the inverter and part way through it switches to gas that is still only one gas ignition for that cooling cycle.

Wouldn't 20A of solar be almost enough to power the fridge (~250W AC) through the inverter without taking from the battery? With and average ON to OFF ratio (if nobody opens the door to gaze in) of 3 to 1, I guess one could calculate the mean current required from the solar chargers?

If I ever noticed the gas having to come on more than once to support the inverter in a cooling cycle I can increase the 76% level in 1*C steps at the click of a soft button. Also as it all runs in code it could quite easily be made adaptive but I've not seen the necessity yet.

 

[wildebus]

I am working on the assumption that when the fridge is in gas mode, the gas is lit and when the cooling cycle is finished say 30 minutes later, the gas stays lit (pilot light) and ready for the next cycle. But if the fridge changes away from gas, the pilot goes off. Could well be a false assumption.
If there is a new ignition each time there is a demand for cooling, then it would make no difference if it is switching between AC and Gad repeatedly.

20A of solar would run the fridge indeed - but it is also going to recharge the battery at the same time remember.

Be interesting to see how it goes. I prefer my approach of a much larger hysterisis between the on and off, but it's a personal thing

 

[xsilvergs]

Our fridge/freezer is a Thetford N3150 series which is left in Auto mode most of the time. On gas it reignites the gas for every cooling cycle.

It would appear, and I take this from the BMV that the solar can be producing a charger equal to that of the inverters demand and the battery will take nothing. Should the solar vary a small amount either side of the inverters demand the battery can be seen to charge or discharge with negligible variation in voltage. So impressed with these batteries.

I've reduced the hysteresis from 5% to 1% and the level down to 75% as this seems to give a early swap from gas in the morning and enough capacity should the sun not shine the following day. The 60% SoC we had this morning should have kept us going for a few days if the fridge was run on gas.

I did require the larger hysteresis with the lead acid battery.