AC Fridge In Campervan -.Power Consumption Test

GEOFF

Full Member
We once had a rep round showing a "soft start" device for electric motors - I would guess that would be something similar. The demo started the AC motor very gently and ramped up to speed. Would that sort of thing help. Geoff.
 

wildebus

Full Member
We once had a rep round showing a "soft start" device for electric motors - I would guess that would be something similar. The demo started the AC motor very gently and ramped up to speed. Would that sort of thing help. Geoff.
I think that is a different kind of thing as the compressor needs a kick to get it started? That device sounds more like these kind of regulators .... https://www.ebay.co.uk/itm/Voltage-Regulator-Adjust-Motor-Speed-Control-Dimmer-Thermostat-AC-220V-4000W/282425934168.
I have one of these arriving hopefully today as it happens to use with my electric water heater to reduce the element wattage.
I could try it on the fridge I guess to see, but the one I am getting is a manually set regulator so don't think it would show anything one way or the other? but I guess could manually ramp up the voltage to see?
 

mistericeman

Full Member
Hard stard kits are basically a large capacitor.... Think of it like a battery that stores current for when it's needed... To give the motor an initial " boost"
I've not come accross them in years as most of our big stuff (open/semi hermetic) used Star/delta wired motors and all our small stuff is now inverter compressors....
Plenty of guides on YouTube of how to wire them in (though mainly American)
 

wildebus

Full Member
Hard stard kits are basically a large capacitor.... Think of it like a battery that stores current for when it's needed... To give the motor an initial " boost"
I've not come accross them in years as most of our big stuff (open/semi hermetic) used Star/delta wired motors and all our small stuff is now inverter compressors....
Plenty of guides on YouTube of how to wire them in (though mainly American)
not found that that sufficiently covers wiring into a Refrigerator though. I am thinking one of the required connections is internal (or just not present?)
 

mistericeman

Full Member
Two terminals is a bit 'odd'.... Most 240v hermetic compressors I've come across have been 3 terminal (C-S-R) capacitor/start/run....

Has it got a wiring diagram anywhere?
 

wildebus

Full Member
Two terminals is a bit 'odd'.... Most 240v hermetic compressors I've come across have been 3 terminal (C-S-R) capacitor/start/run....

Has it got a wiring diagram anywhere?
Maybe the third wire was tucked away and I didn't see it. Could it have been inside a housing?

This is not specfically a photo of the compressor but a fan I added. Maybe there are some clues here though which you can see?
Extra Fan on Fridge Rear by David, on Flickr

this is an image of the rear from the supplier...
 

Duckato

Full Member
IIRC I looked the compressor up on the manufacturers web site a while ago but could not find the exact same model I have since forgotten what it is so I will go and look it up again later I am pretty sure there is a startup cap on the side
 

SquirrellCook

Full Member
I went though this pain trying to find a good inverter to start a domestic fridge. I now run an old victon 12/800 and I think it's only just enough to reliably start the fridge. The new 12/800's are lower wattage so I won't risk one and will use the next size up on the new project. I also purchased various soft start kits with no luck making them work. Most European fridges seem to use a PTC device to change from start to run windings. AC induction motors are not my thing. I know there are capacitor start motors and these must have some kind of switch. Then there are capacitor run motors. Domestic fridges are built as cheap as they can make them regardless of what you spend. I have connected a relay to my PTC to operated a fan, but even the resistance of the relay changes the behaviour of the PTC. Fortunately not enough to make the fridge unusable.

For me the most important thing is that the fridge does not fail. I know I'm not away as long as some of you, but I like my comforts. Being trapped in a hot field away from any town with no fridge is not fun. As the inverter gets a good kicking I won't risk a cheap Chinese one.

Just came back from the Czech republic after being parked up for 4 days. 31 degrees outside and much hotter inside. Fridge was perfect. The relay switches 12volts to two computer style fans. These are mounted in my fridge upper external vent. The theory being if I can pull out the air from the top back of the fridge cooler air fill be drawn in from the lower external vent.

Mark
 

Duckato

Full Member
It does annoy me if I have bought a 500w inverter that is only 400w as Wildebus suggested I was tempted to go for one of their better models but the stupid buzz my existing one makes has put me off, cheap transformers hum but quality ones do not so I have my doubt about this victron.

instead I am going to buy a different make probably a cheapie and leave the victron in situ for emergencies only.
I have plenty of room for it!
 

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SquirrellCook

Full Member
My Victron 12/800 does not hum when running the fridge or even load it enough to start it's internal cooling fan. That said there is a noise on starting the fridge. I suspect the instantaneous on starting is much higher than quoted.

Mark
 

wildebus

Full Member
I am not trying to defend Victron, but they never claimed their 12/500 Inverter is a 500W unit. They use the naming to signify the VA rating rather than the Wattage on all the inverters they currently sell (I think VAs are a more accurate measurement when used with Inverters due to the variable incoming voltage they deal with).
This system is used throughout their range - the 12/800 is a 650W unit for example (but is 800VA), and the 12/3000 Multiplus I have is actually a 2500W inverter.

If it (the 12/500) hums in normal use upto 400W that is not good. If it makes a noise when you are pulling 800W+ through a 400W inverter BUT it still does the job ... I think that is pretty impressive TBH.
 

Duckato

Full Member
My Victron 12/800 does not hum when running the fridge or even load it enough to start it's internal cooling fan. That said there is a noise on starting the fridge. I suspect the instantaneous on starting is much higher than quoted.

Mark
Yes it is the start up noise I am referring to, classic transformer hum, mine is extremely loud considering my inverter is in an external battery box and I can hear it from a considerable distance away. certainly can’t leave it on at night

I am glad I did not waste my money on the 800 if it does the same.

I also have a cheap french inverter (a GYS PSW 8600)
which does not make any noise at all unfortunately although supposedly 600w and 1200w peak it too is not quite powerful enough to cope with the inrush current and the compressor stalls about as often as it does using the victron!
 

wildebus

Full Member
My Victron 12/800 does not hum when running the fridge or even load it enough to start it's internal cooling fan. That said there is a noise on starting the fridge. I suspect the instantaneous on starting is much higher than quoted.

Mark
About 20 x greater!
You won't see it, just hear the noise, but this chart shows what is happening every time the fridge starts on your 12/800 Inverter

MP800-FridgeAC vs Overload
by David, on Flickr
Each start the Inverter overloads - but it is designed to carry on running when overloaded for a short time to specifically cope with compressors and inrush currents.
(the full inrush is not captured each time in this graph, but it does always happen)

This inrush is also the case with 12V Compressor Fridges and why one of those, that draws around 3A when running needs to be installed using 4mm cable (preferably 6mm) for them to start reliably.
Lost count of the number of people I speak to who say their fridge reports low battery (via a warning light) when the battery is fine, and is invariably due to too thin a gauge cable as the installer read the "3A running" bit in the manual and use a cable purely suitable for that low current.
 

Duckato

Full Member
I am not trying to defend Victron, but they never claimed their 12/500 Inverter is a 500W unit. They use the naming to signify the VA rating rather than the Wattage on all the inverters they currently sell (I think VAs are a more accurate measurement when used with Inverters due to the variable incoming voltage they deal with).
This system is used throughout their range - the 12/800 is a 650W unit for example (but is 800VA), and the 12/3000 Multiplus I have is actually a 2500W inverter.

If it (the 12/500) hums in normal use upto 400W that is not good. If it makes a noise when you are pulling 800W+ through a 400W inverter BUT it still does the job ... I think that is pretty impressive TBH.
Oh it is VA! Drat I had not noticed that, yes you are right in that case I definitely need to change it for something else.
 

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