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Post by smileypete on May 13, 2017 11:05:52 GMT
I run a full sized fridge/freezer on an inverter and allowed for a bigger drain and installed a 1Kw PSW inverter. I found that very occasionally the inverter would momentarily go into "fault" as the compressor kicked in ...... not every time just occasionally. (I have since upped the inverter to 2Kw) which allows me to use the supply for other devices drawing intermittent power. Running a full sized fridge/freezer on a 1kW inverter definitely sounds like it's pushing it! If it was marginal an inrush limiter (£5-10 all in) might well have reduced the inrush enough, but yeah as you say it's handy to have surplus capacity if the inverter will be on all the time. Have you got round to trying your immersion directly from the solar panel string?
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Post by JohnV on May 13, 2017 11:21:23 GMT
I run a full sized fridge/freezer on an inverter and allowed for a bigger drain and installed a 1Kw PSW inverter. I found that very occasionally the inverter would momentarily go into "fault" as the compressor kicked in ...... not every time just occasionally. (I have since upped the inverter to 2Kw) which allows me to use the supply for other devices drawing intermittent power. Have you got round to trying your immersion directly from the solar panel string? Yes ...... and no I have been trying a simple way by tapping into the paralleled panels and feeding the 3Kw immersion and on a sunny day (like it is at the moment )it is sticking about 4 amps into the immersion say roughly 300-350w not enough to heat it from cold but more than enough to maintain a high temperature if it has been heated by the central heating in the evening. I have had too many things to do to try a proper system, seriesing the panels to give 120 to 140v but I will do so sometime this summer and I'll let you know ...... but it certainly looks very promising
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Post by smileypete on May 13, 2017 13:52:38 GMT
Have you got round to trying your immersion directly from the solar panel string? Yes ...... and no I have been trying a simple way by tapping into the paralleled panels and feeding the 3Kw immersion and on a sunny day (like it is at the moment )it is sticking about 4 amps into the immersion say roughly 300-350w not enough to heat it from cold but more than enough to maintain a high temperature if it has been heated by the central heating in the evening. I have had too many things to do to try a proper system, seriesing the panels to give 120 to 140v but I will do so sometime this summer and I'll let you know ...... but it certainly looks very promising If you're strugging to find a relay with a high DC break rating, one way round it is to have extra contacts and put them in series: www.plctalk.net/qanda/showthread.php?t=95968So get a 4PCO and use two contacts in series whereever you'd use a single contact with a DPCO, eg: cpc.farnell.com/omron-industrial-automation/my4-12dcs/relay-4pco-12vdc/dp/SW03481 (maybe similar cheaper on ebay?) So although you're breaking 140V when load to the immersion is disconnected, spread across 4 contacts that's about 35V each which isn't too bad. Helps that the immersion is a resistive load.
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Post by JohnV on May 13, 2017 14:33:01 GMT
Yes ...... and no I have been trying a simple way by tapping into the paralleled panels and feeding the 3Kw immersion and on a sunny day (like it is at the moment )it is sticking about 4 amps into the immersion say roughly 300-350w not enough to heat it from cold but more than enough to maintain a high temperature if it has been heated by the central heating in the evening. I have had too many things to do to try a proper system, seriesing the panels to give 120 to 140v but I will do so sometime this summer and I'll let you know ...... but it certainly looks very promising If you're strugging to find a relay with a high DC break rating, one way round it is to have extra contacts and put them in series: www.plctalk.net/qanda/showthread.php?t=95968So get a 4PCO and use two contacts in series whereever you'd use a single contact with a DPCO, eg: cpc.farnell.com/omron-industrial-automation/my4-12dcs/relay-4pco-12vdc/dp/SW03481 (maybe similar cheaper on ebay?) So although you're breaking 140V when load to the immersion is disconnected, spread across 4 contacts that's about 35V each which isn't too bad. Helps that the immersion is a resistive load. Thanks for that .............. the problem is more that I just don't have the time ........... there are far too many other little niggly jobs that need finishing before I start playing. At the moment it's a case of if that works, then move on to the next job That's why I said that I'll try later in the summer ...... I still have a pretty comprehensive supply of relays and contactors of all types in my stores ...... when I closed the company down I hung on to nearly everything ....... most of which I will never use ..... but still
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Post by caneyj on May 15, 2017 11:47:26 GMT
I've done experiments with that LEC counter-top fridge using a watt meter and it draws 480 Watts peak and around 50 Watts whilst running. You will run fine with a 600 Watt modified Inverter.
I've done it using a 32L LEC freezer running as a fridge and it uses less power than my 12V Waeco CF50 Chest Fridge at around 12Amp-Hours over 24-Hours in a room-temperature environment.
See my solution here for doing an power sipping AC fridge on the cheap. Use an AC freezer for it's extra insulation and override it's thermostat as I explain below.
https://www.reddit.com/r/vandwellers/comments/4efrgd/creating_an_effective_and_ultraefficient/
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Post by JohnV on May 15, 2017 12:02:39 GMT
I've done experiments with that LEC counter-top fridge using a watt meter and it draws 480 Watts peak and around 50 Watts whilst running. You will run fine with a 600 Watt modified Inverter. I've done it using a 32L LEC freezer running as a fridge and it uses less power than my 12V Waeco CF50 Chest Fridge at around 12Amp-Hours over 24-Hours in a room-temperature environment. See my solution here for doing an power sipping AC fridge on the cheap. Use an AC freezer for it's extra insulation and override it's thermostat as I explain below. https://www.reddit.com/r/vandwellers/comments/4efrgd/creating_an_effective_and_ultraefficient/ This totally ignores switch on surge of the compressor unless you are measuring with a 'scope that comes over as rude ...... it wasn't meant to be . My experience with a fridge freezer unit (small model, not one of the giant ones) is that the switch on surge is not a constant. I believe it might be that if the thermostat clicks in at the wrong portion of the waveform then the surge is worse. I sugest that running on only 600 watts when the running power is 50 watts is cutting it too fine. (and I totally disagree with running any induction electric motor on bad waveforms, the extra losses, I believe would worsen the figures given and very likely stress the motor)
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Post by JohnV on May 15, 2017 12:07:56 GMT
I've done experiments with that LEC counter-top fridge using a watt meter and it draws 480 Watts peak and around 50 Watts whilst running. You will run fine with a 600 Watt modified Inverter. I've done it using a 32L LEC freezer running as a fridge and it uses less power than my 12V Waeco CF50 Chest Fridge at around 12Amp-Hours over 24-Hours in a room-temperature environment. See my solution here for doing an power sipping AC fridge on the cheap. Use an AC freezer for it's extra insulation and override it's thermostat as I explain below. https://www.reddit.com/r/vandwellers/comments/4efrgd/creating_an_effective_and_ultraefficient/ I still strongly recommend that you only use a pure sine wave inverter when powering anything that uses an induction motor ...... some of them don't like the waveforms from a modified inverter at all.
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Post by JohnV on May 15, 2017 12:25:45 GMT
post before last edited
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Post by Telemachus on May 15, 2017 12:53:42 GMT
Yes a wattmeter will have some lag/damping/slow response and thus wont capture the full extent of the startup transient. One thing that has a big effect on the startup transient is the residual pressure in the fluid. So if the fridge is turned on initially, the surge will be lower than if it has been running, cuts out on the thermostat and then cuts back in again shortly afterwards.
that said, an inverter rated at 600w continuous is likely to have a significant overload capability for a few moments. But bearing in mind the cost differential these days, I'd certainly get a PSW one as apart from anything else, the fridge will use noticably less battery power when fed PSW.
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Post by smileypete on May 15, 2017 13:18:09 GMT
I've done experiments with that LEC counter-top fridge using a watt meter and it draws 480 Watts peak and around 50 Watts whilst running. You will run fine with a 600 Watt modified Inverter. I've done it using a 32L LEC freezer running as a fridge and it uses less power than my 12V Waeco CF50 Chest Fridge at around 12Amp-Hours over 24-Hours in a room-temperature environment. See my solution here for doing an power sipping AC fridge on the cheap. Use an AC freezer for it's extra insulation and override it's thermostat as I explain below. https://www.reddit.com/r/vandwellers/comments/4efrgd/creating_an_effective_and_ultraefficient/ I still strongly recommend that you only use a pure sine wave inverter when powering anything that uses an induction motor ...... some of them don't like the waveforms from a modified inverter at all. Exactly why do they 'not like' it? ISTR it's max 20% more heat in theory, though likely to be a lot less in practice. Best way to improve efficiency and prolong life is to ensure good ventilation for the black condenser grid thing, though it's sometimes built into the sides on some (most?) modern fridges. One can get a reasonable estimate of inrush by measuring the dc resistance of the compressor, eg across the plug LN pins with the unit unplugged and temp turned to max cooling so the thermostat clicks in. MSW is bad news for equipment using 'capacitive droppers' to generate a low voltage, these can include electronic controls on more expensive fridges (digital display, freezer defrost timer), some LED bulbs, electronic plug in timers: en.wikipedia.org/wiki/Capacitive_power_supplyOn a cheap £100ish fridge I'd be happy to risk using MSW, given that it's about £100 cheaper than pure sine. However as said if pure sine is needed for other stuff then go for it.
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Post by JohnV on May 15, 2017 14:12:01 GMT
I still strongly recommend that you only use a pure sine wave inverter when powering anything that uses an induction motor ...... some of them don't like the waveforms from a modified inverter at all. Exactly why do they 'not like' it? Apart from the overheating problem (and as things nowadays are built with the absolute minimum safety margins, I don't think that insignificant) they also can be very noisy operating on poor waveforms. some of the buzzes coming out of an ac cooling fan and also the circulating fan in a "mini oven" that I ran on a MSW inverter were ....... annoying
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Post by smileypete on May 16, 2017 8:38:55 GMT
Exactly why do they 'not like' it? Apart from the overheating problem (and as things nowadays are built with the absolute minimum safety margins, I don't think that insignificant) they also can be very noisy operating on poor waveforms. some of the buzzes coming out of an ac cooling fan and also the circulating fan in a "mini oven" that I ran on a MSW inverter were ....... annoying Totally different sort of motor though, it's like comparing a moped to a 747. Most of the heat in the compressor is from the refrigerant gas being compressed, hence the need for good ventilation. Anyway I expect a fridge running on 220V MSW won't use much more power if any than grid 240V. But If people want to spend ~£250 on fridge + pure sine inverter instead of £150 on fridge + MSW inverter for 'peace of mind' that's fine by me.
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Post by JohnV on May 16, 2017 9:31:57 GMT
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Post by smileypete on May 24, 2017 18:38:42 GMT
Like I said before, if there's a need for a PSW anyway then why not get that, they're getting cheaper these days. As far as heat goes, if you're really fussed you could compare the compressor temp on MSW and PSW/grid. Personally with a £100ish fridge with a simple dial thermostat I'd risk it if a PSW inverter wasn't needed for other things. Wonder what Our Lord Delta went for in the end, or after the baffling techie talk did he end up lying down in a darkened boat with cold beers - from the offie!
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Post by caneyj on Jul 18, 2017 12:22:21 GMT
I run a 32L LEC Counter-Top Freezer (running as a fridge with a thermostat override due to the better insulation) perfectly fine from a 600-Watt Bestek Modified Inverter.
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